Adsorption of phenanthrene and its monohydroxy derivatives on polyvinyl chloride microplastics in aqueous solution: Model fitting and mechanism analysis

Effect of chlorination and ultraviolet on the adsorption of pefloxacin on polystyrene and polyvinyl chloride

During the water treatment process, chlorination and ultraviolet (UV) sterilization can modify microplastics (MPs) and alter their physicochemical properties, causing various changes between MPs and other pollutants. In this study, the impact of chlorination and UV modification on the physicochemical properties of polystyrene (PS) and polyvinyl chloride (PVC) were investigated, and the adsorption behavior of pefloxacin (PEF) before and after modification was examined. The effect of pH, ionic strength, dissolved organic matter, heavy metal ions and other water environmental conditions on adsorption behavior was revealed. The results showed that PS had a higher adsorption capacity of PEF than PVC, and the modification increased the presence of O-containing functional groups in the MPs, thereby enhancing the adsorption capacity of both materials. Chlorination had a more significant impact on the physicochemical properties of MPs compared to UV irradiation within the same time period, leading to better adsorption performance of chlorination. The optimal pH for adsorption was found to be 6, and NaCl, sodium alginate and Cu2+ would inhibit adsorption to varying degrees, among which the inhibition caused by pH was the strongest. Chlorination and UV modification would weaken the inhibitory effect of environmental factors on the adsorption of PEF by MPs. The main mechanisms of adsorption involved electrostatic interaction and hydrogen bonding. The study clarified the effects of modification on the physicochemical properties of MPs, providing reference for subsequent biotoxicity analysis and environmental protection studies.

Polyamide 6 microplastics as carriers led to changes in the fate of bisphenol A and dibutyl phthalate in drinking water distribution systems: The role of adsorption and interfacial partitioning

Microplastics (MPs) co-exist with plastic additives and other emerging pollutants in the drinking water distribution systems (DWDSs). Due to their strong adsorption capacity, MPs may influence the occurrence of additives in DWDSs. The article investigated the occurrence of typical additives bisphenol A (BPA) and dibutyl phthalate (DBP) in DWDSs under the influence of polyamide 6 (PA6) MPs and further discussed the partitioning of BPA/DBP on PA6s, filling a research gap regarding the impact of adsorption between contaminants on their occurrence within DWDSs. In this study, adsorption experiments of BPA/DBP with PA6s and pipe scales were conducted and their interaction mechanisms were investigated. Competitive adsorption experiments of BPA/DBP were also carried out with site energy distribution theory (SEDT) calculations. The results demonstrated that PA6s might contribute to the accumulation of BPA/DBP on pipe scales. The adsorption efficiencies of BPA/DBP with both PA6s and pipe scales were 26.47 and 2.61 times higher than those with only pipe scales. It was noteworthy that BPA had a synergistic effect on the adsorption of DBP on PA6s, resulting in a 26.47 % increase in DBP adsorption. The article provides valuable insights for the compounding effect of different types of additives in water quality monitoring and evaluation.

Effect of Biofouling on the Sorption of Organic Contaminants by Microplastics

Microplastics in the aquatic environment are susceptible to colonization by surrounding microorganisms, which form biofilms over the microplastic's surface. These biofilm-laden microplastics can then interact with a diverse array of contaminants. In the present study, biofilms were grown on microplastics in a laboratory setting using Pseudomonas aeruginosa as a model biofilm-forming bacterium for periods of 5 to 15 days. The sorption of three organic compounds representing different levels of hydrophobicity, namely methylene blue (MB), phenanthrol, and phenanthrene, was used to evaluate the effect of biofilm biomass on the adsorption of organic contaminants to microplastics. The sorption of MB and phenanthrol was found to increase with biofouling time, indicating affinity between these contaminants and the biofilm biomass on the particle. However, the presence of a biofilm did not influence the sorption of phenanthrene on the microplastics. These results suggest that the hydrophobicity of organic contaminants plays a major role in how biofouling of microplastics will influence contaminant sorption by microplastics. For some contaminants, biofilm can enhance the role of microplastics as contaminant vectors. These findings emphasize the need to understand the biomass load on environmental microplastics and the contaminants that associate with it for an accurate representation of the risk associated with microplastics in the environment. Environ Toxicol Chem 2024;43:1973-1981. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Colonization characteristics and surface effects of microplastic biofilms: Implications for environmental behavior of typical pollutants

This paper summarizes the colonization dynamics of biofilms on microplastics (MPs) surfaces in aquatic environments, encompassing bacterial characteristics, environmental factors affecting biofilm formation, and matrix types and characteristics. The interaction between biofilm and MPs was also discussed. Through summarizing recent literatures, it was found that MPs surfaces offer numerous benefits to microorganisms, including nutrient enrichment and enhanced resistance to environmental stress. Biofilm colonization changes the surface physical and chemical properties as well as the transport behavior of MPs. At the same time, biofilms also play an important role in the fragmentation and degradation of MPs. In addition, we also investigated the coexistence level, adsorption mechanism, enrichment, and transformation of MPs by environmental pollutants mediated by biofilms. Moreover, an interesting aspect about the colonization of biofilms was discussed. Biofilm colonization not only had a great effect on the accumulation of heavy metals by MPs, but also affects the interaction between particles and environmental pollutants, thereby changing their toxic effects and increasing the difficulty of MPs treatment. Consequently, further attention and research are warranted to delve into the internal mechanisms, environmental risks, and the control of the coexistence of MPs and biofilms.

Analysis of the Adsorption Behavior of Phenanthrene on Microplastics Based on Two-Dimensional Correlation Spectroscopy

Microplastics (MPs), an emerging pollutant, widely co-occur with polycyclic aromatic hydrocarbons (PAHs) in the environment. Therefore, the interaction between MPs and PAHs has been the focus of much attention in recent years. In this study, three types of MPs, i.e., polypropylene, polystyrene, and poly(vinyl chloride), with the same main chain were selected as the adsorbents, with phenanthrene (PHE) as the representative PAHs. The adsorption mechanisms were explored from the perspective of the molecular spectral level using a combination of Fourier transform infrared spectroscopy (FT-IR) with a two-dimensional correlation technique. The adsorption kinetics results showed that the adsorption of PHE on the three MPs was dominated by chemisorption. However, the FT-IR analysis results indicated that no new covalent bond was created during the adsorption process. Based on the above research, a generalized two-dimensional (2D) correlation spectral technique was employed to investigate the sequence of functional group changes during the adsorption process for different MPs. Furthermore, the hybrid 2D correlation spectral technique explored the effect of side groups attached to the main chain molecules of MPs on adsorption. The results showed that for all three MPs, the functional groups in the side chain have a higher affinity for PHE, which is due to their higher hydrophobicity. This study provides a feasible way to analyze the adsorption of pollutants on MPs, and the results are important for understanding the adsorption interaction between PAHs and MPs in the aquatic environment.

Impacts of microplastic decomposition using heat-activated persulfate on antibiotic adsorption and environmental toxicity

The objective of this study was to determine microplastic-antibiotic interaction by examining how heat-activated persulfate decomposed polyamide adsorbed antibiotics and explored the environmental consequences of treated water. Sulfate radicals roughened the microplastic surfaces, significantly enhancing the adsorption capacity of polyamide. The kinetic and isotherm studies provided confirmation that electrostatic interactions were the primary mechanisms, with a minor contribution from H-bonding, highlighting that antibiotic adsorption was prone to occur, especially on the aged surface. Thermodynamic data indicated that the process was spontaneous and exothermic. The results showed significant negative effects of treated water on seed germination, copepod survival, and cell lines at only a higher concentration, due to a decrease in pH and the potential presence of polymer degradates. Our findings revealed the significant impact of decomposed polyamide on the antibiotic adsorption and offered insight into the potential harm that microplastic-treated water might cause to aquatic and marine ecosystems.

Removal of Cr(VI) by glutaraldehyde-crosslinked chitosan encapsulating microscale zero-valent iron: Synthesis, mechanism, and longevity

Microscale zero-valent iron (mZVI) has shown great potential for groundwater Cr(VI) remediation. However, low Cr(VI) removal capacity caused by passivation restricted the wide use of mZVI. We prepared mZVI/GCS by encapsulating mZVI in a porous glutaraldehyde-crosslinked chitosan matrix, and the formation of the passivation layer was alleviated by reducing the contact between zero-valent iron particles. The average pore diameter of mZVI/GCS was 8.775 nm, which confirmed the mesoporous characteristic of this material. Results of batch experiments demonstrated that mZVI/GCS exhibited high Cr(VI) removal efficiency in a wide range of pH (2-10) and temperature (5-35°C). Common groundwater coexisting ions slightly affected mZVI/GCS. The material showed great reusability, and the average Cr(VI) removal efficiency was 90.41% during eight cycles. In this study, we also conducted kinetics and isotherms analysis. Pseudo-second-order model was the most matched kinetics model. The Cr(VI) adsorption process was fitted by both Langmuir and Freundlich isotherms models, and the maximum Langmuir adsorption capacity of mZVI/GCS reached 243.63 mg/g, which is higher than the adsorption capacities of materials reported in most of the previous studies. Notably, the column capacity for Cr(VI) removal of a mZVI/GCS-packed column was 6.4 times higher than that of a mZVI-packed column in a 50-day experiment. Therefore, mZVI/GCS with a porous structure effectively relieved passivation problems of mZVI and showed practical application prospects as groundwater Cr(VI) remediation material with practical application prospects.

Assessing the adsorption of a diverse range of pharmaceuticals to virgin and aged poly (ethylene terephthalate) microplastics in different environmental matrices

In this study, the adsorption of a mixture of high-consumed drugs onto virgin and aged PET microplastics has been studied for the time ever. The target mixture comprised two anti-inflammatory drugs, diclofenac and ketoprofen, one anti-hypertensive, valsartan, and four common antibiotics, indomethacin, trimethoprim, isoniazid, and metronidazole. Two types of PET MPs (virgin and UV-aged) were used in the experimental procedure. Kinetic studies were conducted, and adsorption isotherms were obtained revealing the possible interactions that take place between adsorbents and adsorbates. Among the studied pharmaceuticals, diclofenac presents the highest uptake due to its hydrophobic nature, while aging appears to induce the adsorption of the drugs in MPs. Factors like pH or the environmental matrix were also evaluated. The results revealed that sorption is pH-dependent, while more complicated matrices like wastewater or seawater exhibit lower uptake than distilled water due to the natural organic matter present or the increased salinity, respectively. Finally, desorption studies were also conducted in three different aqueous solutions examining the pH effect. The desorption of the compounds was higher for diclofenac, followed by valsartan, and ketoprofen. The desorption percentages of antibiotics were quite low.

Effect of ultraviolet aged polytetrafluoroethylene microplastics on copper bioavailability and Microcystis aeruginosa growth

Microplastics (MPs) are ubiquitous in aquatic environments, which can act as carriers to affect the bioavailability of heavy metals. The aging process in the environment changes the physicochemical properties of MPs, thereby affecting their environmental behavior and co-toxicity with other pollutants. However, relevant research is limited. In this study, we compared the properties and Cu2+ adsorption capacity of pristine and aged polytetrafluoroethylene (PTFE) MPs and further explored the influence on copper bioavailability and bio-effects on Microcystis aeruginosa. Aging process induced surface oxidation and cracks of PTFE MPs, and decreased the stability of MPs in water by increasing zeta potential. PTFE MPs had a strong adsorption capacity for Cu2+ and increased the bioavailability of copper to microalgae, which was not affected by the aging process. Pristine and aged PTFE MPs adhered to cyanobacterium surfaces and caused shrinkage and deformation of cells. Inhibition of cyanobacterium growth, photosynthesis and reduction of total antioxidant capacity were observed in the treatment of PTFE MPs. Combined exposure of pristine MPs and Cu2+ had stronger toxic effects to cyanobacterium, and increased Microcystin-LR release, which could cause harm to aquatic environment. Aging reduced the toxic effects of PTFE MPs on microalgae. Furthermore, soluble exopolysaccharide (EPS) content was significantly higher in co-exposure of aged MPs and Cu2+, which could reduce the toxicity to cyanobacterium cells. These results indicate that aging process alleviates the toxicity to microalgae and environmental risks caused by PTFE MPs. This study improves understanding of the combined toxicity of aged MPs and metals in freshwater ecosystems.

Insights into the effect of crystallinity on the sorption of organic pollutants to microplastics

The environmental behavior of microplastics (MPs) has attracted global attention. Research has confirmed that MPs can strongly absorb almost every kind of pollutant and can serve as vectors for pollutant transport. In this research, the sorption isotherms of six organic pollutants with different structure on four virgin plastic particles with different crystallinity were determined. Results indicated that the hydrophobicity (KOW) of organic pollutants and the crystallinity of MPs were the two key factors that affected the sorption process of organic pollutants on MPs. Strong correlations were observed between KOW and the partition coefficient. Hydrophobic partition was one of the major mechanisms regardless of the type of organic chemical (hydrophobic, polar, or dissociable). What is more, the influence of the crystallinity of MPs on the sorption process increased with increasing hydrophobicity of the chemical. Combining this result with analyzing the related literature on the effect of crystallinity, it was concluded that the effect of crystallinity on the sorption of chemicals with strong hydrophobicity was obvious, whereas this effect was negligible for chemicals with weak hydrophobicity. The influence of the crystallinity of MPs on sorption could even exceed the influence of MPs type, so crystallinity should be considered carefully when discussing the sorption capacity of MPs. This study enhances the understanding of the sorption of organic pollutants by MPs.

Cu fate driven by colloidal polystyrene microplastics with pipe scale destabilization in drinking water distribution systems

Microplastics (MPs) and Cu have been detected in drinking water distribution systems (DWDSs). Investigating MP effects on Cu adsorption by pipe scales and concomitant variations of pipe scales was critical for improving the water quality, which remained unclear to date. Therefore, polystyrene microplastics (PSMPs) were adopted for the model MPs to determine their effects on Cu fate and pipe scale stabilization, containing batch adsorption, metal speciation extraction, and Cu release experiments. Findings demonstrated that complexation and electrostatic interactions were involved in Cu adsorption on pipe scales. PSMPs contributed to Cu adsorption via increasing negative charges of pipe scales and providing additional adsorption sites for Cu, which included the carrying and component effects of free and adsorbed PSMPs, respectively. The decreased iron and manganese oxides fraction (45.57 % to 29.91 %) and increased organic fraction (48.51 % to 63.58 %) of Cu in pipe scales when PSMPs were coexisting illustrated that PSMPs had a greater affinity for Cu than pipe scales and thus influenced its mobility. Additionally, the release of Cu could be facilitated by the coexisted PSMPs, with the destabilization of pipe scales. This study was the first to exhibit that Cu fate and pipe scale stabilization were impacted by MPs, providing new insight into MP hazards in DWDSs.

Microplastics and associated polycyclic aromatic hydrocarbons in surface water and sediment of the Bay of Bengal coastal area, India: sources, pathway and ecological risk

In the aquatic environment around the world, microplastic contamination has been a common and ongoing issue. Particularly, the ability of microplastics to absorb persistent organic pollutants (POPs) and then transmit these POPs to aquatic creatures has attracted a lot of interest. A stereomicroscope was used to detect the size, shape, and color of the microplastics (MPs), and Fourier Transform Infrared (FTIR) spectroscopy was used to identify the polymer composition of the MPs. To address MP transit, destiny, and mitigation, a study of MP pollution coastal areas is required. In the current study, MP pollution in the collected sample from upper layer of water and sediment of the Digha and Puri beaches along the coast of BOB was evaluated. The average concentration with SD of MPs observed in water was 5.3 ± 1.8 items/L whereas, in sediments, it was 173.4 ± 40.1 items/kg at Digha beach. The mean MPs abundance in the Puri beach was 6.4 ± 1.7 items/L in the water and 190.4 ± 28.0 items/kg in the sediments. The investigated total 16-PAHs concentrations were 164.7 ng/g, 121.9 ng/g, 73.6 ng/g, and 101.3 ng/g on the MPs surface of foam, fragment, fibers, and film respectively in the studied MPs sample. Smaller than 1000 µm size of MPs are distributed in the largest concentration. Fibers, films, fragments, and foam were the most common shapes of MPs. The molecular structure of MPs in water and sediment samples was analysed i.e., polyesters (PEs), polypropylene (PP), polyethylene (PE), polymethyl methacrylate (PMMA), polystyrene (PS), polyamide (PA), polycarbonates (PC), and polyurethane (PU). The obtained result offers an accurate assessment of the PLI, and the investigated polymer facilitates determining the polymer hazard levels, which emphasizes the risk associated with it.

Microplastics as carriers of toxic pollutants: Source, transport, and toxicological effects

Microplastic pollution has emerged as a new environmental concern due to our reliance on plastic. Recent years have seen an upward trend in scholarly interest in the topic of microplastics carrying contaminants; however, the available review studies have largely focused on specific aspects of this issue, such as sorption, transport, and toxicological effects. Consequently, this review synthesizes the state-of-the-art knowledge on these topics by presenting key findings to guide better policy action toward microplastic management. Microplastics have been reported to absorb pollutants such as persistent organic pollutants, heavy metals, and antibiotics, leading to their bioaccumulation in marine and terrestrial ecosystems. Hydrophobic interactions are found to be the predominant sorption mechanism, especially for organic pollutants, although electrostatic forces, van der Waals forces, hydrogen bonding, and pi-pi interactions are also noteworthy. This review reveals that physicochemical properties of microplastics, such as size, structure, and functional groups, and environmental compartment properties, such as pH, temperature, and salinity, influence the sorption of pollutants by microplastic. It has been found that microplastics influence the growth and metabolism of organisms. Inadequate methods for collection and analysis of environmental samples, lack of replication of real-world settings in laboratories, and a lack of understanding of the sorption mechanism and toxicity of microplastics impede current microplastic research. Therefore, future research should focus on filling in these knowledge gaps.

Atmospheric deposition is an important pathway for inputting microplastics: Insight into the spatiotemporal distribution and deposition flux in a mega city

Microplastics (MPs) refer to plastic particles with a size less than 5 mm, which attracted widespread attention as an emerging pollutant. The monitoring of atmospheric microplastics (AMPs) in a megacity was carried out to study the characteristics and spatiotemporal distribution of AMPs, explore the sources and estimate the deposition flux. The results showed that the annual average abundance of AMPs in Wuhan was 82.85 ± 57.66 n·m-2·day-1. The spatiotemporal distribution characteristics of AMPs show that spring was the highest season, followed by autumn, winter, and summer; the city center was higher than the suburbs. Fiber was the main type of AMPs in Wuhan, followed by fragment, film and pellet. The proportion of AMPs were mainly small (<0.5 mm) and medium (0.5-1.0 mm). Transparent and white were the main colors of AMPs, followed by red, brown. A total of 10 types polymers were detected, polyethylene terephthalate (PET) was dominant. There are positive correlations between AMPs and SO2, NO2 in the atmosphere, indicating that they might be influenced by intense human activity. The polycyclic aromatic hydrocarbons (PAHs) and AMPs in spring showed an extremely significant positive correlation (p < 0.05). AMPs might mainly originate from the wear and tear shedding of textiles, the aging of agricultural films and plastic waste based on their polymer types and main uses. The potential geographical sources of AMPs were mainly the surrounding cities. The annual deposition flux of AMPs was about 308 tons if there were no remove processes, which highlighted the importance of atmospheric transport and deposition of MPs. The analysis of the abundance, morphological characteristics and sources of AMPs can provide data support and reference for mega-cities with high global population activities, or cities in global mid-latitude regions.

Effects of microplastics and phenanthrene on gut microbiome and metabolome alterations in the marine medaka Oryzias melastigma

Plastic pollution of the oceans is increasing, and toxic interactions between microplastics (MPs) and organic pollutants have become a major environmental concern. However, the combined effects of organic pollutants and MPs on microbiomes and metabolomes have not been studied extensively. In the present study, to evaluate whether MPs and phenanthrene (Phe) act synergistically in the guts of marine medaka (Oryzias melastigma), we performed toxicity assessments, 16 S rRNA gene sequencing, and liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyses. Our investigations revealed increased toxicity induced by Phe, as well as disturbances in gut microbiota (known as dysbiosis) when MPs were present. Furthermore, combined exposure to Phe and MPs resulted in greater alterations to microbiota composition and metabolite profiles. Notably, MP exposure was distinctly associated with the abundance of Shewanella and Spongiibacteraceae, while Phe exposure was associated with the abundance of Marimicrobium. Among key microbiota, Marimicrobium and Roseibacillus were significantly correlated with metabolites responsible for coenzyme A and glycerophospholipid metabolism in medaka. These results suggest that interactions between Phe and MPs may have significant effects on the gut microbiota and metabolism of aquatic organisms and underscore the importance of acknowledging the interplay between MPs and contaminants in aquatic environments.

Interaction of fluorene and its analogs with high-density polyethylene microplastics: An assessment of the adsorption mechanism to establish the effects of heteroatoms in the molecule

The threat of microplastics (MP) pollution in aquatic ecosystems can be even more severe for they are able to interact with organic pollutants that can migrate to adjacent environments. The presence of heteroatoms in organic pollutants can directly influence adsorption onto MP. This research evaluated the adsorption of fluorene (FLN) and its heteroatom analogs dibenzothiophene (DBT), dibenzofuran (DBF) and carbazole (CBZ) onto high-density polyethylene (HDPE) MP from residual (HDPEres) and commercial (HDPEcom) sources. The Langmuir isotherm showed a better fit, while DBT showed higher maximum adsorption capacity (19.2 and 15.8 μmol g-1) followed by FLN (13.4 and 11.7 μmol g-1), and DBF (13.5 and 10.3 μmol g-1) to the HDPEcom and HDPEres, respectively, which indicates a direct correlation with the hydrophobicity of the molecules determined by Log Kow. In contrast, CBZ showed no significant interaction with MP, due to their polar characteristic, thus, no kinetic and thermodynamic parameters could be determined. The adsorption process of all PAH was determined to be exothermic and spontaneous, with low temperatures favoring the process. The pseudo-second-order kinetic models have fitted to the adsorption onto both HDPE; intraparticle diffusion was also observed. Computational studies, physical characterization techniques and batch adsorption experiments demonstrated that the mechanism is governed by hydrophobic interactions, with van der Waals forces as a secondary effect in the adsorption of FLN, DBT and DBF onto HDPEres and HDPEcom. Thus, allowing a deeper understanding of the interactions between HDPE MP and FLN as well with its derivatives.

Adsorption of tetracycline on polyvinyl chloride microplastics in aqueous environments

Microplastics (MPs), as carriers of organic pollutants in the environment, have become a growing public concern in recent years. Tetracycline (TTC) is an antibiotic that can be absorbed by MPs and have a harmful effect on human health. Therefore, this study was conducted with the aim of investigating the adsorption rate of TTC onto polyvinyl chloride (PVC) MPs. In addition, the adsorption mechanism of this process was studied using isothermal, kinetic, and thermodynamic models. For this purpose, experimental runs using the Box-Behnken model were designed to investigate the main research parameters, including PVC dose (0.5-2 g/L), reaction time (5-55 min), initial antibiotic concentration (5-15 mg/L), and pH (4-10). Based on the research findings, the highest TTC adsorption rate (93.23%) was obtained at a pH of 10, a contact time of 55 min, an adsorbent dose of 1.25 g/L, and an antibiotic concentration of 10 mg/L. The study found that the adsorption rate of TTC followed the pseudo-second-order and Langmuir models. Thermodynamic data indicated that the process was spontaneous, exothermic, and physical. Increasing ion concentration decreased TTC adsorption, and distilled water had the highest adsorption, while municipal wastewater had the lowest adsorption. These findings provide valuable insights into the behavior of MPs and organic pollutants, underscoring the importance of conducting additional research and implementing measures to mitigate their detrimental effects on human health and the environment.

Microcystins-Loaded Aged Nanoplastics Provoke a Metabolic Shift in Human Liver Cells

Studies concerning the toxicity of pollutant-loaded nanoplastics (NPs) toward humans are still in their infancy. Here, we evaluated the adsorption of microcystins (MCs) by pristine and aged polystyrene nanoplastics (PSNPs), prepared MCs-loaded aged PSNPS (1, 5, 10, 15, and 19 μg/mg), and systematically mapped the key molecular changes induced by aged and MCs-loaded PSNPs to human hepatoblastoma (HepG2) cells. According to the results, MC-LR adsorption is increased 2.64-fold by aging, and PSNP accumulation is detected in HepG2 cells. The cytotoxicity of the MC-LR-loaded aged PSNPs showed a positive relationship with the MC-LR amount, as the cell viability in the 19 μg/mg loading treatment (aPS-MC19) was 10.84% lower than aged PSNPs; meanwhile, more severe oxidative damage was observed. Primary approaches involved stressing the endoplasmic reticulum and reducing protein synthesis that the aged PSNPs posed for HepG2 cells, while the aggravated cytotoxicity in aPS-MC19 treatment was a combined result of the metabolic energy disorder, oxidative damage, endoplasmic reticulum stress, and downregulation of the MC-LR target protein. Our results confirm that the aged PSNPs could bring more MC-LR into the HepG2 cells, significantly interfere with biological processes, and provide new insight into deciphering the risk of NPs to humans.

Interaction behaviors of sulfamethoxazole and microplastics in marine condition: Focusing on the synergistic effects of salinity and temperature

Microplastics and antibiotics are two common pollutants in the ocean. However, due to changes of salinity and temperature in the ocean, their interaction are significantly different from that of fresh water, and the mechanism remains unclear. Here, the interactions of sulfamethoxazole (SMZ) and microplastics were studied at different temperatures and salinities. The saturation adsorption capacity of SMZ in polypropylene (PP), polyethylene (PE), styrene (PS), polyvinyl chloride (PVC), and synthetic resins (ABS) were highest at the temperature of 20 °C, with 0.118 ± 0.002 mg·g^-1, 0.106 ± 0.004 mg·g^-1, 0.083 ± 0.002 mg·g^-1, 0.062 ± 0.007 mg·g^-1 and 0.056 ± 0.003 mg·g^-1, respectively. The effect of temperature reduction is more significant than temperature rise. The intraparticle diffusion model is appropriate to PP, when film diffusion model suited for PS. The salinity has a more significant effect than temperature on different microplastics, due to the electrostatic adsorption and iron exchange. With the increase in salinity from 0.05% to 3.5%, the adsorption capacity of microplastics on SMZ fell by 53.3 ± 5%, and there was no discernible difference of various microplastics. The hydrogen bond and π-π conjugation of microplastics play an important role in the adsorption of SMZ. These findings further deepen the understanding of the interaction between microplastics and antibiotics in the marine environment.

Behavior and mechanisms of ciprofloxacin adsorption on aged polylactic acid and polyethlene microplastics

Microplastics (MPs) and antibiotics are emerging pollutants in aquatic environments. MPs can absorb antibiotics, resulting in compound pollution. Batch adsorption experiments were used to investigate the adsorption behavior of CIP on polylactic (PLA) and polyethlene (PE) under various environmental conditions. After a lengthy aging process, both MPs underwent significant physicochemical changes. The equilibrium adsorption capacities of aged PLA and PE were 0.382 mg/g and 0.28 mg/g, respectively, which increased by 18.06% and 75% compared to pristine PLA and PE. The sorption capacity of MPs increased when the pH of the solution approached the dissociation constant (6.09, 8.74) of CIP. When the salinity of the solution was 3.5%, the adsorption capacity of MPs was reduced by more than 65%. The adsorption capacity of MPs rapidly decreased when 20 mg/L fulvic acid was added. Because norfloxacin (NOR) competes for adsorption sites on the microplastic, CIP adsorption is inhibited. Based on the adsorption models, FTIR, and XPS spectra, we demonstrated that the process was monolayer adsorption, with chemical and physical mechanisms including hydrogen bonding, π-π conjugation, ion exchange, and electrostatic interactions controlling it. Thus, PLA and PE microplastics may be a potential vector for CIP in water, and their interaction is mainly influenced by the physicochemical properties of the MPs and environmental factors.

Adsorption of 2-hydroxynaphthalene, naphthalene, phenanthrene, and pyrene by polyvinyl chloride microplastics in water and their bioaccessibility under in vitro human gastrointestinal system

The interaction of microplastics (MPs) and organic pollutants has recently become a focus of investigation. To understand how microplastic residues affect the migration of organic pollutants, it is necessary to examine the adsorption and desorption behavior of organic pollutants on MPs. In this study, integrated adsorption/desorption experiments and theoretical calculations were used to clarify the adsorption mechanism of 2-hydroxynaphthalene (2-OHN), naphthalene (NAP), phenanthrene (PHE), and pyrene (PYR) by polyvinyl chloride microplastics (PVC-MPs). Based on the phenomenological mathematical models, the rate-limiting step for analyte adsorption onto PVC-MPs was adsorption onto active sites (R² = 0.865-0.995). Except for PHE, analyte adsorption isotherms were well described by the Freundlich model (R² = 0.992-0.998), and adsorption thermodynamics showed that analyte adsorption on PVC-MPs was a spontaneous exothermic process (ΔH⁰ < 0; ΔG⁰ < 0). Based on the order of adsorption efficiency of 2-OHN < NAP < PHE < PYR, which is identical to the competitive adsorption experiment, polycyclic aromatic hydrocarbon (PAH) adsorption on PVC-MPs increased as the aromatic ring number increased and the hydroxyl content decreased. The release of 2-OHN (49 %-52 %) from PVC-MPs into the simulated gastrointestinal environment was greater than that of NAP (5.5 %-5.7 %). Theoretical calculations and adsorption tests indicated that hydrophobic interaction was the primary influence on the adsorption of PAHs and their hydroxylated derivatives by PVC-MPs. These findings improve our understanding of MPs' behavior and dangers as pollutant carriers in the aquatic environment and help us develop recommendations for the pollution control of MPs.

Insights into adsorption mechanisms of nitro polycyclic aromatic hydrocarbons on common microplastic particles: Experimental studies and modeling

Nitro polycyclic aromatic hydrocarbons (NPAHs) and microplastics (MPs) are emerging contaminants that pose a threat to the aquatic ecosystem. Knowledge of the NPAHs and MPs interaction will help the understanding of their fate and risks in natural environment. Here, the adsorption behavior and mechanism of typical NPAHs on microplastics were investigated. The adsorption kinetic and isotherm data showed that the adsorption of NPAHs was controlled by chemical adsorption and hydrophobic partition, because of excellent fit of kinetic and isothermal equations (R² > 0.9). The adsorption capacity (587-744 μg g^-1) was largely dependent on the hydrophobicity of NPAHs. The experiment of environmental factors confirmed the important role of pollutant hydrophobicity, with 1-Npyr of the highest hydrophobicity having the greatest adsorption on MPs (adsorption rate >90%) and less affected by solution pH and ionic strength (changer <5%). In the mixture system, MPs displayed high adsorption capacity for each compound; Interestingly, because compounds with smaller size were easy to occupy the adsorption sites in the pores of MPs, the adsorption of 2-Nflu (724 μg g^-1) was even greater than that of 9-Nant (713 μg g^-1) and 1-Npyr (703 μg g^-1). The model calculation of adsorption also shows that there is surface adsorption and hydrophobic distribution in the adsorption process. The findings provide new insights into the interactions of MPs with organic pollutants in complex environments.

Investigation of the adsorption-desorption behavior of antibiotics by polybutylene succinate and polypropylene aged in different water conditions

Microplastics (MPs) are widely present in aqueous environments and aged by natural components of complex water environments, such as salinity (SI) and dissolved organic matter (DOM). However, the effects of multicondition aging on the physicochemical properties and environmental behavior of MPs have not been completely investigated. In this study, the degradable MP polybutylene succinate (PBS) was used to investigate the environmental behavior of sulfamethoxazole (SMZ) and was compared with polypropylene (PP). The results showed that the single-factor conditions of DOM and SI, particularly DOM, promoted the aging process of MPs more significantly, especially for PBS. The degrees of MP aging under multiple conditions were lower than those under single-factor conditions. Compared with PP, PBS had greater specific surface area, crystallinity, and hydrophilicity and thus a stronger SMZ adsorption capacity. The adsorption behavior of MPs fitted well with the pseudo-second-order kinetic and Freundlich isotherm models, indicating multilayer adsorption. Compared with PP, PBS showed relatively a higher adsorption capacity, for example, for MPs aged under DOM conditions, the adsorption of SMZ by PBS was up to 5.74 mg/g, whereas that for PP was only 3.41 mg/g. The desorption experiments showed that the desorption amount of SMZ on MPs in the simulated intestinal fluid was greater than that in Milli-Q water. In addition, both the original PBS and the aged PBS had stronger desorption capacities than that of PP. The desorption quantity of PBS was 1.23-1.84 times greater than PP, whereas the desorption rates were not significantly different. This experiment provides a theoretical basis for assessing the ecological risks of degradable MPs in complex water conditions.

Occurrence, distribution and risk assessment of microplastics and polycyclic aromatic hydrocarbons in East lake, Hubei, China

The pollution of microplastics (MPs) and polycyclic aromatic hydrocarbons (PAHs) in the environment is a global problem, which has attracted extensive attention of many researchers. In present study, MPs and PAHs are investigated to study the impact of human activities and their possible relationship in China's second largest urban lake, East Lake. The abundance of MPs are 3329.19 ± 2059.26 particles/m³ and 2207.56 ± 1194.04 particles/kg in water and sediment, respectively. MPs are predominantly characterized by fibers, polypropylene (PP) and polyethylene (PE), colorlessness in water and sediment. The abundance of MPs in water with frequent human activities is higher, which is reversed in sediments, indicating that disturbance is not conducive to the enrichment of MPs in sediments. The concentration of 16 PAHs are 36.95 ± 13.76 ng/L and 897.08 ± 232.34 ng/g in water and sediment, respectively. PAHs in water are mainly 2-3-ring, while there are 4-ring PAHs in sediments. The good corresponding relationship between MPs and PAHs indicates that human activities have an important impact on the distribution of pollutants compared to the interaction of pollutants. In addition, the significant positive correlation between lakeshore length and water MPs abundance indicates that surface runoff may be an important source of water MPs. The pollution load index shows that MPs in sediment has reached moderate to severe pollution level, while the water is slightly polluted level. The potential ecological risk assessment results show that more than half of the sediment sites are at dangerous to very dangerous ecological risk level.

Adsorption of typical natural organic matter on microplastics in aqueous solution: Kinetics, isotherm, influence factors and mechanism

With rapid urbanization, microplastics and natural organic matters (NOMs) are ubiquitous in aquatic environment, and microplastics could act as carriers for organic matters in the aqueous solution and may pose a potential risk. In this study, the adsorption behaviors and mechanism of typical NOM, humic acid (HA), on polyvinyl chloride (PVC) and polystyrene (PS) microplastics were investigated. Various influence factors such as solution pH, ions species and concentrations, particle size, and coexisting surfactants were studied. The results suggested that HA adsorption onto PVC and PS was low pH-dependent, and ion species and concentrations have a significant impact on the adsorption capacity. In addition, the particle size of PVC and PS microplastics exhibited a significant correlation with HA adsorption, and the adsorption process was influenced by the surfactant species and concentrations. Moreover, the adsorption behaviors of HA in different real water environments were tested, and UV aging exhibited the opposite effects on adsorption capacity of PVC and PS. Furthermore, the adsorption mechanisms of HA onto PVC and PS were explored, indicating halogen bonding, hydrogen bonding, and π-π interaction play important roles in the adsorption process.

Recent approaches and advanced wastewater treatment technologies for mitigating emerging microplastics contamination - A critical review

Microplastics have been identified as an emerging pollutant due to their irrefutable prevalence in air, soil, and particularly, the aquatic ecosystem. Wastewater treatment plants (WWTPs) are seen as the last line of defense which creates a barrier between microplastics and the environment. These microplastics are discharged in large quantities into aquatic bodies due to their insufficient containment during water treatment. As a result, WWTPs are regarded as point sources of microplastics release into the environment. Assessing the prevalence and behavior of microplastics in WWTPs is therefore critical for their control. The removal efficiency of microplastics was 65 %, 0.2-14 %, and 0.2-2 % after the successful primary, secondary and tertiary treatment phases in WWTPs. In this review, other than conventional treatment methods, advanced treatment methods have also been discussed. For the removal of microplastics in the size range 20-190 μm, advanced treatment methods like membrane bioreactors, rapid sand filtration, electrocoagulation and photocatalytic degradation was found to be effective and these methods helps in increasing the removal efficiency to >99 %. Bioremediation based approaches has found that sea grasses, lugworm and blue mussels has the ability to mitigate microplastics by acting as a natural trap to the microplastics pollutants and could act as candidate species for possible incorporation in WWTPs. Also, there is a need for controlling the use and unchecked release of microplastics into the environment through laws and regulations.

Anchoring ZnO on spinel cobalt ferrite for highly synergic sono-photo-catalytic, surfactant-assisted PAH degradation from soil washing solutions

In this study, the photocatalytic activity of ZnO was effectively improved via its combination with spinel cobalt ferrite (SCF) nanoparticles. The catalytic performance of ZnO@SCF (ZSCF) was investigated in coupling with UV irradiation and ultrasound (US), as a heterogeneous sono-photocatalytic process, for the decontamination of phenanthrene (PHE) from contaminated soil. Soil washing tests were conducted in a batch environment, after extraction assisted by using Tween 80. Several characterization techniques such as XRD, FESEM-EDS, BET, TEM, UV-vis DRS, PL and VSM were utilized to determine the features of the as-prepared catalysts. ZSCF showed an excellent catalytic activity toward degradation of PHE in the presence of US and UV with a significant synergic effect. It was found that more than 93% of PHE (35 mg/L) and 87.5% of TOC could be eliminated by the integrated ZSCF/US/UV system under optimum operational conditions (pH: 8.0, ZSCF: 1.5 g/L, UV power: 6.0 W and US power: 70 W) within 90 min of reaction. After five times of use, ZSCF illustrated good reusability in the decontamination of PHE (87%) and TOC (79%). Quenching tests revealed the contribution of h⁺, HO^• and e^- species during PHE degradation over ZSCF/UV/US and an S-scheme photocatalytic mechanisms was proposed for the possible charge transfer routes under the ZSCF system. This study provides the important role of SCF in enhancing the ZnO photocatalytic activity due to its high performance, easy recovery and excellent durability, which it make an efficient and promising catalyst in environmental clean-up applications.

New insights into the adsorption behavior of thiacloprid at the microfibers/water interface: Role of humic acid

Dissolved organic matter regulates the interaction between microplastics (MPs) and organic pollutants. Here, this paper investigated the effect and mechanism of humic acid (HA) on the adsorption behavior of thiacloprid at two microfibers (MFs)/water interface, and compared the differences in the performance of MFs and pure MPs. The results showed that 10 mg L^-1 HA decreased the adsorption capacity and the partition coefficient K_D of thiacloprid on MFs and pure MPs. Spectral analysis showed that HA could form hydrogen bonds and van der Waals forces with both MPs and thiacloprid, ultimately affecting the adsorption behavior of thiacloprid at MPs/water interface via competitive adsorption and bridging effect. Furthermore, two-dimensional correlation spectroscopy demonstrated that thiacloprid was preferentially adsorbed onto MPs compared with HA. Finally, density functional theory calculation demonstrated that phenolic-OH, -COOH, and alcoholic-OH played critical roles in competing adsorption and bridging effect. This study offers a theoretical foundation for a better comprehension of the adsorption behavior of organic pollutants at the MPs/water interface.

Adsorption behaviors of triclosan by non-biodegradable and biodegradable microplastics: Kinetics and mechanism

Microplastics (MPs) pollution has been becoming serious and widespread in the global environment. Although MPs have been identified as vectors for contaminants, adsorption and desorption behaviors of chemicals with non-biodegradable and biodegradable MPs during the aging process is limited. In this work, the adsorption behaviors of triclosan (TCS) by non-biodegradable polyethylene (PE) and polypropylene (PP), and biodegradable polylactic acid (PLA) were investigated. The differences in morphology, chemical structures, crystallization, and hydrophilicity were investigated after the ultraviolet aging process and compared with the virgin MPs. The results show that the water contact angles of the aged MPs were slightly reduced compared with the virgin MPs. The aged MPs exhibited a stronger adsorption capacity for TCS because of the physical and chemical changes in MPs. The virgin biodegradable PLA had a larger adsorption capacity than the non-biodegradable PE and PP. The adsorption capacity presented the opposite trend after aging. The main adsorption mechanism of MPs relied on hydrophobicity interaction, hydrogen bonding, and electrostatic interaction. The work provides new insights into TCS as hazardous environmental contaminants, which will enhance the vector potential of non-biodegradable and biodegradable MPs.

The effect of adsorption on the fate of colloidal polystyrene microplastics in drinking water distribution system pipe scales

With microplastics (MPs) being continuously found in various environments, the pollution of water supply systems by MPs is receiving increasing attention. As the sediment in drinking water distribution systems (DWDSs), pipe scales act as the interface for complex reactions between bulk water and pipe surfaces. Consequently, the fate of MPs in pipe scales requires exploration, especially colloidal MPs. In this study, MPs were detected in different pipe scale layers, with concentrations of 0.32-3.10 items g^-1. Subsequently, the adsorption interaction mechanisms between pipe scales and colloidal polystyrene microplastics (PSMPs) were investigated through batch adsorption experiments. The findings indicated that pipe scales showed a potential adsorption capacity for PSMPs. The adsorption kinetics and isotherms results demonstrated that the PSMP adsorption process was physically dominant and complicated. van der Waals and electrostatic interactions, hydrogen bonding, and pore filling were the main adsorption mechanisms. These results verify that colloidal MPs can be adsorbed by pipe scales, demonstrating that pipe scales play an essential role in the fate of colloidal MPs in DWDSs and the quality and security of drinking water. The secondary release of MPs from pipe scales is also worthy of attention due to the environmental and health risks.

Impact of simulating real microplastics on toluene removal from contaminated soil using thermally enhanced air injection

This paper investigated the impacts of various real microplastics (MPs), i.e., polyethylene (PE) and polyethylene terephthalate (PET) with different sizes (1000-2000 and 100-200 μm) and different dosages (0.5 and 5% on a dry weight basis), on the toluene removal during the thermally enhanced air injection treatment. First, microscopic tests were carried out to determine the MPs' microstructure and behavior. The PE was mainly a small block, and PET appeared filamentous and sheeted with a larger slenderness ratio. Second, the interactions between MPs and toluene-contaminated soils were revealed by batch adsorption equilibrium experiments and low-field magnetic resonance. The morphological differences and dosage of the MPs impacted soils' total porosity (variation range: 39.2-42.7%) and proportion of the main pores (2-200 μm). Third, the toluene removal during the air injection consisted of compaction, rapid growth, rapid reduction, and tailing stages, and the MPs were regarded as an emerging solid state to affect these removal stages. The final cumulative toluene concentrations of soil-PET mixtures were influenced by total porosity, and those of soil-PE mixtures were controlled by total porosity (influence weight: 0.67) and adsorption capacity (influence weight: 0.33); meanwhile, a self-built comprehensive coefficient of MPs can reflect the relationship between them and cumulative concentrations (correlation coefficient: 0.783).

Quantitative assessment of interactions of hydrophilic organic contaminants with microplastics in natural water environment

The interaction between microplastics (MPs) and hydrophilic organic contaminants (HOCs) in natural water environment has recently raised great public attentions due to the potential toxicity to humans. However, the quantitative assessment is less studied. In this study, the interaction between ciprofloxacin (CIP) and ofloxacin (OFL) (two important HOCs) and virgin and aged polystyrene (PS) was investigated. The aged PS showed higher adsorption rate and capacity than the virgin PS, due to its larger surface area and more O-containing groups. The pH-dependent adsorption of CIP was higher than OFL on both virgin and aged PS; the maximum adsorption for both HOCs occurred at pH 5. The sequential orders of functional groups for the adsorption were discovered according to the study by the 2D correlation Fourier transform infrared spectroscopy. Several mechanisms existed for the interaction: (1) at 3.0 < pH < 5.0, the electrostatic attraction (EA) was inhibited while H-bond (HB) was dominant, accounting for > 60% of the total uptake; (2) at 5.0 < pH < 8.0, the contribution of EA increased to around 50-60% while HB decreased to 30-40%; (3) at 8.0 < pH < 10.0, EA, HB and π-π conjugation caused 30-40%, 25-40% and 20-45% of the total uptake, respectively; (4) at 10.0 < pH < 12.0, π-π conjugation accounted for 90-100%. Notably, higher adsorption of CIP was mainly attributed to the presence of secondary amino groups and its higher pK_a value, correspondingly leading to the additional ordinary HB and negative charge-assisted HB, and EA interactions with PS. This study further provides clear evidences on the risk of MPs and HOCs on humans and aqueous living organisms.

Soil structures and immobilization of typical contaminants in soils in response to diverse microplastics

Microplastics (MPs) accumulation in soil ecosystems has become a worldwide issue. The influence of MPs on soil structures and contaminant transport has not been clearly unraveled. This study conducted soil column experiments covering four different treatments: soil without MPs (CK), soil with 0.5 wt% polyethylene (S+PE), soil with 0.5 wt% polyacrylonitrile (S+PAN), and soil with 0.5 wt% polyethylene terephthalate (S+PET). The interconnections between changes in soil structures and shifts in sorption efficiency for typical hydrophobic organic contaminants (e.g., phenanthrene (PHE)) and heavy metal (e.g., lead (Pb (II)) by soils induced by MPs were explored. MPs-added soils contained fewer macro-aggregates and lower aggregate stability compared to CK. Three MPs, particularly PE, promoted PHE sorption by soils but reduced Pb (II) sorption, which occurred in soils with or without dissolved organic carbon. The comparison between experimental and predicted sorption capacity, as well as the one-point sorption data of different aggregate sizes, showed that such variations in PHE and Pb (II) sorption were related to the shifts in soil aggregates besides from the physical mixture of soils with MPs. This finding is perspective to give an in-depth understanding of the effects of different MPs types on soil micro-environments and transport for contaminants.

Competition adsorption of malachite green and rhodamine B on polyethylene and polyvinyl chloride microplastics in aqueous environment

Microplastics (MPs) will cause compound pollution by combining with organic pollutants in the aqueous environment. It is important for environmental protection to study the adsorption mechanism of different MPs for pollutants. In this study, the adsorption behaviors of malachite green (MG) and rhodamine B (RhB) on polyethylene (PE) and polyvinyl chloride (PVC) were studied in single systems and binary systems, separately. The results show that in single system, the adsorptions of between MPs for pollutants (MG and RhB) are more consistent with the pseudo-second-order kinetics and Freundlich isotherm model, the adsorption capacity of both MPs for MG is greater than that of RhB. The adsorption capacities of MG and RhB were 7.68 mg/g and 2.83 mg/g for PVC, 4.52 mg/g and 1.27 mg/g for PE. In the binary system, there exist competitive adsorption between MG and RhB on MPs. And the adsorption capacities of PVC for the two dyes are stronger than those of PE. This is attributed to the strong halogen-hydrogen bond between the two dyes and PVC, and the larger specific surface area of PVC. This study revealed the interaction and competitive adsorption mechanism between binary dyes and MPs, which is of great significance for understanding the interactions between dyes and MPs in the multi-component systems.

Huge quantities of microplastics are "hidden" in the sediment of China's largest urban lake-Tangxun Lake

Microplastics (MPs) pollution in Tangxun Lake, the largest urban lake in China, was investigated. The average MPs pollution in sediment (1.81 ± 1.75 × 10⁴ items kg^-1) is at a high level, while the MPs in lakeshore water (917.77 ± 742.17 items m^-3) is in the middle to low level compared with existing studies, which is related to the government's protection. Fragments and fibers are the most common shapes in sediment and water, respectively. MPs size <1 mm dominates in the sediment, while the MPs in water has a larger size. The distribution of MPs in the inner lake shows that pellets tend to "hidden" in sediments. Suspected MPs are randomly selected for polymer detection by Micro-Raman microscopy. Polypropylene (PP), polyethylene (PE) and polyethylene terephthalate (PET) are the most common polymer types in water, sediment and atmospheric deposition MPs samples. The input of wastewater, fishery and surrounding human activities are the main sources of MPs in sediment. Atmospheric deposition has a great impact on the distribution of MPs, while the contribution of surface runoff to lake MPs is not remarkable. In addition, MPs in sediments have exceeded the environmental carrying capacity. More attention should be focused on the sediment, where huge amounts of MPs are "hidden".

Preparation of adsorptive polyethyleneimine/polyvinyl chloride electrospun nanofiber membrane: Characterization and application

Landfilling and burning plastic waste, especially waste polyvinyl chloride (PVC), can produce highly toxic and carcinogenic by-products that threaten the ecosystem and human health. However, there is still a lack of proper methods for waste PVC recycling. Therefore, developing feasible ways for waste PVC recovery is urgently needed. The purpose of this study is to analyze the characteristics of PVC-based adsorptive nanofiber membranes and test their ability for the treatment of wastewater containing Cibacron Brilliant Yellow 3G-P, a widely used reactive dye. The polyethylenimine/polyvinyl chloride membrane (PEI/PVCM) was characterized by FTIR, FE-SEM, TGA, tensile analysis, water contact angle measurement, and zeta-potential analysis. The FTIR analysis confirmed that the PEI has successfully crosslinked with PVC. The FE-SEM images showed that the nanofibers constituting PEI/PVCM are compact with an average fiber diameter of 181 nm. The TGA results showed that the membrane was able to remain stable in wastewater below 150 °C. The average stress and strain of the PEI/PVCM were 7.64 ± 0.32 MPa and 934.14 ± 48.12%, respectively. The water contact angle and zeta potential analysis showed that after the introduction of PEI, the membrane converted from hydrophobic to hydrophilic, and the pH_pzc was increased from 3.1 to 1.08. The pure water flux of the membrane was measured at 0.1 MPa and the result was 3013 ± 60 L/m²‧h. The wastewater purification capability of PEI/PVCM was measured at an initial dye concentration of 10 ppm and pH 4-9 at 0.1 MPa. The reusability of PEI/PVCM was verified through three adsorption-desorption cycles. The results demonstrated that the PEI/PVCM is a reusable membrane for efficient purification of wastewater containing reactive dyes over a wide pH range (pH 4-8).

Induced aging, structural change, and adsorption behavior modifications of microplastics by microalgae

The effects of microalgal biofouling on microplastic (MP) may differ from bacterial biofouling. In this study, the influence of microalgae on MP surface alteration, structural change, and adsorption of organic micropollutants was evaluated. Virgin polyethylene (PE), polyvinyl chloride (PVC), and polyamide (PA) were each immersed in algal photobioreactor and river freshwater for 30 days to simulate algal and river microbe biofouling respectively. Consequently, their physicochemical changes and adsorption potential of a mixture of six bisphenol analogues (BPA, BPS, BPE, BPB, BPF, BPAF) and two parabens (propyl-paraben, benzyl-paraben) were investigated. Owing to the algal bioactive compounds, major microalgae-induced biofouling and more MP aging than the river microbe aging were observed through fractures, pits, cracks, and algal attachments. Intrusion of algal organic matter and scission of polymeric functional groups were revealed during microalgal immersion and the potential MP aging pathways were proposed. Algal biofouling considerably altered the intrinsic properties of the MPs, consequently the adsorption capacity of PE and PVC was enhanced by 3.04-6.72 and 2.14-8.72 times, respectively. Adsorption process onto algal-aged MPs was pH-dependent, endothermic, non-spontaneous, and favored by hydrogen bonds. Meanwhile, the amide group in PA structure was conducive to organic micropollutant adsorption, which was likely reduced by algal aging and the erosion of the N-H stretching. Moreover, higher adsorption capacities of organic micropollutants were shown by the algal-biofilm PE and PVC than virgin and river microbial biofilm MPs. This study discloses that, biofouling and aging of MPs by microalgae through their bioactive components would engender more incidences on MP properties, organic micropollutants adsorption with associated environmental and health hazards.

Adsorption of Different Pollutants by Using Microplastic with Different Influencing Factors and Mechanisms in Wastewater: A Review

The studies on microplastics are significant in the world. According to the literature, microplastics have greatly specific surface areas, indicating high adsorption capacities for highly toxic pollutants in aquatic and soil environments, and these could be used as adsorbents. The influencing factors of microplastic adsorption, classification of microplastics, and adsorption mechanisms using microplastics for adsorbing organic, inorganic, and mixed pollutants are summarized in the paper. Furthermore, the influence of pH, temperature, functional groups, aging, and other factors related to the adsorption performances of plastics are discussed in detail. We found that microplastics have greater advantages in efficient adsorption performance and cost-effectiveness. In this paper, the adsorptions of pollutants by microplastics and their performance is proposed, which provides significant guidance for future research in this field.

The Inhibition of Microcystin Adsorption by Microplastics in the Presence of Algal Organic Matters

Microplastics (MPs) could act as vectors of synthetic chemicals; however, their influence on the adsorption of chemicals of natural origin (for example, MC-LR and intracellular organic matter (IOM), which could be concomitantly released by toxic Microcystis in water) is less understood. Here, we explored the adsorption of MC-LR by polyethylene (PE), polystyrene (PS), and polymethyl methacrylate (PMMA). The results showed that the MPs could adsorb both MC-LR and IOM, with the adsorption capability uniformly following the order of PS, PE, and PMMA. However, in the presence of IOM, the adsorption of MC-LR by PE, PS, and PMMA was reduced by 22.3%, 22.7% and 5.4%, respectively. This is because the benzene structure and the specific surface area of PS facilitate the adsorption of MC-LR and IOM, while the formation of Π-Π bonds favor its interaction with IOM. Consequently, the competition for binding sites between MC-LR and IOM hindered MC-LR adsorption. The C=O in PMMA benefits its conjunction with hydroxyl and carboxyl in the IOM through hydrogen bonding; thus, the adsorption of MC-LR is also inhibited. These findings highlight that the adsorption of chemicals of natural origin by MPs is likely overestimated in the presence of metabolites from the same biota.

Sorption of diclofenac by polystyrene microplastics: Kinetics, isotherms and particle size effects

Diclofenac (DCF) is a common pharmaceutical that widely distributed in natural waters, and has been received an increasing attention because of its potential toxicity. Additionally, microplastics are also ubiquitous pollutants in natural waters, but little information is available on their interactions. In this study, the sorption of DCF on polystyrene microplastics (PS MPs) with different particle sizes was investigated, and the influence of environmental factors was also explored. Results indicated that the pseudo-second-order kinetic model was suitable to describe the sorption process. The sorption capacity increased with the increase in particle size. The isotherms data for the sorption of DCF on 0.5 and 1 μm PS MPs were best fitted with the Dubinine-Radushkevich model, but the Freundlich and Langmuir models could best describe the sorption of DCF 5 and 20 μm PS MPs, respectively. It is suggested that the sorption was a chemisorption, which is also verified by Fourier transform infrared spectroscopy (FTIR) results. Furthermore, the sorption capacity decreased as pH increased, and increased as ionic strength increased. These findings give a new perspective that the microplastics with larger sizes hold promise for the treatment of DCF-contaminated water.

Adsorption behaviors and mechanisms of antibiotic norfloxacin on degradable and nondegradable microplastics

The misuse of both antibiotics and plastics significantly increases the environmental pollution problems associated with these contaminants. Moreover, microplastics can adsorb other pollutants in the environment. However, the mechanisms of antibiotic adsorption by degradable and nondegradable microplastics are not completely understood. In this study, we investigated the environmental behavior of norfloxacin (NOR) using polybutylene succinate (PBS), which is a degradable microplastic, and compared it with conventional microplastics, polystyrene (PS) and polyethylene (PE). The order of adsorption capacity was PS > PBS ≫ PE. The adsorption behavior fitted well with the pseudo-second-order kinetic and Langmuir isotherm models, indicating monolayer adsorption. The process is thermodynamically endothermic and non-spontaneous and is controlled by chemical and physical mechanisms, including π-π conjugation, hydrogen bonds, ion exchange, and electrostatic interactions. The adsorption capacity of microplastics was higher when the solution pH was around the pKa value of NOR than at other pH values. Ionic strength and dissolved organic matter inhibited the adsorption process. For PS and PBS, the amount of NOR adsorbed onto MPs initially decreased and then increased with the increase of coexisting heavy metal ions. Zn²⁺ and Pb²⁺ could promote the adsorption of NOR by PE. This study reveals the interaction mechanisms between microplastics and antibiotics and provides a more comprehensive theoretical basis for an ecological environmental risk assessment of different microplastics.

Effects of environmental aging on the adsorption behavior of antibiotics from aqueous solutions in microplastic-graphene coexisting systems

The extensive use of nanofillers, such as graphene oxide (GO) and reduced graphene oxide (rGO), as plastic additives has led to the coexistence of microplastics (MPs) and nanomaterials in aquatic environments. However, there is a lack of studies on the adsorption behavior of MPs when coexisting with GO. Moreover, MPs and GO are prone to undergoing aging processes in real environments under conditions such as sunlight exposure, which changes their physicochemical properties and affects their adsorption behavior. In this study, the aging processes of MPs and GO in a real environment were simulated by ultraviolet (UV) irradiation and thermal treatments, respectively. The adsorption behavior of ciprofloxacin (CIP) on three types of MPs (polypropylene (PP), polyamide (PA), and polystyrene (PS)) before and after aging was explored. The MPs are ordered in terms of CIP adsorption capacity as aged-PA > aged-PS > aged-PP > PA > PP > PS, and the adsorption capacity of aged MPs was approximately twofold higher than that of pristine MPs. This paper also studied the adsorption performance of antibiotics in a coexisting system of aged MPs and GO/rGO, and the tetracycline (TC) adsorption capacity was increased by ~336% in aged PP-GO and ~100% in an aged PP-rGO coexisting system. GO/rGO with high degree of oxidation and concentration in an aged- PP-GO/rGO coexisting system are more conducive to the TC adsorption, due to the contribution of oxygen-containing functional groups. Surface and partition adsorption co-occurred during the TC adsorption process. The TC adsorption behavior in the MPs-GO/rGO coexisting system was strongly dependent on the solution pH, which was more favorable under acidic (pH = 3) or alkaline (pH = 11) conditions. This study improves the understanding of the environmental behavior of MPs, graphene, and antibiotics and guides research on strategies for preventing the migration of antibiotics in MPs-GO/rGO coexisting systems.

Comparing the sorption of pyrene and its derivatives onto polystyrene microplastics: Insights from experimental and computational studies

In this study, the sorption behaviors and mechanisms between polystyrene microplastics (micro-PS) and 4-rings polycyclic aromatic hydrocarbons (PAHs) pyrene (Pyr) and its derivatives (S-Pyr), including 1-methylpyrene (P-CH₃), 1-hydroxypyrene (P-OH), 1-aminopyrene (P-NH₂), 1-pyrenecarboxylic acid (P-COOH) were investigated at neutrality. The results revealed that the sorption rates of micro-PS for S-Pyr were higher than those for parent Pyr. Meanwhile, -CH₃ could slightly facilitate the sorption, whereas -OH, P-NH₂, and P-COOH intensively inhibit the sorption of S-Pyr onto micro-PS. The sorption capacities of Pyr/S-Pyr increased with decreasing size of micro-PS. Besides, the effects of salinity and temperature on the sorption characteristics of micro-PS for Pyr/S-Pyr depended on their substituents. Combined with experimental and computational methods, it could be concluded that the main sorption mechanisms were possibly hydrophobic interaction, π-π interaction and pore-filling. The observations reported here could improve predictions of environmental behaviors and bioavailability of PAHs and micro-PS.

Sorption of endocrine disrupting compounds onto polyamide microplastics under different environmental conditions: Behaviour and mechanism

Microplastics of polyamide are commonly found in aquatic environments and might act as vectors of different contaminants such as endocrine disrupting compounds (EDC). Therefore, sorption of 17α-ethynylestradiol (EE2), 17β-estradiol (E2), and estriol (E3) on polyamide microplastics was studied under different simulated environments. The results suggest that the sorption process was affected by the presence of dissolved organic matter (DOM) and salinity, where both positive and negative effects were observed. Kinetics revealed that the process occurs through multiple steps wherever the sorption rate depicting the transportation of EDC molecules from the liquid phase to the solid boundary of the sorbent, is higher than the intraparticle and pore diffusion process. In addition, the sorption rate of E2 decreased with the increase of water matrix complexity from ultrapure water (UPW) > artificial seawater (ASW) > fulvic acid water (FAW) > artificial seawater with fulvic acid (AS/FAW), while the sorption rate of EE2 decreased from UPW > ASW > FAW and increased in the matrix combining salinity and organic matter (AS/FAW). On the contrary, the E3 sorption rate increased with matrix complexity, from UPW < ASW < FAW and decreased with the influence of salinity and organic matter combination (AS/FAW). The sorption capacity of the EDC reached maximum values of 82% for E2, 90% for EE2 and 56% for E3. Isotherms demonstrated the occurrence of multilayer sorption. A positive relationship has been found between the hydrophobicity of polyamide microplastics and the Log K_ow of EDC, showing an important role of hydrophobic interactions in the sorption process under all the studied conditions. Moreover, hydrogen bonding and binding of contaminants and DOM to microplastics through bridges were also suggested. The results show that salinity and DOM can greatly influence the sorption and transportation of EDC in the aquatic environment and pose a risk to aquatic ecosystems.

Enhanced sorption of the UV filter 4-methylbenzylidene camphor on aged PET microplastics from both experimental and theoretical perspectives

In this study, the morphology and sorption behavior of polyethylene terephthalate (PET) microplastics during the aging process are investigated. To clarify the sorption mechanism of aged PET microplastics, the common sunblock 4-methylbenzylidene camphor (4-MBC) was chosen as the target contaminant, and UV irradiation was used for the laboratory aging simulation. The results show that oxygen-containing functional groups (carboxylic, carbonyl, ketone and hydroxyl groups) increase on the surface of aged PET microplastics. Based on density functional theory (DFT) simulations, the camphor part of 4-MBC acts as a hydrogen bond acceptor, whereas the carboxylic group on aged PET microplastics acts as a hydrogen bond donor. The formation of hydrogen bonding causes increased sorption of 4-MBC on aged PET microplastics. The sorption capacity increased from 5 to 11 μg g^-1 for 50 ppb 4-MBC with 100 mg PET microplastics after a five-day aging process. Other environmental factors that affect sorption were also identified; a higher pH value and the presence of salinity reduced the amount of sorption. The sorption of virgin PET ranged from 8.0 to 3.4 μg g^-1 and the sorption of aged PET ranged from 22 to 5 μg g^-1 at pH 4 to 10. In the presence of salinity (10% seawater), the virgin PET sorption dropped to 2.1 μg g^-1 while the aged PET sorption dropped to 4 μg g^-1. A similar phenomenon was also observed in the sorption behavior under natural sunlight (the sorption of PET increased from 0.4 to 0.8 μg g^-1 after 6 months of aging). The potential risk to ecosystems of aged PET microplastics under prolonged sunlight exposure in the natural environment could be greater than that predicted for virgin microplastics.

The potential of microplastics as adsorbents of sodium dodecyl benzene sulfonate and chromium in an aqueous environment

Considering the omnipresence of microplastics (MPs) in aquatic environments, they are expected to exert significatn impacts as carriers for diverse waterborne pollutants. In this work, the adsorptive behavior of two ionic components (i.e., sodium dodecyl benzene sulfonate (SDBS) and Cr(VI)) has been explored against the two types of MPs as model adsorbents, namely poly (ethylene terephthalate) (PET) and polystyrene (PS). The influence of key variables (e.g., pH, particle size, and dose of the MPs) on their adsorption behavior is evaluated from various respects. The maximum adsorption capacity values of SDBS on PET and PS are estimated to be 4.80 and 4.65 mg⋅g^-1, respectively, while those of Cr(VI) ions are significantly lower at 0.080 and 0.072 mg⋅g^-1, respectively, The adsorptive equilibrium of SDBS is best described in relation to pH and MP size by a Freundlich isotherm. In contrast, the adsorption behavior of Cr(VI) is best accounted for by a Langmuir isotherm to indicate its adsorption across at least two active surface sites.