Eco-Friendly Adsorbents: Innovative Strategies for Pesticide Removal from Soil and Wastewater

Abstract

Pesticide residues from agrochemicals pose significant environmental and public health risks due to their persistence and widespread contamination of soil, water, and crops. The persistent challenge of pesticide contamination requires innovative and sustainable treatment strategies to safeguard public health and environmental integrity. Although wastewater treatment plants (WWTPs) are designed to mitigate these pollutants, their efficiency varies, and certain pesticides persist or transform into more toxic by-products during treatment. Therefore, developing alternative methods for the effective removal of pesticide residues is imperative. This review critically evaluates the potential of adsorption, particularly using green adsorbents, as a sustainable and efficient approach for removing pesticide contaminants from soil and wastewater. Green adsorbents, derived from agricultural and industrial by-products such as sea materials, biomasses, humic acid, spent mushroom substrate, biochar, and cellulose-based adsorbents, offer a cost-effective, abundant, and environmentally friendly solution for soil treatment and water purification. Their high pollutant-binding capacity, selectivity, and affinity make them promising candidates for widespread application in soil and wastewater treatment. Ongoing research focuses on optimizing the scalability and real-world application of these adsorbents for large-scale remediation efforts. In conclusion, addressing the risks posed by pesticide residues necessitates revisiting agricultural practices and wastewater treatment strategies. The integration of green adsorbents offers a sustainable approach to mitigating pesticide contamination, thereby protecting public health and supporting environmental sustainability. This review highlights the importance of adopting green adsorbents as viable alternatives to conventional treatment methods, emphasizing their potential to revolutionize wastewater management and mitigate the adverse impacts of pesticide residues on ecosystems and human well-being.

1. Introduction

The global consumption of pesticides has been steadily increasing over the years. In 2019, the worldwide agricultural use of pesticides reached approximately 4 million metric tonnes (4,168,778 tonnes) of active ingredients [1,2]. This growth underscores the critical role of pesticides in boosting agricultural yields and ensuring food security amid challenges such as climate change and population growth. While pesticides are essential for protecting crops from pests and diseases, their extensive use raises environmental and health concerns. Pesticides can contaminate soil, water, and non-target species, leading to ecosystem disruptions and potential human health risks. Pesticide residues are produced during the production and storage of low-cost plants when agrochemicals, biocides, and fumigants are sprayed on the soil to control pests, particularly fungi and insects [3].

Crops can absorb pesticides and heavy metals from soil and irrigation water, then translocate them to plant parts. This process leads to the contamination of vegetables, greens, fruits, and other plant tissues. Consequently, this phenomenon increases the risk of human exposure to these contaminants and contributes to environmental pollution. A study by USEPA [4] revealed that 64% of vegetables irrigated with treated wastewater contained residues of pesticides such as DEET and triclosan. Wastewater treatment facilities are generally designed to remove pollutants, including pesticides, prior to releasing treated water into the environment. The effectiveness of these treatment processes depends on the particular pesticides used and the methodologies employed. Studies have shown that certain pesticides can persist in wastewater even after treatment, and some compounds may transform into more toxic substances during treatment [5,6,7].

Various approaches have been employed to address wastewater pollution; among these, liquid-solid adsorption has become a preferred method for the effective removal of a diverse array of pollutants [8]. This process is not only economically viable but also technologically straightforward, enabling the production of high-quality water. Consequently, adsorption processes in aqueous solutions play a vital role in numerous applications, including recovery and separation, wastewater decontamination, and water purification [9].

Over the past three decades, the phenomenon of contaminant binding by unconventional green adsorbents through oriented adsorption processes has garnered increasing attention. There is significant potential for leveraging this phenomenon in soil, wastewater, and water treatment. The removal of impurities from soil and aqueous solutions using products and by-products of biological, agricultural, and industrial origin is a fundamental principle of liquid-solid adsorption using green adsorbents [10]. Green adsorbents are cost-effective filter materials that have high capacity, affinity, and selectivity for binding pollutants. They are widespread and abundant, already in large quantities in most places. The long list of green adsorbents includes solid agricultural waste, industrial byproducts, food waste, natural products, carbons from these sources, and much more. Examples of adsorbents are Fungi, plants, algae, biopolymers, hemp, flax, and clay; as well as biological materials such as dead biomass and biopolymers [11,12].

Nowadays, the integration of artificial intelligence (AI) and machine learning (ML) into adsorption science represents a significant advancement. These sophisticated technologies provide solutions to persistent challenges, such as enhancing regeneration efficiency and forecasting adsorption behavior under varying environmental conditions. By utilizing AI and ML, researchers can now design materials and processes with precision, resulting in intelligent adsorbents that dynamically respond to their surroundings. This innovation not only improves the efficacy and environmental sustainability of adsorption techniques but also opens new avenues for addressing complex wastewater treatment issues [10,13,14,15].

Given their biodegradability and potential for reuse, green adsorbents offer significant environmental benefits, thereby minimizing post-treatment disposal challenges. The strategic application of these adsorbents has the potential to enhance sustainable soil and water treatment globally, revolutionizing approaches to pesticide contamination. This review underscores the critical role of green adsorbents in the effective removal of pesticide residues.

2. Pesticide Uses

In recent years, there has been a significant global effort to reduce pesticide usage. Despite these initiatives, many countries continue to use substantial quantities of pesticides annually. Data on pesticide use in agriculture in 2023 reveal that several countries are major consumers (Figure 1).

As shown in Figure 1, the continents with the highest pesticide consumption are South America and Asia. This is also clearly evident in the FAOSTAT data [17] by regions (Figure 2).

Therefore, recent research has highlighted the adverse effects of pesticide exposure, which can pose health risks to farmers and contaminate soil and water supplies, affecting plants, animals, and humans [2,3,18].

3. Pesticide Removal

Chemical degradation and adsorption are the major strategies in terms of pesticide removal [19]. Chemical degradation processes strongly depend on the specific pesticide functional group. Depending on this, the strategy could be either incineration, hydrolysis, ozonation, etc. All of them pose some risks for the environment or are characterized with less efficiency [20].

Thus, nowadays, a lot of attention is paid on the adsorption strategy. The adsorption process is a surface phenomenon in which the adsorbate accumulates on the adsorbent surface. When a solution containing an absorbable solute meets a solid with a highly porous surface structure, some of the solute molecules from the solution concentrate or deposit on the solid surface. This is due to intermolecular attractive forces between the liquid and the solid [21,22]. For bulk materials, other atoms in the material satisfy any ionic, covalent, or metallic bonding requirements of the material’s constituent atoms. However, since the atoms on the surface of the adsorbent are not entirely surrounded by other adsorbent atoms, adsorbates can be attracted to them [21,22,23,24]. The specific type of binding depends on the species; However, the adsorption process can be broadly categorized as either physisorption, in which the adsorbate is bound to the surface by weak van der Waals forces, or chemisorption, in which the adsorbate is bound by covalent bonding [25] or electrostatic attraction [26].

The equilibrium stage of adsorption between the solution and adsorbent is attained (where the adsorption of solute from the bulk onto the adsorbent is minimum), and the adsorption amount (Qe, mg g⁻¹) of the molecules at the equilibrium could be calculated according to the following equation—Equation (1):

$$Qe={\displaystyle \frac{V\left(Co-Ce\right)}{m}}$$

(1)

where V is the solution volume (L), m is the mass of adsorbents (g), and Co and Ce (mg.L⁻¹) are the initial and equilibrium adsorbate concentrations, respectively. In addition, adsorption may be defined as the mass transfer process by which a substance is transferred from the liquid phase to the surface of a solid, where it becomes bound by physical and/or chemical interactions [27]. It is worth noting that the large surface area of the adsorbent enables high adsorption capacity and surface reactivity [27].

Adsorption is a physical-chemical process in which dissolved molecules in impure water are chemically and physically bound to the surface of the adsorbent. Due to its superior pollutant-removal performance compared to conventional methods, adsorption technology is considered an effective technique for removing pollutants from dirty wastewater. Adsorption is known to be a cost-effective process that delivers excellent quality products. On the other hand, biomass-derived adsorbents have become a viable and effective method for treating water contaminated with heavy metals. These adsorbents are typically produced from biomass derived from bacteria, fungi, algae, or agricultural wastes, which are abundant and renewable resources. The process of biosorption involves physicochemical adsorption and ion exchange on the cell surface of these biomasses, which can occur in both living and dead cells. The advantage of this method is that it does not require any metabolism and is therefore effective even on inactive cells that are not affected by toxic pollutants. The versatility of biomass-derived adsorbents is demonstrated by their ability to remove a wide range of pesticides and metal ions from aqueous solutions, including lead, cadmium, cobalt, and copper, which are known for their toxicity and potential for environmental and health problems [28]. The production methods for these adsorbents can vary, but often involve activating the biomass to increase its adsorption capacity. This activation can be achieved through physical or chemical processes that improve the material’s specific surface area and porosity. Activated carbon obtained from biomass is known for its high adsorption capacity and cost-effectiveness. It is worth noting that several factors, including the type of biomass, the activation process, and the physicochemical properties of the metal ions, can influence the efficiency of these adsorbents.

4. Green Adsorbents Strategy for Removing Pesticide Residues

The development of green adsorbents for the removal of pesticide residues from soil and water sources is a critical area of research, particularly considering the increasing global use of pesticides in agriculture. The quest for sustainable and cost-effective solutions has led to the exploration of various materials, including biochars derived from plant materials, which have shown promising adsorption capacities due to their high carbon content. These biochars are not only effective but also advantageous because they can be produced from renewable resources, contributing to a circular economy. The modification of these adsorbents through processes such as alkaline or acid treatment can enhance their performance by increasing porosity and the abundance of functional groups, such as carboxyl and hydroxyl, which are essential for adsorption. This is particularly important for removing organochlorine pesticides, which have long half-lives and tend to bioaccumulate, posing significant health risks. The application of these green adsorbents in field settings, coupled with strategies for post-treatment of spent adsorbents, is the subject of ongoing research. The goal is not only to remediate contaminated water but also to manage adsorbents after use in an environmentally friendly manner. This holistic approach to soil and water treatment using green adsorbents aligns with global sustainability goals and addresses the pressing need for clean water, free from harmful pesticide residues.

5. Types of Green Adsorbents

Adsorbents are frequently divided into two groups based on their source: natural and synthetic. Industrial and agricultural waste, as well as waste sludge, are used as raw materials to produce synthetic adsorbents [29,30]. Conversely, natural adsorbents include clay, zeolites, ores, minerals, and charcoal.

Another way is to divide them into five categories: activated carbon adsorbents, non-conventional low-cost adsorbents, nanomaterial adsorbents, composite and nanocomposite adsorbents, and miscellaneous adsorbents [30].

Active Carbon Adsorbents

Carbon is one of the most widely utilized and conventional adsorbents in industry [31]. Due to its high capacity for adsorbing pollutants, commercial activated carbon (CAC) is considered the most effective. There are two types of activated carbon absorbents: commercial activated carbon (AC) and AC made from water materials.

When the adsorption system is adequately designed, CAC can achieve pollutant concentrations below permissible limits for wastewater. This efficacy is primarily attributed to its chemical composition, which can be easily modified through chemical treatments to enhance its properties, as well as its structural features and porous texture, which provide a large surface area. Activated carbon (AC) is typically introduced into a container with the contaminated solution or the solution is continuously passed through a packed carbon bed in batch processes using these common adsorbents. The convenience, ease of use, and straightforward design of AC adsorption processes further contribute to their appeal [32,33].

However, due to the high cost of CAC, alternative non-conventional adsorbents derived from forestry, agricultural, and biological sectors have been proposed, studied, and utilized as more cost-effective and efficient adsorbents. These adsorbents, known as biosorbents, are valued for their natural origin and their ability to bind and concentrate metal ions from aqueous solutions [34,35]. Biosorbents include biological entities such as algae, bacteria, fungi, and yeast. Other sources could be from decomposing biomass, such as plant material, bark, sawdust, peat, natural fibers (e.g., cotton and flax), and other organic materials (biopolymers or polysaccharides) [11,12]. Examples of polysaccharides used as biosorbents include alginate, chitin, and starch, as well as their derivatives such as chitosan and cyclodextrins. These materials are inexpensive, widely available, and abundant in nature due to their unique structure and physicochemical properties, making them promising candidates for biosorption [36,37,38,39].

Table 1. Several examples of sources of some biosorption substances and types of pollutants absorbed.

Biosorption Source	Biosorbent	Pollutant	Biosorption Capacity	Reference
Agricultural wastes	Cucumber peels modified with ZnO nanoparticles	Metribuzin	200 mg g−1	[40]
	cantaloupe seed shell powder	Butachlor	142.857 mg g−1	[41]
	Coffee residues	Dyes and heavy metals	70 mg/g	[42]
	Wood sawdust, tree bark and wood chips	Dyes		[43]
	Rice straw	Heavy metals	0.1 g/35 ppm Zn (II); 0.1 g/70 ppm Cd (II)	[44]
Agro-industrial	Wood charcoal, fly ash, coconut charcoal, saw dust, coconut fiber, bagasse charcoal	Atrazine	5 g/0.05 or 0.1 ppm atrazine	[45]
	Lignocellulosic substrate	Terbumeton, desethyl terbumeton, dimetomorph	1- 8 g kg−1	[46]
Chitosan	chitosan-zinc oxide nanoparticles	Permethrin	0.5 g per 0.1 mg L−1 permethrin	[47]
Industrial wastes	Oat bran, chitosan, alginate, tree bark, coconut fiber, and lignin	Heavy metals		[48]
	Coal fly ash	Metribuzin, metolachlor, atrazine	0.20, 0.28, and 0.38 mg g−1	[49]
Microbial materials	Fungus Pleurotus mutilus	Metribuzin	3 g per 200 mg L−1	[50]
	fungi, bacteria, yeasts	heavy metal		[51,52]
	Activated sludge	Dyes		[53,54]

lists materials used for biosorption, with a focus on polysaccharide-based adsorbents.

• Non-conventional low-cost adsorbents (NCLCAs)

Non-conventional low-cost adsorbents (NCLCA) are divided into natural materials, bioadsorbents, and industrial and agricultural waste products. Nanoparticles, nanotubes, nanowires, and nanorods are other classifications for absorbable nanomaterials. In recent years, numerous strategies have been explored to develop more cost-effective and efficient adsorbents. Various researchers have proposed innovative, low-cost adsorbents derived from natural materials, biosorbents, and both agricultural and industrial by-products. These materials have demonstrated significant efficacy as sorbents for the removal of dyes from aqueous solutions, pesticides, and heavy metals. Noteworthy examples of agricultural waste include bagasse pulp, corncobs, rice husks, and coconut shells, while industrial waste products comprise carbon sludge and metal hydroxide sludge [40,41,42,43,44,55]. However, the different types of NCLCAs include agricultural solid waste, industrial by-products, waste, natural materials, and sea materials.

Furthermore, biosorbents such as chitosan, peat, and biomass, as well as other materials such as starch, cyclodextrin, and cotton, have been recognized as promising sorbents. There are claims that NCLCA regeneration and reprocessing are carried out using solid agricultural waste, such as sugarcane bagasse, wheat straw, nut shells, plant leaves, and wood chips, as well as industrial waste and by-products, such as red mud and fly ash. Natural materials like silica, clay, and zeolite are also used. Additionally, materials from algae, peat moss, and leftover seafood are utilized to remove dyes from wastewater through various cycles. Various desorbents, including chelating agents, alcohols, and acids, are used to regenerate these materials [55,56,57]. Currently, adsorbents made from agricultural waste are mainly non-renewable. To support sustainable development, there is a need for renewable and recyclable agricultural adsorbents. Many types of agricultural waste have been developed and used as effective adsorbents. Studies show that these wastes have porous structures and contain different functional groups, such as carboxyl and hydroxyl groups. Regenerating these materials for reuse to remove dyes from wastewater is cost-effective and efficient because of their physical and chemical properties [57].

b.

Agricultural solid waste

Many non-renewable materials utilized in contemporary adsorbents are derived from solid agricultural waste. Consequently, sustainable development has been facilitated by the development of recyclable, renewable solid adsorbents tailored for agricultural applications. A diverse range of agricultural solid waste has been engineered and employed as high-value, renewable adsorbents [58,59]. Applicable studies have shown that solid agricultural wastes, however, have porous fibrous structures and a variety of functional groups, including hydroxyl and carboxyl groups [60]. Due to their physicochemical properties, these materials can be economically regenerated and used to remove dyes, pesticides, and heavy metals from wastewater with high adsorption efficiency.

c.

Industrial by-products and solid waste

Tissera et al. [61] conducted a study on the regeneration and reusability of keratin protein derived from 0.5 M wool for the removal of rhodamine B (RhB) from aqueous solutions. The results indicated that, while the desorption capacity remained consistent across three cycles, the dye removal efficiency decreased from 100% to 94% during the fourth cycle when using 0.05% NaOH (pH = 2) as the eluent. All other experimental parameters were maintained constantly, including a RhB concentration of 80 mg/L, a dosage of the charged dye adsorbent at 0.8 g/L, and a contact time of 30 min. Similarly, Thakur and Kaur [62] used paper industry sludge waste as NCLCA and HCl as eluent and reported a similar result.

d.

Natural materials—zeolites

Because they are widely available, natural materials such as hydrous aluminosilicate minerals, namely clays, are used to treat textile wastewater [63]. Both organic and inorganic pollutants can be treated with natural materials such as zeolites, which are aluminosilicates [64]. Most NCLCAs used to remove anionic dyes from aqueous solutions are silicate materials [65]. Clinoptilolites are natural zeolites that are considered low-cost sorbents and have been intensively studied for the removal of pesticides and heavy metals [66,67,68].

e.

Adsorbents from marine organisms

In recent years, increasing attention has been paid to the use of marine organisms and their products for pesticide removal. Studies focused on the polysaccharides chitosan and chitin for the removal of dyes from wastewater and pesticides [65,69,70]. Nevertheless, marine materials are abundant, environmentally friendly, and economically attractive [65,70].

A network visualization generated using VOSviewer (VOSviewer version 1.6.20) is presented in Figure 3, illustrating a keyword co-occurrence network derived from 1331 articles indexed in the Scopus database. This network explicitly investigates the interrelationships between the keyword “Pesticides” and associated terms such as “Adsorbents” and “Agricultural waste.” In the visualization, nodes represent individual keywords, and each node’s size corresponds to the frequency of that keyword’s occurrence in the dataset. Colors are used to group nodes into thematic clusters, indicating distinct but related research areas. Edges (lines) between nodes denote the co-occurrence of keywords within the same publications, with thicker edges indicating stronger co-occurrence.

The spatial arrangement of nodes reflects thematic proximity, with closely positioned nodes indicating greater co-occurrence and conceptual relatedness. At the center of the network lies the keyword “adsorbents,” signifying its central role in the literature. Surrounding this core are prominent terms such as “pesticides,” “removal,” “biochar,” and “pollutants,” which highlight the research community’s focus on the application of adsorbents—particularly biochar derived from agricultural waste—for the remediation of pesticide contamination.

Additional clusters within the network emphasize specific research directions, including the study of pesticide compounds, various adsorbent materials, and broader environmental pollution themes. This visualization provides a valuable analytical tool for identifying key research trends, thematic concentrations, and potential knowledge gaps in the field of pesticide residue management and adsorbent-based removal technologies.

f.

Nanomaterial adsorbents

Nanomaterial adsorbents represent a significant advancement in environmental technology, particularly in the field of water purification. These materials, due to their nanoscale size, exhibit unique properties, such as a high surface area-to-volume ratio, which enhances their capacity to adsorb pollutants from water. Recent studies have shown that nanomaterials can effectively remove heavy metals, organic contaminants, and dyes from wastewater, which are often challenging to eliminate through conventional treatment methods. The versatility of nanomaterials enables the design of adsorbents tailored to target specific contaminants, making them highly efficient and selective. Moreover, the potential for regenerating and reusing these materials makes them a cost-effective and sustainable option for long-term water treatment. As research progresses, the development of novel nanomaterial adsorbents continues to push the boundaries of what is possible in water purification, addressing not only the efficiency of contaminant removal but also the environmental impact of the adsorbents themselves. Innovation in this field is a testament to the importance of interdisciplinary collaboration, combining insights from chemistry, materials science, and environmental engineering to tackle some of the most pressing ecological challenges of our time.

In recent decades, various forms of carbon-based nanomaterials have gained significant attention for their effectiveness in removing heavy metals and dyes. This interest is attributed to their non-toxic nature, availability, straightforward synthesis, large surface area and porosity, structural stability, and substantial sorption capabilities [71,72].

Great interest in carbon-based nanomaterials (CBNs) has arisen due to their unique chemical and physical properties. In-depth studies have been carried out on CBNs in the areas of environmental remediation, analytical chemistry and sensing, antimicrobial activities, microbial fuel cells, renewable energy and energy storage, as well as fullerenes, carbon nanotubes, carbon nanofibers, and carbon quanta [73]. The lack of knowledge about the potential toxicity and health effects of CBNs, challenges with scalability and cost-effectiveness, and biocompatibility in medical applications are among the limitations that still need to be addressed. Therefore, further research is needed to fully explore the potential of CBNs and encourage scientists to develop novel CBNs for use across various sectors. This research should encompass multidisciplinary integration approaches, including engineering, medicine, chemistry, biology, and materials science.

g.

Composite and nanomaterial adsorbents

In materials science, composite and nanomaterials, adsorbents play a pioneering role, especially in environmental remediation. These cutting-edge materials are designed to improve their adsorption properties by fusing nanoscale materials with composite matrices. Due to their unique physicochemical properties, including high surface area, porosity, and reactivity, nanomaterials are the best options for removing pollutants from air and water. Particularly noteworthy are the adsorption properties of carbon-based nanomaterials such as graphene, fullerene, and carbon nanotubes. They can be functionalized with various groups to target specific pollutants, including organic compounds, heavy metals, and biological hazards. The final properties and effectiveness of the adsorbents are determined by the synthesis techniques used for these materials. More recently, combinations of activated carbon and bimetallic composites have been developed that offer improved pollutant removal capacity and selectivity. These nanomaterials are being investigated for use in drug delivery systems and sensors, demonstrating their versatility beyond environmental remediation. The potential of these nanomaterial adsorbents to completely transform the way we deal with pollution and recover resources continues to grow as research advances [10,11,74].

It is obvious that the nanomaterials are promising candidates for pesticide removal. Even though a few considerations should be considered. The adsorption capacity of various nanomaterials is challenging to compare, as complete information is often lacking. The impact on the environment and human health should be carefully determined. The development of the variations should be evaluated based on costs and efficiency [75].

h.

Miscellaneous adsorbents

Adsorbents are indispensable in environmental management, especially in wastewater treatment. These substances can condense from a liquid or gas on their surface. A common adsorbent is activated carbon, which is often used for its exceptional effectiveness in removing pollutants. However, because activated carbon is so expensive, researchers are looking for unconventional adsorbents that are usually cheaper and sometimes even more effective. These include biosorbents derived from biological materials, agricultural solid waste, industrial by-products, and various other adsorbents such as hydrogels and alginates. These unconventional adsorbents were developed to address the urgent need to remove pollutants, especially at trace levels, from the environment cost-effectively and sustainably. Studies on the adsorption mechanisms of these materials and their interactions with various pollutants are the focus of dynamic research in this field. The aim is to reduce costs and environmental impact while optimizing the adsorption capacity and selectivity of the adsorbents. Innovations in adsorption technology reflect a greater commitment to promoting sustainability and environmental protection. According to a study conducted by Kim et al. [76], plant waste from the sea buckthorn oil industry can be used to remove hazardous metals from wastewater due to its high removal efficiency (>80%).

i.

Cellulose-Based Green Adsorbents

To effectively adsorb pollutants, various materials have been developed as adsorbents. Due to their low cost, non-toxicity, and renewability, green adsorbents have attracted significant attention in recent years [77]. Green adsorbents made from sustainable raw materials use less energy to produce, pose few health risks, are recyclable, and break down into smaller pieces that can be brought to market with fewer resources.

Cellulose adsorbents can meet almost all environmental requirements. The most widely used naturally occurring biopolymer that is non-toxic, renewable, and biodegradable is cellulose. Lignocellulosic materials are the primary sources of cellulose, with wood being the most significant. Cellulose-based materials are more attractive for water purification when their structural composition is altered to improve current properties or add new capabilities [78]. A unique platform for significant surface modifications, enabling the grafting of a variety of functional groups or molecules, is made possible by the abundance of hydroxyl groups on the surface of micro- or nanoscale cellulose. This abundance allows binding to the cellulose structure and immobilizing pollutants.

6. Life Cycle of the NCLCAs

Eco-design is a crucial approach in modern product development that integrates environmental considerations from the first design phase through the end of the product life cycle [79]. This concept is not only a cornerstone of sustainable development but also a strategic element for reducing the ecological footprint of products [80,81]. The life cycle assessment is an indispensable tool. It involves several major stages, presented in Figure 4. The application of such an approach would provide a detailed analysis of the environmental impact across all stages of the product’s life cycle, from raw material extraction to disposal. While NCLCAs have traditionally been applied to agricultural soil modifiers and energy byproducts, their use in evaluating alternative adsorbents for wastewater treatment is becoming increasingly important. These adsorbents, often derived from agricultural waste or produced using nanotechnology, offer a promising opportunity to reduce the environmental impact of wastewater management. They are designed to remove pollutants with high efficiency, thereby reducing their release into the environment. Comparative life-cycle assessment studies of these adsorbents are crucial, as they help identify the most sustainable options by considering factors such as resource and energy consumption, and potential emissions throughout the product life cycle. By adopting eco-design principles and using life-cycle assessment in product development, industries can make significant strides towards sustainability and ensure that products make a positive contribution to the environment while meeting consumer needs and maintaining economic viability. The shift towards eco-design reflects a broader recognition of the importance of environmental protection amid global challenges such as climate change and resource depletion. It is a proactive step in line with the principles of the circular economy, aiming to create products that are not only efficient and effective but also environmentally friendly. As demand for sustainable products grows, eco-design will undoubtedly play a crucial role in shaping the future of product development and environmental management.

7. Pesticide Adsorption Strategies with Some Examples of Green Adsorbents

7.1. Pesticide Adsorption by Spent Mushroom Substrate

The use of spent mushroom substrate (SMS) as an adsorbent for pesticides, including fungicides, nematicides, and herbicides, in soil is a promising area of environmental research (Figure 5). SMS, a byproduct of mushroom cultivation, has been shown to effectively immobilize and degrade these chemicals, thereby preventing soil and water contamination. Studies have demonstrated that adding SMS to soil can influence the environmental fate of pesticides, with processes such as adsorption, leaching, and dissipation being significantly affected. This not only helps manage pesticide levels in agricultural settings but also contributes to the sustainability of farming practices by repurposing waste materials. According to Alvarez-Martin et al. [82], the use of spent mushroom substrate (SMS) as an adsorbent for pesticides is a promising approach due to its high organic matter content, which enhances adsorption, especially for non-polar compounds such as tebuconazole and triadimenol. The research indicates that SMS can significantly increase the adsorption capacity of soils for these non-polar pesticides, achieving up to 90% efficiency. This is a substantial improvement over the 56.3% adsorption rate for polar pesticides. The differential adsorption rates suggest that the physicochemical properties of SMS favor non-polar interactions. The increase in soil organic carbon content upon the addition of SMS could be a contributing factor, as it may enhance the soil’s ability to interact with non-polar substances. Consequently, non-polar pesticides can be effectively removed from soil using spent mushroom substrate as an adsorbent.

The spent mushroom can immobilize pesticides applied topically to the soil. The rich organic matter in the spent mushroom substrate, which reduces the bioavailability of pesticides, can also absorb them. Herrero-Hernández et al. [83] studied the distribution of tebuconazole in soil at a depth of up to 50 cm after application of spent mushroom for 124, 209, and 355 days. Compared to non-amended soil, the study showed that the deep layer of amended soil had a higher concentration of fungicides. This was made possible by the influence of soil organic matter from the spent mushroom. The pesticide was observed to bind to the spent mushroom, immobilizing it and preventing its spread in the soil. To avoid contamination of water and soil, field application of fungi and spent mushroom requires data validation by comparing field and laboratory data. In addition, this prevents pesticides from leaching into the soil and water. Because it produces several enzymes, spent mushroom serves as an essential tool for both adsorption and degradation of pesticides [83].

Furthermore, Rodríguez-Cruz et al. [84] also studied how well spent mushroom substrate absorbed linuron, diazinon, and myclobutanil in comparison to grape marc and sewage sludge. According to Rodriguez-Cruz et al. [84], grape marc was effective for adsorbing linuron and diazinon, but spent mushroom substrate was more effective for adsorbing myclobutanil. Thus, it is possible to use spent mushroom substrate to adsorb pesticides from soil; however, this depends on several variables that affect the adsorption of one pesticide but not another. The application of spent mushroom substrate in the field requires careful consideration and investigation of these factors. Sánchez-Martín and Rodríguez-Cruz [84] studied the effectiveness of spent fungal substrate as an adsorbent for fungicides. In this study, eight different fungicides were combined with different types of spent fungal substrate. The authors observed nonlinear sorption isotherms in fungicide adsorption studies through spent fungal substrate. Fourier transform infrared spectroscopy was used to examine spent fungal substrates before and after adsorption. Variations in peak positions and band positions indicated the active groups involved in the adsorption process.

The impact of fresh and composted spent mushroom substrate (SMS) on soil was evaluated for the pesticides penconazole and metalaxyl. SMS increased the immobilization of metalaxyl (water-soluble pesticide) and retention of penconazole (hydrophobic), making it effective for removing metalaxyl from soil [85]. SMS also enhanced organic content and pesticide adsorption in soil. Further experiments assessed the effects of SMS on iprovalicarb, penconazole, metalaxyl, and pyrimethanil fungicides. The degradation rate of all fungicides decreased in composted SMS-amended soil, while only iprovalicarb and penconazole showed reduced degradation in fresh SMS-amended soil. Non-amended soil exhibited the highest mineralization for metalaxyl and penconazole, but fresh SMS-amended soil formed non-extractable residues with metalaxyl. This study highlights the varying degradation rates of fungicides with fresh and composted SMS and the need for a detailed investigation into their application [85].

As it was mentioned above, the chemical structures of various pesticides such as Tebuconazole, Triadimenol, Linuron, Diazinon, Myclobutanil, Penconazole, Metalaxyl, Iprovalicarb, and Pyrimethanil are intricate and serve specific functions in their role as agricultural chemicals. Tebuconazole, for instance, is a systemic fungicide with a molecular formula of C₁₆H₂₂ClN₃O, known for its protective and curative action against a range of pathogenic fungi. Triadimenol, another fungicide, shares similarities in its mode of action, inhibiting the biosynthesis of sterols in fungal cells. Linuron, on the other hand, is an herbicide that acts by inhibiting photosynthesis in target weed species. Diazinon is an organophosphate insecticide that works by disrupting insects’ nervous systems. Myclobutanil, Penconazole, Metalaxyl, Iprovalicarb, and Pyrimethanil are all fungicides with unique chemical structures tailored to combat specific fungal pathogens in crops. Each of these chemicals has been carefully designed to fulfill its role effectively while minimizing harm to the environment and non-target organisms. This balance is critical to the development of pesticides. The precise structures of these compounds are crucial for their function, as even minor alterations can significantly affect their efficacy and safety profile [86].

Some of the limitations existing for the application of SMS as an adsorbent are the cost, as well as the disposal after adsorption [87].

7.2. Pesticide Adsorption by Humic Acid

The persistence and behavior of pesticides are influenced by the nature and quantity of humic compounds, the physicochemical properties of the pesticides, and the environmental conditions of the reaction media. Humic compounds possess various functional groups, including aliphatic and aromatic carboxyls, phenolic hydroxyls, alcoholic hydroxyls, carbonyls, quinones, methoxyls, and amino groups, which serve as reactive sites within the humic molecules (Figure 6). Humic acids are large, complex molecules that arise from the biodegradation of dead organic matter. A heterogeneous mixture of aromatic and aliphatic components, which can include a variety of functional groups such as carboxyl, phenolic, methoxyl, and others, characterizes their structure. Due to the high exchange capacity of humic compounds, exchange reactions significantly contribute to the adsorption of pesticides. The extent of adsorption is directly proportional to the organic matter content [88]. Although humic substances have a complex, poorly understood chemical structure, their main structural component is a polycyclic aromatic core linked to side chains containing metal ions, proteins, peptides, carbohydrates, and phenolic fragments.

The interaction between pesticides and humic acid (HA) is a critical aspect of environmental chemistry, particularly regarding the fate and transport of pesticides in the environment. Humic acid, a major component of soil organic matter, has been shown to have a high affinity for polar ionic pesticides due to specific interactions with its functional groups. This interaction is crucial because it influences the mobility and transformation of pesticides in soil and sediments, potentially affecting their bioavailability and ecological risk. Studies have shown that humic acids can interact effectively with pesticides through sorption or covalent bonding, thereby reducing their mobility and, consequently, bioavailability [89]. Pesticides can bind to humic substances, a major component of soil organic matter, through various mechanisms. Ionic bonding, for instance, involves the attraction between oppositely charged ions, which can help immobilize the pesticide molecules. Charge transfer refers to the sharing or transfer of electrons between the pesticide and the humic substances, leading to a more stable association. Vander Waals forces are weak intermolecular forces that can also contribute to binding, albeit to a lesser extent than other mechanisms [89]. Another important mechanism is ligand exchange, in which a pesticide molecule displaces a weaker ligand bound to a soil particle—typically a water molecule. This exchange strengthens the pesticide’s binding to the soil, potentially affecting its bioavailability. The attraction of non-polar pesticide molecules to the hydrophobic regions of humic substances is called hydrophobic adsorption. This process affects the distribution of pesticides in the soil and is therefore particularly important for those that are difficult to dissolve in water [90,91].

In contrast, partitioning describes the distribution of a pesticide between the pore water and the soil solid phase. This process is controlled by the compound’s hydrophobicity and the amount of organic carbon in the soil. Together, these binding mechanisms control how easily pesticides move through the soil, whether they can contaminate groundwater, and whether or not plants and microbes can absorb them [92].

The sorption capacity of humic acid varies depending on the structural properties of the pesticides; for instance, ionic substances like 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA) exhibit high percentage uptake due to their strong affinity for ionic substances. Conversely, nonionic carbamates such as carbofuran and carbaryl are sorbed to a lesser extent, suggesting that the interaction mechanisms differ for these types of pesticides [93,94]. The sorption process is not only significant for the immobilization of pesticides but also for their desorption, which is a measure of the potential for these compounds to be released back into the environment. For example, humic acid showed noticeable desorption only for 2,4-D, whereas the other studied compounds were released at 4.4–10.8% of the dose sorbed [94]. This suggests that once pesticides are adsorbed by humic acid, they are likely to remain bound, reducing the risk of leaching into water bodies. Understanding pesticide adsorption by humic acid is not only fundamental for predicting the environmental fate of these chemicals but also for developing remediation strategies. For instance, biochar, another organic sorbent, has been compared to humic acid in terms of its ability to adsorb pesticides. The research indicates that biochar, due to its moderately hydrophobic character, preferentially attracts nonionic pesticides with relatively high log p values and low water solubility, unlike the behavior of humic acid [94]. These findings underscore the importance of considering the chemical nature of both the sorbent and the sorbate when assessing the environmental impact of pesticide use and developing sustainable agricultural practices.

The main chemical properties of HAs that appear to influence the adsorption of many organic xenobiotics in soil, including pesticides, are their composition of carboxyl and phenolic hydroxyl groups, the concentration of organic free radicals, and the degree of aromaticity and humification [94,95]. The molecular properties of pesticides are crucial to numerous mechanisms. According to some studies, humic acids have a lower affinity for neutral than for charged pesticides [96]. HAs absorb mostly polar and moderately water-soluble substances through a variety of binding mechanisms, such as charge-transfer, ionic, and hydrogen bonding [97]. Hydrophobic binding is proposed as the preferred mode of interaction for poorly water-soluble nonpolar compounds with hybrid anchors (HAs) [98]. Each fraction of organic matter has a specific adsorption capacity for a particular pesticide, determined by its structure, functionality, and chemical composition [99,100]. Previous studies have shown that high-aliphatic, low-humified HAs from organic amendments usually bind pesticides via hydrophobic interactions, whereas HAs from well-humified soil prefer chemical binding [101].

7.3. Pesticide Adsorption by Biochar

Typically, pyrolysis (first and second steps) is used to produce biochar from biomass under anaerobic conditions. Other methods for producing a mixture of biochar, bio-oil, and syngas include hydrothermal carbonization, gasification, and pyrolysis. Biochar uses include soil improvement, carbon reduction, water storage, and animal feed. Carbon quanta and activated carbon are two other products made from biochar as a precursor. Both biochar and activated carbon are widely used as adsorbents or fillers in the production of composite materials [102]. Because of its many uses and environmental benefits, biochar, a carbon-rich product made from biomass, is becoming increasingly popular. Pyrolysis, the thermal breakdown of organic material under restricted oxygen conditions, is the process used to produce biochar. This process produces syngas and bio-oil, in addition to biochar, each with specific applications in chemical synthesis and energy production.

The diverse uses of biochar, including boosting plant growth, increasing microbial activity, and enhancing soil fertility, demonstrate its adaptability. All of these uses have been known to improve soil health and agricultural productivity. It can function as a water-retainer due to its porous nature, which is especially helpful in arid areas where water conservation is essential. Additionally, because biochar absorbs atmospheric carbon, it acts as a carbon sink, storing carbon in the soil and reducing greenhouse gas concentrations in the atmosphere. This attribute aligns with global efforts to reduce carbon footprints and promote sustainable practices. To improve animal health and reduce odors and pollutants from animal waste, biochar is added to animal feed. Activated carbon, widely used in water treatment systems due to its increased adsorption capacity, is one of the refined carbon-based materials for which biochar serves as a precursor. Biochar, activated carbon, and carbon dots are all carbon-based materials, but they differ significantly in their production, properties, and applications. Biochar is produced by pyrolysis of biomass and is primarily used to improve soil health due to its ability to improve soil fertility and sequester carbon dioxide. Activated carbon, on the other hand, is a form of carbon that has been processed to have small, low-volume pores that increase the surface area available for adsorption or chemical reactions.

Biochar, a highly porous, carbon-rich material derived from biomass pyrolysis, is gaining recognition for its multifaceted role in environmental management and agriculture. Its extensive specific surface area and porosity create a vast network of adsorption sites, making it an effective medium for capturing and immobilizing a range of pollutants. When incorporated into soil, biochar acts as a sponge for pesticides and persistent organic pollutants, sequestering them away from plants and groundwater. This not only mitigates the risk of soil pollution but also reduces the bioavailability of harmful substances, thereby protecting plant health and food safety [103,104]. Peng et al. [105] investigated the influence of biochar on the distribution of imidacloprid within a plant–soil–groundwater system. The study revealed that, relative to the control group, the concentrations of imidacloprid in plants, soil, and groundwater in the biochar treatment group significantly decreased from 3.78%, 36.4%, and 1.76% to 0.57%, 13.4%, and 0.11%, respectively. These findings suggest that biochar enhances the immobilization of imidacloprid by modifying soil physicochemical properties.

The remediation effects of biochar and modified biochar on soils contaminated with endosulfan and thiacloprid were studied [106,107]. Similarly, the environmental behavior of atrazine, nicosulfuron, and oxyfluorfen in soil following the addition of biochar and modified biochar was evaluated by Wang [108] and Wu et al. [109]. Their findings indicated that incorporating biochar enhanced soil adsorption capacity for pesticides and increased the diversity and abundance of soil microbial populations. During pesticide adsorption, biochar adsorbs pesticide molecules on its surface through physical and chemical adsorption, without undergoing chemical reactions, demonstrating its stability [110].

The pesticides that biochar can remove are diverse, reflecting the wide range of compounds used in agricultural practices (Figure 7). These structures often contain aromatic rings, halogens, and various functional groups that determine their reactivity and environmental persistence. Biochar’s porous structure, surface area, and functional groups, such as hydroxyls and carboxyls, contribute to its adsorption capabilities. The interaction between biochar and pesticides typically involves physical adsorption, in which pesticide molecules adsorb to the biochar surface, and chemical adsorption, in which covalent bonds form between the pesticide and the biochar. This dual mechanism enables biochar to effectively immobilize pesticides, reducing their bioavailability and potential environmental toxicity. Production conditions, such as pyrolysis temperature and biomass type, can influence the efficacy of biochar in pesticide removal. Additionally, the soil’s physicochemical properties, the presence of other organic matter, and the specific chemical structure of the pesticide also play significant roles in the remediation process.

7.4. Pesticide Adsorption by Cellulose and Carboxymethyl Cellulose

Adsorption of pesticides by cellulose and carboxymethylcellulose (CMC) is an important area of research, especially in the development of materials for environmental remediation. As a natural polymer, cellulose has inherent properties that facilitate the adsorption of organic compounds, while CMC, a cellulose derivative, is modified to possess carboxymethyl groups that improve its water solubility and adsorption capacity [111]. The high adsorption capacity of biomass derived from cellulose waste is due to the chemical structures of its components, i.e., cellulose, hemicellulose, and lignin [112]. Waste biomass is often referred to as cellulosic biomass because cellulose makes up most of its composition. This advanced technology, known as additive manufacturing, is used to develop a variety of materials [112,113]. While lignin is an aromatic natural polymer produced by phenylpropanoid monomeric units [114,115], distinct rings form hemicelluloses and cellulose macromolecules [116,117,118]. The compositions and percentages of these biopolymers vary by species and geographic region. Since the contents of lignin and cellulosic waste biomass have multiple benzene rings and active OH groups (at C2, C3, and C6) on the cellulose, they can contribute through hydrogen bonds, π-π interactions, and van der Waals interactions between them. Pesticides from contaminated water to remove the benzene rings of biomass and pesticides [116,119].

The potential of cellulose derivatives from various cellulose sources, including carboxymethylcellulose (CMC) and cellulose acetate (CA), activated carbons (ACs), and biochar, was investigated. It was examined whether cellulose nanocomposites, microcrystalline cellulose (MCC), and simple fibrous materials, whether unprocessed or functionalized, can effectively remove pesticides from wastewater [116]. Due to the high moisture absorption tendency, low dimensional and UV stability, and low stability to alkalis and acids exhibited by cellulose biomass, cellulose fibers, and their derivatives, researchers worldwide have worked to functionalize and improve the surface of cellulose derivatives, and their ability to extract pesticides from contaminated water [120,121].

The modification of cotton fibers using diethylenetriamine represents a significant advancement in the field of material science, particularly in the development of specialized textiles with enhanced properties. The process, as outlined, involves a two-step chemical modification in which 6-chlorodeoxycellulose serves as an intermediate. This compound is then aminated with diethylenetriamine, introducing amine groups that alter the fiber’s properties. The subsequent addition of copper particles imbues the fibers with the ability to adsorb specific compounds, such as linuron, from their environment. This capability is particularly valuable in applications that require the selective removal of contaminants from water. The research by Ghali et al. [122] underscores the potential of these modified fibers for environmental cleanup. Further expanding on this concept, the functionalization of cotton and wool fabrics with polyethyleneimine polymers, as reported by Abdelhameed et al. [123], opens new avenues for the removal of organophosphorus pesticides from aqueous solutions. These pesticides are known for their persistence and toxicity, posing significant challenges to environmental health. The use of PEI polymers in textile treatment enhances the fabrics’ adsorption capacity, making them more effective at capturing and isolating these harmful substances. This innovation not only has implications for environmental remediation but also for the development of protective clothing that can safeguard individuals in agricultural or industrial settings from pesticide exposure.

7.5. Nanoadsorption for Pesticide Removal

Nanoadsorption is a cutting-edge approach that utilizes nanoparticles to remove pesticides from water, offering a promising solution to a significant environmental challenge. The increasing use of pesticides in agriculture has led to widespread contamination of water bodies, posing serious health risks to humans and wildlife. Nanoparticles, due to their small size and high surface area, can adsorb and remove these harmful substances more efficiently than traditional methods. Recent studies have highlighted the effectiveness of various nanomaterials, such as carbon nanostructures, metal nanoparticles, and metal–organic frameworks, in capturing and removing organophosphate pesticides from water. These materials can interact with pesticides via electrostatic interactions, hydrogen bonding, and π-π stacking, mechanisms that contribute to the high adsorption capacity of nanoparticles.

Furthermore, the physicochemical properties of nanoadsorbents can be tailored to target specific pesticides, enhancing the selectivity and efficiency of the removal process. The development of sustainable nanoadsorbents from biochar and other plant-derived materials also presents an eco-friendly alternative to conventional adsorbents, which often suffer from poor recyclability and disposal issues. As the field advances, integrating nanotechnology into water treatment systems has the potential to revolutionize how we address pesticide contamination, ensuring cleaner water and a healthier environment. The ongoing research and development in this area are critical for implementing nanoadsorption techniques in real-world applications, and it is an exciting time for scientists and environmentalists working towards a future of clean, safe water [124].

The effectiveness of nanotechnology in removing pesticides from various environmental matrices is well documented. The use of nanoparticles to detect and eliminate organochlorine and organophosphorus pesticides is well established [124,125]. Titanium dioxide (TiO₂) and zero-valent iron nanoparticles have demonstrated exceptional adsorption properties and photocatalytic efficiency in the degradation of organochlorine compounds and their toxic metabolites. Through adsorption, nanomaterials can efficiently remove a variety of pesticides from water bodies. The affinity of nanomaterials for target molecules increases when organic compounds are bound to functional groups [126,127].

By facilitating oxidation and reduction reactions, the mobile electrons and positive surface charges of nanoparticles help break down pollutants. Successful conversion and detoxification of pesticides has been documented using metal nanoparticles, bimetallic nanoparticles, metal oxide nanoparticles, and carbon nanotubes [128,129]. Detection of pesticides has also been enabled by the development of enzyme-based biosensors [130].

8. Conclusions

In conclusion, human exposure to pesticide residues from agrochemicals, primarily through food and water consumption, and increasing environmental pollution underscore the urgency of effective pollutant management. Addressing pesticide contamination requires innovative, sustainable strategies to safeguard public health and environmental integrity. Wastewater treatment plants (WWTPs) vary in efficiency; some pesticides persist or transform into more toxic by-products during treatment. Therefore, developing alternative methods for effective pesticide removal is imperative. Green adsorbents, derived from agricultural and industrial by-products, offer a cost-effective, abundant, and environmentally friendly solution for soil and water purification. Their high pollutant-binding capacity, selectivity, and affinity make them promising candidates for widespread application. Ongoing research focuses on optimizing the scalability and real-world application of these adsorbents for large-scale remediation efforts. The integration of green adsorbents offers a sustainable approach to mitigating pesticide contamination, protecting public health, and supporting environmental sustainability. This review highlights recent developments in various classes of green adsorbents, including examples and available literature data on their effectiveness. Recent advancements in green adsorbent strategies, such as pesticide removal using spent mushroom substrate, biochar, and nanoadsorption, have been discussed. The main goal is to highlight the importance of adopting green adsorbents as viable alternatives to conventional treatment methods, and to underscore their potential to revolutionize wastewater management and mitigate the adverse impacts of pesticide residues on ecosystems and human well-being.