Degradation Of Microplastics Research Articles

Microplastics from face masks: Unraveling combined toxicity with environmental hazards and their impacts on food safety.

Microplastics (MPs) refer to tiny plastic particles, typically smaller than 5mm in size. Due to increased mask usage during COVID-19, improper disposal has led to masks entering the environment and releasing MPs into the surroundings. MPs can absorb environmental hazards and transfer them to humans and animals via the food chain, yet their impacts on food safety and human health are largely neglected. This review summarizes the release process of MPs from face masks, influencing factors, and impacts on food safety. Highlights are given to the prevalence of MPs and their combined toxicities with other environmental hazards. Control strategies are also explored. The release of MPs from face masks is affected by environmental factors like pH, UV light, temperature, ionic strength, and weathering. Due to the chemical active surface and large surface area, MPs can act as vectors for heavy metals, toxins, pesticides, antibiotics and antibiotic resistance genes, and foodborne pathogens through different mechanisms, such as electrostatic interaction, precipitation, and bioaccumulation. After being adsorbed by MPs, the toxicity of these environmental hazards, such as oxidative stress, cell apoptosis, and disruption of metabolic energy levels, can be magnified. However, there is a lack of comprehensive research on both the combined toxicities of MPs and environmental hazards, as well as their corresponding control strategies. Future research should prioritize understanding the interaction of MPs with other hazards in the food chain, their combined toxicity, and integrating MPs detection and degradation methods with other hazards.

Microplastics and their interaction with microorganisms in Bosten Lake water

Microplastic pollution in inland freshwater lakes, formed from melting ice, atmospheric precipitation, and groundwater, remains under-researched. This study examines microplastic (MPS) presence and distribution in Bosten Lake and their interaction with microorganisms. We employed a Confocal Raman spectrometer to identify MPS types and 16S rRNA high-throughput sequencing to analyze microbial diversity and composition. In May, the lake's average microplastic concentration was 108.20 particles per liter (PCS/L), decreasing to 21.67 PCS/L by October. Transparent and yellow fibrous microplastics, predominantly 0.2–0.5 mm in size, were most common. Key microplastics in May included PEEK (27%), PMMA (25%), and PET (9%), while October saw a prevalence of PET (35%), PS (13%), and PA (9%). Higher microplastic concentrations correlated with reduced microbial diversity. In May, the high microplastic concentration group (MH) showed increased Planctomycetota, while in October, Patescibacteria and Bacteroidota rose significantly in the high plastic group (OH), known for microplastic degradation. MH also had a higher abundance of Cryptomycota compared to OH. Functional analysis indicated that MH had more genes related to bisphenol, benzene, and chlorine compounds, whereas OH had genes linked to methane, nitrogen, and organic matter degradation. Microplastic concentrations peaked near the lake inlet and tourist areas, affecting microbial quantity, diversity, structure, and function. This research enhances our understanding of MPS distribution and environmental microbial shifts in similar settings, providing essential data for environmental management strategies at Bosten Lake.

Enhanced degradation of polyethylene terephthalate (PET) microplastics by an engineered Stenotrophomonas pavanii in the presence of biofilm

Polyethylene terephthalate (PET) microplastics pose significant environmental and human health risks due to their resistance to degradation and accumulation in ecosystems. In this study, we engineered Stenotrophomonas pavanii JWG-G1, a robust biofilm-forming bacterium, to overexpress the PET hydrolase (DuraPETase) for PET microplastics degradation at ambient temperature. Nine endogenous PET hydrolases were identified through genome sequencing of S. pavanii, and were successfully expressed in Escherichia coli BL21(DE3). Among them, hydrolase Est_B achieved 100% degradation of bis(2-hydroxyethyl) terephthalate (BHET) at an initial concentration of 0.23 mg/mL at 30 °C within 4 h, identifying it as a novel BHETase. However, the PET degradation performance of all endogenous PET hydrolases was inferior to that of DuraPETase. The engineered strain overexpressing DuraPETase demonstrated a significant enhancement in PET degradation, achieving a 38.04 μM total product release of high-crystallinity PET microplastics after 30 days at 30 °C. The degradation extent was greater than that of low biofilm-forming engineered strains, attributing to the aggregation of DuraPETase on the PET surface in the presence of biofilm. Additionally, this engineered strain also maintained PET degradation activity across various water environments and demonstrated effectiveness in degrading other polyester plastics. This is the first report demonstrating that an engineered strain of Stenotrophomonas species is capable of simultaneously secreting exogenous hydrolase and degrading polyester microplastics, representing a novel approach in the development of engineered bacteria with potential applications in bioreactor systems and environmental remediation.

Engineering sulfur doped flower-like BiOBrxI1-x solid solutions for strengthened photocatalytic activities

In this work, a series of S-doped BiOBrxI1-x solid solutions are fabricated via a simple and rapid solvothermal process. Various characterization techniques are used to thoroughly investigate the as-fabricated solid solutions. Interestingly, compared to BiOBrxI1-x, S-doped BiOBrxI1-x solid solutions exhibit a loose flower-like structure comprised of thinner nanosheets, which contributes to the enhanced specific surface area, as assessed by Brunauer-Emmett-Teller analysis. Furthermore, S-doped BiOBrxI1-x solid solutions reveal boosted visible-light response and rapid separation of photoinduced charge carriers, as verified by optical, photo-electrochemical, and electrochemical analysis. These lead to superior visible-light photocatalytic properties of S-doped BiOBrxI1-x solid solutions on pollutant removal, N2 fixation, and microplastic degradation. The crystal structure, morphology, and photocatalytic stability of the prepared samples are demonstrated by comparing their X-ray diffraction patterns, scanning electron microscopy images, and photocatalytic degradation as well as nitrogen reduction performance before and after six catalytic recycles. Furthermore, based on Density Functional Theory simulations, significant modifications in the band gap of BiOBrxI1-x solid solutions occur as iodine content increases while sulfur doping further refines the electronic features, which aligns with the results of Tauc plots. This research proves that S doping is a viable strategy for modulating the electronic structures of BiOBrxI1-x solid solutions for improving its photocatalytic performance, and provides a new route for optimizing the bandgaps of semiconductors via the non-metallic doping strategy.

Enhancing the degradation of microplastics through combined KMnO4 oxidation and UV radiation

The pervasive issue of microplastics in aquatic environments presents a formidable challenge to traditional water treatment methodologies, including those utilizing KMnO4. This study pioneers advanced oxidation processes (AOPs) method aimed at improving the degradation of PE microplastics by employing a dual treatment strategy that combines KMnO4 oxidation with UV irradiation. Detailed analysis of the surface modifications and chemical functional groups of the treated PE microplastics revealed the establishment of Mn-O-Mn linkages on their surfaces. Weight reductions of 3.9%, 4.9%, and 7.5% were observed for the KMnO4/UVA, KMnO4/UVB, and KMnO4/UVC treatments over seven days, respectively. The emergence of carboxyl and hydroxyl groups played a crucial role in accelerating the degradation process. Notably, the combined application of UVC rays and KMnO4 resulted in the most effective degradation of PE microplastics observed in our study. The process significantly enhanced the formation of MnO2 particles from KMnO4 oxidation, with concentrations ranging from 0.036 to 0.070 mM for KMnO4/UVA, 0.066–0.097 mM for KMnO4/UVB, and 0.086–0.180 mM for KMnO4/UVC. Furthermore, the influence of varying pH levels, KMnO4 concentrations, and different water sources on the degradation efficacy was investigated. The pivotal role of free radicals and reactive manganese species in promoting the degradation of PE microplastics was identified. A comparative evaluation with treatments solely utilizing KMnO4 or UV light highlighted the enhanced effectiveness of the combined approach, demonstrating its potential as an efficient solution for reducing microplastic contamination in aquatic systems.

Enhancing Microplastic Degradation through Synergistic Photocatalytic and Pretreatment Approaches.

Microplastics (MPs) pollution has emerged as a pressing environmental concern in recent years. Owing to their minute dimensions, conventional plastic remediation approaches are inadequate for addressing the challenges posed by MPs. Herein, spherical (BOC-S) and nanosheet (BOC-N) BiOCl photocatalysts were prepared and applied to the degradation of poly(ethylene terephthalate) (PET) MPs after hydrothermal pretreatment. The results indicated that the degradation efficiency of pretreated PET MPs using BOC-S and BOC-N photocatalysts was 8.8 and 6.9 times that of the unpretreated MPs under the same conditions. Comparative experiments confirmed the excellent performance of the photocatalysis-pretreatment system. The creation of pores on the surface of pretreated PET MPs facilitates the entry of active substances into the interior to cause damage, while the enhancement of hydrophilicity and specific surface area facilitates the contact between the catalyst and PET MPs, thus increasing the degradation efficiency. Free radical trapping experiments revealed that hydroxyl radicals (·OH) produced by photocatalysis had the greatest influence on the degradation performance of pretreated PET MPs. Finally, a possible photocatalytic degradation mechanism for PET MPs was proposed. This research offers a novel perspective on MPs degradation, providing valuable insights for advancing the efficacy of the process.

Tandem microplastic degradation and hydrogen production by hierarchical carbon nitride-supported single-atom iron catalysts

Microplastic pollution, an emerging environmental issue, poses significant threats to aquatic ecosystems and human health. In tackling microplastic pollution and advancing green hydrogen production, this study reveals a tandem catalytic microplastic degradation-hydrogen evolution reaction (MPD-HER) process using hierarchical porous carbon nitride-supported single-atom iron catalysts (FeSA-hCN). Through hydrothermal-assisted Fenton-like reactions, we accomplish near-total ultrahigh-molecular-weight-polyethylene degradation into C3-C20 organics with 64% selectivity of carboxylic acid under neutral pH, a leap beyond current capabilities in efficiency, selectivity, eco-friendliness, and stability over six cycles. The system demonstrates versatility by degrading various daily-use plastics across different aquatic settings. The mixture of FeSA-hCN and plastic degradation products further achieves a hydrogen evolution of 42 μmol h‒1 under illumination, outperforming most existing plastic photoreforming methods. This tandem MPD-HER process not only provides a scalable and economically feasible strategy to combat plastic pollution but also contributes to the hydrogen economy, with far-reaching implications for global sustainability initiatives.

Efficient photocatalytic degradation of microplastics by constructing a novel Z-scheme Fe-doped BiO2−x/BiOI heterojunction with full-spectrum response: Mechanistic insights and theory calculations

Recently, microplastics (MPs) have garnered significant attention as a challenging emerging pollutant to address. Here, a full-spectrum light-driven Fe-doping BiO2−x/BiOI (FBI) Z-scheme heterojunction was constructed for efficiently degrading MPs in waters. Compared with BiO2−x, Fe doping BiO2−x, and BiOI, the optimal photocatalyst (40-FBI) can cause deep cracks in the polyethylene terephthalate (PET) within 10 h under the irradiation of full-spectrum light. Meanwhile, FT-IR characterization revealed that the absorption peak intensities of the C-O group, CO group, -CH stretching vibration, and -OH group on the MPs surface gradually increased with degradation time. A series of experiments and theory calculations revealed that the introduction of Fe creates impurity levels, accelerating the separation of photo-generated carriers and reducing the work function of BiO2−x, thereby enhancing the transport of photo-generated carriers between Z-scheme heterojunctions. This study offers a valuable idea for designing an efficient photocatalyst by simultaneously introducing ion doping and constructing heterojunctions for enhancing MPs degradation.

Isolation and Identification of Four Strains of Bacteria with Potential to Biodegrade Polyethylene and Polypropylene from Mangrove.

With the rapid growth of global plastic production, the degradation of microplastics (MPs) has received widespread attention, and the search for efficient biodegradation pathways has become a hot topic. The aim of this study was to screen mangrove sediment and surface water for bacteria capable of degrading polyethylene (PE) and polypropylene (PP) MPs. In this study, two strains of PE-degrading bacteria and two strains of PP-degrading candidate bacteria were obtained from mangrove, named Pseudomonas sp. strain GIA7, Bacillus cereus strain GIA17, Acinetobacter sp. strain GIB8, and Bacillus cereus strain GIB10. The results showed that the degradation rate of the bacteria increased gradually with the increase in degradation time for 60 days. Most of the MP-degrading bacteria had higher degradation rates in the presence of weak acid. The appropriate addition of Mg2+ and K+ was favorable to improve the degradation rate of MPs. Interestingly, high salt concentration inhibited the biodegradation of MPs. Results of scanning electron microscopy (SEM), atomic force microscopy (AFM), and Fourier-transform infrared spectroscopy (FTIR) indicated the degradation and surface changes of PP and PE MPs caused by candidate bacteria, which may depend on the biodegradation-related enzymes laccase and lipase. Our results indicated that these four bacterial strains may contribute to the biodegradation of MPs in the mangrove environment.

Research progress on photocatalytic degradation of microplastics by graphitic carbon nitride

Research progress on photocatalytic degradation of microplastics by graphitic carbon nitride

Impact of high-pressure columbite phase of titanium dioxide (TiO2) on catalytic photoconversion of plastic waste and simultaneous hydrogen (H2) production

Photoreforming is a sustainable photocatalytic process that degrades plastic waste while simultaneously producing hydrogen (H2) from water. However, this process has received limited attention due to the scarcity of effective catalysts capable of both plastic degradation and H2 production, such as titanium dioxide (TiO2). In this study, an active catalyst is developed by stabilizing the high-pressure orthorhombic phase of TiO2, known as columbite, using a high-pressure torsion (HPT) method. This material effectively degrades polyethylene terephthalate (PET) plastic under light, converting it into valuable organic compounds such as formic acid, terephthalate, glycolic acid, and acetic acid. Additionally, it produces a significant amount of H2. The findings show that the high-pressure orthorhombic phase, especially in the presence of oxygen vacancies, enhances catalytic H2 production and microplastic degradation by increasing light absorption, reducing electron-hole recombination, and generating hydroxyl radicals. These results highlight the substantial potential of modified high-pressure TiO2 photocatalysts in simultaneously addressing the plastic waste crisis and the demand for H2 fuel.

Bio-templated micromotors for simultaneous adsorption and degradation of microplastics

Microplastic contamination has increasingly become a focus of public attention due to its ubiquity on earth. As the appearance of microplastics in the human body has raised great concerns about their effects on human health, it is imperative to develop efficient technologies to remove microplastics. In this work, taking advantage of the hollow structure of kapok fibers and low-cost MnO2 catalyst, a tubular self-driven micromotor was synthesized for simultaneous adsorption and degradation of microplastics. Functionalization with polydopamine endowed the micromotors with the ability of on-the-fly capture of microplastics. Attributed to the enhanced diffusion caused by the self-propulsion, the propelled micromotors exhibited an adsorption efficiency 3.41 times that of static micromotors, achieving a removal ratio of 73.57 % in 1 mg/mL polystyrene microspheres dispersion in 30 min without external stirring, which poses a prospective approach for in-situ removal of microplastics. In addition, coupling with photocatalytic CdS, the formed CdS/PDA heterojunction could generate photo-induced charge carriers, which together with the active species produced through the Fenton-like processes contributed to the degradation of microplastics. This work proposed a new platform for the simultaneous adsorption and degradation of microplastics and may provide implications for the removal of microplastics in the environment.

Degradation of Microplastics by Zinc Oxide Nanoparticles Synthesized Using Piper longum Leaf Extract.

Background: The environmental hazards posed by microplastics have drawn considerable concern due to their buildup in ecosystems. Microplastics accumulate in human saliva, skin, and hair. Developing effective technology for managing and degrading microplastics remains a substantial challenge. In a concerted attempt to save the ecology, this study explores the photocatalytic breakdown of common microplastics like polystyrene (PS) microspheres and polyethylene (PE) using green-synthesized zinc oxide nanoparticles (ZnO NPs) under UV light exposure. Aim: To synthesize and characterize zinc oxide nanoparticles prepared using the extract of the leaves of Piper longumand qualitatively assess the photocatalytic degradation potential of the nanoparticles under light microscopy. Material and Methods:A fresh extract of P. longum leaves was used as a reducing agent to synthesize zinc oxide nanoparticles. Fourier transform infrared (FTIR) analysis, X-ray diffraction (XRD) analysis, UV-Vis spectra analysis, and scanning electron microscopy (SEM) analysis were performed to characterize the nanoparticles. Microplastics were isolated from the saliva of 50 healthy patients and were purified and filtered. In a six-well microtiter plate, 0.5 μg of varying concentrations of nanoparticles were added. After fixing with 15% formaldehyde, microplasticswere subjected to UV irradiation for 2 hours with different concentrations of ZnO nanoparticles (25, 50, 75,and 100 µg). Custom photoreactors activated the photocatalysts to degrade the microplastic pollutants. The six-well microtiter plate was viewed under 40x magnification in a light microscope to observe microplastic morphology after 24 hours of degradation. Results: The FTIR spectrum showed distinct peaks at 890.51 cm⁻¹, indicating the involvement of C-N in-plane vibrations of amino acids. XRD analysis revealed three distinct diffraction peaks at 31.68°, 34.39°, and 36.33°, corresponding to the hexagonal wurtzite structure of ZnO nanoparticles. The synthesized ZnO nanoparticles ranged from 50 to 90 nm in size, viewed at 100x magnification on SEM. The highest degradation of microplastics was observed ataZnO NPconcentration of 100 µL, with the ZnO NPs 50-90 nm in size. Conclusion: Zinc oxide nanoparticles synthesized using Piper longum leaf extract effectively degrade microplastics, with the highest degradation observed at a 100 µL concentration of ZnO nanoparticles and optimal degradation occurring at a concentration of 75 µL.

Critical review on unveiling the toxic and recalcitrant effects of microplastics in aquatic ecosystems and their degradation by microbes.

Production of synthetic plastic obtained from fossil fuels are considered as a constantly growing problem and lack in the management of plastic waste has led to severe microplastic pollution in the aquatic ecosystem. Plastic particles less than 5mm are termed as microplastics (MPs), these are pervasive in water and soil, it can also withstand longer period of time with high durability. It can be broken down into smaller particles and can be adsorbed by various life-forms. Most marine organisms tend to consume plastic debris that can be accumulated easily into the vertebrates, invertebrates and planktonic entities. Often these plastic particles surpass the food chain, resulting in the damage of various organs and inhibiting the uptake of food due to the accumulation of microplastics. In this review, the physical and chemical properties of microplastics, as well as their effects on the environment and toxicity of their chemical constituents are discussed. In addition, the paperalso sheds light on the potential of microorganisms such as bacteria, fungi, and algae whichplaya pivotal role in the process of microplasticsdegradation. The mechanism of microbial degradation, the factors that affect degradation, and the current advancements in genetic and metabolic engineering of microbes to promote degradation are also summarized. The paper also provides information on the bacterial, algal and fungal degradation mechanism including the possible enzymes involved in microplastic degradation. It also investigates the difficulties, limitations, and potential developments that may occur in the field of microbial microplastic degradation.

Distinct microbial community structures formed on the biofilms of PLA and PP, influenced by physicochemical factors of sediment and polymer types in a 60-day indoor study

Microplastics (MPs) are colonized by biofilm-forming microbes. Biodegradable plastics, popular replacements for traditional plastics, still have unknown biofilm formation characteristics. We conducted a 60-day indoor experiment, where sediment was exposed to traditional MPs (polypropylene, PP), biodegradable MPs (polylactic acid, PLA), and glass beads (GLASS). The microbial communities in the MPs-biofilm were analyzed using high-throughput sequencing. Results indicated that Proteobacteria was the dominant phylum on all substrates, followed by Actinobacteria, and Firmicutes. At the genus level, the majority of microorganisms colonizing PP possessed nitrification and denitrification capabilities, while the dominant bacteria on PLA were capable of degrading lignin, cellulose and carbon metabolism. The genus Sphingomonas, a promising bacteria capable of degrading biodegradable microplastics, was particularly discovered on the PLA biofilm, meanwhile, bacterial colonization of PLA indirectly increased the potential for human transmission of pathogens. Redundancy analysis revealed that the pH and moisture significantly affected the bacterial communities. Pearson correlation heatmap indicated that the abundance of the majority of dominant bacterial genera of two MPs biofilms is negatively correlated with the physicochemical parameters of sediment (pH, moisture, TN, TP), except for salinity. The microbial communities associated with PP and PLA exhibited distinct differences caused by the combined effects of changes in physicochemical properties of sediment and different material substrates. This study provides further evidence of the significant selective features exhibited by microbial colonization on these two MPs when exposed to the same source community, offering insights into the exploration of promising bacteria for MPs degradation.

The first spatio-temporal study of the microplastics and meso–macroplastics transport in the Romanian Danube

BackgroundTransport, accumulation, and degradation of microplastics (MiPs) in the aquatic environment represent a significant concern to the researchers and policy-makers, due to the detrimental impact on biota and human health through food ingestion. Although consistent investigations and research data are available worldwide, comparing the results is still challenging due to the need for more regulations regarding the sampling methods, analysis, and results reporting. The European regulatory efforts include studies on the MiPs transport in the western basin of the Danube River developed with active nets-based multipoint sampling methods from suspended sediments and proposed for standardization. In this context, the present study aimed to address for the first time the transport of MiPs in the Romanian sector of the Danube, starting after entering the country (Moldova Veche) and before the formation of the Danube Delta (Isaccea).ResultsThe multipoint nets sampling procedure facilitated the collection of suspended sediments in the water columns as deep as 0.0–0.6 and 3.0–3.6 m depths and near riverbed sediments (autumn 2022 sampling) during an extensive spatio-temporal study from spring 2022 until spring 2023. The estimate of the maximum annual transport of 46–51 and 93–100 t·y−1 for MiPs and total (micro–meso–macroplastics) MPs at Moldova Veche was based on 135 collected and processed samples using 2021 water flow data. Polyethylene (58–69%) and polypropylene (21–33%) were the main polymer components in the separated fragments, foils, microfibers, and different colors spheroids of MiPs ( < 5 mm), and the foils and fibers of meso–macroplastics (5–100 mm). Advanced investigations highlighted various microstructural degradations of the plastic fragments at the micro- and nanoscale and attached minerals (clays) and heavy metals.ConclusionThis paper presents the first comprehensive data set for microplastic annual transport in the "Low Danube", filling the need for a complete transport assessment in one of the most significant European rivers. 4–5 times lower values were measured before the entrance to the Danube Delta than those from Moldova Veche. The investigations should continue, including flooding events, and the sampling points should be expanded to deeper water column layers during all the campaigns for further validation.Graphical

Marine plankton community and net primary production responding to island-trapped waves in a stratified oligotrophic ecosystem

The oligotrophic Adriatic Sea is characterized during a typical summer by low productivity caused by strong water column stratification, which inhibits vertical mixing and nutrient supply to the euphotic zone. These conditions can be disrupted by transient physical forcing, which enhances nutrient fluxes and creates localized hotspots of relatively high net primary production. In this study, plankton abundance and diversity were investigated in relation to the physical forcing and nutrient concentrations in an area affected by island-trapped waves (ITWs) near Lastovo Island (Adriatic Sea). The episodic ITW events resulted in enhanced uplift and vertical excursion of the thermocline, marked by anomalously higher nutrient concentrations and a corresponding increase in net primary production in the thermocline layer. Physicochemical properties explained 11.7 % (p = 0.002) of the variability in micro- and nanophytoplankton and 88.9 % (p = 0.001) in the picoplankton community. A significant response to the ITW phenomenon in the plankton community composition (p = 0.001) was observed for bacterioplankton. Among the identified amplicon sequence variances, primary producers were scarce and mainly represented cyanobacteria (Synechococcus strain CC9902), stramenopiles (Pelagomonas), and chlorophytes (Ostreococcus). The remaining amplicon sequence variances were assigned to the classes Copepoda, parasitic fungi (Meyerozyma spp.), mixotrophic dinoflagellates (family Peridiniales, mostly the genus Blastodinium), and parasitic Ciliophora (Scuticociliata). Bacterial ecological functions corresponded to chemoheterotrophic, degradation, and fermentation processes, whereas samples collected after the most intense ITW episode also showed abundant bacteria linked to microplastic degradation and parasitosis. These results highlight the ecological role of localized physical phenomena in enhancing nearshore primary productivity and fine shifts in plankton taxa in oligotrophic systems.

Abundance of microplastics in Cisadane river - Indonesia

Abstract Microplastics have become a serious threat to the aquatic environment, water treatment facilities, and riverside residents because they are persistent. Microplastics generally come from plastic waste produced by human and industrial activities that enter the rivers. In this study, the Cisadane River was studied for microplastic presence. Sampling was conducted at 11 points along the Cisadane River from the upstream (Muria Jaya) to the downstream (Teluk Naga). Samples were taken using a 200-mesh plankton net and then analyzed using a digital microscope for the microplastic’s presence, sizes, and shapes. Furthermore, material identification was conducted using a Raman Spectroscopy Microscope to determine the material type of microplastic in the samples. According to the result, the Cisadane River contains microplastics of various shapes and sizes. The result shows the abundance of microplastics of 0.8-9.6 particles/m3 0.8-26.4 particles/m3 in fibers and fragments, respectively. Microplastics in the form of fragments are the most dominant form. The size of microplastics varies from 65 to 4,932 μm for fibers and 23 to 2,444 μm for fragments. These differences are due to primary and secondary microplastic degradation rates through weathering, abrasion, mechanical disintegration, photolysis, and microbiological activity. The colors of microplastics found were blue, brown, cream, red, black, and transparent, with transparent being the most dominant color. The material types found were polyethylene terephthalate (PET) and polypropylene (PP).

Potential improvement in the mechanical performance and thermal resistance of geopolymer with appropriate microplastic incorporation: A sustainable solution for recycling and reusing microplastics

The accumulation of microplastics (MPs) has been a major threat to the natural environment and human health. However, incineration and landfilling may not be appropriate for the management of MPs. This paper evaluated the feasibility of incorporating MPs with diverse dimensions (50 to 500 μm) and contents (2.5 % to 10 %) into geopolymer cured under different temperatures (40 and 80 °C). The compressive (fc) and flexural strength (ff) after curing and thermal exposure (200 to 600 °C) were determined. When cured at 40 °C, fc and ff decreased with percentages of MPs incorporated. By contrast, when cured at 80 °C, the addition of 2.5 % MPs increased fc and ff by up to 33 % (from 52.2 to 69.4 MPa) and 18 % (from 8.2 to 9.7 MPa), depending on MPs’ sizes. The XRD and TGA results suggested that the observed increases in mechanical properties can be attributed to the formation of more calcium alumino (silicate) hydrates (C-(A)-S-H gels) induced by the incorporation of a small quantity of MPs (2.5 %). The SEM images also showed better adhesion between MPs and geopolymeric products when cured under 80 °C, potentially inhibiting crack development. After being exposed to evaluated temperatures (200 and 400 °C), fc of the specimens with 2.5 % MPs and cured at 80 °C was higher than that without MPs. The fc dropped dramatically due to the degradation of MPs between 400 and 600 °C. The increase in strength and heat resistance (up to 400 °C) of MPs-incorporated geopolymer cured under 80 °C indicated the potential recycling and reuse of MPs for geopolymer materials.

Efficient degradation and mineralization of polyethylene terephthalate microplastics by the synergy of sulfate and hydroxyl radicals in a heterogeneous electro-Fenton-activated persulfate oxidation system

The presence of polyethylene terephthalate (PET) microplastics (MPs) in waters has posed considerable threats to the environment and humans. In this work, a heterogeneous electro-Fenton-activated persulfate oxidation system with the FeS2-modified carbon felt as the cathode (abbreviated as EF-SR) was proposed for the efficient degradation of PET MPs. The results showed that i) the EF-SR system removed 91.3 ± 0.9 % of 100 mg/L PET after 12 h at the expense of trace loss (< 0.07 %) of [Fe] and that ii) dissolved organics and nanoplastics were first formed and accumulated and then quickly consumed in the EF-SR system. In addition to the destruction of the surface morphology, considerable changes in the surface structure of PET were noted after EF-SR treatment. On top of the emergence of the O-H bond, the ratio of C-O/C=O to C-C increased from 0.25 to 0.35, proving the rupture of the backbone of PET and the formation of oxygen-containing groups on the PET surface. With the verified involvement and contributions of SO4•- and •OH, three possible paths were proposed to describe the degradation of PET towards complete mineralization through chain cleavage and oxidation in the EF-SR system.