Search Results (876)

The sustainable valorization of marine shell waste as functional additives for geopolymer materials represents a promising strategy for developing multifunctional materials for environmental remediation. In this study, metakaolin-based geopolymers were modified with calcium-rich particles obtained by calcination of five marine shell species (Chamelea gallina, Mya arenaria, Mytilus edulis, Pecten maximus, and Rapana venosa) under identical synthesis conditions to evaluate the influence of shell mineralogy on the structural, textural, adsorption, and antibacterial properties of the resulting composites. The materials were comprehensively characterized by Fourier transform infrared spectroscopy in attenuated total reflectance (ATR-FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and nitrogen adsorption–desorption (BET/BJH) analyses. Functional performance was assessed through methylene blue (MB) adsorption experiments, adsorption kinetic modeling, and antibacterial tests against Escherichia coli (E. coli). ATR-FTIR and XRD analyses confirmed the formation of a stable amorphous geopolymer network containing residual crystalline phases together with shell-derived calcium carbonate, predominantly as calcite or aragonite depending on shell origin. The incorporation of shell-derived particles modified the pore architecture of the geopolymers. GP-SJ exhibited the highest BET specific surface area (94.30 m² g⁻¹) and the most developed mesoporous structure. Among the investigated formulations, GP-RP showed the most favorable overall combination of functional properties under the investigated conditions, exhibiting the highest methylene blue removal efficiency (63.97%) and experimental adsorption capacity at 160 min (9.60 mg g⁻¹), together with a comparatively high reduction in recoverable E. coli colonies during preliminary antibacterial screening. The combined structural and functional analyses demonstrate that the environmental performance of shell-modified geopolymers cannot be predicted from a single parameter such as BET surface area or calcium content alone, but results from the synergistic interaction between mineralogical composition, particle dispersion, pore accessibility, and matrix compactness. Under the investigated conditions, these findings provide evidence for proposed structure–property correlations under the investigated conditions and suggests that shell-derived calcium particles act as microstructural regulators of geopolymer matrices, providing a basis for the further development of sustainable multifunctional materials for simultaneous dye removal and bacterial reduction in wastewater treatment. Full article

The presence of plastic marine litter (ML) and its associated negative environmental impacts have been documented in all existing parts of the marine and coastal environment, including protected areas (PAs). The aim of this study is to identify gaps in existing research related to the lack of standardization of methods and scarcity of detailed information on the characteristics of ML found. This systematic review provides current information on the methods and results of studies focused on the problem of ML and microplastic (MP) pollution on the coastlines of PAs. This study was conducted in accordance with the PRISMA 2020 statement. It is based on 28 peer-reviewed publications from four online databases and search platforms: ScienceDirect, PubMed, MDPI and Google Scholar, published between 2021 and 2025. The presence of ML was detected in all 28 studies (100%), confirming the relevance of the problem along the coastlines of PAs, even those far from industrial centers. The reported densities, however, ranged from a few fragments of litter to several thousand items. Plastic was the most common material of ML among all the peer-reviewed publications analyzed. Most of the studies showed that polyethylene (PE) fragments were the dominant type of microplastic (MP) found in coastal environments of PAs. However, despite the growing research on this topic, the problems of lack of detailed information and standardization of methods remain unresolved. This review emphasizes the importance of applying unified methods and conducting long-term monitoring experiments in future research. Full article

Atmospheric PM₁₀ was investigated across Campania, southern Italy, during August 2024 to assess its elemental composition and probable sources. In total, 132 daily samples were collected at six ARPAC sites representing harbor, traffic, industrial, school, and regional-background conditions. PM₁₀ concentrations ranged from 2 to 72 µg m⁻³, with the highest and lowest values recorded at the traffic and background sites, respectively. Elemental composition was determined by particle-induced X-ray emission and complemented by SEM–EDS. Elemental-based Positive Matrix Factorization (PMF) resolved six profiles, tentatively assigned to S-rich secondary aerosol, Cl-rich marine aerosol, mixed combustion/industrial emissions, Cu-rich traffic emissions, Ca–Sr-rich road dust, and Pb–Zn-rich waste combustion. At the industrial site, the three anthropogenic profiles together represented 74% of the apportioned mass. Traffic-related, marine, and S-rich secondary aerosol represented 49%, 65%, and 30% at the traffic, harbor, and background sites, respectively. SEM–EDS identified representative irregular S–K-rich and Ca-rich particles, crystalline Na–Cl-rich particles, and fine spherical metal-rich particles. Conditional probability function and trajectory analyses indicated local and regional influences, including a possible secondary sulfate contribution from the Mount Etna region. As the PMF analysis relied exclusively on elemental data, these source assignments should be regarded as indicative rather than definitive. Full article

The discharge of metal-rich mining effluents and waste into marine environments represents a significant environmental challenge, with impacts extending from coastal to deep-sea ecosystems. This study presents a scoping review conducted in accordance with PRISMA-ScR guidelines to identify, classify, and synthesise evidence on the effects of large-scale mining waste disposal in coastal and marine settings. Searches of Web of Science, Scopus, and relevant grey literature sources yielded 147 eligible publications from an initial dataset of 563 records. The evidence reviewed enabled the identification of 81 distinct impacts systematically grouped into nine primary categories spanning physical, geotechnical, hydrodynamic, geochemical, biological, ecological, and socio-economic dimensions. Marine tailings deposits behave as dynamic systems that facilitate the transport of contaminants beyond disposal sites through processes such as plume dispersion, sediment resuspension, turbidity currents, and porewater exchange. Geochemical reactions and geotechnical failures can increase environmental vulnerability, a risk further exacerbated by ocean warming, acidification, and changing circulation patterns. Beyond highlighting the need for precautionary, integrated, and adaptive management approaches, this review provides the first comprehensive global inventory of impact categories and assessment factors associated with marine mining waste disposal, establishing a reference framework to guide future research, environmental management, regulatory evaluations, and industry decision-making. Full article

In recent years, plastic litter in marine ecosystems has emerged as a global concern. Consequently, efforts to control, mitigate, and remove micro- and macroplastics from marine systems have intensified. In order to thoroughly analyze this topic, the present work provides a comprehensive overview of various strategies aimed at reducing plastic waste pollution spread in marine areas. Based on this, worldwide regulations limiting single-use plastic (SUP) products and microplastics in health care products were discussed. Further attention was also paid to bioplastic production as a potential alternative to non-degradable ones, with particular attention to their different degradability rates in various environmental compartments. Finally, strategies for the reduction in plastic pollution were specifically analyzed through a review of plastic litter collection/removal systems from beaches and the marine environment as well as different waterways. According to the above-mentioned aspects, this work highlights the significance of marine plastic litter pollution and provides support for the identification and selection of effective strategies for the mitigation of the impact of such litter on the environment. Full article

Processing crabs for meat generates large quantities of waste (secondary raw materials). Internal organs are typically discarded, which causes environmental problems and highlights the need for the integrated use of marine bioresources. The red king crab hepatopancreas is an excellent source of various proteins, including enzymes with different substrate specificities. In this study, an improved method was developed for producing a complex enzyme preparation from the hepatopancreas of red king crab (Paralithodes camtschaticus) harvested by a large industrial enterprise in the Barents Sea. Physicochemical analysis revealed high protein (16%) and lipid (10%) contents in the hepatopancreas. The developed method involves centrifugation to rapidly separate the fat fraction from the aqueous protein fraction and acetone washing to remove residual lipids. The use of low temperatures (0 to 5 °C) for autolysis is justified to prevent a decrease in enzymatic activity of the final preparation. Obtained enzyme preparations were analyzed for protease, collagenase, and endo- and exochitinase activity. They exhibited high proteolytic (A_prot = 252 μmol Tyr⋅g⁻¹⋅min⁻¹), exochitinolytic (A_exo = 0.94 μmol GlcNAc⋅g⁻¹⋅min⁻¹), and collagenolytic (A_col = 210 mIU·mg⁻¹) activities. It has been shown that enzymatic activities depend on seasonality (winter and summer) of the crab catch, which is due to differences in the physiological processes of crabs during seasonal cyclical temperature changes in their natural habitat. The developed process flowsheet for producing an enzyme preparation from the red king crab hepatopancreas can be used as the basis for technology by enterprises engaged in the comprehensive processing of marine bioresources. Full article

The accumulation and persistence of plastic waste have made microbial plastic biodegradation an important topic in pollution control, environmental remediation, and sustainable materials management. This study combines a mini-review with bibliometric analysis to link mechanistic understanding with global research trends in microbial plastic biodegradation from 2000 to 2025. The mini-review summarizes polymer weathering and fragmentation, microbial colonization and biofilm formation, extracellular depolymerization or oxidative chain cleavage, uptake and intracellular catabolism of plastic-derived intermediates, physiological regulation, ecological interactions, and potential applications in bioremediation and upcycling. Bibliographic records were retrieved from the Web of Science Core Collection and analyzed using bibliometrix, VOSviewer, CiteSpace, and SCImago Graphica. A total of 2959 publications were identified. Publication output increased markedly, especially after 2018, reaching 617 publications in 2025; cumulative citations reached 31,373. China, India, and the United States were the leading contributors. Journal and keyword analyses showed strong links among environmental science, polymer science, microbiology, biotechnology, and engineering. Highly cited publications mainly focused on plastic biodegradability, biodegradable polymers, engineered PET depolymerization, polyethylene degradation, and microbial or enzymatic degradation mechanisms. Keyword evolution revealed a shift from material-oriented topics, including polymer blends, poly(vinyl alcohol), polyesters, morphology, mechanical properties, composites, and polyhydroxyalkanoates, toward degrading enzymes, cutinase-like enzymes, plastic-degrading strains, microbial colonization, fungi, and marine environmental degradation. Overall, microbial plastic biodegradation has evolved from material-centered biodegradability evaluation toward a mechanism-oriented and environment-oriented interdisciplinary field. Full article

It is crucial to develop advanced fluorescence sensing platforms for precise detection of metal pollutants in environmental monitoring. However, traditional fluorescent probes are often limited by aggregation-caused quenching (ACQ). In contrast, clusterization-triggered emission (CTE) probes, based on non-conjugated systems, exhibit excellent photostability by relying on spatial clusterization to restrict molecular motion. Crab shells, an abundant aquatic waste, are rich in chitin (20–30%). Following deacetylation, chitin is converted into chitosan, a biocompatible and biodegradable biopolymer with excellent potential for chemical modification. In this study, a novel chitosan-based CTE fluorescent probe (CS-FA) was synthesized via a facile cross-linking condensation reaction between chitosan and formaldehyde. This process successfully restricts intramolecular motion and promotes the tight clustering of electron-rich heteroatoms, thereby activating the CTE mechanism. The resultant CS-FA probe exhibits strong and stable blue fluorescence and demonstrates high selectivity and sensitivity toward Fe³⁺ in aqueous media. In the concentration range of 10–100 µM, the fluorescence intensity decreases linearly with the Fe³⁺ concentration, yielding a competitive limit of detection (LOD) of 0.52 µM. Mechanistically, the specific coordination between Fe³⁺ and the cross-linked polymer provides a dominant non-radiative decay pathway, leading to significant fluorescence quenching. Ultimately, this work not only proposes an innovative strategy for constructing sensitive and biomass-derived probes for Fe³⁺ monitoring but also broadens the high-value utilization pathways of marine waste, thereby providing a sustainable waste-to-resource strategy. Full article

Construction and demolition waste remains a major sustainability challenge, while the use of mixed recycled aggregates in structural concrete is still limited due to concerns over variability, water absorption, and durability. This study investigates whether washed mixed recycled coarse aggregate can partially or fully replace natural coarse aggregate in concrete for seawall block applications. The recycled aggregate was characterized and then upgraded through simple washing and grading to remove fines and contaminants. Concrete mixes incorporating 0%, 5%, 1780, 20%, 50%, and 100% recycled aggregate replacement were produced and tested for workability, compressive strength, flexural strength, density, and water absorption under both tap-water and saline curing conditions. The results demonstrate that washing significantly improves aggregate quality, enabling compressive strength comparable to the reference mix at replacement levels up to approximately 20%. Higher replacement levels led to reductions in workability, flexural strength, and density; however, performance remained within technically acceptable limits. Overall, the findings indicate that washed mixed recycled coarse aggregate is a viable material for seawall concrete, supporting more circular and sustainable use of construction and demolition waste in marine infrastructure. Full article

Fish processing generates substantial quantities of by-products, creating important management and valorization challenges, particularly in insular regions. This study provides a first-order quantification of fishery and aquaculture wastes in the Madeira archipelago. The methodology combined a feed-based mass-balance model, targeted data collection, stakeholder analysis, and valorization assessment. Organic matter (OM) released from marine cage aquaculture was estimated at approximately 851.6 t yr⁻¹ (dry weight), while fish by-products from processing activities in factories and retail stores generated approximately 938 t yr⁻¹ (wet weight). These waste streams differ substantially in their physical characteristics and management pathways, with aquaculture producing diffuse environmental discharges and processing activities generating concentrated and potentially recoverable residues. Structured stakeholder interviews identified limited scale and insufficient raw materials, logistics and labor as the main factors affecting valorization initiatives. A comparative multi-criteria assessment further evaluated potential valorization strategies based on environmental performance and economic viability. Despite the generation of organic residues, the results suggest that effective valorization is constrained less by total waste generation than by biomass fragmentation, logistical limitations, and restricted economies of scale, emphasizing the need for integrated circular management approaches. A combined approach, integrating farm usage of decaying OM from cage systems and locally supported valorization strategies is required to transition towards a more resource-efficient production system. Full article

The growing demand for sustainable protein sources is driving the development of marine by-product utilization. Mussel byssus, which is currently discarded during mussel processing, could be used to produce collagen-derived biomaterials. This study tested the hypothesis that ultrasound-assisted extraction could improve collagen recovery by comparing its efficiency with that of conventional pepsin-assisted extraction. The latter is time-consuming and inefficient. While conventional pepsin-assisted extraction achieved a higher collagen-derived material recovery yield (10.7%) than ultrasound-assisted extraction (5.1%), ultrasound reduced the extraction time from 72 h to just two hours. Fourier transform infrared spectroscopy (FTIR) confirmed that the characteristic amide bands were preserved in the collagen-derived material extracted using both methods. Differential scanning calorimetry (DSC) revealed thermal transitions at 59 °C for pepsin-assisted extracts and 57 °C for ultrasound-assisted extracts, indicating comparable thermal stability. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed predominantly low-molecular-weight protein fragments (<20 kDa), suggesting the presence of collagen-derived peptides rather than intact native collagen. Overall, ultrasound-assisted extraction preserved the structural and thermal characteristics of the extracted material while drastically reducing processing time. This highlights its potential as a rapid, environmentally friendly and sustainable technology for the valorization of mussel byssus within a circular bioeconomy. Full article

Astaxanthin is a high-value xanthophyll carotenoid known for its antioxidant activity and potential health benefits that is becoming increasingly important in food, nutraceutical, and health-related applications. In recent years, growing interest in natural bioactive compounds has driven research on astaxanthin sources, bioactivity, functional properties, and its applications in food, nutraceutical, and health-related subjects. This review synthesizes current knowledge on the natural sources, extraction methods, stability, biological activities, and food applications of astaxanthin, with particular attention to challenges and opportunities relevant to food systems. The review discusses a food science-oriented perspective that connects molecular properties and biological functionality with processing stability, formulation strategies, and regulatory considerations. Special emphasis is given to emerging extraction and encapsulation methods, interactions with complex food matrices, and technological limitations affecting bioavailability and consumer acceptance. The review also highlights recent advances in sustainable production, valorization of marine by-products, and the potential role of astaxanthin in personalized nutrition and precision health frameworks. These approaches contribute to circular food systems by reducing food-processing waste, replacing synthetic antioxidants with natural alternatives, and supporting more resource-efficient and environmentally sustainable food production. Full article

The instability of marine low-sulfur fuel oil caused by asphaltene precipitation poses significant operational challenges in the shipping industry. This study systematically investigates the dispersing effects of biodiesel derived from three different feedstocks—palm oil, waste cooking oil (WCO), and microalgae oil—and their individual fatty acid methyl ester components on asphaltenes extracted from VLSFO. Biodiesel was selected as a dispersant due to its renewable nature, polar ester functional groups, and variable unsaturation levels, which enable favorable interactions with asphaltene molecules through hydrogen bonding and π-π stacking. Using UV–Visible spectrophotometry, the dispersion performance was quantitatively evaluated under various conditions including dispersant concentration, temperature, storage time, and molecular structural characteristics. The results demonstrate that microalgae oil biodiesel exhibits the most superior asphaltene dispersion capability among the three biodiesels, with a dispersion improvement index of 35% at 12 g/L, compared to 28% and 22% for waste cooking and palm oil biodiesels. Optimal performance is achieved at 80 °C, where the asphaltene concentration increases by 68% relative to the control, and remains stable within the first 10 days of storage but deteriorates significantly after 30 days due to oxidative degradation. Among individual FAME components, the dispersion effectiveness increases with alkyl chain length from C10 to C20, with the latter reaching a 30% improvement index. Functional group polarity plays a critical role, with carboxylic acid exhibiting a 45% improvement at 14 g/L, substantially outperforming alcohol at 32% and ester at 28%. The degree of unsaturation further enhances dispersion, as the improvement index rises progressively from 20% for saturated methyl stearate to 42% for tri-unsaturated methyl linolenate, representing a 2.1-fold increase. Dynamic light scattering (DLS) measurements confirm that biodiesel addition reduces asphaltene particle size from the micrometer range of 2 to 5 μm down to submicron levels of 200 to 500 nm, while microscopic observations reveal inhibited aggregation. These findings provide theoretical foundations for biodiesel application in marine fuel systems. Full article

The relationship between rheological properties and printability in 3D-printed recycled concrete incorporating calcined oyster shell powder (COSP) remains insufficiently understood. The unstable rheological behavior and insufficient buildability of 3D-printed recycled concrete limit its application in digital construction. In this study, the COSP, a marine solid waste-derived functional powder, was incorporated into 3D-printed recycled concrete to improve rheological behavior and printability. The effects of different COSP contents on rheological properties and structure build-up were assessed. In addition, MIP, XRD, and SEM analyses were used to clarify the underlying regulation mechanism. The results showed that COSP significantly improved the rheological properties of fresh paste. As the COSP content increased from 0% to 5%, the static yield stress, dynamic yield stress, and thixotropic recovery degree increased from 1703 Pa to 4561 Pa, from 92 Pa to 375 Pa, and from 56% to 87%, respectively. Meanwhile, the structural deformation rate decreased from 12.3% to 6.37%, corresponding to a reduction of approximately 48%. An appropriate COSP content also improved the mechanical properties, with the flexural strengths in the X and Y directions increasing to 5.17 MPa and 4.99 MPa, respectively, and the compressive strengths increasing to 26.04 MPa and 25.48 MPa, respectively. The microscopic performance results indicated that COSP refined the pore structure, promoted the formation of hydration products, and improved compactness. This study offers preliminary evidence for improving the printability of 3D-printed recycled concrete, while addressing the urgent environmental challenge of marine solid waste utilization and enhancing the economic feasibility and production efficiency of 3D-printed concrete. Full article

Polyhydroxybutyrate (PHB), a microbial polyester belonging to the polyhydroxyalkanoate (PHA) family, has emerged as one of the most promising biodegradable alternatives to conventional petroleum-derived plastics. Its inherent marine biodegradability (typically mineralizing within months depending on material geometry and ambient temperature), biocompatibility, and ability to be synthesised from renewable and waste-derived feedstocks position PHB as a key candidate for supporting the transition towards a circular bioeconomy. Despite these advantages, widespread commercial adoption remains limited by high production costs, processing challenges, and performance constraints relative to established commodity plastics and competing biopolymers. This review critically evaluates the current state of PHB development from the perspective of sustainable commercialisation. Key aspects discussed include microbial biosynthesis pathways, feedstock selection, upstream fermentation strategies, downstream recovery technologies, and technoeconomic considerations influencing industrial feasibility. The intrinsic thermal, mechanical, and degradation characteristics of PHB are examined alongside modification approaches such as copolymerisation, polymer blending, plasticisation, and composite reinforcement that have been developed to overcome certain inherent physical–mechanical properties, narrow processing windows, and limited functional performance. Furthermore, characterisation methodologies, environmental degradation behaviour, and emerging industrial applications are assessed within the context of market requirements and sustainability objectives. Particular emphasis is placed on identifying the interconnected technical and economic bottlenecks that continue to hinder large-scale deployment, including feedstock costs, fermentation scalability, downstream processing expenses, and material performance trade-offs. By integrating advances across the entire PHB value chain, this review highlights current opportunities, remaining challenges, and future priorities required to enable the sustainable and economically viable commercialisation of PHB-based materials. Full article