Research Trends of Microplastics: A Systematic Review and Bibliometric Analysis Using the Methodi Ordinatio Approach

Abstract

Microplastic pollution is a major environmental concern due to its persistence, global distribution, and potential impacts on ecosystems and human health. This systematic review, conducted according to PRISMA 2020 guidelines, analyzes research trends in microplastics with a focus on physicochemical characterization and removal technologies. A literature search was performed in Scopus and Web of Science (1972–2025) using predefined inclusion and exclusion criteria. After screening and duplicate removal, 89 studies were included in the final analysis. It is considered that with this dataset, it is possible to capture the main analytical and technological developments in the field. As a bibliometric-oriented study, no formal risk-of-bias assessment was conducted. However, a qualitative consideration of potential biases was undertaken, particularly regarding publication bias, database coverage limitations, and the predominance of English-language peer-reviewed studies. These aspects were considered when interpreting the results. The Methodi Ordinatio approach was then used to rank publications based on scientific relevance and citation impact. Results show the predominance of FTIR and Raman spectroscopy for microplastic characterization, while removal technologies remain heterogeneous and less standardized, with most approaches still at laboratory scale. Key gaps include the lack of standardized analytical protocols and limited integration between detection and remediation strategies. Overall, this review highlights critical research trends and supports the development of scalable solutions for microplastic pollution.

1. Introduction

Microplastics (MPs), defined as plastic particles smaller than 5 mm, have become a symbol of the modern environmental crisis. Their presence extends from oceans to drinking water, accumulating in ecosystems and organisms, with consequences that are not yet fully understood [1,2]. These materials, derived from malleable and durable synthetic polymers, persist in the environment for centuries due to their chemical stability and slow degradation [3,4]. Plastic presence in marine ecosystems has been documented since the 1970s, including records of plastic fragments in seabirds. Pioneering studies in the Sargasso Sea detected up to 3500 particles/km², providing evidence of early contamination [5]. Currently, it is estimated that between 82 and 358 trillion plastic particles float in the oceans [6], reflecting accelerated contamination since the early 21st century. This issue extends beyond environmental concerns, as MPs interact with pollutants such as heavy metals and toxic substances, amplifying risks to human health by infiltrating the food chain and biological tissues [7]. Their origins are diverse, including primary MPs (microbeads in personal care products, industrial pellets) and secondary MPs (from the degradation of single-use plastics), accelerated by ultraviolet radiation, which degrades and fragments polymers [1,5]. Although their detection has been reported even in remote high-altitude lakes [8], even though significant progress has been made in identifying microplastic sources and impacts, critical gaps remain in understanding their global distribution, particularly due to methodological inconsistencies and fragmented reporting across studies. In this context, the present review aims to address this limitation by systematically analyzing detection techniques and occurrence data, providing a more integrated perspective on microplastic distribution patterns in aquatic environments [9], alongside the challenge of methodological standardization for characterization and removal. Recent studies show inconsistencies in sampling and analysis protocols, hindering comparisons between investigations [10,11]. A clear example is found in drinking water treatment plants, where, despite current technologies, the persistence of MPs particles less than 10 µm is evident, showing methodological failures in the process. This technical gap is exacerbated by the growing evidence that nanoplastics (smaller and less studied particles) may have greater toxicological impacts [12].

Research on MPs has experienced exponential growth since 2016, with notable contributions from different regions of the world, including Asia, Europe, and North America [7]. However, despite significant advances in the understanding of microplastic occurrence, fate, and toxicity, the translation of this knowledge into comprehensive practical solutions remains limited. Current challenges include the lack of standardized detection methodologies, limitations in the efficiency and scalability of removal technologies, and insufficient implementation at full-scale wastewater treatment systems due to the lack of consistent, long-term statistical data [13,14,15,16], limiting the evaluation of environmental policy effectiveness, such as the International Convention for the Prevention of Pollution from Ships (MARPOL), which seeks to control plastic pollution in international waters but faces implementation challenges [17]. Inadequate solid waste management, projected to triple by 2050 according to global estimates, exacerbates the environmental crisis. Lack of infrastructure in vulnerable regions worsens this situation, as waste cannot be properly processed or disposed of, facilitating MPs’ release to the environment. Furthermore, the disintegration of “biodegradable” plastics releases non-degradable particles, further intensifying plastic contamination. This underscores the urgent need to innovate technologies for MPs removal and filtration. To address this issue, evidence-based policies guiding proper waste management and the development of more sustainable technologies are essential; otherwise, negative impacts will continue to escalate [4,17].

Considering all the above, there is a clear need to understand and analyze MPs’ presence in order to identify potential solutions to mitigate their negative effects. Critical research on advances in physicochemical characterization (primarily through techniques such as spectroscopy, microscopy, thermal analysis, and filtration methods) is therefore not only urgent but essential to connect scattered findings, i.e., from early photographic analyses of particles in the Atlantic [18] to current challenges like nanoplastics, to guide future research toward scalable and equitable solutions. In this regard, this review aims to address knowledge gaps by analyzing recent MPs research related to innovative physicochemical characterization methods and current removal technologies. For this purpose, a bibliometric analysis was conducted to identify the main research lines and commonly used methodological approaches in MPs studies, specifically regarding available technologies and methods for physicochemical characterization and filtration/removal. This type of review provides an overview of current scientific progress, detecting the most relevant trends and emerging areas. Based on this overview, the analysis explores the most used characterization techniques, such as spectroscopy, electron microscopy, and chemical methods, as well as applied removal and filtration procedures in different environments, including wastewater and soils. Despite the rapid growth of publications, the field remains fragmented, with limited integration between physicochemical characterization and removal technologies. A structured synthesis is therefore necessary to clarify research trends and methodological gaps.

Therefore, this study conducts a systematic review guided by the PRISMA 2020 framework, combined with a Methodi Ordinatio bibliometric ranking approach, to identify, classify, and analyze research trends in physicochemical characterization techniques and removal technologies for microplastics. The objective is to (i) determine the predominant analytical methods, (ii) evaluate current remediation strategies, and (iii) identify structural knowledge gaps limiting technological scalability and standardization.

2. Materials and Methods

The bibliometric analysis was conducted using a core dataset of 705 publications selected through a PRISMA-based screening process and subsequently ranked using the Methodi Ordinatio approach [19]. The discussion was further supported by additional literature to provide a broader context, particularly in emerging areas such as nanoplastics.

Articles were retrieved from Scopus and Web of Science (WoS), selected for their extensive coverage and multidisciplinary scope. Searches were performed using advanced queries with Boolean operators (AND, OR), targeting the two thematic axes of the study: physicochemical characterization methods and removal/filtration strategies. The search period covered 1972 to 2025, and the complete search strings are provided in

Table A1. Boolean Search Strategy for Topic 1: Physicochemical Characterization of Microplastics.

Data base	Search Query
Scopus	TITLE-ABS-KEY (“microplastics” OR “plastic pollution” OR “microplastic particles”) AND TITLE-ABS-KEY (“characterization” OR “properties” OR “analysis” OR “chemical” OR “physical”) AND TITLE-ABS-KEY (“experimental” OR “lab-based” OR “study”) AND TITLE-ABS-KEY (“aquatic” OR “marine” OR “freshwater”) AND (DOCTYPE (“re”) OR DOCTYPE (“review”)) AND (LIMIT-TO (OA, “all”))
Web of Science (WoS)	TS = (“microplastics” OR “plastic pollution” OR “microplastic particles”) AND TS = (“characterization” OR “properties” OR “analysis” OR “chemical” OR “physical”) AND TS = (“experimental” OR “lab-based” OR “study”) AND TS = (“aquatic” OR “marine” OR “freshwater”) AND (DT = (“Review”) OR DT = (“Article”))

and

Table A2. Boolean Search Strategy for Topic 2: Microplastic Removal Methods.

Data Base	Search Query
Scopus	TITLE-ABS-KEY (“microplastics” OR “plastic pollution” OR “microplastic particles”) AND TITLE-ABS-KEY (“filtration” OR “removal” OR “elimination” OR “treatment” OR “separation”) AND TITLE-ABS-KEY (“experimental” OR “lab-based” OR “study”) AND TITLE-ABS-KEY (“aquatic” OR “marine” OR “freshwater”) AND (DOCTYPE (“re”) OR DOCTYPE (“review”))
Web of Science (WoS)	TS = (“microplastics” OR “plastic pollution” OR “microplastic particles”) AND TS = (“filtration” OR “removal” OR “elimination” OR “treatment” OR “separation”) AND TS = (“experimental” OR “lab-based” OR “study”) AND TS = (“aquatic” OR “marine” OR “freshwater”) AND (DT = (“Review”) OR DT = (“Article”))

. Only peer-reviewed journal articles published in English were considered to ensure consistency in data extraction and analysis. While this criterion may introduce language bias, preliminary database screening in Scopus and Web of Science indicated that the vast majority of relevant studies on microplastics are published in English. Therefore, the exclusion of non-English articles is not expected to significantly affect the overall trends and conclusions of this review. Nevertheless, this limitation is acknowledged, particularly considering the global scope of microplastic pollution.

2.1. Study Selection

The selection process included initial screening of titles and abstracts to identify articles relevant to the study focus, followed by full-text reviews to confirm eligibility. Duplicates across databases were removed. Studies were selected based on predefined inclusion criteria aligned with the study objectives. Eligible studies were required to focus on (i) physicochemical characterization of microplastics (e.g., identification, quantification, or analytical methods) and/or (ii) removal, filtration, or treatment strategies targeting microplastics in aquatic environments. Studies were excluded if they were not peer-reviewed research articles and did not address the physicochemical analysis or treatment.

The overall selection and filtering process is summarized in Figure 1 (PRISMA 2020 flow diagram), generated using the official PRISMA 2020 tool [20], providing a transparent and reproducible visualization of the screening, eligibility, and inclusion stages.

2.2. Data Extraction and Analysis

For each selected article, metadata, methodological details, and reported outcomes were extracted. The Methodi Ordinatio procedure was applied to rank publications using the InOrdinatio index, which considers impact factor, number of citations, and publication year. This approach allowed the identification of predominant methods, emerging trends, and gaps in current research, supporting a structured synthesis of the literature in the field.

2.2.1. Methodi Ordinatio Overview

This bibliometric study focuses on the analysis of scientific literature related to physicochemical characterization and filtration/removal technologies for microplastics, which constitute the main variables of interest. Methodi Ordinatio was employed as a bibliometric prioritization approach to rank and systematize the selected literature based on scientific relevance, citation impact, and journal quality. Unlike traditional bibliometric techniques that primarily emphasize relational structures (e.g., co-citation, co-authorship, or keyword co-occurrence networks), this method enables a direct and quantitative ranking of individual publications by integrating multiple indicators into a single relevance score. This feature makes it particularly suitable for studies aiming to complement thematic mapping with an assessment of scientific influence within a defined corpus. Additionally, Methodi Ordinatio is particularly advantageous in studies covering extended temporal ranges, as it helps to balance the representation of publications across different periods. Traditional bibliometric approaches may be biased toward highly cited or older studies, as well as frequency-driven indicators that overrepresent established works. In contrast, Methodi Ordinatio incorporates citation impact together with journal quality and publication characteristics, enabling the identification of both foundational and more recent influential contributions. This contributes to a more balanced and updated perspective of research development over time.

In this context, Methodi Ordinatio was used to support the identification of the most relevant characterization techniques (e.g., spectroscopy, electron microscopy, and chemical-based methods) and removal technologies applied in different environmental matrices. Rather than focusing solely on the frequency of methods, this approach allows methodological choices to be interpreted in relation to research context and application objectives. It is important to highlight that methodological diversity is a characteristic feature of microplastic research, reflecting the complexity of sample matrices and the lack of standardized analytical protocols. This diversity reinforces the need for integrative approaches capable of combining thematic analysis with relevance-based prioritization of scientific contributions [21].

2.2.2. Methodology and Data Collection

This research used an adaptation of the Methodi Ordinatio method [22] to ensure a rigorous and hierarchical selection process. For the prioritization of the relevant studies, two parallel analyses were conducted, which will be explained in the following section. Data were collected from Scopus and Web of Science (WoS), key databases recognized for their academic rigor and multidisciplinary scope. The analysis not only identified predominant techniques (e.g., Raman spectroscopy for characterization and membranes for removal) but also highlighted scientific and technological advances in well-established areas. It further revealed missing technologies, such as high-sensitivity on-site detection systems or scalable remediation methods, the absence of which limits practical applications. This gap underscores the need to promote the development of innovative applied technologies capable of improving the accuracy, efficiency, and environmental relevance of scientific studies focused on MPs.

The flow diagram of the analysis presented in Figure 2, which is based on an adaptation of Methodi Ordinatio [22], reoriented towards a segmented search along two thematic axes: physicochemical techniques and filtration/removal methods.

It is important to note that Methodi Ordinatio consists of nine specific stages, designed to organize and hierarchically rank scientific literature in a systematic way. A description of each one of the stages is presented below.

Phase 1. Research intention: The purpose of gathering information for portfolio preparation is to obtain relevant documents on physicochemical characterization techniques and available filtration or removal methods. Since MPs, as well as their remediation strategies, are emerging topics, it is important to identify current trends and areas of knowledge that allow recognizing technological developments that will result in future research.

Phase 2. Preliminary Research: An initial search was conducted in the Web of Science (WoS) and Scopus databases as a starting point for the analysis, using a combination of Boolean operators and specific keywords (Table A1 and Table A2; in Appendix A). However, the initial results showed low thematic specificity for the objectives of this research. Among the topics of these articles, studies on theoretical chemistry, biomedical applications, and ecotoxicology predominated. This discrepancy revealed a significant gap relative to the original search strategy and the study object, leading to a redefinition of the selection criteria.

Phase 3. Keyword refinement: After identifying trends in Phase 2, an individual approach was adopted to select keywords, resulting in parallel searches (Figure 2, Phase 3). The Boolean operators and keywords used are detailed in Table A1. This strategy allowed prioritization of review articles and experimental studies.

Phase 4. Final database search: Once the variables were defined, the article search was carried out, identifying a total of 705 scientific articles across the two analyzed databases. The specific distribution of these documents, by platform and thematic area, is presented in Table A2. Subsequently, VOSviewer software was used to explore relationships among keywords.

Phase 5. Filtering process: A filtering process was implemented to select exclusively documents aligned with the study objectives (Figure 2). This process was structured according to the following criteria: (I) the initial raw set of articles identified in the databases; (II) elimination of duplicate articles, identified through metadata comparison (title, DOI, and authorship); and (III) exclusion of discarded articles, which are those that did not meet the defined parameters (

Table A3. Article Screening and Portfolio Consolidation by Database and Topic.

Search	WoS (Papers Found)	Scopus (Papers Found)
Physicochemical Characterization	177	234
Removal Methods	158	136
Total Articles (Grosso Portfolio)	705
Articles Considered (Final Portfolio)	89
Duplicated Articles	75
Discarded Articles	541

).

Phase 6. Identification of impact factor, publication year, and citation count: These parameters are fundamental for assessing the relevance and quality of the analyzed articles, allowing evaluation of both the impact of the work on the scientific community and the novelty of its contributions. Objective criteria are thus established, contributing to a more rigorous and reliable selection of literature.

Phase 7. InOrdinatio ranking calculation: The InOrdinatio equation is used to evaluate the relevance of a publication based on three factors: impact factor, publication year, and number of citations. The equation combines these elements to assign a value for each article, reflecting its scientific relevance according to the aforementioned parameters, and allowing publications to be ranked according to their importance in a research context. The InOrdinatio ranking is calculated using the following equation [18]:

$$\mathrm{InOrdinatio}=1000\mathrm{IF}\times \mathrm{\alpha }\left[10-\left(\mathrm{Research}\mathrm{Year}-\mathrm{Publiaction}\mathrm{Year}\right)\right]+\sum \mathrm{Ci}$$

(1)

where

IF = Impact factor (represents the quality of the publishing journal); Research Year: 2025; Publication Year: year of the article (publication year introduces a temporal component that prioritizes more recent contributions when similar levels of impact are observed); ∑Ci = total number of citations (citation counts reflect the scientific influence and recognition of each study); α = 9 (value assigned to prioritize studies with high scientific impact and temporal relevance);. The parameter α was set to 9 in accordance with the original methodological framework proposed by Pagani [22]. Specifically, the alpha (α) value plays a crucial role in capturing emerging thematic and technological advances in a dynamic field like MPs research. This parameter adjusts the weight of publication age, minimizing the influence of outdated studies while highlighting more recent research. By balancing quantitative metrics such as citations, a higher α value increases the sensitivity of the analysis toward scientific innovations, facilitating the identification of emerging and relevant research lines. This value is not arbitrary within the context of this study, as it follows the standard configuration originally defined for the method to ensure comparability and methodological consistency across applications. Rather than being tuned or optimized, α is part of the validated structure of the InOrdinatio index and is commonly used in bibliometric studies. In this context, from an initial search of 705 articles, the filtering process (which included duplicate removal and exclusion of non-relevant articles) reduced the final portfolio to a total of 89 selected publications. This approach ensures that the analysis aligns with the most current and relevant advances in the field, optimizing the quality of the selected studies.

Phase 8. Article retrieval: At this stage, the selected articles were obtained. As established at the beginning of the analysis, Open Access articles were prioritized, both for immediate availability and to ensure accessibility throughout the analysis phases. This dual approach optimized the document search results, ensuring that the articles met the stipulated search criteria.

Phase 9. Final reading and systematic analysis of documents.

3. Results

3.1. Review of the Physicochemical Characterization and Removal

Keyword Co-Occurrence and Thematic Mapping of Microplastic Technologies

As part of the bibliometric analysis, a keyword co-occurrence network was generated using VOSviewer Version 1.6.20 (Figure 3), where each term is represented as a node. Node size reflects the frequency of occurrence, node position indicates co-occurrence relationships between terms, and colors represent distinct thematic clusters identified by the software. This approach enables the visualization of the conceptual structure of the field and the identification of major thematic groupings and interconnections between research topics.

In Figure 3a, the co-occurrence network of characterization keywords reflects a research axis primarily oriented toward analytical determination, where the structure of the network, defined by node prominence (frequency), connectivity, and central positioning, highlights a strong emphasis on quantification, polymer identification, and measurement accuracy. This is supported by the clustering of terms related to spectroscopy, particle size analysis, and sampling, indicating that studies in this domain prioritize the development and application of precise analytical techniques. In contrast, Figure 3b, which represents filtration and/or removal method keywords, reveals a shift toward a process-oriented perspective, where the network structure, as reflected by node prominence and connectivity patterns, emphasizes treatment strategies, particle transport, and environmental fate. The relative prominence and interconnection of terms associated with removal processes indicate that this axis is less focused on analytical precision and more concerned with mitigation approaches and system-level interactions.

MPs research relies on a wide range of analytical methodologies and experimental approaches. For a better comprehension of the overall methodological landscape of this field, it is essential to identify and quantify the application of these different techniques. Figure 4 also presents a Sankey-type diagram synthesizing the methodological structure corresponding to the two main thematic axes in MPs research. This diagram serves as an indicator of scientific priorities, enabling quantitative visualization of the frequency with which certain techniques are used, and highlighting trends and areas of greatest interest within the field.

According to Figure 4, physicochemical characterization methods are highly concentrated in spectroscopic techniques, which account for 56.4% of the total (n = 35 out of 62). This proportion was determined by classifying each study according to its primary analytical technique, based on a systematic assessment of the title, abstract, and methodology sections, ensuring that each study was assigned to a single category and avoiding overlap. Within this group, FTIR emerges as the dominant method, indicating a clear methodological preference in the field. This predominance can be attributed to its robustness, widespread availability, and suitability for analyzing diverse environmental matrices, which have facilitated its consolidation as a standard technique in microplastic research. However, despite its advantages, FTIR presents limitations in detecting particles below 20 μm, which may introduce a methodological bias in microplastic assessments. Consequently, studies relying predominantly on FTIR may underestimate the abundance of smaller microplastics, potentially skewing size distribution profiles and global pollution estimates. In contrast, techniques such as Raman spectroscopy offer higher spatial resolution, enabling the detection of smaller particles, although often with increased analytical complexity. In contrast, removal technologies remain fragmented across a variety of approaches, primarily implemented in wastewater treatment plants (WWTPs), which serve as the main large-scale infrastructure for mitigating microplastic discharge. Common methods include chemical coagulation, flocculation, and sieving. More advanced systems, such as membrane filtration and biodigesters, have demonstrated high removal efficiencies; however, they face significant limitations. Membrane-based processes are highly susceptible to fouling, which reduces performance and increases maintenance costs, while biodigesters often require substantial infrastructure that may become underutilized or obsolete after their operational lifespan. These technical and operational constraints contribute to the lack of a universally applicable removal strategy. A trend toward gradual innovation is also observed: promising solutions such as electrocoagulation, magnetic extraction, and pyrolysis-GC/MS are emerging technologies in development and consolidation compared to established methods like TGA. Pyrolysis-GC/MS, although increasingly adopted, is considered here as a physicochemical characterization technique. Unlike TGA, which only measures mass loss, pyrolysis-GC/MS enables specific identification and quantification of polymers even in complex matrices. Figure 4 illustrates the frequency of certain techniques in the selected articles, based on the categories of physicochemical characterization and filtration/removal techniques. The prominence of FTIR spectroscopy in characterization reflects established analytical trends, while remediation techniques such as WWTPs’ adsorption and coagulation indicate a multifocal approach that has not yet been fully consolidated. Although removal technologies remain fragmented, the gap between emerging and consolidated solutions is narrowing in terms of performance and conceptual development, as observed in approaches such as advanced oxidation processes (AOPs) and magnetic extraction. This convergence highlights key opportunities to integrate innovative techniques into existing treatment frameworks [23]. However, a major limitation remains in large-scale applications: while some techniques can be easily implemented industrially, others still face scalability barriers. Addressing these challenges is essential to overcome fragmented approaches for an environmental problem that requires interdisciplinary responses.

Table 1. Dataset-Based Synthesis of Physicochemical Characterization and Removal Approaches in Microplastic Research.

Category		Specific Technique/Approach/Research Element	Description	References
Physicochemical Characterization	Spectroscopy	FTIR	Polymer identification	[24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45]
		Raman	Molecular analysis (polymers)	[27,30,31,34,38,41,42,43,46,47,48]
		Microscopy (SEM, TEM, Optical, SEM-EDS)	Detailed morphological information	[26,27,28,30,31,33,34,38,40,42,43,49,50,51,52,53]
		Micro-FTIR with FPA	Automation and high throughput	[32]
		Pyrolysis + Mass Spectrometry	Rapid detection <1 µm	[54]
		Standardized databases	Polymer identification	[55]
		Nanoplastics as toxic vectors	Contaminant transport	[56]
Removal/Filtration	Conventional remotional	Filtration	High efficiency >1 mm	[43]
		Chemical coagulation	High efficiency for PS and PE	[57]
		Electrocoagulation–electroflotation	Efficiency >50 µm	[58]
		Magnetic separation	Efficiency 10–100 µm	[59]
	Advanced remotion	Advanced oxidation processes	Degradation of polyester microfibers	[60]
		Adsorption	Retention based on surface properties	[31]
		Magnetic extraction	Ferromagnetic/functionalized particles	[61]
	Other Key Approaches	Biodegradation	Promising in aquaculture and marine settings	[23]

Table 1. Dataset-Based Synthesis of Physicochemical Characterization and Removal Approaches in Microplastic Research.

Category		Specific Technique/Approach/Research Element	Description	References
Physicochemical Characterization	Spectroscopy	FTIR	Polymer identification	[24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45]
		Raman	Molecular analysis (polymers)	[27,30,31,34,38,41,42,43,46,47,48]
		Microscopy (SEM, TEM, Optical, SEM-EDS)	Detailed morphological information	[26,27,28,30,31,33,34,38,40,42,43,49,50,51,52,53]
		Micro-FTIR with FPA	Automation and high throughput	[32]
		Pyrolysis + Mass Spectrometry	Rapid detection <1 µm	[54]
		Standardized databases	Polymer identification	[55]
		Nanoplastics as toxic vectors	Contaminant transport	[56]
Removal/Filtration	Conventional remotional	Filtration	High efficiency >1 mm	[43]
		Chemical coagulation	High efficiency for PS and PE	[57]
		Electrocoagulation–electroflotation	Efficiency >50 µm	[58]
		Magnetic separation	Efficiency 10–100 µm	[59]
	Advanced remotion	Advanced oxidation processes	Degradation of polyester microfibers	[60]
		Adsorption	Retention based on surface properties	[31]
		Magnetic extraction	Ferromagnetic/functionalized particles	[61]
	Other Key Approaches	Biodegradation	Promising in aquaculture and marine settings	[23]

Table 1 summarizes the most frequently reported physicochemical characterization techniques, removal methods and related research element identified across the selected literature included in this bibliometric analysis. The classification reflects the frequency of occurrence of techniques as reported in each study, based on their presence in the title, abstract, and methodological sections of the analyzed articles. The results show a high prevalence of spectroscopic techniques, particularly FTIR and Raman spectroscopy [31,43], which are consistently reported across the dataset. This frequency reflects their consolidated use in microplastic research for polymer identification and structural analysis in different environmental matrices. Regarding removal technologies, membrane filtration and sieving methods are commonly reported for the separation of larger particles (>1 mm), although their efficiency decreases for smaller size fractions. Chemical coagulation and electrocoagulation-electroflotation are also frequently reported, particularly for wastewater treatment applications, while magnetic separation and magnetic extraction are mainly associated with functionalized or metal-coated microplastics [58,59,62,63]. These methodological categories are derived directly from the analyzed dataset and provide a structured overview of the analytical and remediation approaches reported in the selected studies. Rather than representing a comprehensive review of all possible techniques, the classification reflects their relative frequency within the corpus, allowing the identification of dominant and emerging methodological approaches. Overall, the distribution of techniques indicates a field characterized by methodological diversification, ranging from conventional approaches such as filtration and chemical coagulation to emerging technologies including electroflotation, advanced oxidation processes, magnetic extraction, and biodegradation. This distribution suggests that methodological selection is influenced by multiple factors, including particle size, matrix complexity, operational cost, and technological maturity.

3.2. Visual Analysis of Scientific Production: Main Trend and Journals

To explore the evolution, distribution, and relationships among the most important scientific journals publishing on MPs, complementary visualizations were used. These approaches provide insights into how scientific productivity has evolved over time.

Trends in Impact Factors and Citations

Another approach for exploring evolution, distribution, and relationships among the main scientific journals publishing on MPs involves the use of visualizations and network diagrams. These tools provide insights into how scientific productivity and impact have evolved over time, Figure 5 presents two complementary bibliometric indicators describing journal impact factors and citations in the analyzed distributions.

Figure 5a shows the temporal distribution of impact factors for the journals included in the dataset. Each point represents a journal-year observation. The variability observed reflects differences in journal scope and specialization rather than changes in the intrinsic quality or relevance of the research field. Overall, the distribution indicates that microplastic-related studies are published across journals with heterogeneous impact levels. This visualization allows observing how journals are distributed based on their impact factor, reflecting the relative quality of their publications. Furthermore, over time, an increase in impact factors is observed, along with a greater dispersion of these values, indicating growing attention from both researchers and journals, which reflects the increasing thematic relevance and international visibility of the field. On the other hand, Figure 5b summarizes the annual citation counts of the included publications. Differences in citation volume across years reflect the influence of individual studies and the temporal accumulation of citations. Citation peaks may correspond to highly cited publications or periods of increased research activity in specific subtopics. While older articles are expected to accumulate more citations due to longer exposure, temporal differences reveal peaks of scientific attention. These peaks can be associated with the publication of key studies or the emergence of new research lines in the field.

Overall, these visualizations provide a comprehensive perspective on the evolution of impact and scientific relevance of the reviewed publications. While the scatter plot offers a detailed view of the editorial quality achieved by the studies, the bar chart synthesizes their reception within the scientific community. This analysis allows exploration not only of how knowledge has been disseminated in terms of citations, but also the extent to which MPs research has been positioned in high-visibility scientific venues.

In Figure 6a, the proportion of articles published by each of the most relevant journals is shown, together with a category labeled “Others”. This category groups journals that contribute a limited number of publications within the dataset. Its purpose is to improve visualization clarity and reduce excessive fragmentation of low-frequency entries, which may hinder a clear presentation of the data. No information is excluded from the analysis, as all journals included in the “Others” category are reported in the Supplementary Information. The resulting representation allows identification of the main publication outlets while maintaining a global view of the remaining contributions.

Figure 6b presents a chord diagram (circos-type) illustrating correlations in annual productivity among the eight journals with the most statistically significant correlations. Values were derived from the number of articles published by each journal per year over the period of interest (

Table A4. Ranked Final Article Portfolio According to the Methodi Ordinatio (α = 9).

Number	Authors	Title	Source Title	IF	Cited by	Year	Alfa	InOrdinatio α = 9
1	Li, J., et al.	Microplastics in freshwater systems: a review on occurrence, environmental effects, and methods for microplastics detection	Water research	13.4	1540	2018	9	1490.4
2	Sun, J., et al.	Microplastics in wastewater treatment plants: detection, occurrence and removal	Water research	13.4	1357	2019	9	1316.4
3	Lusher, A.L., et al.	Sampling, isolating and identifying microplastics ingested by fish and invertebrates	Analytical methods	3.399	763	2017	9	694.4
4	Prata, J.C., et al.	Methods for sampling and detection of microplastics in water and sediment: a critical review	Trac-trends in analytical chemistry	9.027	681	2019	9	636.03
5	Talvitie, J., et al.	Solutions to microplastic pollution—removal of microplastics from wastewater effluent with advanced wastewater treatment technologies	Water research	13.4	638	2017	9	579.4
6	Mason, S.A., et al.	Microplastic pollution is widely detected in us municipal wastewater treatment plant effluent	Environmental pollution	9.9	630	2016	9	558.9
7	Löder, et al.	Focal plane array detector-based micro-fourier-transform infrared imaging for the analysis of microplastics in environmental samples	Environmental chemistry	4.966	410	2015	9	324.97
8	Ragus, et al.	Raman microspectroscopy detection and characterization of microplastics in human breastmilk	Polymers	4.967	340	2022	9	317.97
9	Primpke, et al.	Reference database design for the automated analysis of microplastic samples based on fourier transform infrared (ftir) spectroscopy	Analytical and bioanalytical chemistry	4.142	338	2018	9	279.14
10	Stock, F., et al.	Sampling techniques and preparation methods for microplastic analyses in the aquatic environment—a review	Trac-trends in analytical chemistry	12.296	311	2019	9	269.3
11	Iyare, P.U., et al.	Microplastics removal in wastewater treatment plants: a critical review	Environmental science: water research and technology	7.345	290	2020	9	252.35
12	Primpke, et al.	An automated approach for microplastics analysis using focal plane array (fpa) ftir microscopy and image analysis	Analytical methods	3.399	320	2017	9	251.4
13	Mai, L., et al.	A review of methods for measuring microplastics in aquatic environments	Environmental science and pollution research	5.19	282	2018	9	224.19
14	Dey, T., et al.	Detection and removal of microplastics in wastewater: evolution and impact	Environmental science and pollution research	5.19	174	2021	9	143.19
15	Liu, Y., et al.	Microplastics are a hotspot for antibiotic resistance genes: progress and perspective	Science of the total environment	10.753	168	2021	9	142.75
16	Thomas, D., et al.	Sample preparation techniques for the analysis of microplastics in soil—a review	Sustainability (switzerland)	3.9	142	2020	9	100.9
17	Lee, J., et al.	A systematic protocol of microplastics analysis from their identification to quantification in water environment: a comprehensive review	Journal of hazardous materials	14.224	118	2021	9	96.224
18	Razeghi, N., et al.	Microplastic sampling techniques in freshwaters and sediments: a review	Environmental chemistry letters	9	122	2021	9	95
19	Cutroneo, L., et al.	Microplastics in seawater: sampling strategies, laboratory methodologies, and identification techniques applied to port environment	Environmental science and pollution research	5.2	125	2020	9	85.2
20	Schymanski, et al.	Analysis of microplastics in drinking water and other clean water samples with micro-raman and micro-infrared spectroscopy: minimum requirements and best practice guidelines	Analytical and bioanalytical chemistry	4.142	116	2021	9	84.142
21	Zhao, K., et al.	Separation and characterization of microplastic and nanoplastic particles in marine environment	Environmental pollution	9.988	98	2022	9	80.988
22	Hou, L., et al.	Conversion and removal strategies for microplastics in wastewater treatment plants and landfills	Chemical engineering journal	16.7	95	2021	9	75.7
23	Pan, Y., et al.	Removing microplastics from aquatic environments: a critical review	Environmental science and ecotechnology	11.4	71	2023	9	64.4
24	Xu, X., et al.	Microplastics in the wastewater treatment plants (wwtps): occurrence and removal	Chemosphere	8.9	106	2019	9	60.9
25	Zhou, G., et al.	Removal of polystyrene and polyethylene microplastics using pac and fecl3 coagulation: performance and mechanism	Science of the total environment	10.8	86	2021	9	60.8
26	Ahmed, A.A.S. et al.	Microplastics in aquatic environments: a comprehensive review of toxicity, removal, and remediation strategies	Science of the total environment	10.753	65	2023	9	57.753
27	Sun, C., et al.	Fabrication of robust and compressive chitin and graphene oxide sponges for removal of microplastics with different functional groups	Chemical engineering journal	16.7	85	2020	9	56.7
28	Zhang, Y., et al.	Removal efficiency of micro- and nanoplastics (180 nm–125 μm) during drinking water treatment	Science of the total environment	10.8	90	2020	9	55.8
29	Skaf, D.W., et al.	Removal of micron-sized microplastic particles from simulated drinking water via alum coagulation	Chemical engineering journal	16.7	83	2020	9	54.7
30	Campanale, et al.	Fourier transform infrared spectroscopy to assess the degree of alteration of artificially aged and environmentally weathered microplastics	Polymers	4.967	65	2023	9	51.967
31	Golgoli, M., et al.	Microplastics fouling and interaction with polymeric membranes: a review	Chemosphere	8.943	79	2021	9	51.943
32	Dos Santos, et al.	Insights into the removal of microplastics and microfibres by advanced oxidation processes	Science of the total environment	10.8	54	2023	9	46.8
33	Shi, et al.	(Nano)microplastics promote the propagation of antibiotic resistance genes in landfill leachate	Environmental science-nano	7.683	82	2020	9	44.683
34	Cristaldi, A., et al.	Efficiency of wastewater treatment plants (wwtps) for microplastic removal: a systematic review	International journal of environmental research and public health	4.614	83	2020	9	42.614
35	Tursi, A., et al.	Microplastics in aquatic systems, a comprehensive review: origination, accumulation, impact, and removal technologies	Rsc advances	4	63	2022	9	40
36	Shi, C., et al.	Experimental study on removal of microplastics from aqueous solution by magnetic force effecton the magnetic sepiolite	Separation and purification technology	7.312	55	2022	9	35.312
37	Pandey, B., et al.	Microplastics in the ecosystem: an overview on detection, removal, toxicity assessment, and control release	Water (switzerland)	3.4	46	2023	9	31.4
38	Razeghi, N., et al.	Sample preparation methods for the analysis of microplastics in freshwater ecosystems: a review	Environmental chemistry letters	13.615	41	2022	9	27.615
39	Zhang, et al.	Rapid monitoring approach for microplastics using portable pyrolysis-mass spectrometry	Analytical chemistry	9.558	62	2020	9	26.558
40	Kalčíková, G., et al.	Beyond ingestion: adhesion of microplastics to aquatic organisms	Aquatic toxicology	5.2	36	2023	9	23.2
41	Cunsolo, et al.	Optimising sample preparation for ftir-based microplastic analysis in wastewater and sludge samples: multiple digestions	Analytical and bioanalytical chemistry	4.144	49	2021	9	17.144
42	Peng, et al.	Development and application of a mass spectrometry method for quantifying nylon microplastics in environment	Analytical chemistry	9.558	51	2020	9	15.558
43	Fernández-gonzález, et al.	Misidentification of pvc microplastics in marine environmental samples	Trac-trends in analytical chemistry	12.296	30	2022	9	15.296
44	Rani, et al.	A complete guide to extraction methods of microplastics from complex environmental matrices	Molecules	4.927	28	2023	9	14.927
45	Wiesheu, et al.	Raman microspectroscopic analysis of fibers in beverages	Analytical methods	3.4	91	2016	9	13.4
46	Birch, et al.	Isotope ratio mass spectrometry and spectroscopic techniques for microplastics characterization	Talanta	6.557	41	2021	9	11.557
47	Peydayesh, M., et al.	Sustainable removal of microplastics and natural organic matter from water by coagulation-flocculation with protein amyloid fibrils	Environmental science and technology	11.4	36	2021	9	11.4
48	Mustapha, et al.	Technological approaches for removal of microplastics and nanoplastics in the environment	Journal of environmental chemical engineering	7.968	11	2024	9	9.968
49	Carnevale Miino, M., et al.	Microplastics removal in wastewater treatment plants: a review of the different approaches to limit their release in the environment	Science of the total environment	10.8	7	2024	9	8.8
50	Woo, et al.	Methods of analyzing microsized plastics in the environment	Applied sciences-basel	2.838	41	2021	9	7.838
51	Leone, G., et al.	A comprehensive assessment of plastic remediation technologies	Environment international	13.352	12	2023	9	7.352
52	Withana, P.A., et al.	Soil microplastic analysis: a harmonized methodology	Critical reviews in environmental science and technology	12.561	3	2024	9	6.561
53	Shrivastava, A., et al.	Removal of micro- and nano-plastics from aqueous matrices using modified biochar—a review of synthesis, applications, interaction, and regeneration	Journal of hazardous materials advances	14.22	1	2024	9	6.22
54	Caldwell, et al.	Submicron- and nanoplastic detection at low micro- to nanogram concentrations using gold nanostar-based surface-enhanced raman scattering (sers) substrates	Environmental science-nano	9.473	4	2024	9	4.473
55	Moses, et al.	Comparison of two rapid automated analysis tools for large ftir microplastic datasets	Analytical and bioanalytical chemistry	4.142	18	2023	9	4.142
56	Kara, et al.	Characterization and removal of microplastics in landfill leachate treatment plants in istanbul, turkey	Analytical letters	2.012	20	2023	9	4.012
57	Meng, X., et al.	A review of sources, hazards, and removal methods of microplastics in the environment	Water (switzerland)	3.4	0	2025	9	3.4
58	Romphophak, et al.	Removal of microplastics and nanoplastics in water treatment processes: a systematic literature review	Journal of water process engineering	7.34	4	2024	9	2.34
59	Raymond, et al.	Sub-100 nm nanoplastics: potent carriers of tributyltin in marine water	Environmental science-nano	9.473	1	2024	9	1.473
60	Gao, et al.	Labeling microplastics with fluorescent dyes for detection, recovery, and degradation experiments	Molecules	4.927	22	2022	9	−0.073
61	Wang, et al.	Sustainable removal of nano/microplastics in water by solar energy	Chemical engineering journal	16.7	10	2022	9	−0.3
62	Yang, J., et al.	Microplastics in different water samples (seawater, freshwater, and wastewater): removal efficiency of membrane treatment processes	Water research	13.4	3	2023	9	−1.6
63	Dalmau-soler, et al.	Routine method for the analysis of microplastics in natural and drinking water by pyrolysis coupled to gas chromatography-mass spectrometry	Journal of chromatography a	4.759	1	2024	9	−3.241
64	Garfansa, et al.	Research and trends of filtration for removing microplastics in freshwater environments	Environmental quality management	1.5	4	2024	9	−3.5
65	Zhang, et al.	Removal of nanoplastics from copollutant systems using seaweed cellulose nanofibers	Journal of agricultural and food chemistry	5.279	0	2024	9	−3.721
66	Vicente-martínez, et al.	Development of a fast and efficient strategy based on nanomagnetic materials to remove polystyrene spheres from the aquatic environment	Molecules	4.927	0	2024	9	−4.073
67	Miserli, K., et al.	Screening of microplastics in aquaculture systems (fish, mussel, and water samples) by ftir, scanning electron microscopy-energy dispersive spectroscopy and micro-raman spectroscopies	Applied sciences-basel	2.838	10	2023	9	−5.162
68	Bodzek, et al.	Microplastics in wastewater treatment plants: characteristics, occurrence and removal technologies	Water (switzerland)	3.53	0	2024	9	−5.47
69	Ramadani, et al.	The study of removal of polyvinyl chloride (pvc) particles from wastewater through electrocoagulation	Indonesian journal of chemistry	3.3	0	2024	9	−5.7
70	Yang, et al.	Removal technologies of microplastics in soil and water environments: review on sources, ecotoxicity, and removal technologies	Applied biological chemistry	3.27	0	2024	9	−5.73
71	Cerasa, et al.	Searching nanoplastics: from sampling to sample processing	Polymers	4.967	25	2021	9	−6.033
72	Di fiore, et al.	First approach for defining an analytical protocol for the determination of microplastics in cheese using pyrolysis-gas chromatography-mass spectrometry	Applied sciences-basel	2.838	0	2024	9	−6.162
73	Lee, J., et al.	Complementary analysis for undetectable microplastics from contact lenses to aquatic environments via fourier transform infrared spectroscopy	Molecules	4.927	6	2023	9	−7.073
74	Li, et al.	A novel high-throughput analytical method to quantify microplastics in water by flow cytometry	Green analytical chemistry	3	7	2023	9	−8
75	Liu, et al.	Visual detection of microplastics using raman spectroscopic imaging	Analyst	5.227	4	2023	9	−8.773
76	Mukotaka, et al.	Rapid analytical method for characterization and quantification of microplastics in tap water using a fourier-transform infrared microscope	Science of the total environment	10.8	16	2021	9	−9.2
77	Easton, T., et al.	Removal of polyester fibre microplastics from wastewater using a uv/h2o2oxidation process	Journal of environmental chemical engineering	7	1	2023	9	−10
78	Xu, J., et al.	Recent study of separation and identification of micro- and nanoplastics for aquatic products	Polymers	4.3	1	2023	9	−12.7
79	Budhiraja, et al.	Magnetic extraction of weathered tire wear particles and polyethylene microplastics	Polymers	4.967	9	2022	9	−13.03
80	Banica, et al.	Assessment of microplastics in personal care products by microscopic methods and vibrational spectroscopy	Scientific study and research-chemistry and chemical engineering biotechnology food industry	0	4	2023	9	−14
81	Escalona-segura, et al.	A methodology for the sampling and identification of microplastics in bird nests	Green analytical chemistry	3	8	2022	9	−16
82	Silva, et al.	Optimization of an analytical protocol for the extraction of microplastics from seafood samples with different levels of fat	Molecules	4.927	6	2022	9	−16.07
83	Akarsu, C., et al.	Removal of microplastics from wastewater through electrocoagulation-electroflotation and membrane filtration processes	Water science and technology	2.5	17	2021	9	−16.5
84	Choi, et al.	Characterization of microplastics released based on polyester fabric construction during washing and drying	Polymers	4.967	14	2021	9	−17.03
85	Nkosi, et al.	Microplastics and heavy metals removal from fresh water and wastewater systems using a membrane	Separations	3.5	5	2022	9	−18.5
86	Saboor, et al.	Microplastics in aquatic environments: recent advances in separation techniques	Periodica polytechnica chemical engineering	2	4	2022	9	−21
84	Conesa, et al.	Reuse of water contaminated by microplastics, the effectiveness of filtration processes: a review	Energies	3.2	2	2022	9	−21.8
88	Pervez, et al.	Stereomicroscopic and fourier transform infrared (ftir) spectroscopic characterization of the abundance, distribution and composition of microplastics in the beaches of qingdao, china	Analytical letters	2.012	16	2020	9	−26.99
89	Gunes-durak, et al.	Investigation of microplastics removal methods from aquatic environments	Heritage and sustainable development	0	3	2021	9	−33

), constructed based on the temporal similarity of productivity (IF, citations, year). This diagram highlights common patterns and significant relationships between journals. The connections represent degrees of similarity in publication trends over time, enabling the identification of shared trends, emerging areas, and potential synergies within the field.

This focused analysis of the main journals provides a comprehensive view of editorial and scientific dynamics, offering insights into the evolution and structure of scientific production in the field of MP´s.

The editorial dispersion in MPs research is clearly reflected in the bibliometric results: the 52 articles grouped under the “Others” category (60.2% of the total analyzed) are distributed across 38 different journals, each one with no more than two publications. This fragmentation reflects the multidisciplinary nature of the field, where studies on the topic appear in journals specialized in 26 diverse areas, ranging from aquatic toxicology to polymer science. Notably, 73% of these journals are either recently established or have a specific thematic focus, highlighting how the MPs issue transcends traditional disciplinary boundaries.

When comparing productivity and editorial impact, as shown in

Table 2. Journals with highest productivity, number of published articles, and impact factor.

Journal	Total Articles	Impact Factor
Science of the total environment	7	8.8
Polymers	7	4.9
Analytical and bioanalytical chemistry	6	3.8
Environmental science and pollution research	5	5.8
Water research	4	11.4
Chemical Engineering Journal	4	13.3
Molecules	4	4.6
Others	52	-

, a notable contrast emerges. The journals Polymers and Molecules published seven articles each, while Chemical Engineering Journal accounted for a total of four publications. This indicates that productivity does not directly correlate to impact factor but rather depends on thematic specialization and editorial accessibility. Chemical Engineering Journal stands out for articles focused on advanced removal technologies, consolidating it as a strategic platform for disseminating research in this area. In contrast, Analytical and Bioanalytical Chemistry maintains a consistent focus on detection methodologies, with 83% of its contributions dedicated to characterization techniques.

These editorial patterns reveal differentiated opportunities: studies on physicochemical characterization are effectively disseminated in more accessible journals, such as Polymers, whereas innovative developments in scalable remediation achieve greater visibility in high-impact journals, such as Water Research or Chemical Engineering Journal. Understanding these trends allows for strategic guidance in publishing results and fosters scientific collaborations aligned with global priorities in MPs mitigation.

The analysis of temporal correlations (Figure 7) quantifies the synchrony in the publication of articles on MPs in the leading journals. Pearson correlation coefficients between the most productive journals in the dataset, based on annual publication counts per journal. Each journal is represented by a discrete time series corresponding to the number of articles published per year over the study period (Table A4). For each pair of journals, Pearson’s correlation coefficient (r) was computed using aligned yearly vectors. The sample size (n) for each correlation corresponds to the number of overlapping years in which both journals reported non-zero publication counts within the dataset. Due to differences in journal activity across time, n varies slightly between pairs. No statistical inference tests (e.g., p-values) were applied, as the objective of this analysis is exploratory and focused on describing temporal co-variation patterns rather than establishing statistically significant dependencies.

Although this analysis is based solely on publication synchrony, it allows for the identification of structural patterns of integration and thematic fragmentation, revealing which journals act as strategic nodes and which remain isolated. For example, Environmental Science and Pollution Research emerges as an interdisciplinary platform, with significant correlations both with analytical and engineering domains, positioning it as an ideal journal for emerging areas such as nanoplastic toxicology, where coordination between characterization and remediation is crucial. For the scientific community, these findings allow for the identification of strategic publication opportunities and optimization of technological transfer by selecting journals with high editorial synchrony. For R&D managers, the analysis based on Figure 6 acts as a diagnostic tool, highlighting critical areas for interdisciplinary funding and strengthening research planning where methodology integration is required. These correlations reflect structural and editorial visibility trends, but do not imply direct causality on the published experimental results.

These results provide an analytical foundation that connects identified editorial trends with strategic research planning. The following section explores in detail the implications of these trends, focusing on their potential to guide decisions on publication, funding, and methodological coordination.

4. Discussion

4.1. Trends and Findings in Physicochemical Characterization Methods for MPs

The detailed identification of MPs in different environmental matrices is essential to understand their distribution, composition, and potential impacts. As shown in Table 3, various physicochemical techniques have been developed and optimized to facilitate the analysis of their chemical, morphological, and thermal properties, which is key for determining both polymer type and particle size. Among the most used methodologies are Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermal analyses, such as thermogravimetric analysis (TGA). In recent years, emerging and automated techniques have appeared, such as pyrolysis coupled with gas chromatography (Py-GC/MS), which incorporate artificial intelligence tools to streamline and enhance processes, proving particularly useful for detecting MPs as particle size decreases.

To complement this information, the table provides a comparative summary of these techniques, highlighting their principles, applications, advantages, and limitations, along with representative examples from recent experimental studies.

4.1.1. Degradation, Aging, and Sources of MPs

Research on MPs has significantly advanced the understanding of their degradation processes and main sources of environmental release [26,42,50]. Recently, the complexity of these processes has been demonstrated in both marine and terrestrial environments. Abaroa-Pérez et al. [64] analyzed marine degradation, revealing how MPs’ color may influence their capacity to adsorb contaminants. Meanwhile, C. De Monte et al. [65] quantified in situ fragmentation rates under real environmental conditions, providing key data to evaluate persistence. These findings are complemented by Rios Mendoza et al. [66], who identified the presence of toxic chemicals associated with degraded MPs, highlighting their potential ecological impacts. Regarding sources of release, several studies have quantified significant contributions. S. Choi et al. [67] evaluated the discharge of textile microfibers during laundry, observing variations depending on fiber type. Goehler et al. [68] determined that tires are a significant source of MPs in urban environments. Similarly, J. Cho et al. [69] characterized the presence of these contaminants in sewage sludge, highlighting their role as vectors for dispersal into soils and waters. Collectively, these studies emphasize the need to address both degradation mechanisms and major sources of MPs to develop effective mitigation strategies.

4.1.2. Methodological Advances in Consolidation

The scientific community has developed significant innovations in MPs research, including improved sampling devices through Computational Fluid Dynamics (CFD) analyses [70,71,72,73], specific protocols for analyzing complex samples such as dairy products [3,74], and advanced combined methods such as TG-FTIR-GC-MS [25,75,76,77]. Despite these advances, critical challenges remain that require attention. The standardization of protocols remains a necessity [29,38,78,79,80], as well as improvements in the detection of nanoplastics [81] and accurate characterization in complex matrices [47,82]. Recent studies identifying MPs in human tissues highlight the need to refine analytical techniques to assess the impact of these particles. The integration of multiple analytical techniques, as proposed by multiple studies [36,83,84,85], represents the most promising approach for achieving comprehensive physicochemical characterization of MPs in aquatic systems.

4.1.3. Comprehensive Analysis of MPs in Environmental Matrices

Accurate characterization of MPs in environmental matrices is key to understanding their distribution, composition, and potential impacts [38,86,87,88]. As shown in Table 3, various physicochemical techniques have been optimized to identify and analyze their chemical, morphological, and thermal properties, which are essential for determining both polymer type and particle size. In this context, the most commonly employed techniques include Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermal analysis methods such as thermogravimetric analysis (TGA) [35,37,49,89]. In recent years, emerging and automated approaches, such as pyrolysis coupled to gas chromatography and mass spectrometry (Py-GC/MS), have incorporated artificial intelligence tools to accelerate processes and improve accuracy, especially for detecting nanosized particles [90,91,92].

Table 3. Comparative Overview of Microplastic Characterization Techniques.

Technique	Description	Applications	Advantages	Limitations	References
FTIR	Technique to identify polymers through infrared absorption of functional groups	Chemical identification in particles ≥20 µm in water, sediments, and biota	Non-destructive; qualitative and quantitative analysis; widely available	Limited resolution for particles <20 µm; interference from organic matter	[34,36]
SEM	High-resolution imaging to analyze morphology and texture; can be combined with EDS for elemental composition	Morphological analysis, size, texture, and elemental composition	High resolution; analysis of submicron particles; combination with EDS	Requires conductive coating; qualitative analysis; time-consuming	[34,93]
Raman	Technique based on inelastic light scattering to identify characteristic molecular vibrations	Chemical identification of small particles and in aqueous matrices	High spatial resolution; minimal sample preparation; water-compatible	Fluorescence interference; high cost; specialized equipment required	[34,47]
Thermal Analysis (TGA, DSC, Py-GC/MS)	Methods assessing thermal stability, composition, and polymer degradation through mass changes and decomposition products	Quantification and thermal/chemical characterization in complex matrices	High specificity; applicable in challenging matrices	Destructive process; expensive equipment; strict sample preparation	[80,94]
Emerging and Automated Techniques	Methods combining microscopy, spectroscopy, and artificial intelligence to accelerate and improve analysis	Rapid, automated analysis of large datasets; nanoplastics detection	High speed; reduced bias; sensitive detection	High cost; need for specialized training; under development	[95,96]

Table 3. Comparative Overview of Microplastic Characterization Techniques.

Technique	Description	Applications	Advantages	Limitations	References
FTIR	Technique to identify polymers through infrared absorption of functional groups	Chemical identification in particles ≥20 µm in water, sediments, and biota	Non-destructive; qualitative and quantitative analysis; widely available	Limited resolution for particles <20 µm; interference from organic matter	[34,36]
SEM	High-resolution imaging to analyze morphology and texture; can be combined with EDS for elemental composition	Morphological analysis, size, texture, and elemental composition	High resolution; analysis of submicron particles; combination with EDS	Requires conductive coating; qualitative analysis; time-consuming	[34,93]
Raman	Technique based on inelastic light scattering to identify characteristic molecular vibrations	Chemical identification of small particles and in aqueous matrices	High spatial resolution; minimal sample preparation; water-compatible	Fluorescence interference; high cost; specialized equipment required	[34,47]
Thermal Analysis (TGA, DSC, Py-GC/MS)	Methods assessing thermal stability, composition, and polymer degradation through mass changes and decomposition products	Quantification and thermal/chemical characterization in complex matrices	High specificity; applicable in challenging matrices	Destructive process; expensive equipment; strict sample preparation	[80,94]
Emerging and Automated Techniques	Methods combining microscopy, spectroscopy, and artificial intelligence to accelerate and improve analysis	Rapid, automated analysis of large datasets; nanoplastics detection	High speed; reduced bias; sensitive detection	High cost; need for specialized training; under development	[95,96]

4.2. Spectroscopic and Thermal Characterization Techniques

Spectroscopic techniques have experienced notable improvements in recent years. Raman spectroscopy, highlighted by Anger et al. [97] for its capability to identify particles down to 1 µm has been complemented with innovations such as pretreatment protocols to improve analytical outcomes. Comparative studies reveal that methodological choices significantly affect quantitative results when analyzing environmental samples with different approaches [46]. Raman spectroscopy has proven to be an indispensable tool for the chemical identification of MPs, particularly in complex environmental studies. Its ability to analyze particles as small as 1 µm, as well as its effectiveness in marine sample analysis, provides valuable insights into polymer degradation [97,98]. Recent studies have optimized this technique through the development of standardized protocols and the implementation of alcohol-based pretreatments to reduce interferences [41,99]. Infrared spectroscopy has also evolved significantly, with notable advances in detecting particles below 20 µm when compared to techniques such as FTIR-ATR and Raman. FTIR provides faster analytical throughput, albeit with lower detail [100]. Moreover, the integration of μFTIR with machine learning algorithms has enabled the automated identification of polymers in complex environmental samples [96]. Additionally, thermal analyses have emerged as a quantitative alternative for MPs characterization. Robust protocols have been established for one or more specific polymers, such as polyethylene and polypropylene, using TGA-DSC [101]. For complex organic matrices, the TGA-MS variant has been applied [102]. These methods offer significant advantages in absolute quantification, although they are limited in assessing morphological characteristics [103].

4.2.1. Raman Spectroscopy

Raman spectroscopy enables chemical identification of MPs through the inelastic scattering of laser light, which excites polymer-specific molecular vibrations [34,41,47]. This methodology is particularly valued for its high spatial resolution and its ability to analyze micrometer and submicrometer-sized particles, even in aqueous matrices, without requiring extensive sample preparation [46,104].

Several studies [73,105,106] agree that Raman offers significant advantages over conventional techniques such as FTIR, including greater sensitivity for detecting smaller particles and the ability to differentiate similar polymers based on their distinctive vibrational spectra. However, limitations such as fluorescence interference, especially in complex environmental matrices, and the high cost of equipment are recognized [98,107].

Experimental studies have advanced the optimization of Raman for environmental impact assessment to detect MPs in human breast milk [47], demonstrating its sensitivity for quantifying particles approaching the nanoscale [34] combined Raman with SEM-EDS for detailed morphological and chemical analysis in aquatic systems, while [107] developed protocols to minimize fluorescent interference through specific pretreatments and optimized experimental setups. Additionally, Raman spectroscopy coupled with spectral imaging has facilitated automation and processing of large datasets, as reported by Qing [96] and Hufnagl [39], who integrated artificial intelligence algorithms to classify and quantify particles with high precision, representing a crucial advancement for large-scale studies. Innovative applications also include fluorescent labeling of MPs to facilitate detection and tracking in environmental experiments [108], and using Raman to differentiate MPs released from textiles during domestic processes [49]. Raman spectroscopy is positioned as a fundamental technique in modern MP characterization, particularly for small particles and complex environments, remaining an active area of research and development.

4.2.2. FTIR

Fourier-transform infrared spectroscopy (FTIR) is widely used for the chemical identification of MPs due to its ability to detect polymer-specific functional groups through infrared absorption [34,36,55]. This technique enables qualitative and quantitative analysis of particles typically larger than 20 µm in diverse environmental matrices such as water, sediments, and biota [24,50]. Review studies have indicated that FTIR provides a robust and reproducible methodology for MPs characterization, facilitating the development of spectral databases that enhance automated identification [55,106]. However, it presents limitations in detecting nanosized particles and may be affected by interferences from organic matter or contaminants in samples [73,107]. This limitation may introduce a methodological bias, as studies relying predominantly on FTIR could underestimate the presence of smaller microplastics, potentially skewing particle size distributions and influencing global estimates of microplastic pollution. Additionally, the lack of standardized protocols and harmonized analytical frameworks further contributes to variability in results, complicating cross-study comparisons and reinforcing uncertainties in reported data. Experimental research has also explored different FTIR modalities, including FPA-FTIR microscopy, which provides high-resolution spectral imaging for detailed quantification and characterization of MPs in complex samples [32,34]. Moreover, the use of complementary techniques, such as Raman microscopy, enhances analytical capability for particles that are difficult to identify using FTIR solely [30]. Recent studies have also focused on optimizing sample preparation for FTIR, addressing issues such as interference removal and particle concentration [25,36]. Furthermore, automated analysis software has accelerated data processing and reduced human bias in results interpretation [35]. FTIR has been successfully applied to characterize MPs in various environmental and food contexts, from drinking water samples to marine sediments and seafood, highlighting its versatility and relevance in environmental studies [24,80,95]. In conclusion, FTIR is an essential tool for chemical characterization of MPs, complementing other techniques and evolving through innovations in microscopy and automation.

4.2.3. SEM

Scanning electron microscopy (SEM) is crucial for morphological and surface characterization of MPs, using an electron beam to obtain high-resolution images, allowing analysis of particle shape, size, texture, and structure at a level of detail unattainable with conventional optical microscopes [34,93]. When combined with energy-dispersive X-ray spectroscopy (EDS), SEM also enables elemental identification of contaminants and additives in particles [34,98]. This technique is particularly useful for detecting submicrometer MPs and evaluating surface alterations due to environmental aging, abrasion, or biofouling [65,93]. However, SEM requires samples to be conductive or coated with a conductive material, which may limit analysis of some samples or alter their surface [40,51,109]. In experimental studies in the literature [34], SEM-EDS has been applied to characterize MPs in aquatic samples, revealing morphologic differences associated with different types of polymers and degradation levels. Some authors [93] have reported analysis of MPs in the stomach content of marine organisms, where SEM was a fundamental technique for the observation of physical interaction between MPs and biota. Additionally, studies like that of Dąbrowska [98] highlighted SEM’s utility in complementing spectroscopic techniques, providing morphological information that can be linked to particle origin and environmental fate.

4.2.4. Thermal Analysis

Thermal analysis methods, such as thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and pyrolysis coupled with gas chromatography-mass spectrometry (Py-GC/MS), have emerged as powerful techniques for identifying and quantifying MPs in complex environmental matrices [80,94].

TGA measures mass loss of a sample as a function of temperature, providing information on polymer thermal stability and composition, while DSC evaluates thermal transitions such as melting and crystallization, which are specific to different plastic materials [101,102]. Pyrolysis (Py-GC/MS) involves controlled thermal decomposition of the sample, followed by separation and detection of generated products, allowing specific identification of polymers and additives, even at very low concentrations [80,94,110,111]. Experimental studies have demonstrated the efficacy of these methods in overcoming limitations of spectroscopic techniques, especially in samples with high chemical complexity or organic content [101]. These methods are also valuable for precise MPs quantification, enabling differentiation of polymer types and assessment of polymer mixtures [73,92].

However, thermal analysis is inherently destructive, requires expensive equipment, and advanced technical expertise, which may limit routine application [94,102]. Thermal analysis methods constitute essential complementary tools for the characterization of MPs, particularly in studies demanding precise quantification and analysis of complex compositions in environmental and food matrices.

4.2.5. Emerging and Automated Techniques

In response to the increasing demand for rapid, precise, and large-scale analysis of MPs [28,86,112,113,114,115], emerging techniques have been developed that combine traditional spectroscopic methods with advanced technologies such as hyperspectral imaging microscopy, artificial intelligence (AI), and machine learning [55,95,96]. These automated techniques employ image processing and spectral analysis algorithms to classify and quantify particles in large datasets, significantly reducing time and human bias in interpretation [35,55]. For example, the integration of focal plane array (FPA) detectors in FTIR enables the acquisition of high-resolution spectral images, which can be analyzed using AI to detect micro and nanoplastics [32,96]. Similarly, Surface-Enhanced Raman Spectroscopy (SERS)-based techniques, such as the use of substrates with metallic nanoparticles, have enhanced sensitivity for detecting particles at extremely low concentrations [34,54,95]. These innovations open possibilities for monitoring MPs in previously difficult-to-analyze environments, such as drinking water and food products [92,95].

The adoption of portable devices and field methods is also expanding, allowing in situ characterization and enabling environmental studies with broader geographic coverage [24,36,61,116]. However, these emerging technologies face challenges related to the high cost of the equipment, the need for specialized training, and the standardization of protocols to ensure reproducibility and comparability of results [35,56,96,117]. In conclusion, emerging and automated techniques represent the state-of-the-art in MP characterization, offering innovative solutions to overcome the limitations of traditional methods and enhancing the analysis of large datasets with high precision and efficiency.

4.3. Separation and Filtration Strategies for Microplastic Removal, Efficiency and Challenges

Filtration is one of the most widely used strategies for MPs removal in various environmental systems, particularly in wastewater treatment plants (WWTPs) and in natural freshwater and drinking water systems [58,118]. These techniques rely on the physical separation of suspended solid particles using barriers or membranes with controlled pore sizes, capable of retaining particles ranging from microscopic to nanoscale [113,119]. Given the growing concern about the persistent and ubiquitous presence of MPs in water, the development and optimization of efficient filtration methods is crucial to reduce contamination and minimize impacts on ecosystems and human health [30,33,52,120,121]. WWTPs, in particular, play a key role as critical points for intercepting MPs before they are released into receiving bodies, although their efficiency can vary considerably depending on the design and technologies implemented [27,28].

Table 4. Comparative Summary of Filtration Methods for MPs Removal.

Filtration Technique	Description	Main Applications	Advantages	Limitations	References
Conventional Filtration	Use of meshes, sand filters, or sieves to retain particles >20 µm	Wastewater treatment plants, surface water treatment	Low cost, easy implementation	Low efficiency for small particles and nanoplastics	[119,122]
Membrane Filtration	Ultrafiltration, nanofiltration, and microfiltration for submicron particles	Advanced treatment of wastewater and drinking water	High efficiency for microparticles and nanoplastics	Fouling issues, high costs	[123,124]
Coagulation–Flocculation	Use of coagulants and flocculants to agglomerate particles and facilitate removal	Pretreatment and filtration improvement in WWTPs	Better removal of small particles, turbidity reduction	Requires chemical handling and sludge generation	[57,125]
Electrocoagulation and Electroflotation	Electrical techniques to coagulate and separate suspended particles	Wastewater with high microplastic load	Sustainable processes, no added chemicals	Requires specialized equipment	[58,63]
Advanced Oxidation (UV/H2O2, etc.)	Chemical oxidation to degrade MPs and facilitate their removal	Urban wastewater with synthetic fibers	Degradation of MPs, improved filtration efficiency	Operational costs, byproduct management	[126]
Magnetic Adsorption	Use of modified magnetic materials to capture MPs and facilitate separation	Water treatment and rapid extraction	High selectivity, rapid separation	Limited to certain types of MPs	[59,62]
Bioadsorption (Algal biomass, biochar)	Use of biological materials to adsorb MPs in natural waters	Natural and complementary treatment	Sustainable, low toxicity	Variable efficiency, dependent on environmental conditions	[127,128]
Innovative Adsorbent Materials	Sponges, nanofibers, and other materials designed to adsorb MPs	Selective removal in laboratory and pilot scale	High adsorption capacity, reusable	Still in experimental development	[43,54]

presents a summary of the main filtration technologies, their fundamental characteristics, applications, advantages, and limitations, based on a comprehensive review of recent literature. This information provides an integrated view to understanding the capabilities and challenges associated with each technique, facilitating appropriate selection according to the application context.

According to Table 4, filtration techniques for MPs removal encompass several approaches with different levels of efficiency, which depend both on the nature of the contaminant and the type of treated matrix [38,119,129,130]. Conventional technologies, such as sieve filtration or sand beds, continue to be used as a first barrier [60,120,121,123], although their capacity to retain small particles, such as nanoplastics, is limited, which has motivated the development of more advanced methods [28,125,131,132]. In this context, membrane-based technologies, such as microfiltration, ultrafiltration, and nanofiltration, have demonstrated a significantly higher ability to capture smaller particles [133,134,135]. However, their large-scale application still faces operational challenges related to fouling and maintenance costs [113,123,133,136]. This reflects a general pattern observed in Table 4, where higher removal efficiency is often associated with increased economic and operational demands. The use of coagulation-flocculation processes represents an effective complementary strategy, especially when aiming to improve the overall efficiency of conventional treatment systems by facilitating the aggregation of dispersed particles [57,120,124,128,129,134,137]. These processes, applied with metallic salts or natural flocculants, have shown variable efficiencies depending on the type of MPs and the treated matrix [108,125,138,139]. As indicated in Table 4, their main advantage lies in their scalability and compatibility with existing infrastructure, although they may generate secondary residues that require further management.

Additionally, more innovative approaches have emerged, relying on alternative physicochemical principles. Electrocoagulation and electroflotation, for example, allow MPs to be removed without adding chemical reagents, making them attractive from an environmental sustainability perspective [58,63,125,135]. However, Table 4 indicates that these techniques may be limited by energy requirements and the need for specialized equipment. Likewise, advanced oxidation methods, such as UV/H₂O₂ or peroxide treatments, have been explored for their ability to partially degrade polymers, reducing their size or modifying their surface to facilitate subsequent removal [60,122,126,140]. In this sense, Table 4 suggests that these methods are generally more effective as complementary treatments rather than standalone solutions.

Another emerging field involves magnetic adsorption and bioadsorption, where functionalized materials (materials with specific chemical groups incorporated into their surface or structure) or biological agents are used to selectively capture MPs. These technologies offer promising solutions for more eco-friendly and targeted treatments [59,62,119,127,141], although their applicability is still at the research stage. Similarly, the design of new materials, such as chitin sponges, cellulose nanofibers, or hybrid composites, continues to expand the range of available solutions [43,54,141], although their implementation under real conditions still requires validation at pilot or industrial scale. According to Table 4, these emerging approaches show high selectivity and adsorption capacity but remain limited in terms of scalability and consistency under real environmental conditions. Overall, comparative analysis of these technologies shows that there is no single ideal technique. Optimal selection will depend on the type of water (wastewater, drinking, or surface), the characteristics of the MPs present (shape, size, density), and the available resources [27,58,116,121,126,128]. Studies agree that an integrated approach, combining conventional methods with advanced technologies, is the most promising strategy to effectively address MPs pollution in aquatic systems [15,44,45,132,136,142].

4.4. Nanoplastics as an Intrinsic Fraction of Microplastic Pollution

Nanoplastics represent the smallest size fraction generated from the fragmentation and degradation of larger plastic debris and therefore constitute an intrinsic component of microplastic pollution. Rather than being independent, they arise from environmental aging, mechanical breakdown, and physicochemical transformation processes affecting microplastics across aquatic and terrestrial systems [143]. Despite their increasing environmental and toxicological relevance, largely attributed to their high surface area, reactivity, and enhanced potential for biological interactions, their study remains methodologically distinct from that of microplastics. Current analytical limitations, including insufficient detection thresholds, lack of standardized protocols, and difficulties in polymer-specific identification within complex environmental matrices, continue to hinder their systematic incorporation into large-scale assessments [13,14,15,16]. However, recent advances in nanoplastic research have focused on the development of high-resolution analytical techniques, including thermal analysis-based methods, advanced spectroscopic approaches, and nanoparticle tracking systems, which have improved detection capabilities under controlled conditions. In parallel, emerging remediation strategies (such as advanced membrane processes and functionalized adsorbent materials) have shown potential for capturing or transforming nanoscale plastic particles. However, these approaches remain highly heterogeneous, are often limited to laboratory-scale validation, and lack standardized methodologies for consistent application across environmental systems [85,115,128,130,140].

From a technological perspective, these limitations are also reflected in removal efficiency. Most conventional filtration and separation techniques exhibit a marked decline in performance as particle size approaches the nanoscale, highlighting a critical boundary in current treatment systems and reinforcing the need for integrated or hybrid approaches capable of addressing multiple size fractions simultaneously [115,128,133]. Overall, while significant progress has been made, the field of nanoplastic research remains under active development, with substantial knowledge gaps in detection, standardization, and large-scale remediation. These challenges position nanoplastics as a critical frontier for future research, closely linked to—but not yet fully integrated within—the established framework of microplastic studies.

5. Conclusions

The bibliometric review conducted using the Methodi Ordinatio approach provides a structured and quantitative assessment of the current research landscape on microplastics (MPs), revealing a clear imbalance between advances in physicochemical characterization and the development of effective removal technologies, where spectroscopic and microscopic techniques, particularly FTIR and Raman, remain the backbone of MPs identification while their widespread use contrasts with the limited translation of analytical knowledge into scalable remediation solutions. A key finding is the persistent fragmentation across methodologies, sample matrices, and analytical protocols, which continues to hinder comparability and reproducibility of results and limits the evaluation of removal technologies under realistic environmental conditions, while emerging strategies, especially filtration-based and hybrid systems, show significant potential but remain constrained at large scale by operational complexity, economic viability, and insufficient long-term performance data.

Importantly, this review positions nanoplastics not as an isolated domain but as an inherent extension of microplastic degradation pathways, emphasizing the need for integrated analytical frameworks capable of addressing the full-size continuum of plastic pollution, as current limitations in detecting and removing nanoscale particles reinforce the urgency of developing multi-technique approaches and standardized workflows. By applying the Methodi Ordinatio framework across both characterization and removal domains, this study identifies critical knowledge gaps and priority research directions, highlighting the need for protocol harmonization, validation under real-world conditions, and interdisciplinary approaches that bridge laboratory-scale insights with environmental applications, ultimately supporting a transition toward more effective and scalable solutions for microplastic pollution.