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It is well known that microplastics (MPs) may experience weathering and aging under ultraviolet light (UV) irradiation, but it remains unclear if these processes are impacted by natural components, such as clay minerals. In this study, we systematically investigated the photodegradation behaviors of polyvinyl chloride (PVC) and poly (ethylene terephthalate) (PET), two utmost used plastics, in the presence of clay minerals (kaolinite and montmorillonite). The results demonstrated that the clay minerals, particularly kaolinite, significantly promoted the MPs photodegradation, and the aging of PET was more prominent. The photodegradation was the most distinct at pH 7.0, regardless of the presence or absence of the clay minerals. The results of electron paramagnetic resonance and inhibition experiments of reactive oxygen species indicated that the minerals, particularly kaolinite, remarkably facilitated production of •OH, which was the key species contributing to the photodegradation of MPs. Specifically, UV irradiation facilitated the photo-ionization of MPs, producing hydrated electrons and MP radical cations (MP+). The Lewis base sites prevalent on the clay siloxane surfaces could stabilize the MP radical cations and prevent their recombination with hydrated electrons, which promoted the generation of •OH under aerobic conditions, and facilitated the degradation of MP. Two-dimensional (2D) Fourier transformation infrared (FTIR) correlation spectroscopy (COS) analysis and ultra-high-performance liquid chromatography coupled to a Q Exactive Orbitrap HF mass spectrometer were used to identify the sequential changes of functional groups, and the degradation products of the MPs. This study improves our understanding on the aging of MPs in the complex natural environment.

Microcystis aeruginosa (M. aeruginosa), as the representative hazardous algae in cyanobacteria blooms, has long posed a threat to aquatic ecosystems. Here, a self-cooling dielectric barrier discharge plasma (DBDP) reactor was used to eliminate M. aeruginosa in water. The removal efficiency and mechanism of DBDP for M. aeruginosa and its toxin release during the treatment process was investigated. The results showed that over 99% of M. aeruginosa cells were removed by DBDP over 60 min under optimal conditions, and treated M. aeruginosa lost their ability to reproduce entirely. Reactive species generated in the self-cooling DBDP reactor damaged the membrane of M. aeruginosa, leading to leakage and degradation of dissolved organic matter. Increased intracellular reactive oxygen species accelerated the breakdown of protein and enzyme, and causes cell cytolysis. Eventually, M. aeruginosa was mineralized and lost its activity. The ·OH, 1O2 and ·O2- were crucial for inactivating M. aeruginosa. During the treatment process, the toxin microcystin-LR increased in the first 20 min, but declined over time: its concentration fell below 1 μg·mL-1 after 60 min. This study provides insight into M. aeruginosa’ s elimination in water by DBDP and has significant implications for developing a plasma technique to curtail cyanobacteria bloom.

Classical chemical precipitation technology is inefficient for the removal of heavy metal-organic complexes from wastewater. In this study, a novel and green strategy of coupling bicarbonate-activated hydrogen peroxide (BHP) oxidation and alkaline precipitation was proposed for simultaneous decomplexation of Cu-ethylenediaminetetraacetic acid (Cu-EDTA) and Cu precipitation. The Cu-EDTA decomplexation efficiency reached 92.0% within 60 min of the BHP treatment, and the decomplexation process was spontaneous and endothermic. Reactive substances such as O2−, OH, and 1O2 were identified, and O2− was predominant in the Cu-EDTA decomplexation. The weak alkaline environment provided by bicarbonate favored the generation of the reactive substances and subsequent Cu-EDTA decomplexation. Relatively higher H2O2 dosage favored Cu-EDTA decomplexation, while excessive bicarbonate dosage inhibited the reaction. TOC removal efficiency and Cu removal efficiency reached 78.4% and 68.3% after 60 min treatment, respectively. The Cu O and Cu N bonds in Cu-EDTA were destroyed by the reactive substances, and a series of Cu-containing intermediates, small organic molecules such as ethanamine, ethylene glycol and butanediol, and NO3− were produced. The released Cu ions were precipitated as Cu2(OH)2CO3, CuCO3, Cu(OH)2, and CuO. Possible pathways of Cu-EDTA decomplexation in this system were proposed.

EDTA-chelated metals, which widely occur during heavy metal contaminated-soil remediation by EDTA washing, are difficult to remove by traditional chemical precipitation because of the strong complexation between EDTA and heavy metal ions. A strategy, i.e., non-thermal plasma (NTP) oxidation/alkaline precipitation, was developed to remove the EDTA-chelated metals; EDTA-chelated copper (EDTA-Cu) was used as the model pollutant and the influences of some concomitant ions on EDTA-Cu decomplexation and Cu release were evaluated. The concomitant anions Cl− and NO3− favored EDTA-Cu decomplexation, whereas CO32− disfavored this process; the concomitant positive ions Ni2+ and Fe3+ both promoted EDTA-Cu decomplexation via replacement or Fenton-like effects. These effects were also characterized by total organic carbon and Cu2+ release analysis. The contributions of O3, O, 1O2, OH, and O2− to EDTA-Cu decomplexation were quantitatively analyzed. Ethanamine, acetamide, glycolic acid, acetic acid, formamide, ethylene glycol, and butanedioic acid were monitored using gas chromatography-mass spectrometry, and a possible decomposition pathway of EDTA-Cu was proposed. Furthermore, the chemical compositions of the precipitates were diagnosed by energy dispersive X-ray spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and thermal gravimetric analysis.

The application of Ag3PO4 as a commonly used photocatalyst is limited by its high recombination potency and electron–hole pairs with weak redox potential. It is significant to enhance the photocata...

Transformation of PAHs, i.e., anthracene, and production of environmentally persistent free radicals (EPFRs) on seven types of representative soils were investigated, focusing on the influences of soil characteristics and ambient conditions on these reactions. The transformation rate of anthracene exhibits the order of red earth > yellow earth > latosol ∼ fluvo-aquic soil > brown earth > chernozem > calcic brown soil, which is positively correlated with Fe content in soils. Afterwards, batch reactions on pure representatives of soil minerals, including Fe2O3, Fe3O4, FeOOH, and MnO2, demonstrate that anthracene is prone to mineral-promoted transformation. The presence of higher amount of organic carbon lower the transformation rate of anthracene, whereas the formed EPFRs can be stabilized for a longer time. Subsequent experiments associated with the influences of environmental conditions on mineral-promoted reactions suggest that both anthracene transformation and EPFRs generation readily occur under dry condition. Light irradiation not only promotes the formation of EPFRs, but also greatly accelerates the decay of EPFRs and the 1/e lifetime decreases from 5 to 20 d in dark to approximately 1 d. Meanwhile, the anoxic condition is favorable for the persistence of EPFRs. The obtained results suggested the potential environmental risks association with EPFRs in PAHs-contaminated soils.

Non-thermal plasma technology can inactivate microorganisms that maybe used in the food processing industry. This study mainly aims to evaluate the effect of a gas-phase surface discharge plasma system with a spray reactor on yeasts (Zygosaccharomyces rouxii LB and 1130) in apple juice. This method avoids the limitation of liquid penetration depths in plasma treatment, expanding the processing capacity. Owing to this advantage, this approach can be used to industrialize liquid food sterilization. Experimental results showed that the number of Z. rouxii LB and 1130 cells decreased by about 6.58 and 6.82 log reductions, respectively, in apple juice after discharge plasma treatment for 30 min. The treatment used a voltage of 21.3 kV and inactivation followed the downward concave Weibull kinetics. Longer plasma exposure times with higher discharge voltages and regulated volume flow rate for both gas and liquid phases resulted in greater inactivation rates. Scanning electron microscopy revealed that the structures of plasma-treated cells were severely damaged during the discharge plasma process. Plasma-generated compounds in liquid, such as hydrogen peroxide and ozone in the liquid phase, are generally responsible for the inactivation of microorganisms.

Phthalates, as additives in the plastic production process, were able to enter the soil, causing huge risks to soil environment and human health. The potential of phthalates elimination in soil using dielectric barrier discharge (DBD) plasma was evaluated, with dimethyl phthalate (DMP) as a model pollutant. The experimental results demonstrated that DMP in soil could be decomposed by the DBD plasma oxidation. DMP concentration was reduced from 200 mg kg−1 to 87 mg kg−1 after 60 min’s DBD plasma oxidation, and its decomposition process fitted well with the first-order kinetics. Soil moisture was an important parameter affecting DMP decomposition in soil. Lower initial concentration was beneficial for DMP degradation. Analysis on types and action ranges of reactive oxygen species participating in DMP decomposition demonstrated that oxygen-containing species and electron played crucial roles. DMP molecular structure was destroyed in the DBD plasma processing, and phthalic acid monomethyl ester, phthalic acid, acetic acid, and oxalic acid were detected as the main intermediates. DBD plasma oxidation decreased the toxicity of DMP to seed germination and growth. Germination rate of wheat seed and activity of root system both increased, while free radical damage to cell membrane was significantly alleviated after 60 min’s DBD plasma oxidation.

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are global environmental pollutants and pose significant threats to environmental safety and human health. Defluorination of PFOA and PFOS was investigated theoretically and practically in a mesoporous plasma system in this study. Rapid and highly efficient defluorination was realized, and 98% and 65% defluorination rate for PFOA and PFOS, respectively, were obtained within 60 min of treatment. Electrons generated in the mesoporous plasma system played a decisive role in PFOA and PFOS defluorination; other species, including 1O2 and ·OH, also contributed to defluorination. C-F, C-C, and C-S bonds were broken by plasma oxidation; various shorter-chain perfluorocarboxylic acids, polyfluoroalkyl substances, and alcohols were produced. PFOA and PFOS decomposition mechanisms involved electron transfer, defluorination, decarboxylation, and hydroxylation reactions. Desulfonation reactions were also involved in PFOS decomposition. Density functional theory calculations identified sites susceptible to be attacked and the main degradation pathways. Effective defluorination of PFOA and PFOS reduced their toxicities. Furthermore, its potential for actual surface water treatment was also determined.

Polycyclic aromatic hydrocarbons (PAHs) are important mutagen prevalent in the contaminated sites, bringing potential risks to human health. Iron oxides are important natural components in soils. Pyrene removal in soil using persulfate (PS) oxidation activated by microwave (MW) and magnetite (Fe3O4) was investigated. Fe3O4 significantly promoted pyrene removal in the soil; 91.7 % of pyrene was degraded within 45 min treatment. Pyrene removal rate in the Fe3O4/MW/PS system was 5.18 and 3.00 times higher than that in the Fe3O4/PS and MW/PS systems. Increasing in Fe3O4 dosage, PS concentration, MW temperature, and soil moisture content in the selected range were conducive for pyrene degradation. SO4•−, •OH, O2•−, and 1O2 were responsible for pyrene degradation, and the conversion of Fe (Ⅱ) in the Fe3O4 to Fe (Ⅲ) contributed to the formation of O2•− and 1O2. Characteristic bands of pyrene were more obviously destroyed by the Fe3O4/MW/PS oxidation, in comparison with MW/PS oxidation. Ring hydroxylation and ring-opening reactions were the main degradation pathways of pyrene. The toxicities of the formed byproducts were significantly reduced after treatment. This study provided a promising option for pyrene contaminated soil remediation.

Per- and polyfluoroalkyl substances (PFASs) have been found to be widely present in soil. Dissolved organic matter (DOM) in soil are supposed to greatly affect the bioavailability of PFASs in soil. Herein, hydroponic experiments were conducted to understand the impacts of two kinds of typical DOM, bovine serum albumin (BSA) and humic acid (HA), on the uptake and translocation of legacy PFASs and their emerging alternatives, perfluorooctane sulfonic acid (PFOS), perfluorooctane acid (PFOA), perfluorohexane sulfonic (PFHxS) and 6:2 chlorinated polyfluoroalkyl ether sulfonate (6:2 Cl-PFESA) in wheat (Triticum aestivum L.). The results indicated that both HA and BSA significantly inhibited the bioaccumulation and translocation of PFASs in the roots and shoots of wheat, and the impacts of BSA were greater than HA. This difference was explained by the greater binding affinities of the four PFASs with BSA than with HA, as evidenced by the equilibrium dialysis and isothermal titration calorimetry (ITC) analyses. It was noting that inhibition impacts of the BSA-HA mixture (1:1) were lower than BSA alone. The results of Fourier transform infrared (FT-IR) spectroscopy and excitation-emission matrix (EEM) fluorescence spectroscopy suggested that HA could bind with the fluorescent tryptophan residues in BSA greatly, competing the binding sites with PFASs and forming a cover on the surface of BSA. As a result, the binding of PFASs with BSA-HA complex was much lower than that with BSA, but close to HA. The results of this study shed light on the impacts of DOM in soil on the bioaccumulation and translocation of PFASs in plants.

The heavy metal-organic complexes and heavy metal ions pose great threats to human health, and their elimination from water environment is quite urgent. Simultaneous decomplexation of heavy metal complex Cu-EDTA and reduction of Cr(VI) was performed in a persulfate (PS)/formate (FA) system. Oxidizing species and reductive species were simultaneously produced in this PS/FA system, which realized 96.6% of Cu-EDTA decomplexation and 100% of Cr(VI) reduction within 90 min treatment under the solution pH 3.60. Higher solution temperature and acidic conditions favored Cu-EDTA decomplexation and Cr(VI) reduction. There existed an appropriate molar ratio of FA and PS to simultaneously realize high-efficient Cu-EDTA decomplexation and Cr(VI) reduction. SO4•-, •OH, and 1O2 drove the Cu-EDTA decomplexation, which destroyed the chelating sites of Cu and EDTA, and finally it was oxidized to small molecular alcohols, organic acids, and Cu2+. Reductive species CO2•− was produced by the reaction of SO4•− and FA, as well as •OH and FA, which dominated the reduction of Cr(VI) to Cr3+. Carbonates, hydroxides, and oxides including Cu(OH)2, CuCO3, Cu2CO3(OH)2, CuO, Cr(OH)3, and Cr2O3 were the main composites in precipitates after Cu2+ and Cr3+ were precipitated. Furthermore, Cu-EDTA decomplexation and Cr(VI) reduction processes induced by PS/FA were put forward.

Phenol-formaldehyde resin microplastic (PF-MP) is one of the major inhalable microplastics in environments released from the manufacture, processing and usage of PF materials. The associated toxicities of PF-MP might be affected by photoaging. In this study, the dynamic evolutions of the oxidative potential (OP) and redox-active species, including environmentally persistent free radicals (EPFRs), reactive oxygen species (ROS), peroxides and conjugated carbonyls, as well as the associated cytotoxicity of PF-MP were systematically investigated as a result of the simulated sunlight irradiation. As the photoaging time extended, the OP of PF-MP increased. The contents of the produced conjugated carbonyls, ROS and PF-bound EPFRs due to light irradiation increased as well, and displayed significant correlations with the OP (Spearman r > 0.6, p

Contaminated sites from pesticide industry have attracted global concern due to the characteristics of organic pollution with high concentrations and complete loss of habitat conditions. Remediation of organophosphorus pesticide polluted soil using microwave-activated persulfate (MW/PS) oxidation was investigated in this study, with parathion as the representative pesticide. Approximately 90 % of parathion was degraded after 90 min of MW/PS oxidation treatment, which was superior to those by single PS or MW treatment. Relatively greater performances for parathion degradation were obtained in a relatively larger PS dosage, higher microwave temperature, and lower organic matter content. Appropriate soil moisture favored parathion degradation in soil. SO4 −, OH, O2 −, and 1O2 generated in the MW/PS system all contributed to parathion degradation. Multiple spectroscopy analyses indicated that P O and P S bonds in parathion were destroyed after MW/PS oxidation, accompanied by generation of hydroxylated and carbonylated byproducts. The soil safety after parathion degradation was assessed via model prediction. Furthermore, MW/PS oxidation also exhibited great performance for degradation of other organophosphorus pesticides, including ethion, phorate, and terbufos.

As emerging alternatives of legacy perfluoroalkyl substances, 6:2 fluorotelomer sulfonate (6:2 FTS), 6:2 chlorinated polyfluoroalkyl ether sulfonates (6:2 Cl-PFESA), and perfluorophosphinates (C6/C6 and C8/C8 PFPiAs) are supposed to be partitioned to soil and highly persistent in the environment. The uptake of novel per- and polyfluoroalkyl substances (PFASs) by plants represents a potential pathway for their transfer in the food chain. In this study, the bioavailability of these four novel PFASs in soil and the bioaccumulation characteristics in greenhouse-grown wheat (

A large number of plastic products potentially become smaller particles, including nanoplastics, under multiple actions in the environment. The interactions between nanoplastic particles and constituents in the environment, such as minerals, would greatly affect the transport, fate and toxic effects of nanoplastics. In this study, the interactions of polystyrene nanoplastic (PSNP) with four typical minerals, including goethite, magnetite, kaolinite and montmorillonite, in aqueous phase were investigated. The stability of PSNP colloidal suspension decreased in the presence of the positively charged goethite or magnetite, while it was not affected by the negatively charged montmorillonite and kaolinite, suggesting that there was a strong electrostatic attraction between PSNP and the two iron oxides. Incubation of PSNP with other three metal oxides with different surface charges, MnO2, Al2O3 and SiO2, confirmed the importance of electrostatic interaction in the stability of PSNP suspension. The transmission electron microscopy (TEM) analysis and batch adsorption experiments indicated that PSNP was effectively adsorbed on goethite or magnetite due to the strong electrostatic attraction between them. The Fourier transform infrared spectra (FTIR) and two-dimensional correlation spectroscopy (2D-COS) analyses indicated that there was strong hydrogen bonding between the –OH (γ-FeOOH) of goethite and PSNP, contributing to the higher adsorption of PSNP on goethite than magnetite. These findings shed light on the interactions of PSNP with mineral surfaces, and potential fate of PSNP under natural conditions in the water environment.

Carbon spheres (CS) were synthesized from monosaccharides (glucose), disaccharides (β-cyclodextrin), and polysaccharides (sucrose) using surfactants, and then by hydrothermal treatment with g-C3N4 ...

Phthalates, as additives in the plastic production process, were able to enter the water environment, causing huge risks to ecological environment and human health. The potential of phthalates elimination in aqueous using sodium percarbonate (SPC) activated by discharge plasma (marked as “SPC + plasma”) was evaluated, with dimethyl phthalate (DMP) as a model pollutant. Experimental results showed that about 92.1% of DMP was eliminated in the “SPC + plasma” system with the treatment time of 30 min, which was 30.7% higher than that in sole plasma system, and the synergetic intensity for DMP elimination reached up to 127.0; and the energy yield was also raised by 131%. H2O2 and OH radicals formation were promoted but ozone concentration decreased in the “SPC + plasma” system. Appropriate SPC dosage benefited DMP elimination, and the synergetic intensity increased from 2.0 to 127.0 as the SPC dosage increased from 0.06 mmol L−1 to 0.12 mmol L−1. OH radicals, O2·−, 1O2, and CO3·− played crucial roles in DMP elimination, and the roles of O2·− and 1O2 were strengthened in the “SPC + plasma” system. Ultraviolet–visible spectroscopy measurement, total content of organic carbon, atomic force microscopy and three-dimensional fluorescence analysis demonstrated that DMP molecular structure was destroyed during treatment, and some smaller molecular fractions were generated. The main intermediates included phthalic acid monomethyl ester, phthalic acid, o-phthalic anhydride, acetic acid, formic acid, and oxalic acid. The possible enhancement mechanisms for DMP elimination in the “SPC + plasma” system were proposed.

Antibiotic-resistant bacteria (ARB) and their resistance genes (ARGs), which are commonly detected in waters, are emerging environmental contaminants with strong pathogenicity. Simultaneous removal of ARB and ARGs in water by mesoporous plasma was explored in this study, focusing on evaluating the impacts of common inorganic ions on ARB inactivation, antibiotic resistance reduction, and change in ARGs profiles. The antibiotic-resistant Escherichia coli (AR E. coli) was selected as the model ARB. The experimental results demonstrated that the presence of NO3−, Cu2+, and Fe2+ all promoted AR E. coli inactivation and ARGs elimination, reduced its antibiotic resistance, and also inhibited horizontal gene transfer of ARGs; whereas CO32− inhibited these processes, and SO42− did not have distinct effect. During the plasma treatment process, Fe2+ significant enhancement on OH formation via reactions with H2O, the highest performance was observed in the presence of Fe2+. The membrane structure, disruption of biological processes, dissolution of intracellular components, and DNA. These finding shed light on the potential effects of inorganic ions on ARB and ARGs elimination induced by the mesoporous plasma.

Heavy metal–organic complexes are difficult to remove by classic precipitation methods. In this study, MIL-53(Fe) photocatalyst was successfully synthesized and its photocatalytic activity for the decomplexation of heavy metal–organic complex was explored. Ethylenediaminetetraacetic acid complexed copper (Cu-EDTA) was chosen as the target. Experimental results showed that approximately 91% of Cu-EDTA was decomposed within 60 min under ultraviolet irradiation (UV), and 64% was mineralized within 120 min. Cu-EDTA decomplexation was mainly driven by the production of h+, HO• and 1O2 from the MIL-53(Fe). Fe(III) released from the MIL-53(Fe) was reduced by the photogenerated electrons and Cu(I) to form Fe(Ⅱ), which inhibited the recombination of photogenerated electrons and h+. More importantly, Fenton-like reactions and coprecipitation derived from the released Fe(III) promoted the decomplexation of Cu-EDTA. As a result, some small molecular compounds, including glycine, acetic acid, nitrilotriacetic acid, oxalic acid, oxamic acid, and NO3–, were generated. The possible decomplexation pathways of Cu-EDTA by MIL-53(Fe) photocatalysis were proposed. Effects of coexisting inorganic ions and organic matter on Cu-EDTA decomplexation were evaluated. Furthermore, the photocatalytic degradation potentials for other heavy metal complexes were also explored.

Antibiotic resistant bacteria (ARB) and resistance genes (ARGs) are emerging environmental pollutants with strong pathogenicity. In this study, surface plasma was developed to inactivate the donor ARB with Escherichia coli (AR E. coli) as a model, eliminate ARGs, and inhibit conjugative transfer of ARGs in water, highlighting the influences of concomitant inorganic ions. Surface plasma oxidation significantly inactivated AR E. coli, eliminated ARGs, and inhibited conjugative transfer of ARGs, and the presence of NO3-, Cu2+, and Fe2+ all promoted these processes, and SO42- did not have distinct effect. Approximately 4.5log AR E. coli was inactivated within 10 min treatment, and it increased to 7.4log AR E. coli after adding Fe2+. Integrons intI1 decreased by 3.10log (without Fe2+) and 4.43log (adding Fe2+); the addition of Fe2+ in the surface plasma induced 99.8% decline in the conjugative transfer frequency. The inhibition effects on the conjugative transfer of ARGs were mainly attributed to the reduced reactive oxygen species levels, decreased DNA damage-induced response, decreased intercellular contact, and down-regulated expression of plasmid transfer genes. This study disclosed underlying mechanisms for inhibiting ARGs transfer, and supplied a prospective technique for ARGs control.

Atmospheric dielectric barrier discharge (DBD) was attempted to improve the resistance of wheat seed to drought stress. Effects of DBD plasma on wheat seed germination, seedling growth, osmotic-adjustment products, lipid peroxidation, reactive oxygen species (ROS), antioxidant enzyme activity, abscisic acid, and drought resistant related genes expression under drought stress were investigated. The changes of the wheat seed coat before and after the DBD plasma treatment were explored. Experimental results showed that the DBD plasma treatment could alleviate the adverse effects of drought stress on wheat seed germination and seedling growth; the germination potential and germination rate increased by 27.2% and 27.6%, and the root length and shoot length of the wheat seedlings also increased. Proline and soluble sugar levels under drought stress were improved after the DBD plasma treatment, whereas the malondialdehyde content decreased. ROS contents under drought stress were reduced after the DBD plasma treatment, whereas the activities of superoxide dismutase, catalase, and peroxidase were promoted. DBD plasma treatment promoted abscisic acid generation in wheat seedlings, and it also regulated functional gene LEA1 and stimulated regulation genes SnRK2 and P5CS to resist drought stress. Etching effect and surface modification occurred on the seed coat after the DBD plasma treatment.

It is difficult to remove heavy metal-organic complexes from water by chemical precipitation because of the strong complexation ability between heavy metal ions and organics. In this study, the removal of the Cu-ethylenediaminetetraacetic acid (Cu-EDTA) complex using autocatalytic persulfate (PS) oxidation was investigated. The Cu-EDTA removal efficiency reached up to 96.57% after 90 min of treatment by PS oxidation. A higher PS concentration favored Cu-EDTA removal; An increase in the initial concentration of Cu-EDTA benefited PS activation, and a greater removal performance was obtained at a lower Cu-EDTA initial concentration (0.1 mmol L−1). Excessive Cu2+ accelerated Cu-EDTA removal, while superfluous EDTA suppressed it. Relatively lower initial solution pH value favored Cu-EDTA removal. SO4•-, •OH, and 1O2 displayed significant roles in the Cu-EDTA removal process, as they destroyed the chelating sites of the Cu(II) and EDTA molecules; finally small molecular organic acids, alcohols, and NO3− were produced. The released Cu(II) existed in the precipitates in the forms of Cu-based carbonates, Cu-based hydroxides, and copper oxide. A possible decomposition pathway of Cu-EDTA was proposed. Overall, multipathway activation of PS induced by heavy metal complexes could be an effective technique for the removal of the heavy metal complexes.

Chitosan is widely used in antibacterial, hypolipidemic, and anticancer fields, and the preparation of low molecular weight chitosan with excellent solubility and hydrophilicity is beneficial for its application. In this study, simultaneous production of low molecular weight chitosan and reducing sugars via chitosan depolymerization by surface discharge plasma was developed. More than 95% of the chitosan with an initial molecular weight of 682.5 kDa was depolymerized after 60 min of treatment, with the reducing sugar yield of 23.7%. ·OH, O2·-, and 1O2 played important roles in chitosan depolymerization; they preferentially attacked the amorphous structure of chitosan, resulting in breakage of the intra- and intermolecular hydrogen bonds and β-(1,4) glycosidic bonds, thereby forming low molecular weight chitosan. More electrons and hydrogen atoms would be provided by prepared low molecular weight chitosan due to the decreased intra- and intermolecular hydrogen bonds, and a high biological activity was finally attained. Overall, discharge plasma could be used as an effective technique for chitosan depolymerization, which widens its potential applications.

Polycyclic aromatic hydrocarbons (PAHs) contaminated sites have attracted worldwide concern due to their carcinogenic, mutagenic, and teratogenic natures. Crystallographic manganese oxides (MnxOy) are ubiquitous in soils. In this study, MnxOy enhanced PAHs contaminated soil remediation in a microwave activated persulfate (MW/PS) system was conducted, and pyrene was selected as a target pollutant. Significant enhancement performance on pyrene removal was observed after adding MnxOy, which ranked as β-MnO2 > α-MnO2 > γ-MnO2 > Mn2O3. Pyrene removal efficiency was enhanced from 65.7% to 85.6% within 15 min of treatment when β-MnO2 dosage increased from 0 to 0.1 g. MnxOy in the MW/PS system improved the production of active substances and converted radical process into non-radical process via conversion of Mn(IV) to Mn(III) and Mn-O-Mn to Mn-O-X. 1O2 played significant roles in pyrene degradation, whereas the presence of β-MnO2 alleviated the shielding effects of SO4 − and OH scavengers. Pyrene molecular structures were destroyed, and some ring-opening and/or lower ring byproducts were generated. Residual toxicity of pyrene and its degradation byproducts was predicted. This work provided a potential pathway to promote PAHs contaminated soil remediation via MnxOy enhanced MW/PS oxidation, and highlighted new insights into the mechanism of PS activation by metal oxides.

The reactivity of oxidizing materials is highly related to the exposed crystal facets. Herein, δ-MnO2 with different exposure facets were synthesized and the oxidative activities of the as-prepared materials were evaluated by degrading phenol in water without light. The degradation rate of phenol by δ-MnO2-{−111} was significantly higher than that by δ-MnO2-{001}. δ-MnO2-{−111} also displayed high degradation efficiency to a variety of other organic pollutants, such as ciprofloxacin, bisphenol A, 3-chlorophenol and sulfadiazine. Comprehensive characterization and theoretical calculation verified that the {−111} facet had high density of Mn3+, thus displaying enhanced direct oxidative capacity to degrade organic pollutants. In addition, the dominant {−111} facet promoted adsorption/activation of O2, thus favored the generation of superoxide radical (O2•−), which actively participated in the degradation of pollutants. The phenol degradation kinetics could be divided into two distinct phases: the rapid phase (k1obs = 0.468 min−1) induced by Mn3+ and the slower phase (k2obs = 0.048 min−1) dominated by O2•−. The synergistically promoted non-radical and radical based reactions resulted in greatly enhanced the oxidative activity of the δ-MnO2-{−111}. These findings deepen the understanding of facet-dependent oxidative performance of materials and provided valuable insights into the possible practical application of δ-MnO2 for water purification.

Patulin is a neurotoxic secondary metabolite and is widely present in fruit-based products and even in drinking water. The low-temperature discharge plasma approach was developed to detoxify patulin in water. Patulin decomposition and mineralization efficiencies reached 93% and 74% at an applied voltage of 16 kV in a 30 min treatment period, respectively. 1O2, OH, O2 −, and hydrated electrons generated in the discharge plasma process contributed to patulin decomposition. The lactone and hemiacetal groups that are responsible for the toxicity of patulin were significantly destroyed by discharge plasma oxidation, and some ring-opening intermediates, such as ethers, organic acids, and alcohols, were generated. Patulin decomposition pathways in this low-temperature discharge plasma process were then proposed. Model prediction indicated that acute oral toxicity in rats and developmental toxicity decreased after discharge plasma treatment, which was verified by actual cytotoxicity tests using yeast cells and HepG2 human hepatocellular carcinoma cells.

Air atmospheric dielectric barrier discharge plasma (DBD) was attempted to pretreat wheat seed to improve its germination and growth in this study. The effects of the DBD plasma treatment on the wheat seed germination, seedling growth, osmotic-adjustment products, lipid peroxidation level, and antioxidant enzymes activity were investigated. The experimental results showed that the DBD plasma treatment with an appropriate time scale could promote the wheat seed germination and seedling growth. The germination potential, germination rate, germination index, and vigor index increased by 26.7, 9.1, 16.9, and 46.9% after 7 min’s DBD plasma treatment, respectively; the root length, shoot length, fresh weight, and dry weight of the seedlings also increased after the DBD plasma treatment. The osmotic-adjustment products, proline and soluble sugar contents, in the wheat seedlings were significantly enhanced after the DBD plasma treatment with an appropriate time scale, while the malondialdehyde content decreased. Moreover, the activities of superoxide dismutase and peroxidase also increased after the DBD plasma treatment. The DBD plasma treatment led to etching effect on the wheat seed coat, resulting in the improvement of its water absorption capacity.

Humic acid (HA) was a predominant natural organic matter in ground water and surface waters. The removal of HA from micro-polluted source water using a gas phase surface discharge plasma at different grounding modes was studied, and three kinds of grounding modes (iron wire mesh, aluminized paper, and water) were selected. The experimental results illustrated that approximately 95.3% of HA in water was removed within 30 min’s discharge plasma treatment in the iron wire mesh electrode system, and it was 89.5% and 84.6% in the aluminized paper electrode system and water electrode system, respectively; although the strongest streamer discharge and the highest ozone equivalent concentration were both observed in the iron wire mesh electrode system. The discharge plasma treatment resulted in a relatively more homogeneous surface topography in the HA molecules as analyzed by scanning electron microscope (SEM), especially in the iron wire mesh electrode system and in the aluminized paper electrode system. The decomposition process of HA at different grounding modes was analyzed and compared via the evolution of the UV–Vis spectrum, dissolved organic carbon (DOC), specific ultraviolet absorbance (SUVA) and UV absorption ratios with treatment time. In addition, the HA removal efficacy in this study was comparable with those of some other techniques.

To enhance the photocatalytic activity of TiO2, reduced graphene oxide–TiO2 (RGO–TiO2) composites with sandwich-like structure were synthesized using a simple solvothermal method. The morphology, crystalline information, and structural property of the photocatalyst were characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Fourier transmission infrared spectroscopy. The photocatalytic performances of the RGO–TiO2 composites were evaluated by the degradation of orange II (AO7) in water under UV light irradiation. The results showed that the RGO–TiO2 composites exhibited much higher photocatalytic activity than TiO2 and that the removal efficiency of AO7 could reach above 95% only after 20 min of UV light irradiation under the optimum condition. The improved photocatalytic activity might be attributed to the improved charge transfer and significant separation of the photoinduced electrons and holes in the presence of a two-dimensional graphene network. The results of recycling experiments show that RGO–TiO2 composites have a high photostability, which is expected in the practical application. Radical trapping experiments indicated that ·OH plays a crucial role in the process of AO7 degradation.

Glyphosate was one of the most widely used herbicides in the world. Remediation of glyphosate-contaminated soil was conducted using atmospheric pressure dielectric barrier discharge (DBD) plasma. The feasibility of glyphosate degradation in soil was explored, and the soil leachate toxicity after remediation was assessed via a seed germination test. The experimental results showed that approximately 93.9% of glyphosate was degraded within 45 min of DBD plasma treatment with an energy yield of 0.47 g kWh⿿1, and the degradation process fitted the first-order kinetic model. Increasing the discharge voltage and decreasing the organic matter content of the soil were both found to facilitate glyphosate degradation. There existed appropriate soil moisture to realize high glyphosate degradation efficiency. Glyphosate mineralization was confirmed by changes of total organic carbon (TOC), chemical oxygen demand (COD), PO43⿿ and NO3⿿. The degradation intermediates including glycine, aminomethylphosphonic acid, acetic acid, formic acid, PO43⿿ and NO3⿿, CO2 and CO were observed. A possible pathway for glyphosate degradation in the soil using this system was proposed. Based on the soil leachate toxicity test using wheat seed germination, the soil did not exhibit any hazardous effects following high-efficiency glyphosate degradation.

Microplastics (MPs) are presumed to be inert during aging under ambient conditions. In this study, four types of virgin MPs, including polystyrene (PS), phenol-formaldehyde resin (PF), polyethylene (PE), and polyvinyl chloride (PVC), were aged under simulated solar light irradiation. Surprisingly, several environmentally persistent free radicals (EPFRs), which are considered to be a type of emerging contaminant, were detected on the irradiated PS and PF, rather than PE and PVC, by electron paramagnetic resonance (EPR) spectroscopy. Depending on the photoaging duration time, the characteristic g-factors of the EPFRs produced on PS and PF were 2.0044-2.0049 and 2.0043-2.0044, respectively. The generated EPFRs on PS and PF decayed rapidly at the initial stage and then slowly disappeared with the elapsed aging time. Analyses by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance (NMR), and gel permeation chromatography (GPC) suggested that MPs might experience chemical chain scission, O2/H2O addition, and EPFR formation under the light irradiation. Accompanying with the formation of EPFRs, reactive oxygen species, such as O2•- and •OH, were also observed. The findings provide a novel insight to evaluate the potential hazards of MPs to organisms and ecosystems.

Cu 2+ readily complexes with ethylenediaminetetraacetic acid (EDTA) to form a heavy metal complex (Cu-EDTA) that is typical in the effluents from mining and electroplating industries. It was difficult for the classical alkaline precipitation method to eliminate the heavy metal complex due to the strong bonding ability between Cu(II) and EDTA. Cu(II) release and removal performance after Cu-EDTA decomplexation in a non-thermal plasma oxidation system was carried out in this study. The removal process was characterized by chemical oxygen demand, total organic carbon, atomic force microscopy, and electroconductivity analysis. The toxicity effect of the treated Cu-EDTA solution was also tested by photobacterium bioassay. The experimental results showed that 80.2% of Cu was released and removed within 60 min of the non-thermal plasma treatment/alkaline precipitation. Relatively higher energy input, lower Cu-EDTA concentration, and acidic conditions were necessary to obtain greater Cu release and removal performance, and there existed an appropriate air flow rate for high-efficient Cu release and removal. O 2 − , OH, 1 O 2 , and O 3 were the main active substances leading to Cu 2+ release. Its residual toxicity to P.phosphoreum sp.-T3 was significantly reduced after treatment.

In this study, we discovered and isolated a new genus Brevibacillus strain from effluent of dyeing and finishing factory containing highly toxic p-chloroanilines (PCA). Based on the morphological, physiological and biochemical characteristics, as well as 16S rDNA sequence, the strain was identified and denominated as Brevibacillus S-618. Co-metabolism effect was found with extra carbon sources including sodium succinate, sodium citrate, ammonium chloride and glucose which can efficiently promote the biodegradation process of PCA. Under the optimal growth conditions at temperature of 30 °C, pH˜7 and air-water ratio of 0.3 m3/m3·min, the degradation rate of PCA in a 2 L pilot bioreactor with high concentration of 180 mg/L increased from 86.7% to 100% within 72 h after adding sodium succinate. The release of chloride ions during the growth process of the strain was equivalent to the degradation amount of PCA. Meanwhile, the cleavage pathway of PCA degradation by Brevibacillus S-618 was proposed by analysis of enzyme activities of microorganism and intermediate products in the reaction. Benefiting from excellent degradation ability and unique characters in high pollutant contents, high efficient bioreactor can easily be scale up for industrial application. Our study provides a facile route for cost-effectively and environmental-friendly degrading hazardous chemicals.

Naphthols are industrial contaminants occurring widely in soils and waters. Remediation of organic pollutants can be done by chemical oxidation using persulfate. However, most research experiments testing degradation of organic pollutants have been done in ideal conditions, e.g. using a pure compound in pure water, and thus are weakly representative of real natural conditions where pollutants occur in complex mixtures of numerous organic compounds. Therefore we tested here the effect of the presence of small organic acids, as typical compounds occurring in natural media, on the degradation of 1-napthol with persulfate and iron oxides. Results show that organic acids decreased naphthol transformation by 3.7% for malic acid, 53.2% for tartaric acid, 72.3% for citric acid and 77% for oxalic acids, in a magnetite/persulfate system during 10 h. Meanwhile, the dissolved Fe species increased gradually with the reaction time; the highest concentration of Fe ions reached to similar to 18 mu M L-1 in aqueous phase. Electron paramagnetic resonance technique was applied to determine reactive oxygen species (ROS). The spin density of center dot OH, detected as the main ROS, decreased initially, followed by gradually increase, suggesting that organic acids might inhibit the degradation of 1-naphthol by competing with center dot OH. These findings disclose the high inhibition of the transformation by organic acids, and thus, more generally, imply that studies using only pure contaminants are weakly representative for remediation of real, natural samples.

In this study, legacy and novel per and polyfluoroalkyl substances (PFASs) were measured in groundwater samples collected from the Loess Plateau of China to understand their occurrence, sources and health risks. The total concentration of PFASs ranged from 2.78 to 115 ng/L, with perfluorooctanoic acid (PFOA) as the dominant compound. Many emerging PFASs, including 6:2 fluorotelomer sulfonates (FTS), 6:2 chlorinated polyfluorinated ether sulfonic acid (Cl-PFESAs), ammonium 4,8-dioxa-3H-perfluorononanoate (ADONA), and hexafluoropropylene oxide (HFPO) homologues were frequently detected in 96.7–100% of the samples. Multiple source apportionment analyses indicated that the PFASs in the groundwater mainly originated from industrial activities, but in rural areas, agricultural activities also contributed. The total oxidizable precursor (TOP) assay indicated that there were substantial unknown precursors of perfluoroalkyl acids (PFAAs) in the groundwater samples. The total concentration of PFASs decreased with the well depth, while the PFAA-precursors displayed contrasting vertical profile trends, which might be due to the suppressed microbial transformation in the groundwater. The potential human health risk caused by PFAS exposure via drinking groundwater in the Loess Plateau was low, except for one site that was close to the industry bases.

Organic-heavy metal complexes, with strongly chemical stability and high solubility in water, are difficult to eliminate by traditional chemical precipitation. An efficient strategy, i.e., high-frequency non-thermal plasma (NTP) oxidation/alkaline precipitation, was employed to decompose organic-heavy metal complexes and precipitate free metal ions. Cu-ethylene diamine tetraacetic acid (Cu-EDTA) was chosen as the model. The experimental results showed that Cu-EDTA removal efficiency reached 98.8% at 6 kV after 10 min NTP treatment with air as the carrier gas. Relatively greater removal performance of Cu-EDTA was observed at a lower initial concentration and acidic conditions. Oxygen feeding favored Cu-EDTA decomplexation. Excessive Cu2+ could promote Cu-EDTA decomplexation, whereas excessive EDTA disfavored this process. OH and O2− generated in the NTP system exhibited significant roles in the Cu-EDTA decomposition process, as analyzed by radical quenching tests. Cu-EDTA decomplexation process was analyzed by spectroscopic and chromatographic techniques. Some small organic substances and inorganic anions, including crotonic acid, acrylic acid, lactic acid, ethylene glycol, acetamide, acetic acid and NO3−, were detected as the main intermediate byproducts. The residual toxicity after NTP treatment was evaluated via toxicity prediction. Furthermore, Cu(II) removal and precipitation processes were explored by X-ray diffraction, Fourier transform infrared spectroscopy and Raman spectroscopy.

Microplastics (MPs) are becoming one class of pollutants with high global concerns. Information regarding aging behaviors of MPs in complicated natural conditions is still lacking due to the very slow aging processes. In this study, discharge plasma oxidation was applied to simulate the various radical oxidation and physical effects naturally occurring in the environment to shed light on the aging behaviors and mechanisms of MPs, with polyvinyl chloride microplastic (PVC-MP) as a model. The surface morphology, particle size, specific surface area, crystallinity, and chemical compositions of PVC-MP were comprehensively characterized as a result of aging. The aging degree indicated by carbonyl index and oxygen-to-carbon ratio increased with the plasma oxidation intensity and duration. The aged PVC-MP was characterized as more O-containing functional groups, smaller particle size, larger specific surface area, higher hydrophilicity, and higher crystallinity. Consequently, the aged PVC-MP provided more sites for adsorption of tetrabromobisphenol (TBBPA) in solutions by forming hydrogen-bonds, and electrostatic force. The changes in the properties of the aged PVC-MP, and the strong adsorption with TBBPA led to unexpected synergistic toxic effects to Scenedesmus obliquus. The results provide direct evidences of aging processes of MPs and the potential environmental risks due to aging in the environment.

It is difficult to remove heavy metals-humid acid (HA) complexes with stable properties by traditional precipitation method, and they can bring potential threats to human health. The decomplexation of heavy metal-HA complex (Cu-HA as a model) was explored using non-thermal plasma (NTP) in this study, and influences of coexisting ions on Cu-HA decomplexation were assessed. High-efficient Cu-HA decomplexation performance was obtained by the NTP oxidation, and it reached 89.3% in a treatment period of 15 min; and the pseudo-first order kinetics was suitable to describe this process. The presence of Fe2+ favored Cu-HA decomplexation process via displacement and Fenton-like effects. Whereas some amounts of Cl−, NO3− and SO42− with low dosages promoted this process. Active species including O3, O2 − and OH played primary roles in Cu-HA decomplexation, but the role of high-energy electrons could be neglected. NTP oxidation broke the chromophoric group, Cu O, Cu N, and unsaturated bonds of the Cu-HA complex. Some decomplexation intermediates including benzoic acids, amines, esters, and phenols were generated. Meanwhile, the precipitation processes were analyzed via energy dispersive X-ray, X-ray photoelectron spectrum, thermal stability, fourier transform infrared spectroscopy, and X-ray diffraction.

In order to improve the photocatalytic performance of TiO2 in pulsed discharge plasma systems, easily recycled multi-walled carbon nanotubes (MWCNTs)-TiO2 supported on γ-Al2O3 (MWCNTs-TiO2/γ-Al2O3) composite photocatalyst were prepared. The morphology and physicochemical properties of the prepared catalysts were investigated using XRD, SEM, FTIR and UV-vis spectroscopy. The photocatalytic activity was evaluated by degradation of azo dye acid orange II (AO7) in wastewater under pulsed discharge plasma. The results indicate that the MWCNTs-TiO2/γ-Al2O3 composite catalyst possesses enhanced photocatalytic activity facilitating the decomposition of AO7 compared with TiO2/γ-Al2O3 composite in pulsed discharge plasma systems. Under pulsed discharge plasma, almost 100% AO7 is degraded by the MWCNTs-TiO2/γ-Al2O3 composite after 60 min at optimal conditions. The degradation efficiency of AO7 is also affected by the dosage of the composite catalyst and pulsed discharge peak voltage. As the amount of MWCNTs-TiO2/γ-Al2O3 composite and pulsed discharge peak voltage increases, the degradation efficiency of AO7 increases. The photocatalyst was implemented for 6 cycles and the degradation efficiency of AO7 remains higher than 85% under pulsed discharge plasma. Results indicate that the catalyst displays easy separation and minimal deactivation after several uses. Possible decomposition mechanisms were also investigated. MWCNTs are capable of improving the photocatalytic activity of TiO2/γ-Al2O3 composite in pulsed discharge plasma systems primarily due to the photo-induced-electron absorption effect and the electron trap effect of MWCNTs. The results of this study establish the feasibility and potential implementation of MWCNTs-TiO2/γ-Al2O3 composites in pulsed discharge plasma systems for the degradation of dye wastewater.

Pulsed discharge plasma (PDP) combined with charcoal (PDP-charcoal) was employed to treat dye wastewater, with methyl orange (MO) as the model pollutant. The charcoal was prepared using spent tea leaves and was characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, and Boehm titration to investigate the adsorption and catalytic characteristics before and after adsorption and PDP treatment. The prepared charcoal exhibited a high MO adsorption capacity, and the adsorption process followed the pseudo-second-order kinetic model and the Freundlich model. The MO decoloration efficiency reached 69.8 % within 7.5 min of treatment in the PDP-charcoal system, whereas values of 29.2 and 25.9 % were achieved in individual PDP and charcoal systems, respectively. The addition of n-butanol and H2PO4 (-) presented inhibitive effects on MO decoloration in the PDP system. However, these effects were much weaker in the PDP-charcoal system. In addition, the effects of charcoal on O3 and H2O2 formation were evaluated, and the results showed that both the O3 and H2O2 concentrations decreased in the presence of charcoal. The MO decomposition intermediates were analyzed using UV-Vis spectrometry and GC-MS. 1,4-Benzoquinone, 4-nitrophenol, 4-hydroxyaniline, and N,N'-dimethylaniline were detected. A possible pathway for MO decomposition in this system was proposed.

The oxidation characteristics of mixed NO and Hg0 were investigated using active species injection under oxygen atmosphere, namely, a surface dielectric barrier discharge plasma (SDBD) reactor inserted in simulated flue duct was used to generate and inject the oxygen-based active species into the flue gas to simultaneously oxidize NO and Hg0 at 110 °C. Approximately 92.5% and 99.1% of NO and Hg0 were oxidized at 301.8 J L−1, respectively, a reaction competition between NO and Hg0 with active species existed, and the NO oxidation was faster. The effects of important flue gas components on NO and Hg0 oxidation were investigated. H2O enhanced the NO oxidation, but inhibited the Hg0 oxidation. HCl exhibited a promotional effect on the Hg0 oxidation, but displayed no effect on the NO oxidation. SO2 and H2O showed obviously inhibitory effect on the NO and Hg0 oxidation. Ozone and O2 metastable states contributed to the NO and Hg0 oxidation. NO2, HNO3 and N2O5 were observed by Fourier transform infrared spectroscopy (FTIR).

p -Nitrophenol (PNP) removal in dredged sediment during pulsed discharge plasma process was studied in terms of adjustable trim capacitance, electrode distance and gas-flow rate. PNP degradation efficiency reached up to 88.5% under the conditions of adjustable trim capacitance of 2.0 nF, electrode distance of 16 mm, and air flow rate of 0.8 L min −1 . To a certain extent, increasing the adjustable trim capacitance and decreasing the electrode distance leaded to high PNP degradation efficiency. An appropriate air flow rate was determined for gaining relatively high PNP removal efficacy. PNP mineralization was analyzed by UV–Vis spectrum, COD, and TOC evolution.

Manganese oxide (MnO2) plays an important role in the transformation of organic contaminants, such as polycyclic aromatic hydrocarbons (PAHs), in environmental compartments. In this study, various MnO2 polymorphs were prepared, and their catalytic activities were evaluated using anthracene (ANT) as a model molecule without light irradiation. Among the obtained MnO2 materials, amorphous MnO2 exhibited the highest catalytic activity to degrade ANT. The reaction rate constant (kobs) positively correlated with the content of Mn3+ in the MnO2 catalysts. Moreover, the production of Mn3+ enhanced the concentration of oxygen vacancies which were conducive to the adsorption of O2 by MnO2, leading to an enhanced level of superoxide radicals O2 − generated on the MnO2 surface. MnO2-mediated degradation of ANT was a combination of non-radical oxidation by Mn3+ and radical-based degradation by O2 −. These findings provided valuable insights into the environmental fate of PAHs and the potential application of MnO2-based materials for PAHs remediation.

Advanced persulfate oxidation technology is widely used in organic pollution control of super fund sites. In recent years, microwave radiation has been proven a promising method for persulfate activation. However, most of the prior works were focused on the treatment of polluted water, but there are few reports aiming at contaminated sites, especially the knowledge of using microwave activated persulfate technology to repair pesticide-contaminated sites. In this study, an effective activation/oxidation method for the remediation of pesticide-contaminated soil, i.e., microwave/persulfate, was developed to treat soil containing ethyl-parathion. The concentration of persulfate, reaction temperature, and time were optimised. The results showed that up to 77.32% of ethyl-parathion was removed with the addition of 0.1 mmol·persulfate·g−1 soil under the microwave temperature of 60 °C. In comparison, 19.43% of ethyl-parathion was removed at the same reaction temperature under the condition of water bath activated persulfate. Electron paramagnetic resonance (EPR) spectroscopy combined with spin-trapping technology was used to detect reactive oxidation species, and OH and SO4− were observed in the microwave/persulfate system. Quenching experiments suggested that ethyl-parathion was degraded by the generated OH and SO4− . Paraoxon, phenylphosphoric acid, 4-nitrophenol, dimethyl ester phosphate, and some alkanes were the dominant oxidative products identified by gas chromatography–mass spectrometry (GC-MS) analysis. A possible pathway for ethyl-parathion degradation was proposed in this study. The results obtained serve as the guidance to the development of remediation technologies involving persulfate and microwave for soil contaminated by organic contaminants such as pesticides.

Soil microbial community structures and enzymatic activity are important indicators for judging biochemical process intensity and soil quality. Non-thermal discharge plasma (NDP), an advanced oxidation technique, has received great attention in soil remediation. Potential impact of NDP treatment on microbial community structures and enzymatic activities in uncontaminated soil samples was evaluated in this study. The NDP treatment significantly altered soil microbial community structures and enzymatic activity. The exposure of soil samples to NDP decreased the enzymatic activities including glutamic acid enzyme, arylsulphatase, leucine enzyme, acetyl glucosaccharase, glucosaccharase, cellulose, phosphatase, and ligninase. The contents of some soil microbes including Gram-negative bacteria, Fungi, Anaerobes, AM Fungi, Eukaryotes, and Actinomycetes also decreased after NDP treatment, as well as the diversity index and equitability index of the soil microbes. In addition, the total phospholipid fatty acid (PLFA), Fungi PLFA, bacteria PLFA, and Actinomycetes PLFA of the soil microbes were also reduced after treatment. Principal component analysis confirmed these changes. Actinomycetes and Fungi were the most sensitive microbes to the NDP, and Phosphatase activity and Cellulose activity were relatively insensitive to the NDP. The potential impacts could be attributed to chemically active substances and ultraviolet irradiation.

Brominated flame retardants are widely used in fire protection area, but also bring great threats to ecological environment and human health. In this study, the potential of brominated flame retardant removal in wastewater by dielectric barrier discharge (DBD) plasma was investigated, with Tetrabromobisphenol A (TBBPA) as a model pollutant. The experimental results showed that TBBPA could be effectively removed by the DBD plasma oxidation. Almost all of the TBBPA in wastewater could be successfully decomposed within 15 min’s oxidation treatment, and the decomposition process fitted well with the pseudo-first-order kinetic model. Relatively lower TBBPA initial concentration favored its decomposition; and the effect of solution pH value on the oxidation process was negligible in the selected pH range. Electron paramagnetic resonance analysis showed that O2–, OH, and 1O2 were produced in the DBD plasma process; and O2– was the main reactive species for TBBPA decomposition, OH and 1O2 also played important roles. The molecular structure of TBBPA was effectively destroyed, and some byproducts including bisphenol A, and dibromophenol were generated. The possible decomposition pathways for TBBPA degradation were proposed. Furthermore, the acute toxicity and bioaccumulation factor of intermediate byproducts were alleviated via the analysis of Toxicity Estimation Software Tool.

Microplastics released into the environment undergo a variety of aging processes, however, information about the influence of aging on the adsorption behavior of microplastics is limited. In order to better understand the effect of aging polystyrene (PS) on the ability to adsorb heavy metal, H2O2 and Fenton reagent were used to investigate the aging properties of PS. Aging PS with these two different aging agents at pH = 4 and room temperature for the same time. Physical and chemical characterization indicated that aging caused oxidation of the surface of PS and the formation of surface micro-cracks. Based on the 2D-COS analysis, the aging process of PS functional groups could occur in the following sequence: 1375 (C-OH) > 1739 (C=O) > 1182 cm−1 (C−O−C) > 1716 (O−C=O). The adsorption experiments for Cd2+ with two different concentrations were carried out by PS with different aging time at room temperature. The adsorption data showed that the adsorption capacity of Cd2+ was significantly enhanced after aging compared with pristine PS, and the adsorption capacity of PS after Fenton aging treatment is much stronger than that after H2O2 aging treatment. The kinetic analysis of the adsorption data indicates that the adsorption process is more consistent with the second-order kinetics than the first-order kinetics, and it is further concluded that the adsorption of Cd2+ by PS is a relatively complicated process. According to the fitting results of adsorption isotherms, the adsorption process of pristine PS mainly occurs on the surface, but with the continuous aging, more adsorption sites may be exposed on the surface of PS, so it can be concluded that the adsorption mechanism of Cd2+ by PS is the coexistence of physics and chemistry. This study indicates aging microplastics may have a significant impact on the destination and migration of metal contaminants, which deserves to be further concerned.

Heavy metals and natural organic matters (NOM) form very stable heavy metal-NOM complexes in aqueous, facilitating the migration of heavy metals and enhancing their potential risks. In this study, non-thermal plasma oxidation was attempted to destroy the heavy metal-NOM complexes, with Cu-humate (Cu-HA) as a model. The decomplexation efficiency reached 86.1 % within 50 min of plasma oxidation at 16 kV. The generated reactive species by the non-thermal plasma, including O2 −, 1O2, OH, attacked the carboxyl and hydroxyl functional groups of HA, leading to cleavage of the Cu-O bonds, decomplexation of Cu-HA, and release of free Cu(II). Meanwhile, a variety of small molecular intermediates, including phenols, benzoic acids, esters, amines, ketones, acetic acid, formic acid, and oxalic acid, were generated due to attack by the oxidative species on the aromatic moiety and double bonds in Cu-HA. As a consequence of decomplexation, the residual toxicity of Cu-HA to Scenedesmus obliquus was distinctly reduced. This study provides a potential technique to decomplex heavy metal-NOM complexes, and reduces their toxicity to typical Scenedesmus obliquus.

Plasticizers are widely present in water and soil environment, and they can bring enormous threats to environmental safety and human health. A discharge plasma system driven by a high-frequency electric source was used to remove the plasticizer from wastewater; and dimethyl phthalate (DMP) was chosen as the representative of plasticizer. DMP elimination performance at various operating parameters, roles of active species in DMP degradation, DMP decomposition process, and its residual toxicity after decomposition were systematically investigated. The experimental results demonstrated that almost all of the DMP and 80.4% of the total organic carbon (TOC) were removed after 30 min of treatment. The DMP decomposition process fitted well with the first-order kinetic model. Relatively higher applied voltage, lower initial concentration, and alkaline conditions favored its decomposition. •OH was the decisive species for DMP decomposition, in addition to •O2- and 1O2; while the role of hydrated electrons was negligible. The analysis of DMP decomposition process showed that the molecular structures of the DMP were destroyed, and 3-hydroxy-dimethyl phthalate, monomethyl phthalate, and phthalic acid were detected. Furthermore, the residual toxicity after DMP decomposition was analyzed via seed germination and photobacterium bioassay.