Insights into the removal of polystyrene nanoplastics using the contaminated corncob-derived mesoporous biochar from mining area

Microplastics removal from stormwater runoff by bioretention cells: A review

Microplastics (MPs), as a new category of environmental pollutant, have been the hotspot of eco-friendly issues nowadays. Studies based on the aging process, the migration pattern of MPs in runoff rainwater, and the use of bioretention cells to remove MPs from runoff rainwater are beginning to attract widespread attention. This review analyses the migration patterns of MPs in rainwater runoff through their sources, structure and characteristics. The mechanism of removing MPs from runoff stormwater, the purification efficiency of different fillers and their influencing factors, and the accumulation, fate, and aging of MPs in bioretention cells are described. Furthermore, the hazards of MP accumulation on the performance of bioretention cells are summarised. Future directions for removing MPs in bioretention cells are proposed: (1) research on MPs smaller than 100 µm; (2) influence of MPs aging process on bioretention cells; (3) exploration of more effective fillers to enhance their removal efficiency; (4) research on synergistic removal mechanism of MPs and other pollution.

Robust polyaniline coating magnetic biochar nanoparticles for fast and wide pH and temperature range removal of nanoplastics and achieving label free detection

Nanoplastics as an emerging pollutant are ubiquitous in water and still not easy to measure and remove. In this regard, polyaniline coating magnetic biochar nanoparticles constructed by pyrolysis of ferrate pretreated bagasse and ball milling and coating surface with polyaniline (PA@MBCBM) were tested for their capability to attach and remove polystyrene nanoplastics in water. Porousness and rich functional groups and positive charging property of PA@MBCBM was responsible for fast, high capacity and robust attaching of nanoplastics. 94.9 % - 99.0 % of nanoplastics were removed at wide range of pH conditions (1 - 10) and PA@MBCBM was reusable for seven times with less changing of performance, and maximum adsorption capacities reached 276.24 - 334.45 mg/g at both cold and warm temperatures (5 - 35 °C). Moreover, taking advantages of efficient nanoplastics adhesion, high conductivity and electrochemical activity, the PA@MBCBM, was tested to fabricate a label free screen-printed electrode for nanoplastics detection, and achieved reasonable sensitivity with the lowest detection limit being 1.26 μg/L. In addition, exceptional performances of adsorption and detection in real water samples were also successfully realized. The proposed PA@MBCBM having dual function of robust and efficient adsorption removal, and label free and sensitive determination of nanoplastics, would be greatly constructive for reliable, cost effective and effective control and monitoring of the nanoplastics contamination.

Review of Techniques for the Detection, Removal, and Transformation of Environmental Microplastics and Nanoplastics

Plastic residues have emerged as a significant challenge in the environmental sector. Microplastics, which are plastic fragments smaller than 5 mm, have the ability to disperse through the atmosphere, oceans, and land, posing a serious threat to human health by accumulating in the food chain. However, their minuscule size makes it difficult to effectively remove them from the environment using the current technologies. This work provides a comprehensive overview of recent advancements in microplastic detection and removal technologies. For detection methods, we discuss commonly used techniques such as microscopic analysis, thermal analysis, mass spectrometry, spectroscopic analysis, and energy spectrometry. We also emphasize the importance of integrating various analytical and data-processing techniques to achieve efficient and nondestructive detection of microplastics. In terms of removal strategies, we explored innovative methods and technologies for extracting microplastics from the environment. These include physical techniques like filtration, adsorption, and magnetic separation; chemical techniques such as coagulation-flocculation-sedimentation and photocatalytic conversion; and bioseparation methods such as activated sludge and biodegradation. We also highlight the promising potential for converting microplastic contaminants into high-value chemicals. Additionally, we identify current technical challenges and suggest future research directions for the detection and removal of microplastics. We advocate for the development of unified and standardized analytical methods to guide further research on the removal and transformation of microplastics.

Coupled Influence of Magnetic Biochar and Solution Chemistries on Retention and Release of Nanoplastics in Porous Media

Magnetic biochar (MBC), as an environmentally friendly material, has been extensively used for the remediation of soil and groundwater contamination. The retention and release of nanoplastics (NPs) with carboxyl (NPs-COOH) or amino functionalization (NPs- NH2) in saturated porous media were investigated under varying conditions of ionic strength (IS), MBC addition, humic acid (HA) concentration, and cation types. The reversible and irreversible retention of NPs was examined by altering the IS, increasing the solution pH, and inducing cation exchange. The results revealed that MBC enhanced the surface roughness of the media, thereby inhibiting NPs' transport. The HA promoted NPs-NH2 transport more effectively than NPs-COOH due to electrostatic repulsion, steric hindrance, and competition for deposition sites. Under a reduced IS and increased pH, a portion of the retained NPs was released, with NPs-NH2 showing a greater release than NPs-COOH, indicating reversible retention. Additionally, the stronger charge-shielding and cation-bridging effects of Ca2+ significantly enhanced the retention of NPs. Cation exchange resulted in less NPs being released, as most were irreversibly retained in deeper primary minima. However, a small number of retained NPs were remobilized by electrical double layer expansion, surface deprotonation, and cation exchange, indicating reversible retention. These findings provide valuable insights into the fate of NPs in the environment.

Efficient removal of nanoplastics by iron-modified biochar: Understanding the removal mechanisms

Tiny plastic particles, particularly nanoplastics, are becoming major threats to aquatic and biotic life owing to their unique physico-chemical characteristics. Thus, in the present work, biochar (BC) was fabricated using "Ulva prolifera green tide" as a biowaste raw material by slow pyrolysis technique to examine its potential in removing nanoplastics from the environment. The findings depicted that nanoplastics removal efficiency by BC was V-shaped with initial pH increased from 2 to 11, and the main removal mechanism changed from adsorption to heterogeneous aggregation between nanoplastics, biochar colloids, and leached substances from BC. When the solution pH crossed the pHpzc of BC (2.3), the aggregation kinetics were well-fitted by the logistic model and displayed as an S-shaped curve with a lag period. Characterization results indicated that biochar colloids were the key enabler with a critical concentration of 72.01 mg L-1 at neutral pH. Keeping in mind the removal mechanisms and contribution of biochar colloids, iron-modified biochar (Fe-BC) was produced to enhance the overall removal efficiency. The Fe-BC demonstrated a two-phase removal process of pre-adsorption and post-aggregation, successfully realized to minimize lag time and enhance aggregation performance. The theoretical removal capacity of Fe-BC against nanoplastics could reach up to 1626.3 mg g-1, which was three-fold higher than that of BC. Further, the Fe-BC was suggested to be recycled and reused at least three times by ultrasound, followed by co-pyrolysis for green and efficient degradation of nanoplastics. Overall, the findings offer a promising approach for removing and recycling nanoplastics in the environment.

Heteroaggregation, disaggregation, and migration of nanoplastics with nanosized activated carbon in aquatic environments: Effects of particle property, water chemistry, and hydrodynamic condition

Nanosized activated carbon (NAC) as emerging engineered nanomaterials may interact with nanoplastics prevalent in aquatic environments to affect their fate and transport. This study investigated the effects of particle property (charge and concentration), water chemistry [electrolytes, pH, humic acid (HA), and sodium alginate (SA)], and hydrodynamic condition [wave (i.e., sonication) and turbulence (i.e., stirring)] on the heteroaggregation, disaggregation, and migration of NAC with positively charged amino-modified polystyrene (APS) or negatively charged bare polystyrene (BPS) nanoplastics. The homoaggregation rate of APS was slower than its heteroaggregation rate with NAC, with critical coagulation concentrations (CCC) decreasing at higher NAC concentrations. However, the homoaggregation rate of BPS was intermediate between its heteroaggregation rates under low (10 mg/L) and high (40 mg/L) NAC concentrations. The heteroaggregation rate of APS+NAC enhanced as pH increasing from 3 to 10, whereas the opposite trend was observed for BPS+NAC. In NaCl solution or at CaCl2 concentration below 2.5 mM, HA stabilized APS+NAC and BPS+NAC via steric hindrance more effectively than SA. Above 2.5 mM CaCl2, SA destabilized APS+NAC and BPS+NAC by calcium bridging more strongly than HA. The migration process of heteroaggregates was simulated in nearshore environments. The simulation suggests that without hydrodynamic disturbance, APS+NAC (971 m) may travel farther than BPS+NAC (901 m). Mild wave (30-s sonication) and intense turbulence (1500-rpm stirring) could induce disaggregation of heteroaggregates, thus potentially extending the migration distances of APS+NAC and BPS+NAC to 1611 and 2160 m, respectively. Conversely, intense wave (20-min sonication) and mild turbulence (150-rpm stirring) may further promote aggregation of heteroaggregates, shortening the migration distances of APS+NAC and BPS+NAC to 262 and 552 m, respectively. Particle interactions mainly involved van der Waals attraction, electrostatic repulsion, steric hindrance, calcium bridging, π-π interactions, hydrogen bonding, and hydrophobic interactions. These findings highlight the important influence of NAC on the fate, transport, and risks of nanoplastics in aquatic environments.

Exploring the potential of biochar for the remediation of microbial communities and element cycling in microplastic-contaminated soil

The detrimental effects of microplastics (MPs) on soil microbial and elemental raise significant environmental concerns. The potential of remediation with biochar to mitigate these negative impacts remains an open question. The remediation effects of biochar derived from corn and cotton straw on MPs concerning soil microorganisms and element cycling were investigated. Specifically, biochar induced substantial remediations in microbial community structure following MP exposure, restoring and fortifying the symbiotic network while exerting dominance over microbial community changes. A combined treatment of biochar and MPs exhibited a noteworthy increase in the abundance of NH4+, NO3-, and available phosphorous by 0.46-2.1 times, reversing the declining trend of dissolved organic carbon, showing a remarkable increase by 0.36 times. This combined treatment also led to a reduction in the abundance of the nitrogen fixation gene nifH by 0.46 times, while significantly increasing the expression of nitrification genes (amoA and amoB) and denitrification genes (nirS and nirK) by 22.5 times and 1.7 times, respectively. Additionally, the carbon cycle cbbLG gene showed a 2.3-fold increase, and the phosphorus cycle gene phoD increased by 0.1-fold. The mixed treatment enriched element-cycling microorganisms by 4.8-9.6 times. In summary, the addition of biochar repaired the negative effects of MPs in terms of microbial community dynamics, element content, gene expression, and functional microbiota. These findings underscore the crucial role of biochar in alleviating the adverse effects of MPs on microbial communities and elemental cycling, providing valuable insights into sustainable environmental remediation strategies.

Monitoring Poly(methyl methacrylate) and Polyvinyl Dichloride Micro/Nanoplastics in Water by Direct Solid-Phase Microextraction Coupled to Gas Chromatography-Mass Spectrometry

A simple, sustainable, and sensitive monitoring approach of micro/nanoplastics (MNPs) in aqueous samples is crucial since it helps in assessing the extent of contamination and understanding the potential risks associated with their presence without causing additional stress to the environment. In this study, a novel strategy for qualitative and quantitative determination of MNPs in water by direct solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS) was proposed for the first time. Spherical poly(methyl methacrylate) (PMMA) and irregularly shaped polyvinyl dichloride (PVDC) were used to evaluate the feasibility and performance of the proposed method. The results demonstrated that both PMMA and PVDC MNPs were efficiently extracted by the homemade SPME coating of nitrogen-doped porous carbons (N-SPCs) and exhibited sufficient thermal decomposition in the GC-MS injection port. Excellent extraction performances of N-SPCs coating for MNPs are attributed to hydrophobic cross-linking, electrostatic forcing, hydrogen bonding, and pore trapping. Methyl methacrylate was identified as the marker for PMMA, while 1,3-dichlorobenzene and 1,3,5-trichlorobenzene were the indicators for PVDC. Under the optimal extraction and decomposition conditions, the proposed method exhibited ultrahigh sensitivity, with a limit of detection of 0.0041 μg/L for PMMA and 0.0054 μg/L for PVDC. Notably, a programmed temperature strategy for the GC-MS injector was developed to discriminate and eliminate the potential interferences of intrinsic indicator compounds. Owing to the integration of sampling, extraction, injection, and decomposition into one step by SPME, the proposed method demonstrates exceptional sensitivity, eliminating the necessity for complex sample pretreatment procedures and the use of organic solvents. Finally, the proposed method was successfully applied in the determination of PMMA and PVDC MNPs in real aqueous samples.

Microplastics and nanoplastics: Exposure and toxicological effects require important analysis considerations

Microplastics (MPs) and nanoplastics (NPs) pervade both the environment and the food chain, originating from the degradation of plastic materials from various sources. Their ubiquitous presence raises concerns for ecosystem safety, as well as the health of animals and humans. While evidence suggests their infiltration into mammalian and human tissues and their association with several diseases, the precise toxicological effects remain elusive and require further investigation. MPs and NPs sample preparation and analytical methods are quite scattered without harmonized strategies to exist at the moment. A significant challenge lies in the limited availability of methods for the chemical characterization and quantification of these contaminants. MPs and NPs can undergo further degradation, driven by abiotic or biotic factors, resulting in the formation of cyclic or linear oligomers. These oligomers can serve as indicative markers for the presence or exposure to MPs and NPs. Moreover, recent finding concerning the aggregation of oligomers to form NPs, makes their analysis as markers very important. Recent advancements have led to the development of sensitive and robust analytical methods for identifying and (semi)quantifying these oligomers in environmental, food, and biological samples. These methods offer a valuable complementary approach for determining the presence of MPs and NPs and assessing their risk to human health and the environment.

Effective removal of microplastics by filamentous algae and its magnetic biochar: Performance and mechanism

In recent years, filamentous algae blooms and microplastics (MPs) pollution have become two major ecological and environmental problems in urban water systems. In order to solve these two problems at the same time, this study explored the loading capacity of MPs on fresh filamentous algae, and successfully synthesized magnetic filamentous algae biochar loading with Fe3O4 by hydrothermal method, with the purpose of removing MPs from water. The magnetic filamentous algal biochar was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and so on. Experiments on adsorption kinetics, adsorption isotherms and optimum pH were carried out to explore the adsorption mechanism of MPs on magnetic filamentous algal biochar. The adsorption kinetics and adsorption isotherm models were evaluated, and the selection criterion for the appropriate model was determined by using the residual sum of squares (RSS) and Bayesian information criterion (BIC). Microscope images revealed that fresh filamentous algae could interact with MPs in the form of entanglement, adhesion and encapsulation. The average load of MPs in filamentous algae samples was 14.1 ± 5 items/g dry weight. The theoretical maximum adsorption capacities of polystyrene MPs (PS-MPs) by raw biochar (A500) and magnetic biochar with Fe3O4 (M2A500) were 176.99 mg/g and 215.58 mg/g, respectively. The adsorbent materials gave better reusability because they could be reused up to five times. Overall, these findings have provided new insights into the use of filamentous algae for in situ remediation of fluvial MPs pollution, as well as feasible strategies for the recycling of algal waste.

Removal of Nanoplastics from Copollutant Systems Using Seaweed Cellulose Nanofibers

Nanoplastic pollution poses a significant global concern for public health due to the potential toxicity it induces in the human body through food and water intake. Consequently, the urgent task of removing nanoplastics, especially from water resources, is paramount for enhancing food safety, and developing eco-friendly materials capable of efficiently removing nanoplastics is crucial. In this context, we propose the use of biodegradable anionic seaweed cellulose nanofibers (TEMPO-mediated seaweed cellulose nanofibers, TCNFs) and cationic seaweed cellulose nanofibers (quaternized seaweed cellulose nanofibers, QCNFs) for nanoplastic removal in both single- and copollutant systems. In our experiments under simulated practical conditions, we revealed that TCNFs and QCNFs achieved an average removal efficiency of 98.71% against nanoplastic particles. Moreover, TCNFs and QCNFs exhibited higher adsorption capacities compared to those of existing materials, potentially offering a cost-effective advantage. Toxicity assessments conducted with mammalian cells further confirmed the biosafety of TCNFs and QCNFs. This study contributes to the scientific and theoretical understanding of using edible seaweed as well as offers promising solutions for food safety control in an efficient, cost-effective, and eco-friendly manner.

From organic fertilizer to the soils: What happens to the microplastics? A critical review

In recent, soil microplastic pollution arising from organic fertilizers has been of a great increasing concern. In response to this concern, this review presents a comprehensive analysis of the occurrence and evolution of microplastics in organic fertilizers, their ingress into the soil, and the subsequent impacts. Organic fertilizers are primarily derived from solid organic waste generated by anthropocentric activities including urban (daily-life, municipal wastes and sludge), agricultural (manure, straw), and industrial (like food industrial waste etc.) processes. In order to produce organic fertilizer, the organic solid wastes are generally treated by aerobic composting or anaerobic digestion. Currently, microplastics have been widely detected in the raw materials and products of organic fertilizer. During the process of converting organic solid waste materials into fertilizer, intense oxidation, hydrolysis, and microbial actions significantly alter the physical, chemical, and surface biofilm properties of the plastics. After the organic fertilizer application, the abundances of microplastics significantly increased in the soil. Additionally, the degradation of these microplastics often promotes the adsorption of organic pollutants and affects their retention time in the soil. These microplastics, covered by biofilms, also significantly alter soil ecology due to the unique properties of the biofilm. Furthermore, the biofilms also play a role in the degradation of microplastics in the soil environment. This review offers a new perspective on the soil environmental processes involving microplastics from organic fertilizer sources and highlights the challenges associated with further research on organic fertilizers and microplastics.

Microplastic pollutants in water: A comprehensive review on their remediation by adsorption using various adsorbents

Microplastics (MPs), as emerging pollutants, have attracted the attention of environmentalists, statespersons, and the scientific community over the last few decades. To address the spread of MPs in the environment, it is imperative to develop various removal techniques and materials that are effective, scalable, and ecologically benign. However, to the best of our knowledge, no review has systematically examined the removal of MPs using adsorption or provided an in-depth discussion on various adsorbents. Adsorption is an inexpensive and effective technology for wastewater treatment. Recently, many researchers have conducted studies on MP remediation using diverse adsorbent materials, such as biochar, activated carbon, sponges, carbon nanotubes, metal-layered oxides, metal-organic frameworks (MOFs), and zeolites. Each adsorbent has advantages and disadvantages. To overcome their disadvantages, researchers have been designing and developing hybrid adsorbents for MP remediation. This review provides insights into these individual adsorbents and also discusses hybrid adsorbents for MP removal. Finally, the review elaborates on future possibilities and ways to enable more efficient, scalable, and environmentally friendly MP cleanup. Overall, this review bridges the gap between contemporary MP remediation using adsorption techniques and adsorbent development.

Application of carbon-based adsorbents in the remediation of micro- and nanoplastics

Micro-nano plastics (MNPs) are emerging contaminants that can easily enter the food chain, posing risks to both the aquatic ecosystem and human health. Various physical, biological, and chemical methods have been explored to remove MNPs from water, and recently, adsorption technology has gained attention as an effective approach. Among the potential candidates, carbon-based adsorbent has emerged as a promising choice due to their low cost, eco-friendly nature, and sustainability. This paper summarizes recent advancements in MNP removal using carbon-based adsorbents, with a focus on the modification methods and adsorption mechanisms. Additionally, the factors influencing the adsorption performance and the methods for characterizing the adsorption mechanism are analyzed. Finally, the advantages and disadvantages of carbon-based adsorbents over other adsorbents are discussed, along with the current state of sustainable recycling and future research prospects.

Control strategies for microplastic pollution in groundwater

Groundwater is the primary source of water that occurs below the earth's surface. However, the advancement in technology and the increasing population, which lead to the discharge of contaminants such as microplastics (MPs), have an adverse impact on the quality of groundwater. MPs are ubiquitous pollutants that are widely found throughout the world. The maximum abundance of MPs is 4 items/L and 15.2 items/L in groundwater at the specific location of China and USA. Various factors can affect the migration of MPs from soil to groundwater. The occurrence of MPs in water causes serious health issues. Therefore, taking appropriate strategies to control MP contamination in groundwater is urgent and important. This review summarizes the current literature on the migration process of MPs from soil to groundwater along with possible methods for the remediation of MP-polluted groundwater. The main objective of the review is to summarize the technical parameters, process, mechanism, and characteristics of various remediation methods and to analyze strategies for controlling MP pollution in groundwater, providing a reference for future research. Possible control strategies for MP pollution in groundwater include two aspects: i) prevention of MPs from entering groundwater; ii) remediation of polluted groundwater with MPs (ectopic remediation and in-situ remediation). Formulating legislative measures, strengthening public awareness and producing more environment-friendly alternatives can be helpful to reduce the production of MPs from the source. Manage plastic waste reasonably is also a good strategy and the most important part of the management is recycling. The shortcomings of the current study and the direction of future research are also highlighted in the review.

Clean water production from plastic and heavy metal contaminated waters using redox-sensitive iron nanoparticle-loaded biochar

The unceasing release of tiny plastics (microplastics and nanoplastics) and their additives, like metal ions, into the aquatic systems from industries and other sources is a globally escalating problem. Their combined toxic effects and human health hazard are already proven; hence, their remediation is requisite. This study utilised the nano-zerovalent iron-loaded sugarcane bagasse-derived biochar (nZVI-SBC) for simultaneous removal of Nanoplastics (NPs) of different functionality and size along with metal ions (Ni2+, Cd2+, AsO43-, and CrO42-). Batch and column experiments were conducted, and the results showed an efficient removal of contaminants with maximum sorption of carboxylate-modified NPs of size 500 nm (qmax = 90.3 mg/g) among all three NPs types. Significant removal was observed in Cd2+ in case of cations and CrO42- in case of anions with qmax = 44.0 and 87.8 mg/g, respectively. Kinetics and the isotherm modelling better fitted the pseudo-second-order kinetic model and Sips isotherm model, respectively for both NPs and metal ions. The designed material worked well in pH range of 4-8, ionic strength 1-20 mM and in complex aqueous matrices, with >90% removal. FTIR, zeta potential and the imaging analysis of the reaction precipitates confirmed the electrostatic attraction, pore retention and complexation as the potential mechanisms for removing NPs, whereas, XPS studies confirmed the reduction co-precipitation and surface complexation as the possible mechanism for removing metal ions. High values of attachment efficiency factor calculated from colloidal filtration theory (CFT) validated the experimental results and justified the high sorption of carboxylate modified 500 nm NPs particles. The synthesized material successfully removed both NPs of varying size and functionality and metal ions simultaneously with significant efficacy in complex environmental samples proving the broad applicability of material in realistic environmental conditions and different types of water treatment processes.

Removal of oxytetracycline from wastewater by biochar modified with biosynthesized iron oxide nanoparticles and carbon nanotubes: Modification performance and adsorption mechanism

The pollution problem of oxytetracycline (OTC) from wastewater becomes more serious, so an efficient, economical, and green adsorption material is urgently explored. In this study, the multilayer porous biochar (OBC) was prepared by coupling carbon nanotubes with iron oxide nanoparticles synthesized by Aquabacterium sp. XL4 to modify corncobs under medium temperature (600 °C) conditions. The adsorption capacity of OBC could reach 72.59 mg g-1 after preparation and operation parameters were optimized. In addition, various adsorption models suggested that OTC removal resulted from the combined effect of chemisorption, multilayer interaction, and disordered diffusion. Meanwhile, the OBC was fully characterized and exhibited a large specific surface area (237.51 m2 g-1), abundant functional groups, stable crystal structure, high graphitization, and mild magnetic properties (0.8 emu g-1). The OTC removal mechanisms mainly included electrostatic interactions, ligand exchange, π-π bonding reactions, hydrogen bonds, and complexation. pH and coexistence substance experiments revealed that the OBC possesses a wide pH adaptation range and excellent anti-interference ability. Finally, the safety and reusability of OBC were confirmed by repeated experiments. In summary, OBC as a biosynthetic material shows considerable potential for application in the field of purifying new pollution from wastewater.

Fate and environmental behaviors of microplastics through the lens of free radical

Microplastics (MPs), as plastics with a size of less than 5 mm, are ubiquitously present in the environment and become an increasing environmental concern. The fate and environmental behavior of MPs are significantly influenced by the presence of free radicals. Free radicals can cause surface breakage, chemical release, change in crystallinity and hydrophilicity, and aggregation of MPs. On the other hand, the generation of free radicals with a high concentration and oxidation potential can effectively degrade MPs. There is a limited review article to bridge the fate and environmental behaviors of MP with free radicals and their reactions. This paper reviews the sources, types, detection methods, generation mechanisms, and influencing factors of free radicals affecting the environmental processes of MPs, the environmental effects of MPs controlled by free radicals, and the degradation strategies of MPs based on free radical-associated technologies. Moreover, this review elaborates on the limitations of the current research and provides ideas for future research on the interactions between MPs and free radicals to better explain their environmental impacts and control their risks. This article aims to keep the reader abreast of the latest development in the fate and environmental behaviors of MP with free radicals and their reactions and to bridge free radical chemistry with MP control methodology.

Recent advances towards micro(nano)plastics research in wetland ecosystems: A systematic review on sources, removal, and ecological impacts

In recent years, microplastics/nanoplastics (MPs/NPs) have received substantial attention worldwide owing to their wide applications, persistence, and potential risks. Wetland systems are considered to be an important "sink" for MPs/NPs, which can have potential ecological and environmental effects on the ecosystem. This paper provides a comprehensive and systematic review of the sources and characteristics of MPs/NPs in wetland ecosystems, together with a detailed analysis of MP/NP removal and associated mechanisms in wetland systems. In addition, the eco-toxicological effects of MPs/NPs in wetland ecosystems, including plant, animal, and microbial responses, were reviewed with a focus on changes in the microbial community relevant to pollutant removal. The effects of MPs/NPs exposure on conventional pollutant removal by wetland systems and their greenhouse gas emissions are also discussed. Finally, current knowledge gaps and future recommendations are presented, including the ecological impact of exposure to various MPs/NPs on wetland ecosystems and the ecological risks of MPs/NPs associated with the migration of different contaminants and antibiotic resistance genes. This work will facilitate a better understanding of the sources, characteristics, and environmental and ecological impacts of MPs/NPs in wetland ecosystems, and provide a new perspective to promote development in this field.

Mechanisms of polystyrene nanoplastics adsorption onto activated carbon modified by ZnCl2

In this study, the adsorption capacity of activated carbon was enhanced after zinc chloride activation. The effects of pore filling, n-π and π-π interaction and electrostatic interaction on the adsorption of polystyrene nanoplastics (PSNPs) by activated carbon were determined by SEM, BET, Raman spectrum, FTIR and surface Zeta potential. Pore filling, electrostatic interaction and n-π interaction and π-π interaction all played a role in the adsorption process, but n-π interaction and π-π interaction was not the decisive role. The adsorption of PSNPs on activated carbon conformed to the pseudo-second-order kinetics and Langmuir isotherm, and there was spontaneous physical adsorption process driven by entropy in the adsorption process. Further, the effects of common anions SO₄^2-, HCO₃^-, and Cl^- in water on the adsorption of PSNPs by activated carbon were investigated, and the results showed that the presence of these ions could increase the adsorption capacity to some extent. ZCAC has a stable adsorption capacity under tap water, but its adsorption capacity is affected under lake water. In addition, the reuse of activated carbon was investugated, and the adsorption capacity of activated carbon was fully recovered after high temperature calcination. This study provided a direction for materials modification of adsorbed nanoplastics and a feasible method for removal of nanoplastics in drinking water treatment plants.

Destabilization of polystyrene nanoplastics with different surface charge and particle size by Fe electrocoagulation

Nanoplastics (NPs) discharged from wastewater could pose a major threat to organisms in aquatic environments. Effective removal of NPs by the current conventional coagulation-sedimentation process is not yet satisfactory. This study aimed to investigate the destabilization mechanism of polystyrene NPs (PS-NPs) with different surface properties and sizes (i.e., 90 nm, 200 nm, and 500 nm) by Fe electrocoagulation (EC). Two types of PS-NPs were prepared by a nanoprecipitation method using sodium dodecyl sulfate and cetrimonium bromide solutions to produce negatively-charged SDS-NPs and positively-charged CTAB-NPs. For both NPs, obvious floc aggregation from 7 μm to 14 μm was observed only at pH 7 with particulate Fe accounted for >90 %. At pH 7, Fe EC removed 85.3 %, 82.8 %, and 74.7 % of the negatively-charged SDS-NPs at small-, mid-, and large-sizes from 90 nm, 200 nm, to 500 nm, respectively. Small-size SDS-NPs_{(90 nm)} were destabilized through physical adsorption on the surface of Fe flocs, while the main removal mechanism of mid- and large-SDS-NPs_{(200 nm and 500 nm)} involved the enmeshment of large Fe flocs. Compared to SDS-NPs_{(200 nm and 500 nm)}, Fe EC performed similar destabilization behavior to two CTAB-NPs_{(200 nm and 500 nm)}, but it resulted in much lower removal rates of 54.8 % - 77.9 %. The Fe EC also exhibited no removal (<1 %) ability toward the small-size and positively-charged CTAB-NPs_{(90 nm)} due to insufficient formation of effective Fe flocs. Our results provide insight into the destabilization of PS in nano-scale with different sizes and surface properties, which clarifies the behavior of complex NPs in a Fe EC-system.

Innovations in the Development of Promising Adsorbents for the Remediation of Microplastics and Nanoplastics - A Critical Review

Microplastics and nanoplastics are being assumed as emerging toxic pollutants owing to their unique persistent physicochemical attributes, chemical stability, and nonbiodegradable nature. Owing to their possible toxicological impacts (not only on aquatic biota but also on humans), scientific communities are developing innovative technologies to remove microplastics and nanoplastics from polluted waters. Various technologies, including adsorption, coagulation, photocatalysis, bioremediation, and filtration, have been developed and employed to eliminate microplastics and nanoplastics. Recently, adsorption technology has been getting great interest in capturing microplastics and nanoplastics and achieving excellent removal performance. Therefore, this review is designed to discuss recent innovations in developing promising adsorbents for the remediation of microplastics and nanoplastics from wastewater and natural water. The developed adsorbents have been classified into four main classes: sponge/aerogel-based, metal-based, biochar-based, and other developed adsorbents, and their performance efficiencies have been critically examined. Further, the influence of various pertinent factors, including adsorbents' characteristics, microplastics/nanoplastics' characteristics, solution pH, reaction temperature, natural organic matter, and co-existing/interfering ions on the removal performance of advanced adsorbents, have been critically assessed. Importantly, the particle application of the developed adsorbents in removing microplastics and nanoplastics from natural water has been elucidated. In addition, barriers to market penetration of the developed adsorbents are briefly discussed to help experts transfer adsorption-based technology from laboratory-scale to commercial applications. Finally, the current knowledge gaps and future recommendations are highlighted to assist scientific communal for improving adsorption-based technologies to battle against microplastics and nanoplastics pollution.

Nontargeted metabolomic analysis to unravel alleviation mechanisms of carbon nanotubes on inhibition of alfalfa growth under pyrene stress

Carbon nanotubes have displayed great potential in enhancing phytoremediation of PAHs polluted soils. However, the response of plants to the coexistence of carbon nanotubes and PAHs and the associated influencing mechanisms remain largely unknown. Here, the effect of carbon nanotubes on alfalfa growth and pyrene uptake under exposure to pyrene was evaluated through sand culture experiment and gas chromatography time-of-flight mass spectrometer (GC-TOF-MS) based metabolomics. Results showed that pyrene at 10 mg kg^-1 obviously reduced the shoot fresh weight of alfalfa by 18.3 %. Multiwall carbon nanotubes (MWCNTs) at 25 and 50 mg kg^-1 significantly enhanced the shoot fresh weight in a dose-dependent manner, nearly by 80 % at 50 mg kg^-1. Pyrene was mainly accumulated in alfalfa roots, in which the concentration was 35 times as much as that in shoots. MWCNTs greatly enhanced the accumulation of pyrene in alfalfa roots, almost by two times at 50 mg kg^-1, while decreased pyrene concentration in shoots, from 0.11 mg kg^-1 to 0.044 mg kg^-1 at MWCNTs concentration of 50 mg kg^-1. Metabolomics data revealed that pyrene at 10 mg kg^-1 trigged significant metabolic changes in alfalfa root exudates, downregulating 27 metabolites. MWCNTs generated an increase in the contents of some downregulated metabolites caused by pyrene stress, which were restored to the original level or even higher, mainly including organic acids and amino acids. MWNCTs significantly enriched some metabolic pathways positively correlated with shoot growth and pyrene accumulation in shoots under exposure to pyrene, including TCA cycle, glyoxylate and dicarboxylate metabolism, cysteine and methione metabolism as well as alanine, aspartate and glutamate metabolism. This work highlights the regulation effect of MWCNTs on the metabolism of root exudates, which are helpful for alfalfa to alleviate the stress from pyrene contamination.

Remediation technology towards zero plastic pollution: Recent advance and perspectives

The rapid growth of plastic wastes exceeds efforts to eliminate plastic pollution owing to the outbreak of COVID-19 in 2020 and then aggravates inherent environmental threats to the ecosystem. The paper provided a short introduction relating to the hazards of plastic wastes on environment and a detailed statement about plastic toxicity on human. The article stated on plastic how to enter the body and cause harm for us step by step. Given the toxicity and harm of plastic wastes on human, the degradation of plastic wastes via the physical, chemical and biotic methodologies is looked back. The advanced physical techniques are introduced briefly at firstly. Additionally, evaluate on chemical method for plastic decomposition and review on biotic degradation of plastic. The reactive oxygen species and the enzymes play a crucial role in chemical and biotic degradation processes, respectively. The reactive oxygen species are derived from the activated state of oxides, and the enzymes that aid the microorganism to ingest plastic through its metabolic mechanism are secreted by the microorganism. Subsequently, the potential possibility of upcycling plastic is analyzed from two aspects of the technology and application. The innovative technology utilizes sunlight as driver-power of plastic upcycling. And the carbon capture, utilization and sequestration and the growth substrate provided the novel guided directions for plastic recycle. Lastly, the three suggestions on plastic waste management are expected to establish an economy and efficient plastic sorting system, and two engineering solutions on plastic recycle are to make a contribution for sustainable upcycling of plastic.