Adsorption mechanisms of five bisphenol analogues on PVC microplastics

Insight into the adsorption mechanisms of ionizable imidazolinone herbicides in sediments: Kinetics, adsorption model, and influencing factors

To reveal the adsorption mechanisms of imazamox, imazapic, and imazethapyr on sediment and batch experiments were carried out in this study. The adsorption kinetics of three imidazolinone herbicides on sediment were accurately described by the pseudo-second-order kinetic model(R² > 0.9004). The values of adsorption capacity (Q_e.cal) were ranged from 0.0183 to 0.0859 mg kg^-1 for three herbicides. Adsorption equilibrium was reached within 24 h for three herbicides on sediment, and well fitted by the Freundlich model(R² > 0.9561). The K_F of values for adsorption obtained sediment samples were ranged from 0.2501 to 1.322 L^1/n mg^1-1/n kg^-1for three herbicides. These results indicated that intraparticle diffusion and external mass transport were the main rate controlling steps of the adsorption of herbicides on sediment and that the chemical adsorption was dominant during the adsorption processes. The calculated hysteresis coefficient H were 0.9422,0.7877 and 0.744 for imazmox, imazapic and imazethapyr in raw sediment, respectively, indicating that there is a hysteresis in desorption. The influences of solution pH and sediment organic carbon content on the imidazolinone herbicide adsorption behaviors were also examined. Which shown that the adsorption process for herbicides was highly pH-dependent and adsorption efficiency was closely related to the organic matter content of the sediment, suggesting that electrostatic interactions played crucial roles in the adsorption behavior between sediment and imidazolinone herbicides, and the herbicides were mostly absorbed by the amorphous materials of sediment. These research findings are important for assessing the fate and transport of imidazolinone herbicides in water-sediment systems.

Adsorption behavior of organic pollutants on microplastics

Microplastics (MPs) are emerging pollutants that act as a carrier of toxic pollutants, release toxic substances, and aggregate in biota. The adsorption behavior of MPs has recently become a research hot spot. The objective of this study was to summarize the main mechanisms by which MPs adsorb organic pollutants, introduce some mathematical models commonly used to study the adsorption behavior of MPs, and discuss the factors affecting the adsorption capacity from three perspectives, i.e., the properties of MPs and organic pollutants, and environmental factors. Adsorption kinetics and isothermal adsorption models are commonly used to study the adsorption of organic pollutants on MPs. We observed that hydrophobic interaction is the most common mechanism by which MPs adsorb organic pollutants, and also reportedly controls the portion of organic pollutants. Additionally, electrostatic interaction and other non-covalent forces, such as hydrogen bonds, halogen bonds, and π-π interactions, are also mechanisms of organic pollutant adsorption on MPs. The particle size, specific surface area, aging degree, crystallinity, and polarity of MPs, and organic pollutant properties (hydrophobicity and dissociated forms) are key factors affecting adsorption capacity. Changes in the pH, temperature, and ionic strength also affect the adsorption capacity. Current research on the adsorption behavior of MPs has mainly been conducted in laboratories, and in-depth studies on the adsorption mechanism and influencing factors are limited. Therefore, studies on the adsorption behavior of MPs in the environment are required, and this study will contribute to a better understanding of this topic.

Are microplastics destabilizing the global network of terrestrial and aquatic ecosystem services?

Plastic has created a new man-made ecosystem called plastisphere. The plastic pieces including microplastics (MPs) and nanoplastics (NPs) have emerged as a global concern due to their omnipresence in ecosystems and their ability to interact with the biological systems. Nevertheless, the long-term impacts of MPs on biotic and abiotic resources are not completely understood, and existing evidence suggests that MPs are hazardous to various keystones species of the global biomes. MP-contaminated ecosystems show reduced floral and faunal biomass, productivity, nitrogen cycling, oxygen-generation and carbon sequestration, suggesting that MPs have already started affecting ecological biomes. However, not much is known about the influence of MPs towards the ecosystem services (ESs) cascade and its correlation with the biodiversity loss. MPs are perceived as a menace to the global ecosystems, but their possible impacts on the provisional, regulatory, and socio-economic ESs have not been extensively studied. This review investigates not only the potentiality of MPs to perturb the functioning of terrestrial and aquatic biomes, but also the associated social, ecological and economic repercussions. The possible long-term fluxes in the ES network of terrestrial and aquatic niches are also discussed.

A review of human and animals exposure to polycyclic aromatic hydrocarbons: Health risk and adverse effects, photo-induced toxicity and regulating effect of microplastics

Polycyclic aromatic hydrocarbons (PAHs) are one of the most widely distributed persistent organic pollutants (POPs) in the environmental media. PAHs have been widely concerned due to their significant health risk and adverse effects to human and animals. Currently, the main sources of PAHs in the environment are the incomplete combustion of fossil fuels, as well as municipal waste incineration and agricultural non-surface source emissions. In this work, the scope of our attention includes 16 typical PAHs themselves without involving their metabolites and industrial by-products. Exposure of human and animals to PAHs can lead to a variety of adverse effects, including carcinogenicity and teratogenicity, genotoxicity, reproductive- and endocrine-disrupting effects, immunotoxicity and neurotoxicity, the type and severity of which depend on a variety of factors. On the other hand, the regulatory effect of microplastics (MPs) on the bio-toxicity and bioaccumulation capacity of PAHs has now gradually attracted attention. We critically reviewed the adsorption capacity and mechanisms of MPs on PAHs as well as the effects of MPs on PAHs toxicity, thus highlighting the importance of paying attention to the joint bio-toxicity caused by PAHs-MPs interactions. In addition, due to the extensive nature of the common exposure pathway of PAHs and ultraviolet ray, an accurate understanding of biological processes exposed to both PAHs and UV light is necessary to develop effective protective strategies. Finally, based on the above critical review, we highlighted the research gaps and pointed out the priority of further studies.

Bisfenol A adsorption using a low-cost adsorbent prepared from residues of babassu coconut peels

Nowadays, the occurrence of microcontaminants in water resources has become a worldwide concern. Among them, it can be mentioned Bisphenol A, a substance widely used in the chemical composition of plastic such as manufacture of packages, bottles, toiletries, among others. Its use may cause adverse effects on human health and the environment. Thus, a treatment is necessary to remove this compound and adsorption is an interesting alternative due to its low cost, operation and high efficiency. The objective of the present study was to evaluate the adsorption capacity of bisphenol in babassu activated carbon. The obtained results were satisfactory and the best experimental conditions were at 318 K temperature, 1 g L^-1 adsorbent concentration and 720 min equilibrium time, resulting in the maximum adsorptive capacity of 49.61 mg g^-1. The experimental data fit best with the pseudo-second order and Langmuir models for the kinetic and equilibrium studies, respectively. Thermodynamic parameters indicated endothermic, spontaneous and reversible process. The main adsorption mechanisms were hydrogen bonds and π-π interactions. In addition, the material regeneration study allowed to verify its possibility of reuse. Therefore, it was noticed that babassu activated carbon has high potential applicability in the treatment of contaminated water.

Sorption and desorption of petroleum hydrocarbons on biodegradable and nondegradable microplastics

Both biodegradable and nondegradable plastics are widely used. However, their interactions with petroleum hydrocarbons (PHs) have not been sufficiently studied. In this study, a type of biodegradable [polylactic acid (PLA)] and five types of nondegradable microplastics [polyamide (PA), polyethylene (PE), polyethylene terephthalate (PET), polystyrene (PS), and polyvinyl chloride (PVC)] were selected to investigate the sorption and desorption mechanisms of PHs. The sorption kinetics of the six types of microplastics followed a pseudo-second-order kinetics model (R² ranged from 0.956 to 0.999) and indicated that chemical sorption dominated the sorption process. The key rate-controlling steps of the sorption of PHs on microplastics were intraparticle diffusion and liquid film diffusion. The sorption capacity of PHs on microplastics followed the order of PA > PE > PS > PET > PLA > PVC. The difference in sorption capacity might be due to the crystallinity, and rubber or glass state of the microplastics. In addition, all types of microplastics exhibited reversible sorption without noticeable desorption hysteresis. No obvious differences were observed in the sorption and desorption of PHs between biodegradable and nondegradable microplastics. Both biodegradable and nondegradable microplastics could sorb/desorb PHs and serve as transportation vectors.

Adsorption of fulvic acid onto polyamide 6 microplastics: Influencing factors, kinetics modeling, site energy distribution and interaction mechanisms

Information on the interactions of microplastics (MPs) with dissolved organic matter (DOM) is essential for understanding their environmental impacts. This study selected fulvic acid (FA) as a typical DOM to investigate the influence of contact time, temperature, dosage, solution pH, salinity, and coexisting metal ions on the adsorption of FA onto polyamide 6 (PA6) MPs. The adsorption kinetic and isotherm can be successfully described by mixed-order (MO) and Freundlich models. The adsorption site energy distribution based on the Freundlich equation was applied to analyze the interaction between FA and PA6-MPs and the adsorption site heterogeneity. Thermodynamic analysis demonstrated that the values of parameters (ΔG_ads^°, ΔS_ads^°, ΔH_ads^°) were significantly affected by initial solution concentrations and the adsorption process was spontaneous, endothermic, and randomness-increased. Fourier transform-infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) revealed the importance of amide functional groups of PA6-MPs in controlling FA adsorption. Hydrogen bonds, hydrophobic, electrostatic, and n-π electron donor-acceptor (n-π EDA) interactions played different roles on adsorption of FA under different conditions of solution chemistry. These findings are beneficial to provide new insights involving the adsorption behavior and interaction mechanisms of FA onto PA6-MPs for the environmental risk assessment of MPs.

Polycyclic aromatic hydrocarbon accumulation in aged and unaged polyurethane microplastics in contaminated soil

The interaction of microplastics (MPs) and common environmental organic pollutants has been a frequently discussed topic in recent years. Although the estimated contamination caused by MPs in terrestrial ecosystems is one order of magnitude higher than that in the oceans, experiments have been conducted solely in an aqueous matrix. Therefore, an experiment was carried out with two soils differing in their concentrations of polycyclic aromatic hydrocarbons (PAHs) and polyurethane foams used for scent fences along roads and crop fields. Two types of polyurethane foam (biodegradable and conventional in aged and unaged form) were exposed to soils containing PAHs that originated from historically contaminated localities. The exposure lasted 28 days, and a newly developed three-step procedure to separate MPs from soil was then applied. Biodegradable polyurethane MPs exhibited a strong tendency to accumulate PAHs after 7 days, and their concentrations significantly grew over time. In contrast, the sorption of PAHs on conventional polyurethane MPs was substantially lower (a maximum of 3.6 times higher concentration than that in the soil). Neither type of foam changed their sorption behaviors after the aging procedure. The results indicate that the flexibility of the polyurethane polymeric network could be the main driving factor for the sorption.

Efficient removal of bisphenol pollutants on imine-based covalent organic frameworks: adsorption behavior and mechanism

The extensive use of bisphenol analogues in industry has aggravated the contamination of the water environment, and how to effectively remove them has become a research hotspot. This study presents two imine-based covalent organic frameworks with different pore sizes (COFs) [TAPB (1,3,5-tris(4-aminophenyl)benzene)-Dva (2,5-divinylterephthaldehyde)-PDA (terephthalaldehyde) (COF-1), and TAPB (1,3,5-tris(4-aminophenyl)benzene)-Dva (2,5-divinylterephthaldehyde)-BPDA (biphenyl dialdehyde) (COF-2)], which have achieved the efficient adsorption of bisphenol S (BPS) and bisphenol A (BPA). The maximum adsorption capacity of COF-2 for BPS and BPA obtained from Langmuir isotherms were calculated as 200.00 mg g⁻¹ and 149.25 mg g⁻¹. Both hydrogen bonding and π–π interactions might have been responsible for the adsorption of BPS and BPA on the COFs, where the high adsorption capacity of COFs was due to their unique pore dimensions and structures. Different types of pharmaceutical adsorption studies indicated that COF-2 exhibited a higher adsorption performance for different types of pharmaceuticals than COF-1, and the adsorption capacity was ranked as follows: bisphenol pharmaceuticals > anti-inflammatory pharmaceuticals > sulfa pharmaceuticals. These results confirmed that COFs with larger pore sizes were more conducive to the adsorption of pollutants with smaller molecular dimensions. Moreover, COF-1 and COF-2 possessed excellent pH stability and recyclability, which suggested strong potential applications for these novel adsorbents in the remediation of organic pollutants in natural waterways and aqueous ecosystems.

Two imine-based covalent organic frameworks with different pore sizes were synthesized, and can be used as adsorbents for the removal of bisphenol pollutants, showing high affinity toward bisphenol S and bisphenol A.

Sorption and leaching behaviors between aged MPs and BPA in water: The role of BPA binding modes within plastic matrix

Due to the hydrophobicity and large specific surface area microplastics (MPs) have become the vector for the migration of environmental organic pollutants. Environmental aging process affects the physiochemical structure of MPs and their corresponding environmental behaviors, in which the effect of bisphenol A (BPA) binding mode within plastic matrix on aging behaviors of MPs is not reported. In this work, the structural properties and BPA sorption behaviors of low density polyethylene (LDPE) MPs with BPA additives and polycarbonate (PC) MPs with BPA monomers exposed to three types of artificial accelerated aging processes including UV/H₂O, UV/H₂O₂, and UV/Cl₂ systems were comparatively investigated. Virgin LDPE and PC exhibited obvious leakage of BPA additives or monomers. Aged LDPE had stronger sorption ability towards BPA in water environment with no observed leakage of BPA additives. While, aged PC had extremely high leakage of BPA monomers, which is similar to virgin PCs and was proved to be a persistent source of BPA release. The BPA sorption on aged LDPE or leaching from aged PC was influenced by aging processes, water pH, salinity, co-existing estradiol (E2), and water sources. This study reveals the potential ecological and environmental risks of MPs containing toxic additives/monomers during aging processes from a new perspective.

Mechanism analysis of heavy metal lead captured by natural-aged microplastics

In this paper, the mechanism of lead (Pb(II)) captured by natural-aged microplastics in aqueous medium was explored. Compared with pristine microplastics, the natural-aged microplastics were more efficient for adsorbing Pb(II). After treated by hydrochloric acid (HCl) or sodium hydroxide (NaOH), the organic film was damaged and the adsorption efficiency decreased obviously, which proved that the organic film played an important role in Pb(II) capture. The fitting results of the isothermal adsorption model showed that this adsorption process was more in line with Langmuir model than with Freundlich model, and the maximum adsorption amount (13.60 mg/g) could also be obtained from the Langmuir model. Based on the comprehensive analysis of XRD, XPS and FTIR results, it was found that Pb(II) capture by natural-aged microplastics was mainly determined by the oxygen containing functional groups (carboxyl and hydroxyl groups) on the organic film. Besides, the measurement results of Zeta potential and pH effect showed that electrostatic interaction was mainly responsible for the Pb(II) capture process.

A review: Research progress on microplastic pollutants in aquatic environments

The ubiquitous problems of microplastics in waters are receiving global attention as microplastics can harm aquatic organisms, and finally can accumulate in the human body through biological chain amplification. In addition, microplastics act as a carrier capable of carrying heavy metals, organics, which form complex pollutants. These new combinations of pollutants, once ingested by aquatic organisms, are amplified through the food chain and can have unpredictable ramifications for aquatic organisms and human beings. Therefore, human beings are not only the source of plastic pollution, but also the sink of microplastic pollution. Therefore, this study reviews the source and distribution of microplastics, and their combined ability with heavy metals, antibiotics, and persistent organic pollutants in aquatic environments. Furthermore, it describes the interaction between aquatic organisms and microplastics. Finally, some suggestions are put forward to promote the sustainable application of microplastics. This work provides theoretical guidance for combining microplastics with other pollutants in water, and the accumulation of microplastics in food chain.

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

The pervasiveness of microplastics, which can absorb pollutants, has a certain impact on pollutant migration in natural waters. Differences in functional groups, such as the hydroxyl group, of pollutants will affect their adsorption on microplastics. In this study, the adsorption of phenanthrene (PHE) or its monohydroxy derivatives, including 1-hydroxyphenanthrene (1-OHP), 2-hydroxyphenanthrene (2-OHP), 4-hydroxyphenanthrene (4-OHP), and 9-hydroxyphenanthrene (9-OHP), on polyvinyl chloride (PVC, measured mean particle size = 134 μm) microplastics was studied. The adsorption efficiency of PHE was shown to be higher than that of either of OHPs. A better fit for pseudo-second-order and Freundlich isotherm models was obtained, indicating different binding sites on the surface of PVC microplastics. The adsorption processes of PHE and OHPs on PVC microplastics were demonstrated to be exothermic and spontaneous. Combined with FT-IR analysis, theoretical calculation, and comparative adsorption experiments, hydrophobic interaction was the dominant mechanism during the adsorption process. In contrast, electrostatic repulsion, CH/π interaction, and halogen bonding played a minor role, to an extent, in the adsorption of PHE/OHPs on PVC microplastics. These findings indicate the influence of the hydroxyl group on adsorption and improve the understanding of interactions between PVC microplastics and PHE/OHPs.

An innovative evaluation method based on polymer mass detection to evaluate the contribution of microfibers from laundry process to municipal wastewater

Clothes washing releases numerous microfibers, including microplastic fibers (MPFs). Although MPFs in laundry wastewater are an important source of microplastics (MPs) in wastewater treatment plants (WWTPs), credible quantitative assessments of their contributions remain limited. Polyester fiber is the most important textile fiber. Its component, polyethylene terephthalate (PET) polymer, can be quantified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The release of MPFs from polyester clothes through washing was quantified via simulation experiments, and the MPFs in two WWTPs were measured by microscopic counting and LC-MS/MS. Direct comparison of the abundances of PET MPFs in laundry wastewater and WWTP influents led to an undervalued contribution rate of 9%-11% of the PET MPFs in laundry wastewater to those in WWTP influents. However, comparison of the mass of PET MPFs in laundry wastewater and WWTPs influents revealed that the PET MPFs from laundry contributed approximately 50% of those in the WWTPs. The latter was confirmed by comparing the number of polyester fibers released during clothes washing to the calculated number of "model MPFs" in WWTPs according to the PET mass concentration. Based on the PET concentration, the annual discharge of PET MPs from WWTPs to the water environment could also be estimated.

Insight into the characteristics and sorption behaviors of aged polystyrene microplastics through three type of accelerated oxidation processes

Ageing process can significantly alter the structural properties, environmental behaviors and potential ecotoxicity of microplastics (MPs) in water. In this study, the structural properties of aged polystyrene (PS) MPs being exposed to UV/H₂O, UV/H₂O₂ and UV/Cl₂ artificially accelerated oxidation processes and related sorption behaviors of bisphenol A (BPA) on those virgin/aged PS were investigated. The surface oxidation and hydrophilicity of aged PS were significantly increased according to infrared spectroscopy (IR) and water contact angle (CA) measurements. The differential scanning calorimetric (DSC) and gel permeation chromatography (GPC) revealed apparent degradation of aged PS especially in their amorphous domain. Obviously deteriorative BPA sorption capacity on aged PS was observed compared with that of virgin PS. The sorption rates of BPA on aged PS were accelerated and sorption of BPA shifted from partition dominant mechanism on virgin PS to the adsorption dominant mechanism through being fitted with the dual-mode sorption model. Besides, ageing in UV/Cl₂ system introduces C-Cl groups on the surface of PS which strengthen the combination with BPA through halogen bonding interaction. Salt and dissolved organic matters (DOM) in marine water may increase the BPA sorption on aged MPs due to enhanced polar interaction.

Remarkable adsorbent for removal of bisphenol A and S from water: Porous carbon derived from melamine/polyaniline

Recently, contamination of water resources with various organics such as bisphenols is a problem worldwide. Here, we developed nitrogen-enriched porous carbons (N-PDCs) from pyrolysis of melamine-loaded polyaniline (PANI), for the first time. The N-PDCs and PANI-derived carbons (PDCs, without using melamine) were characterized and applied in adsorptive removal of two typical bisphenols, such as bisphenol A and S (BPA and BPS, respectively), from water under a wide range of conditions. Via this research, we found that one N-PDC (N-PDC-700, obtained at 700 °C) showed very remarkable performances in adsorption of BPA (Q₀: 961 mg/g) and BPS (Q₀: 971 mg/g) under pH of 7.0. In other words, N-PDC-700 has Q₀ value for BPS around 2 times as much as that of the most effective adsorbent, MIL-101-NH₂. Moreover, the Q₀ value of N-PDC-700 for BPA is the second highest, after the sp² C dominant N-doped carbon. The plausible adsorption mechanism could be suggested based on the adsorption of BPA under a wide range of pH values. Finally, the N-PDC-700 was easily recycled for several uses, suggesting the potential application in adsorption of bisphenols from water.

Microplastics with adsorbed contaminants: Mechanisms and Treatment

Plastic pollution has been a significant and widespread global issue, and the recent COVID-19 pandemic has been attributed to its worsening effect as plastics have been contaminated with the deadly infectious virus. Microplastics (MPs) may have played a role as a vector that carries hazardous microbes such as emerging bacterial threats (i.e. antibiotic resistant bacteria) and deadly viruses (e.g., coronavirus); this causes great concern over microplastics contaminated with emerging contaminants. Mitigation and treatment of MPs are challenging because of a range of factors including but not limited to physicochemical properties and composition of MPs and pH and salinity of the solution. Despite the heterogeneous nature of aquatic systems, research has overlooked interactions between contaminants and MPs under environmental conditions, degradation pathways of MPs with adsorbed contaminants, and, especially, the role of adsorbed contaminants in the efficiency of MP treatment through membrane filtration, in comparison with other treatment methods. This review aims to (1) analyze an assortment of factors that could influence the removal of MPs and mechanisms of contaminant adsorption on MPs, (2) identify mechanisms influencing membrane filtration of MPs, (3) examine the fate and transport of MPs with adsorbed contaminants, (4) evaluate membrane filtration of contaminant-adsorbing MPs in comparison to other treatment methods, and (5) draw conclusions and the future outlook based on a literature analysis.

Investigation on the adsorption and desorption behaviors of heavy metals by tire wear particles with or without UV ageing processes

In recent years, tire wear particles (TWP), as the significant proportion of microplastics (MPs), has adsorbed much attention due to its widespread presence in aquatic ecosystem. Compared with typical MPs, TWP exists significant differences in composition, additives, characteristics and so on. With TWP and polypropylene (PP) as target MPs, Cd²⁺ and Pb²⁺ as target pollutants, the adsorption-desorption characteristics of heavy metal ions on original and aged MPs were studied. Compare with the PP, the S_BET of TWP increased more significantly after the UV ageing process. Meanwhile, the zeta potential of TWP increased from -8.01 to -14.6 mV and PP from -5.36 to -9.52 mV, and the surface of the TWP were more negatively-charged. In addition, the hydrophilicity of MPs enhanced due to the increased oxygen-containing functional groups after ageing process. Compared with PP, the physicochemical properties of TWP changed more obviously during UV ageing processes. The adsorption results showed that the pseudo-second-order model could better describe the adsorption processes of Cd²⁺ and Pb²⁺ on MPs. Meanwhile, the orders of adsorption capacity of MPs for Cd²⁺ and Pb²⁺ were aged TWP > aged PP > original TWP > original PP. The phenomenon of adsorption confirmed that TWP had better vector effects for heavy metal ions than PP, and the ageing processes could enhance the adsorption capacity of MPs. Moreover, the desorption results demonstrated that, compared with PP, the TWP (with higher adsorption capacity) also had the better desorption capacity for heavy metal ions in simulated gastric fluid. Compared with PP, the TWP might cause a more serious hazard to aquatic environment and organisms. These investigations would contribute to assessing the potential environmental and biological risk of TWP, especially considering the effect of the ageing process.

Double-side microcantilevers as a key to understand the adsorption mechanisms and kinetics of chemical warfare agents on vertically-aligned TiO2 nanotubes

Microgravimetric sensor platforms with physico- or chemo-selective interfaces offer promising sensing properties. They are widely used to detect chemical warfare agents (CWAs). However, a comprehensive insight into adsorption mechanisms and interactions between low concentrations of these adsorbates and low-mass adsorbents is still lacking. In this study, we report a complete and detailed analytical method to model the adsorption processes of low traces of vapor-phase DiMethyl MethylPhosphonate (DMMP), a conventional simulant of CWAs, on a double-side nanostructured microcantilever coated with vertically-aligned titanium dioxide nanotubes (TiO₂-NTs). We find that the geometrical configuration of NTs plays an important role in the diffusion regimes of molecules during the adsorption. This study shines light on the adsorption and kinetic mechanisms of low-traces DMMP offering opportunities to have a better insight of the adsorption of CWAs on complex nanostructures and to improve microcantilever sensors.

Sorption of tetrabromobisphenol A onto microplastics: Behavior, mechanisms, and the effects of sorbent and environmental factors

Microplastics (MPs) and halogenated organic pollutants coexist in ambient water and MPs tend to sorb organic pollutants from surrounding environments. Herein, a study on the sorption behavior of tetrabromobisphenol-A (TBBPA) onto four different MPs, namely, polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC) was carried out. Effects of MPs properties and environmental factors, including the type, surface charge and pore volume as well as the ionic strength (Ca²⁺) and humic acid (HA) on the sorption of TBBPA were discussed. Results showed that the sorption of TBBPA onto the MPs could reached an equilibrium within 24 h, and the sorption capacities decreased in the following order -PVC (101.85 mg kg^-1) >PS (78.95 mg kg^-1) >PP (58.57 mg kg^-1) >PE (49.43 mg kg^-1). Adsorption kinetics data fitted by intraparticle diffusion model revealed both surface sorption and intraparticle diffusion contributed, in the interfacial diffusion stage approximately 11-29% of TBBPA slowly diffused onto the surface of the MPs, and finally, in the intraparticle diffusion stage. The increase of Ca²⁺ concentration could promote the sorption of TBBPA by PE, PP, and PS, but no significant alteration for PVC. For all the four MPs, HA was found to exert a negative effect on TBBPA sorption. The adsorption was mainly driven by hydrophobic partition and electrostatic interactions.

Sorption of chemical contaminants on degradable and non-degradable microplastics: Recent progress and research trends

Microplastics (<5 mm) are ubiquitous contaminants of growing concern. These have been found in multiple environmental compartments, including remote sites where anthropogenic activity is null. Once released, microplastics interact with multiple chemicals in the environment, many of which are classified as organic contaminants or heavy metals. Some contaminants have an affinity for microplastics, attributed to certain sorption mechanisms, and thus become vectors of hazardous chemicals. Here, we focused on the sorption behavior of degradable and non-degradable microplastics, including field and laboratory experiments. We reviewed the sorption mechanisms, namely hydrophobic interactions, electrostatic interactions, pore-filling, Van der Waals forces, hydrogen bonding, and π-π interactions, and the factors strengthening or weakening these mechanisms. Then, we analyzed the literature investigating the sorption behavior of a wide range of chemicals contaminants on microplastics, and the current knowledge regarding the occurrence of organic contaminants and heavy metals on microplastics extracted from the environment. The future perspectives and research priorities were discussed. It is apparent that degradable microplastics, such as polylactic acid or polybutylene succinate, have a greater affinity for hydrophobic contaminants than conventional synthetic non-degradable microplastics according to recent studies. However, studies assessing degradable microplastics are scarce and much research is required to further prove this point. We stated several knowledge gaps in this new line of research and suggest the future studies to follow an integrative approach, allowing to comprehend the multiple factors involved, such as ecotoxicity, bioaccumulation, and fate of the chemical contaminants.

Organic Contaminants and Interactions with Micro- and Nano-Plastics in the Aqueous Environment: Review of Analytical Methods

Micro- and nanoplastic particles are increasingly seen not only as contaminants themselves, but also as potential vectors for trace organic chemicals (TOrCs) that might sorb onto these particles. An analysis of the sorbed TOrCs can either be performed directly from the particle or TOrCs can be extracted from the particle with a solvent. Another possibility is to analyze the remaining concentration in the aqueous phase by a differential approach. In this review, the focus is on analytical methods that are suitable for identifying and quantifying sorbed TOrCs on micro- and nano-plastics. Specific gas chromatography (GC), liquid chromatography (LC) and ultraviolet-visible spectroscopy (UV-VIS) methods are considered. The respective advantages of each method are explained in detail. In addition, influencing factors for sorption in the first place are being discussed including particle size and shape (especially micro and nanoparticles) and the type of polymer, as well as methods for determining sorption kinetics. Since the particles are not present in the environment in a virgin state, the influence of aging on sorption is also considered.

Estimation of the mass of microplastics ingested - A pivotal first step towards human health risk assessment

The ubiquitous presence of microplastics in the food web has been established. However, the mass of microplastics exposure to humans is not defined, impeding the human health risk assessment. Our objectives were to extract the data from the available evidence on the number and mass of microplastics from various sources, to determine the uncertainties in the existing data, to set future research directions, and derive a global average rate of microplastic ingestion to assist in the development of human health risk assessments and effective management and policy options. To enable the comparison of microplastics exposure across a range of sources, data extraction and standardization was coupled with the adoption of conservative assumptions. Following the analysis of data from fifty-nine publications, an average mass for individual microplastics in the 0-1 mm size range was calculated. Subsequently, we estimated that globally on average, humans may ingest 0.1-5 g of microplastics weekly through various exposure pathways. This was the first attempt to transform microplastic counts into a mass value relevant to human toxicology. The determination of an ingestion rate is fundamental to assess the human health risks of microplastic ingestion. These findings will contribute to future human health risk assessment frameworks.

Interfacial interactions between collected nylon microplastics and three divalent metal ions (Cu(II), Ni(II), Zn(II)) in aqueous solutions

In water environments, nylon microplastics (MPs) and heavy metals are two kinds of common pollutants. This study investigated the adsorption of three divalent metals (Cu(II), Ni(II), Zn(II)) onto collected nylon MPs as function of contact time, temperature, solution pH, ionic strength and concentration of fulvic acid (FA). The kinetic data fitted well with the Elovich and pseudo-second order equations. The result of shrinking core model (SCM) confirms that the adsorption of Cu(II) and Zn(II) was mainly controlled by intraparticle diffusion. The adsorption of three metal ions onto collected nylon MPs is spontaneous, endothermic, with an increased randomness in nature. The Langmuir and Freundlich models successfully described the adsorption isotherms. The speciation distributions of three divalent metals in aqueous solutions were identified to analyze the effects of initial solution pH, ionic strength and fulvic acid concentrations on the adsorption amounts. X-ray photoelectron spectroscopy (XPS) analysis indicates the importance of surface O-containing groups of collected nylon MPs in controlling the adsorption of three metal ions. This research provides a clear theoretical basis for the behavior of nylon MPs as heavy metals (Cu(II), Ni(II), Zn(II)) carrier and highlights their environmental toxicity, which deserves to be further concerned.

One-pot fabrication of lignin-based aromatic porous polymers for efficient removal of bisphenol AF from water

To remove the bisphenol AF (BPAF) from aqueous solution, two different types of lignin-based aromatic porous polymers (LAPP-1 and LAPP-2) were fabricated via one-pot crosslinking of lignin with 1,4-dichloroxylene and 4,4'-bis(chloromethyl)-1,1'-biphenyl, respectively. The successful synthesis of LAPPs was confirmed by FTIR and XPS, SEM, TEM and N₂ adsorption-desorption analysis. Then, batch adsorption experiments were conducted to investigate adsorption properties toward BPAF. Based on the results, the adsorption processes were in accordance with the pseudo-second-order kinetic model and the Freundlich isotherm model, and the thermodynamic studies showed that the adsorption was a spontaneous and exothermic process. It is remarkable that LAPPs exhibited good adsorption performance in wide ranges of pH and ionic strength as well as in recycling process. Notably, compared to LAPP-1, LAPP-2 exhibited higher adsorption capacity for BPAF, which can be ascribed to its higher porosity and content of aromatic ring. Moreover, the comprehensive analysis of experimental and theoretical results indicated that the π-π interactions and pore adsorption may jointly drive the uptake process of BPAF. Considering the simple fabrication method employed and excellent BPAF adsorption performance, LAPPs provided new insights into the development of advanced lignin-based adsorbents for removal of BPAF from water.

Elucidating the co-transport of bisphenol A with polyethylene terephthalate (PET) nanoplastics: A theoretical study of the adsorption mechanism

Polyethylene terephthalate (PET) is a possible key component of nanoplastics in water environments, which can migrate pollutants through co-transport. In this regard, the co-transport of endocrine disruptors (such as bisphenol A, BPA) by nanoplastics is of emergent concern because of its cytotoxicity/bioaccumulation effects in aquatic organisms. In this work, a computational study is performed to reveal the BPA adsorption mechanism onto PET nanoplastics (nanoPET). It is found that the outer surface of nanoPET has a nucleophilic nature, allowing to increase the mass transfer and intraparticle diffusion into the nanoplastic to form stable complexes by inner and outer surface adsorption. The maximum adsorption energy is similar (even higher) in magnitude with respect to nanostructured adsorbents such as graphene, carbon nanotubes, activated carbon, and inorganic surfaces, indicating the worrying adsorption properties of nanoPET. The adsorption mechanism is driven by the interplay of dispersion (38-49%) and electrostatics effects (43-50%); specifically, dispersion effects dominate the inner surface adsorption, while electrostatics energies dominate the outer surface adsorption. It is also determined that π-π stacking is not a reliable interaction mechanism for aromatics on nanoPET. The formed complexes are also highly soluble, and water molecules behave as non-competitive factors, establishing the high risk of nanoPET to adsorb and migrate pollutants in water ecosystems. Furthermore, the adsorption performance is decreased (but not inhibited) at high ionic strength in salt-containing waters. Finally, these results give relevant information for environmental risk assessment, such as quantitative data and interaction mechanisms for non-biodegradable nanoplastics that establish strong interactions with pollutants in water.

Hexabromocyclododecane alters malachite green and lead(II) adsorption behaviors onto polystyrene microplastics: Interaction mechanism and competitive effect

The role of microplastics (MPs) as a carrier of pollutants in water environment is an emerging issue; however, information regarding the underlying mechanisms for malachite green (MG) and Pb(II) adsorption onto hexabromocyclododecane (HBCD)-polystyrene (PS) composites MPs (HBCD-PS MPs) is still lacking. In this study, the adsorption behaviors and mechanisms of MG and Pb(II) onto PS and HBCD-PS MPs were investigated in batch adsorption experiments. The amounts of MG and Pb(II) adsorbed onto PS MPs were negligible while the presence of HBCD significantly enhanced the adsorption of MG and Pb(II) onto HBCD-PS MPs. The results of intra-particle and film diffusion model confirmed that the adsorption of MG and Pb(II) onto HBCD-PS MPs was dominated by intra-particle diffusion. The maximum adsorption amount (q_m) of Pb(II) and MG onto HBCD-PS MPs followed the sequence of Pb(II) (3.33 μmol g^-1) > MG (1.87 μmol g^-1). In binary systems, MG and Pb(II) showed competitive adsorption onto HBCD-PS MPs, and Pb(II) exhibited relatively higher affinity to be adsorbed onto HBCD-PS MPs. Solution pH and salinity played a crucial role in the adsorption process. XPS analysis suggested that the -Br participated in the adsorption process as an electron-withdrawing group. Overall, electrostatic interaction regulated the adsorption of MG and Pb(II) onto HBCD-PS MPs. Results from this study demonstrated that HBCD could enhance the role of MPs in the MG and Pb(II) migration by changing their adsorption behavior onto MPs.

The occurrence of bisphenol compounds in animal feed plastic packaging and migration into feed

Animal-derived food plays an important role in human exposure to bisphenol compounds (BPs), potentially as a result of the presence of BPs in animal feed. Even so, there have been few studies regarding the source of BPs in animal feed. The objective of the present study was to assess both the occurrence of BPs in animal feed packaging and the migration of BPs from feed packaging into animal feed. Thirteen BPs were monitored in 30 used animal feed plastic packaging samples previously employed for different animal feedstuffs and made of polypropylene (PP) or polyethylene (PE). Six and two BPs were found in PP-based woven bags and PE-based films, respectively. Bisphenol A (BPA) was the predominant analogue with a wide range of concentrations in both the PP- and PE-based packaging. A migration experiment was performed and provided the first-ever confirmation that BPA is able to migrate from plastic packaging into solid feed. Both contact time and the initial BP concentration affected the extent of migration. These results expand our knowledge regarding the origin of BPs in the food chain and suggest that further study of the bioaccumulation of BPs in animals is warranted.

Comparative analysis of kinetics and mechanisms for Pb(II) sorption onto three kinds of microplastics

Microplastics (MPs), a kind of novel contaminant, have potential to concentrate and transport heavy metals in the aquatic environment. This feature may affect the distribution and bioavailability of heavy metals. In order to determine the sorption behaviors of heavy metals onto the MPs, the sorption kinetics and mechanisms were investigated between the MPs (polyvinylchloride PVC, polyethylene PE, polystyrene PS) and Pb(II). The results suggested that the Pb(II) sorption onto the MPs were pH- and ionic strength-dependent. The sorption processes were best fitted by the pseudo-second-order model, and the rate-limiting steps were the intraparticle diffusion and final equilibrium process. The maximum sorption capacities of PVC, PE and PS were 483.1 μg/g, 416.7 μg/g and 128.5 μg/g under the condition of 0.01 M NaCl, pH 6.0, T = 298 K. The sorption rate constants were in the following order: PVC<PE<PS. According to the Fourier transformed infrared and X-ray photoelectron spectroscopy, no new bonds were formed between the MPs and Pb(II). Physisorption was the main driven force for Pb(II) sorption. In summary, the investigation reveals the Pb(II) sorption kinetics and mechanisms onto the MPs, which will improve the understanding of the interactions between the MPs and heavy metals.

Adsorption of ciprofloxacin to functionalized nano-sized polystyrene plastic: Kinetics, thermochemistry and toxicity

Plastic debris is ubiquitous in aquatic systems and has been proven vehicles for the transport of various pollutants including trace organic compounds. Nanoplastics have large specific surface area and hydrophobic characteristics and therefore are capable of adsorbing other organic or inorganic chemicals from the environment. Antibiotics, as another class of emerging contaminants, have raised significant research concern in recent years as they pose threats to the ecosytems and human health. Nevertheless, little information is available on the adsorption behaviors of antibiotics onto nano-sized plastics. The toxicity of combined nanoplastics and antibiotics is also largely unknown. In this study, the physicochemical and thermodynamic interactions between representative nanoplastics, which containing a carboxyl functional group of polystyrene nanoplastics (PS-COOH), and typical antibiotic, i.e., ciprofloxacin (CIP) were investigated in a batch adsorption experiment. The specific thermodynamic correlation function of PS-COOH combined with CIP was obtained through isothermal titration microcalorimetry (ITC) analysis. The adsorption kinetics and isotherm of CIP on PS-COOH closely fit the pseudo-second-order kinetic model (r² = 0.99) and Freundlich isotherm (r² = 0.99). The ITC results showed that the adsorption reaction of PS-COOH with CIP was a spontaneous exothermic reaction. The adsorption of antibiotics on nanoplastics may aggravate the negative impacts of these two pollutants on aqueous ecosystems, and we hypothesized that would be reflected in the survival rate of model organism of Caenorhabditis elegans when exposed to this combination. This work used a mechanistic approach to unravel the adsorption behavior of antibiotics on nanoplastics and shed light on their potential impact on aquatic ecosystems.

Different bisphenols induce non-monotonous changes in miRNA expression and LINE-1 methylation in two cell lines

4,4'-Isopropylidenediphenol (bisphenol A, BPA), a chemical substance that is widely used mainly as a monomer in the production of polycarbonates, in epoxy resins, and in thermal papers, is suspected to cause epigenetic modifications with potentially toxic consequences. Due to its negative health effects, BPA is banned in several products and is replaced by other bisphenols such as bisphenol S and bisphenol F. The present study examined the effects of BPA, bisphenol S, bisphenol F, p,p'-oxybisphenol, and the BPA metabolite BPA β-d-glucuronide on the expression of a set of microRNAs (miRNAs) as well as long interspersed nuclear element-1 methylation in human lung fibroblast and Caco-2 cells. The results demonstrated a significant modulation of the expression of different miRNAs in both cell lines including miR-24, miR-155, miR-21, and miR-146a, known for their regulatory functions of cell cycle, metabolism, and inflammation. At concentrations between 0.001 and 10 µg/ml, especially the data of miR-155 and miR-24 displayed non-monotonous and often significant dose-response curves that were U- or bell-shaped for different substances. Additionally, BPA β-d-glucuronide also exerted significant changes in the miRNA expression. miRNA prediction analysis indicated effects on multiple molecular pathways with relevance for toxicity. Besides, long interspersed nuclear element-1 methylation, a marker for the global DNA methylation status, was significantly modulated by two concentrations of BPA and p,p'-oxybisphenol. This pilot study suggests that various bisphenols, including BPA β-d-glucuronide, affect epigenetic mechanisms, especially miRNAs. These results should stimulate extended toxicological studies of multiple bisphenols and a potential use of miRNAs as markers.

Microplastics Pollution as an Invisible Potential Threat to Food Safety and Security, Policy Challenges and the Way Forward

Technological advances, coupled with increasing demands by consumers, have led to a drastic increase in plastic production. After serving their purposes, these plastics reach our water bodies as their destination and become ingested by aquatic organisms. This ubiquitous phenomenon has exposed humans to microplastics mostly through the consumption of sea food. This has led the World Health Organization (WHO) to make an urgent call for the assessment of environmental pollution due to microplastics and its effect on human health. This review summarizes studies between 1999 and 2020 in relation to microplastics in aquatic ecosystems and human food products, their potential toxic effects as elicited in animal studies, and policies on their use and disposal. There is a paucity of information on the toxicity mechanisms of microplastics in animal studies, and despite their documented presence in food products, no policy has been in place so far, to monitor and regulates microplastics in commercial foods meant for human consumption. Although there are policies and regulations with respect to plastics, these are only in a few countries and in most instances are not fully implemented due to socioeconomic reasons, so they do not address the problem across the entire life cycle of plastics from production to disposal. More animal research to elucidate pathways and early biomarkers of microplastic toxicity that can easily be detected in humans is needed. This is to create awareness and influence policies that will address this neglected threat to food safety and security.

Interactions between microplastics and organic pollutants: Effects on toxicity, bioaccumulation, degradation, and transport

Microplastics (MPs), defined as particles with diameters <5 mm and including nanoplastics (NPs), with diameters <1 μm, are characterized by large specific surface areas and hydrophobicity. In aquatic and terrestrial environments, MPs interact with co-occurring organic pollutants through sorption and desorption, which alters the environmental behavior of the pollutants, such as their toxicity, bioaccumulation, degradation, and transport. In this review, we summarize the results of current studies of the interactions between MPs and organic contaminants, and focus on the different mechanisms and subsequent ecological risks of contaminant transfer among environmental media, MPs and organisms. The sorption/desorption of organic pollutants on/from MPs is discussed with respect to solution conditions and the properties of both the MPs and the pollutants. More importantly, the ability of MPs to alter the toxicity, bioaccumulation, degradation, and transport of organic pollutants through these interactions is considered as well. We then examine the interrelationships of the different environmental behaviors of MPs and organic pollutants and the roles played by environmental processes. Finally, we identify the remaining knowledge gaps that must be filled in further studies in order to accurately evaluate the environmental risks of MPs and their associated organic pollutants.

Adsorption of microplastic-derived organic matter onto minerals

Microplastic (MP) pollution is an increasing global problem due to the ubiquity of these particles in the environment and the uncertainty surrounding their fate. Most MPs undergo extensive weathering in the environment, which may result in the release of dissolved organic matter (DOM) into the aqueous phase. In this study, for the first time, we examined the adsorptive behavior of MP-derived DOM (MP-DOM) on minerals (kaolinite and goethite) using DOM samples leached from commercial plastics including polyvinylchloride (PVC) and polystyrene (PS) under dark and ultraviolet (UV) irradiation conditions. MP-DOM was characterized by a higher distribution of relatively smaller-sized molecules than natural organic matter (NOM). The PS-derived DOM (PS-DOM) leached under UV treatment exhibited more oxygen-containing groups than their counterparts in the dark. MP-DOM also exhibited net negative charges at neutral pH ranges. Adsorption isotherm experiments revealed that the mineral surfaces had high adsorption affinities for both types of MP-DOM, which is likely associated with both electrostatic attraction and ligand exchange. The extent of adsorption was greater for the UV-irradiated than the dark-treated DOM, and on goethite compared to kaolinite. The Fourier-transform infrared (FTIR) spectra of the residual PS-DOM after adsorption revealed differences in the adsorption affinities between its functional groups. Two-dimensional correlation spectroscopy for the irradiated PS-DOM showed that preferential adsorption occurred on minerals in the sequential order of oxidized structures → (PS monomers) → carboxylates in additives → carbonyl groups. The adsorption isotherm model parameters for MP-DOM were comparable to those obtained from aquatic/terrestrial NOM, which suggests that plastic-derived DOM can interact with minerals as strongly as NOM. This study highlights the overlooked role played by plastic-derived DOM in mineral-enriched environments, opening new opportunities for improving our understanding of the fate and environmental impacts of MPs.

Strong sorption of two fungicides onto biodegradable microplastics with emphasis on the negligible role of environmental factors

Microplastics have attracted much attention in recent years because they are able to interact with other pollutants including pesticides, with implications for the potential risks to biota. However, the sorption behavior of pesticides on microplastics, especially on biodegradable microplastics which are promising alternatives to conventional polymers, has been insufficiently studied. In this study, triadimefon and difenoconazole were selected as model triazole fungicides, and their sorption behavior on a typical biodegradable microplastics (PBS: polybutylene succinate) and two conventional polyethylene (PE) and polyvinyl chloride (PVC) microplastics was investigated with batch experiments in an aqueous solution. PBS presented the highest sorption capacity for triadimefon (104.2 ± 4.8 μg g^-1) and difenoconazole (192.8 ± 2.3 μg g^-1), which was 1.8- and 1.3-fold that on PE and 4.4- and 7.4-fold that of PVC, respectively. The results of sorption kinetic and isotherm modeling were better fit by a pseudo-second order model and linear model, respectively. More importantly, the effects of environmental factors (pH, salinity and dissolved organic matter) on the sorption behavior were investigated. Fungicide sorption on PBS was generally not affected by salinity, pH or dissolved organic matter. However, in contrast, salinity and dissolved organic matter both significantly decreased sorption on PE and PVC. The results showed that not only the sorption capacities of biodegradable microplastics but also their responses to environmental factors are quite different from those of conventional microplastics. This finding highlights the importance of the role played by biodegradable microplastics in the accumulation and transportation of organic pollutants.

Detection of Metal-Doped Fluorescent PVC Microplastics in Freshwater Mussels

The large-scale production of plastic and the resulting release of waste is leading to a huge accumulation of micro-sized particles in the environment that could have an impact on not only aquatic organisms but also on humans. Despite the extensive literature on the subject, there is still an insufficient harmonization of methodologies for the collection and analysis of microplastics (MPs) in complex matrices; especially for high density polymers; such as polyvinyl chloride (PVC), which tend to sink and accumulate in sediments, becoming available to benthonic organisms. In this article, mussels have been chosen as model for microplastic accumulation due to their extensive filtering activity and their wide distribution in both fresh and salt water basins. To facilitate the identification and quantification of microplastics taken up by mussels, novel fluorescent and metal-doped PVC microplastics (PVC-Platinum octaethylporphyrin (PtOEP) MPs in the size range of 100 µm) have been synthesized and characterized. For the analysis of the mussels following exposure, an enzymatic protocol using amylase, lipase, papain, and SDS for organic material digestion and a sucrose-ZnCl₂ density gradient for the selective separation of ingested microplastics has been developed. The final identification of MPs was performed by fluorescence microscopy. This work can greatly benefit the scientific community by providing a means to study the behavior of PVC MPs, which represent an example of a very relevant yet poorly studied high density polymeric contaminant commonly found in complex environmental matrices.

Source, occurrence, migration and potential environmental risk of microplastics in sewage sludge and during sludge amendment to soil

Microplastics (MPs) are an emerging global pollutant. MPs research is mainly concentrated on water, with limited research on MPs in sewage sludge. MPs from various sources are collected into sewage and most of the MPs are trapped in the sludge during the sewage treatment process. Sludge is not only a sink of MPs, but also a source. Soil amendment with sludge provides nutrients into the soil, but it can also import substantial MPs into the soil, which has certain environmental risks. Therefore, we focused on the MPs in sludge and sludge-amended soil and conducted a literature review to summarize the sources, physical properties and fate of the MPs in sludge, as well as their separation, identification and statistical methods. MPs can accumulate in the soil, influence the properties of the soil, and also migrate, which might result in the pollution of deep soils and groundwater. In addition, the adsorption by MPs of heavy metals, organic pollutants, antibiotics and antibiotic resistance genes cannot be ignored as sewage sludge generally contains substantial concentrations of these pollutants. They can be adsorbed by the MPs and transferred into the soil with sludge amendment of soil. The combination and interaction of MPs with its adsorbed pollutants might increase environmental risk, further leading to possibility of them being uptaken by plants. The specific long-term risks to the environment caused by MPs in soil with sludge amendment require further exploration and investigation.

Synthesis of magnetic nanocomposite microparticles for binding of chlorinated organics in contaminated water sources

In this work, the development of novel magnetic nanocomposite microparticles (MNMs) via free radical polymerization for their application in the remediation of contaminated water is presented. Acrylated plant-based polyphenols, curcumin multiacrylate (CMA) and quercetin multiacrylate (QMA), were incorporated as functional monomers to create high affinity binding sites for the capture of polychlorinated biphenyls (PCBs), as a model pollutant. The MNMs were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, dynamic light scattering, and UV-visible spectroscopy. The affinity of these novel materials for PCB 126 was evaluated and fitted to the nonlinear Langmuir model to determine binding affinities (K D). The results suggest the presence of the polyphenolic moieties enhances the binding affinity for PCB 126, with K D values comparable to that of antibodies. This demonstrates that these nanocomposite materials have promising potential as environmental remediation adsorbents for harmful contaminants.

Current research and perspective of microplastics (MPs) in soils (dusts), rivers (lakes), and marine environments in China

In this study, we first reviewed the current research progress regarding the presence of environmental microplastics (MPs) in environment in China from 2010 to 2019. Results showed that: (1) current research has primarily focused on river and marine environments rather than soils and dusts, mainly located in eastern China, i.e., the Yangtze river, Poyang lake, Dongting lake, Yellow sea, and Bohai sea; (2) the abundance of MPs found in water bodies (sediments) of the rivers in China ranged from 3.9 to 7900 items·m^-3 (19.0 × 10³-13600.5 × 10³ items·km^-2), and 20-24300 items·kg^-2 (170-5500 × 10⁶ items·km^-2) in the sediments, respectively; in lake water the range was 340-8900 items·m^-3 (5 × 10³-340 × 10⁵ items·km^-2) and 8 to 1200 items·m^-2/25-300 items·kg^-1 in the sediments, respectively; in marine water the range was 0.003-540 items·m^-3 (0-380,100 item·km^-2) and 1.3-14700 item·kg^-1 in the sediments, respectively; in fish, shellfish, and natural planktons from ocean and freshwater, the range was 0-57 items·individuals^-1 (0-168 items·g^-1); (3) The absorption and toxicological effects of MPs in freshwater and oceans have mainly focused on polyethylene (PE), polypropylene (PP), and polystyrene (PS); (4) the sources of microplastics in soils and dusts primarily come from urban/town activities; for rivers and lakes (estuary), they primarily come from urban activities; for coastal waters, fishing gear and nets, and the maritime activities were the main sources.

Sorption of five organic compounds by polar and nonpolar microplastics

Microplastics (MPs) could act as a vector for various kinds of pollutants due to their small size. Compared to nonpolar and nondegradabale MPs, the sorption of organic pollutants on polar and degradable MPs has been seldom studied. In this study, the sorption behavior of two nonpolar polycyclic aromatic hydrocarbons (PAHs, phenanthrene and pyrene), two polar derivates of PAHs (1-nitronapthalene and 1-napthylamine) and a heterocyclic chemical (atrazine) by three polar MPs including polybutylene succinate (PBS), polycaprolactone (PCL) and polyurethane (PU) and a typical nonpolar MP, polystyrene (PS) were investigated. The sorption followed the pseudo-second-order kinetics and sorption equilibrium was achieved within 5 days. Sorption isotherms could be well fitted by both Linear (R²>0.946) and Freundich models (R²>0.945) and the values of nonlinear index (n) from Freundlich model in most cases were close to 1, suggesting that hydrophobic partition was a primary process controlling the sorption. The sorption coefficients (K_d) of the five organic compounds ranged from 29. 6 to 1.42 × 10⁵ (L/kg). The log K_OC/log K_OW of PAHs and derivates of PAHs on polar MPs were greater than 1, especially for 1-naphthylamine (1.30-1.40), confirming the great contribution of hydrogen bonding. PU contains a benzene ring and showed greater sorption compared the other two polar MPs, indicating the existence of π (n) -π electron donor-acceptor interactions. Morevoer, the sorption of phenanthrene and pyrene on PU were better fitted by Langmuir model and the maximum adsorption capacities were 1.06 × 10⁴ and 5.87 × 10³ mg/kg, respectively.

Interfacial interaction between micro/nanoplastics and typical PPCPs and nanoplastics removal via electrosorption from an aqueous solution

Micro/nanoplastics have raised worldwide concern with extensive research on its transfer, toxicity and removal. However, the primary environmental process-adsorption of nanoplastics has not been uncovered since the discovery of nanosized plastics. Here, we synthesized nanoscale polystyrene (PS) particles with mean diameter of ∼40 nm to avoid unknown properties from purchased ones, and thoroughly investigated its adsorption towards two typical pharmaceuticals and personal care products (PPCPs) with distinct characteristics, which are antibiotic (ciprofloxacin) and endocrine disruptor (bisphenol-A). Moreover, UV radiation is applied to simulate aging process in natural cases, and the carbonyl index derived from FTIR spectra increased clearly from 0.183 to 0.387. The adsorption capacity at equilibrium of CIP and BPA increased from 0.15 to 4.07 to 4.92 and 8.71 mg/g after weathering, respectively. Besides, the effect of environmental factors (pH, humic acid, salinity and cations) was also studied. Furthermore, electrosorption technology is applied to remove nanoplastics in solution for the first time, with the capacity of 0.707 g nano-polystyrene/g AC and 0.322 g aged-nano-polystyrene/g AC, suggesting that adsorption under electric field is presumably a feasible tertiary treatment method targeted at nanoplastics in wastewater treatment plants (WWTPs).

Sorption behaviors of crude oil on polyethylene microplastics in seawater and digestive tract under simulated real-world conditions

The role of plastic as a vector for bioaccumulation of hydrophobic organic pollutants has been widely studied. However, the interactions between microplastics (MPs) and crude oil, and the transfer kinetics of sorbed oil from ingested MPs into aquatic biota are largely unknown. In this study, interactions between MPs and crude oil in seawater and digestive tract mimic of aquatic biota have been examined. To mimic the living, transportation and cooking conditions of aquatic organisms, sorption and desorption behaviors were investigated under room temperature-bath (25 °C), ice-bath (0∼4 °C) and boiling water-bath (95∼100 °C), and pH was set as 4 and 7 for the simulated gut fluid. The results showed that sorption capacity of polyethylene (PE) MPs for crude oil in seawater was higher than that in intestinal tract, indicating more oil residue in aqueous phase of gut fluid in the present of organic particles. The sorption kinetics models were well fitted to the pseudo-order model, and isotherms models were well fitted to the Freundlich model. In addition, the results demonstrated that temperature played a significant effect on crude oil viscosity, and the sorption capacity under different temperatures was in the order of 25 °C > 95∼100 °C > 0∼4 °C, indicating that more oil was remained in aqueous phase at boiling water-bath and ice-bath. The increment of pH enhances the sorption capacities of PE MPs. Moreover, the desorption experiment has supplemented the current findings from the sorption experiments.

Strong influence of surfactants on virgin hydrophobic microplastics adsorbing ionic organic pollutants

Microplastic (MP) pollution has become an area of increasing concern because MPs accumulate various types of pollutants. Many previous studies have explored the interactions between MPs and hydrophobic pollutants. However, little research has been conducted on hydrophilic pollutants, which are of much higher concentration and ubiquitous in environment. Surfactants cause hydrophobic MPs to become hydrophilic, which may significantly enhance their capacities to adsorb hydrophilic pollutants. This study explored the influence of co-existing surfactants on the adsorption of ionic organic pollutants by MPs, and found that the presence of an ionic surfactant could significantly enhance the capacity of polyvinyl chloride (PVC, 0.2 mm) MPs to adsorb pollutants with opposite charges. The Langmuir methylene blue adsorption capacity of PVC could be increased from 172 to 4417 ppm in the presence of a sodium dodecyl benzene sulfonate surfactant. Nonionic surfactants impeded the adsorption of both cationic and anionic pollutants due to the steric resistance of the hydrophilic polyethelene glycol chains. The electrostatic interaction mechanism dominated the interfacial behaviors of ionic pollutants on surfactant-adsorbed MP interfaces. The effects of the surfactants were further verified using four different model pollutants and six surfactants. The adsorption capacities of real environmental MPs, including PVC, polyethylene (PE), polypropylene (PP), and polystyrene (PS), increased by three to twenty-six times. The adsorption properties of MPs may be determined by the presence of co-existing surfactants, rather than their polymer species or additives.

Interactions between microplastics and organic compounds in aquatic environments: A mini review

Microplastics (MPs) are widely distributed in aquatic environments. They may release toxic substances or act as carriers for other organic compounds and pathogens, with potential to cause harm to the ecological environment and human health. A key concern is how MPs interact with organic compounds. We reviewed related works conducted under both laboratory conditions and in field aquatic environments to investigate the mechanisms of interactions between MPs and organic compounds from three perspectives: MPs, organic compounds, and environmental factors. The crystallinity and specific surface area of the MPs, and the functional groups, ionic form and strength of both MPs and organic compounds are key factors affecting their interactions. Environmentally realistic concentration settings for both MPs and organic compounds are critical for interpretation of the results of sorption experiments. The effect of salinity on interactions is mainly due to changes in pH. These results contribute to a better understanding of the environmental behavior, and potential ecological and human health risks of microplastics.

Effects of bisphenol A and nanoscale and microscale polystyrene plastic exposure on particle uptake and toxicity in human Caco-2 cells

Microplastics are abundant in oceans, lakes, soils and even air, and can pose potential threats to human health through food or respiratory intake. Moreover, microplastics have synergistic toxicity to the body after absorbing organic pollutants. In this study, laser scanning confocal microscope and flow cytometry were used to observe the intake of colonic cancer Caco-2 cells to polystyrene plastic with five different particlesizes (300 nm, 500 nm, 1 μm, 3 μm, 6 μm). The uptake rates of microplastics with different particle sizes were 73%, 71%, 49%, 43%, and 30%, respectively. Then, High Performance Liquid Chromatography (HPLC) was used to analyze the adsorption differences of polystyrene plastic with different particle sizes to bisphenol A (BPA). Finally, the proliferation toxicity of polystyrene microplastics with different particle sizeson Caco-2 cells before and after adsorption of BPA was compared. MTT experiments confirmed that microplastics caused an increase in cytotoxicity. This result may be related to increased cellular oxidative stress and mitochondrial depolarization. This hypothesis has been confirmed in reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) assays because nanoscale microplastics cause a large amount of ROS on Caco-2 cells after microplastic exposure, and micron-scale microplastics cause a significant decrease in MMP. At the same time, nanoscale microplastics can cause further depolarization of mitochondria due to their large specific surface area adsorption of BPA, which leads to enhanced cytotoxicity of microplastics after BPA adsorption. The results of this study are of great significance in the evaluation of the safety of microplastics in the human body.

Reporting Guidelines to Increase the Reproducibility and Comparability of Research on Microplastics

The ubiquitous pollution of the environment with microplastics, a diverse suite of contaminants, is of growing concern for science and currently receives considerable public, political, and academic attention. The potential impact of microplastics in the environment has prompted a great deal of research in recent years. Many diverse methods have been developed to answer different questions about microplastic pollution, from sources, transport, and fate in the environment, and about effects on humans and wildlife. These methods are often insufficiently described, making studies neither comparable nor reproducible. The proliferation of new microplastic investigations and cross-study syntheses to answer larger scale questions are hampered. This diverse group of 23 researchers think these issues can begin to be overcome through the adoption of a set of reporting guidelines. This collaboration was created using an open science framework that we detail for future use. Here, we suggest harmonized reporting guidelines for microplastic studies in environmental and laboratory settings through all steps of a typical study, including best practices for reporting materials, quality assurance/quality control, data, field sampling, sample preparation, microplastic identification, microplastic categorization, microplastic quantification, and considerations for toxicology studies. We developed three easy to use documents, a detailed document, a checklist, and a mind map, that can be used to reference the reporting guidelines quickly. We intend that these reporting guidelines support the annotation, dissemination, interpretation, reviewing, and synthesis of microplastic research. Through open access licensing (CC BY 4.0), these documents aim to increase the validity, reproducibility, and comparability of studies in this field for the benefit of the global community.

Nano-plastics and their analytical characterisation and fate in the marine environment: From source to sea

Polymer contamination is a major pollutant in all waterways and a significant concern of the 21st Century, gaining extensive research, media, and public attention. The polymer pollution problem is so vast; plastics are now observed in some of the Earth's most remote regions such as the Mariana trench. These polymers enter the waterways, migrate, breakdown; albeit slowly, and then interact with the environment and the surrounding biodiversity. It is these biodiversity and ecosystem interactions that are causing the most nervousness, where health researchers have demonstrated that plastics have entered the human food chain, also showing that plastics are damaging organisms, animals, and plants. Many researchers have focused on reviewing the macro and micro-forms of these polymer contaminants, demonstrating a lack of scientific data and also a lack of investigation regarding nano-sized polymers. It is these nano-polymers that have the greatest potential to cause the most harm to our oceans, waterways, and wildlife. This review has been especially ruthless in discussing nano-sized polymers, their ability to interact with organisms, and the potential for these nano-polymers to cause environmental damage in the marine environment. This review details the breakdown of macro-, micro-, and nano-polymer contamination, examining the sources, the interactions, and the fates of all of these polymer sizes in the environment. The main focus of this review is to perform a comprehensive examination of the literature of the interaction of nanoplastics with organisms, soils, and waters; followed by the discussion of toxicological issues. A significant focus of the review is also on current analytical characterisation techniques for nanoplastics, which will enable researchers to develop protocols for nanopolymer analysis and enhance understanding of nanoplastics in the marine environment.

The influence of polyethylene microplastics on pesticide residue and degradation in the aquatic environment

Microplastics pollution has become a global concern in recent years. In this work, the potential influences of polyethylene (PE) microplastics on the residue, degradation and distribution behaviors of eight pesticides (epoxiconazole, tebuconazole, myclobutanil, azoxystrobin, simazine, terbuthylazine, atrazine and metolachlor) in the aquatic environment were investigated. The results showed that the presence of 2-50 g L^-1 microplastics could decrease the pesticide residues in water. The adsorption isotherms were linear, indicating the process was dominated by partitioning into the bulk polymer. The desorption kinetics data implied the desorption process obeyed a pseudo-second-order kinetic model, with R² above 0.99 in most cases. Aging treatment of microplastics had no significant effects on the interaction with the pesticides. The presence of PE microplastics could significantly prolong the degradation half-lives of pesticides in water, especially for those with moderate degradation half-lives and high log K_ow values. Take terbuthylazine as an example, its half-life significantly increased from 31.8 days to 45.2 days in the presence of 10 g L^-1 microplastics. Besides, PE microplastics had little impact on the behavior of the pesticides in the water-sediment system. The findings of this study indicated that PE could adsorb pesticides through partitioning, thus influencing the persistence of the pesticides in water.