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In this study, nano-CaO2 (nCaO2 ) was successfully synthesized and constituted the nCaO2 /Fe(II) system applying to remediate BTEX, which are typical mixed pollutants in contaminated groundwater. The particle size of the synthesized nCaO2 was 108.91 nm, and it displayed better BTEX remediation performance than that of commercial CaO2 . The innovative generation pattern of hydroxyl radicals ( HO · ) in the nCaO2 /Fe(II) system has been investigated using benzoic acid as the HO · probe, and the proper molar ratio of nCaO2 /Fe(II) was optimized as 1/1. Over 90% of BTEX was removed in 180 min with the nCaO2 /Fe(II)/BTEX molar ratio of 40/40/1. Further experiments evaluated the influence of co-existence of mixed pollutants chlorinated hydrocarbon compounds (CHCs) or surfactant constituents on BTEX remediation performance. The experimental results suggested that CHCs have limited influence on BTEX removal rate and surfactants have negative effects on BTEX remediation performance in the experimental conditions. In conclusion, the findings in this study could give some inspirations to apply the nCaO2 /Fe(II) process in remediating co-existing pollutants in contaminated groundwater. PRACTITIONER POINTS: nCaO2 /Fe(II) system applied to remediate mixed contaminants. HO · generation pattern of the nCaO2 /Fe(II) system has been investigated. The influence of chloride hydrocarbon compounds have been studied. The effects of surfactants were evaluated.

The performance of trichloroethylene (TCE) degradation by sodium percarbonate (SPC) activated with Fe(II) in the presence of 3.0 g/L sodium dodecyl sulfate (SDS) as well as the role of SDS in the SPC/Fe(II) system was investigated since SDS is a common surfactant used in groundwater remediation for improving TCE dissolution to the aqueous phase. The results showed that though the introduction of SDS could inhibit the TCE degradation, the inhibiting effect was less with the increasing SDS dose. In the presence of SDS, TCE could be completely removed with the SPC/Fe(II)/TCE molar ratio of 40/80/1. Experiments with free radical probe compounds and radical scavengers elucidated that TCE was mainly oxidized by both HO· and O 2 - · . A weakly acidic environment was more favorable to TCE degradation. Nevertheless, HCO 3 - at a high concentration had a strongly inhibitive effect on the TCE degradation but the influence of Cl- was negligible. Finally, the excellent TCE degradation achieved in actual groundwater demonstrated that Fe(II) activated SPC technique was applicable in the remediation of TCE contaminated groundwater in the presence of SDS. PRACTITIONER POINTS: The effects of SDS were evaluated SPC/Fe(II)/SDS system applied to remediate TCE The mechanism of HO· and O 2 - · generation had been investigated Cl- and HCO 3 - affected TCE degradation at different levels The performance of TCE removal in actual groundwater had been studied.

Unused or expired pharmaceutical and personal care products (PPCPs) are usually discharged into municipal solid wastes, then travel to landfills, and eventually percolate into leachates. However, knowledge of their occurrence and temporal dynamics in leachates is limited, making landfill leachate an underappreciated emission source of PPCPs. Furthermore, the differences in PPCP variations in landfill leachates emphasize the necessity for identifying the influencing factors and elucidating the mechanisms for PPCP fluctuations. In this study, successive monthly monitoring of PPCPs in leachates throughout an entire year was performed to determine their seasonal variations and identify their influencing factors. Furthermore, five pairs of additional sampling campaigns were conducted before and after rainfall events during wet seasons to elucidate the influencing mechanisms. The results showed that there was a distinct seasonal variation in PPCPs in landfill leachates-elevated levels during the wet period (from April to September, with a mean concentration of 17.0 μg/L for total monitored PPCPs)-when compared to other months (mean concentration of 3.8 μg/L). Rainfall played a considerable role in mediating PPCP concentrations in leachates. The PPCP responses to five rainfall episodes further verified the influence of rainfall and demonstrated that the tendency to PPCP concentration increase was related to rainfall precipitation. Torrential rain events (i.e., 24 h cumulative precipitation of 50-99.9 mm) led to the most significant increases in PPCP concentrations in landfill leachates. In addition, the hydrophilicity of PPCPs contributed to the different fluctuations during the 1 year investigation and different responses to rainfall. To the best of our knowledge, this study provides the first direct evidence supporting the influence of rainfall on PPCPs in landfill leachates, which can help better understand the occurrence and behavior of emerging contaminants in this underappreciated emission source.

Calcium peroxide (CaO2) is a stable hydrogen peroxide (H2O2) carrier, and the CaO2/Fe(II) system has been applied for treatment of various pollutants. It is commonly reported in the literature that hydroxyl radical (HO ) and superoxide radical anions (O2 −) are the two main reactive oxygen species (ROSs) generated in the CaO2/Fe(II) system. However, many of the reported results were deduced from degradation performance rather than specific testing of radical generation. Thus, the specific generation of ROSs and the influence of system conditions on ROSs yield are still unclear. To our knowledge, this is the first study specifically focusing on the generation of HO and O2 − in the CaO2/Fe(II) system. Experimental conditions were optimized to investigate the production of HO and O2 −. The results showed the influences of CaO2, Fe(II), and solution pH on HO and O2 − generation, and the HO generation efficiency was reported for the first time. In addition, the ROSs generation pathways in the CaO2/Fe(II) system were elucidated. A strategy for enhancing HO yield is developed, based on the continuously dosing Fe(II). This proposed strategy has implications for the effective application of in situ chemical oxidation employing CaO2/Fe(II) for groundwater remediation.

The ability of SO4 − based advanced oxidation processes activated by nano zero-valent iron (nZVI) on reduced graphene oxide (rGO) functionalized by polydopamine (PDA) (nZVI-PDA@rGO) in degradation of phenanthrene (PHE) was investigated under various environmental conditions. The results showed that, compared with nZVI, the catalytic degradation of PHE was enhanced after anchoring nZVI on the PDA@rGO nanosheet in the activation of sodium persulfate (SPS) and peroxymonosulfate (PMS). The maximum PHE removal efficiency reached 95.9% and 98.7% in the nZVI-PDA@rGO/SPS (50 mg L−1/0.3 mM) and nZVI-PDA@rGO/PMS (50 mg L−1/0.0375 mM) systems, respectively. The effects of pH, anions and humic acid (HA) on the PHE degradation were tested in the nZVI-PDA@rGO coupling with PMS or SPS system. The higher PHE removal could be maintained in the nZVI-PDA@rGO/SPS system at pH up to 7.74 and in the nZVI-PDA@rGO/PMS system at pH up to 7.86, respectively. Cl− had a positive effect on PHE removal in both SPS and PMS systems, while a negative effect was observed in the presence of SO42−, NO3− and HCO3− (HCO3− > SO42− > NO3−). In addition, the PHE removal was inhibited significantly after addition of 50 mg L−1 HA. The radical scavenger tests were carried out to identify the dominant reactive oxygen species (ROSs), which demonstrated that SO4 − and HO were the two primary ROSs responsible for the PHE removal. The intermediate products were identified by LC-MS and the degradation pathway of PHE was proposed.

Occurrence of eleven pharmaceuticals and personal care products (PPCPs) along Huangpu River, a representative urban river of megacity Shanghai, was investigated in four sampling campaigns. The overall concentrations of PPCPs ranged fromLOQ to 1455 ng/L, and untreated domestic wastewater was proposed as an important source of PPCPs in Huangpu River. Higher contamination levels of target PPCPs were detected in the lower reach (urban area) and dry season, compared to those in the upper reach (rural area) and wet season, respectively. The influence of rainfall on the occurrence of PPCPs was also extensively discussed in different regions along Huangpu River. At sampling sites in the rural area, similar or even lower concentrations of PPCPs were detected after rainfall; while increased concentrations of PPCPs were observed at most sampling sites, especially in the urban area, suggesting that overflow of untreated wastewater exceeding the capacity of wastewater treatment plants and leachates generated at temporary storage and transfer station of solid wastes might be the additional sources of PPCPs in the urban area in rainy days. These findings indicated that management of wastewater or/and solid wastes was more important to solve the problem of PPCPs contamination in the urban river of megacity.

The degradation of carbon tetrachloride (CT) by Fe(II) activated calcium peroxide (CaO2) in the presence of ethanol (CH3CH2OH, EtOH) was investigated. The results showed that CT could be completely degraded in 20 min with 3.90 mmol L−1 CaO2, 5.20 mmol L−1 Fe(II) and 1.30 mmol L−1 EtOH in CaO2/Fe(II)/EtOH system. Superoxide radical anion (O2•−) and hydroxyethyl radical (•CHCH3OH, HER) were demonstrated as the main radicals for CT degradation which were confirmed by scavenging tests and electron paramagnetic resonance (EPR) detection. The mechanism of CT degradation was mainly due to the split of C–Cl and CT degradation pathway was proposed accordingly. Further investigation suggested that the solution pH in range of 3–5 were favorable to CT degradation. Both Cl− and HCO3− had inhibitive effect on CT removal, while the influence of NO3− and SO42− could be negligible. Moreover, the results of experiments performed using actual groundwater demonstrated that an adverse impact occurred on CT degradation, but this drawback could be overcome by increasing reagent dosages. In summary, CT degradation in Fe(II) activated CaO2 system can be significantly promoted by EtOH addition, and this finding, for the first time, provides an innovative technology for degradation of the highly oxidized organic contaminants.

In this study, the common chlorinated solvent trichloroethene (TCE) was selected as the target contaminant. The aqueous solution after solubilization treatment (containing TCE and sodium dodecyl sulfate (SDS)) was used as the research object to carry out the remediation technology research of citric acid (CA) enhanced Fe(II) activation in sodium percarbonate (SPC) system. In 0.15 mM TCE and 1 critical micelle concentration (CMC) SDS solution, CA chelating Fe(II) activated SPC could effectively promote 93.2% degradation of TCE when the dosages of SPC, Fe(II) and CA were 3.0, 6.0 and 3.0 mM, respectively. SDS had a significant inhibitory effect on the degradation of TCE, and the surface tension changed after the reaction. The addition of CA greatly increased the generation of hydroxyl radicals (HO ) in the system, while the removal of TCE was mainly attributed to HO , and the removed TCE was almost completely dechlorinated. The pH range from 3 to 7 could keep the TCE degradation above 80.0%. In the actual groundwater remediation, this technique could also efficiently degrade TCE (including SDS), showing a great application potential and development prospective in practice.

The feasibility of an advanced oxidation process based upon sodium persulfate (SPS) activated simultaneously by heat (50 °C) and nanoscale zero-valent iron (nZVI) on benzene removal was investigated. The experimental results strongly showed the synergistic effect of thermal and nZVI activation to SPS and benzene removal was enhanced with the increase of SPS/nZVI/benzene molar ratio. Specifically, 94% of benzene could be removed in 1 hr at 50 °C at the SPS/nZVI/benzene molar ratio of 10/5/1. The radical scavenger tests and electron paramagnetic resonance (EPR) analysis confirmed that SO4•− was the predominant species contributing to benzene degradation. Further, the effects of the solution matrix on benzene elimination were investigated. The results indicated that benzene destruction in the thermally activated SPS/nZVI system performed better under acidic conditions, and the high concentration of both Cl− and HCO3− had adverse effects on benzene elimination. The test for the performance of benzene degradation in the actual groundwater demonstrated that benzene could be degraded entirely at SPS/nZVI/benzene molar ratio of 40/40/1 at 50 °C, indicating that the synergistic catalysis of thermal and nZVI activation to SPS is exploitable and the thermally activated SPS/nZVI system can be applicable to the remediation of benzene contaminated groundwater.

The source apportionment of pharmaceuticals and personal care products (PPCPs) in the water environment based on indicators (i-PPCPs) requires a comprehensive characterization of various emission sources using reliable analytical methods for a wide spectrum of PPCPs. In this study, a robust and sensitive method based on solid phase extraction (SPE) and ultra-high performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS) for analyzing 70 PPCPs belonging to 17 therapeutic classes in landfill leachates and livestock wastewaters was developed. The SPE cartridges, sample pH, elution solvents and chelating agent additions were optimized, and acceptable recoveries (60– 130% for 67 target compounds), low method quantification limits (landfill leachate: 3– 1309 ng/L; livestock wastewater: 3– 686 ng/L) and high precisions (repeatability: 0– 20% for over 99% injections; reproducibility: 0– 20% for over 90% injections) were obtained. Using the optimized analytical method to characterize PPCPs in the typical landfill leachate and livestock wastewater in Yangtze River Delta, China, we found anthelmintics, which were first reported in landfill leachates globally, exhibited the highest concentration (albendazole, maximum concentration of 61.6 μg/L), and therefore proposed albendazole as one of the promising i-PPCP candidates in landfill leachates. In livestock wastewaters, antibiotics lincomycin was the most abundant PPCP (maximum concentration: 735 μg/L) and identified as an i-PPCP candidate for livestock-originated contamination. In addition, 15 non-antibiotic PPCPs were first investigated in the livestock wastewater in China and some non-steroidal anti-inflammatory drugs, acetaminophen, diclofenac and naproxen, were detected at similar concentration level (1.16– 91.1 μg/L) to antibiotics, highlighting the necessity to include representative non-antibiotic PPCPs in the studies of emerging contaminants in livestock wastewaters. The developed method provides a tool to comprehensively investigate PPCPs in high-strength wastewater, and the preliminary findings in the characterization of typical landfill leachates and livestock wastewaters are helpful to select i-PPCPs for the source apportionment of PPCPs in Yangtze River Delta, China.

The extensive application of plastic in human life brings about microplastic (MP) pollution in the environment. Identifying the potential sources of MPs is necessary to diminish its pollution. In this study, the occurrence, composition and distribution of MPs in the influents and effluents from 9 domestic wastewater treatment plants (WWTPs), 5 industrial WWTPs, wastewater of 10 industrial plants, 4 livestock farms and 4 fish ponds in China were investigated. Water samples were enzymatically treated followed by digestion with hydrogen peroxide and density separation. MPs were characterized using micro-Raman spectroscopy and were categorized by shape, size and color. Results showed that MP abundance in the influents and effluents of domestic WWTPs was 18–890 and 6–26 n·L−1, respectively, with the removal efficiency ranging from 35 to 98%. The effluents of industrial WWTPs contained 6–12 n·L−1 and the levels of MPs in the wastewater of industrial plants, livestock farms and fish ponds were in the range of 8–23, 8–40 and 13–27 n·L−1, respectively. No significant differences of MP abundance were demonstrated among effluents or wastewater of different sources, indicating they all constitute sources of MP pollution. Polyethylene (PE), polypropylene (PP) and polystyrene (PS) made up almost 83% of the total MPs. Fragment and film were the most abundant shapes and the majority of MPs were smaller than 500 μm. Polymer type and shape in different sources did not vary statistically, however, there were slight differences among different sources concerning size and color of MPs. This study could fill MP data gaps regarding different sources, guide future monitoring work and policy making.

The performance of trichloroethene (TCE) removal was initially investigated in sodium persulfate (SPS) or potassium monopersulfate triple salt (PMS) oxidative environment by reduced graphene oxide (rGO) supported nZVI (nZVI-rGO) catalyst and further the role of sulphur by anchoring nano FeS on nZVI-rGO (FeS@nZVI-rGO) was evaluated. The high usage of oxidants and stability of FeS@nZVI-rGO catalyst were significantly improved due to the insoluble nature of this innovative catalyst by involvement of nano FeS which limited the rapid iron loss caused by the corrosion of active sites and mitigated rapid oxidants decomposition in FeS@nZVI-rGO/SPS and FeS@nZVI-rGO/PMS systems. The tests for target contaminant removal showed that over 95% TCE could be removed at 100 mg L(−1) FeS@nZVI-rGO and 1.2 mM SPS or 0.3 mM PMS dosages, in which over 85% TCE could be dechlorinated. The reactive oxygen radicals (ROSs) generation mechanisms and their contribution to TCE removal were investigated through radical scavenge tests in both systems, indicating that both HO(•) and SO(4)(−•) were the major ROSs rather than O(2)(−•). In conclusion, this study revealed the well function and fundamental mechanism of this innovative catalyst by anchoring nano FeS and worth of further demonstration of this technique in TCE contaminated groundwater remediation application.

Landfill leachates are identified as a significant source of pharmaceutical and personal care products (PPCPs), which might pose a threat to groundwater and surface water nearby the landfill. However, knowledge of PPCP contamination in the surrounding water environment of landfills is very limited. Here we investigated eighteen PPCPs in water environment near the largest landfill in China, focusing on their occurrences and spatial distribution, as well as the environmental risks. The results showed the concentration of target PPCPs was below the limit of quantification (< LOQ) to 53.6 ng/L in the adjacent groundwater samples, decreasing with the distance of sampling sites from landfill. The composition pattern of PPCPs in the groundwater was similar to that in raw landfill leachate. These observations indicated a considerable impact of raw landfill leachates on PPCP contamination in the nearby groundwater. In surface water samples, the occurrence of PPCPs was not consistent with that in raw or treated landfill leachates, but similar to that in the same watershed far away from landfill. Spatially, no obvious difference in the PPCPs concentrations was observed, indicating negligible contribution of landfill on PPCPs in surrounding surface water. The findings allowed the first insights into the impacts of well-constructed and managed landfills on PPCP contamination in the surrounding water environment. National Natural Science Foundation of ChinaNational Natural Science Foundation of China [21577033, 21777042, 51408425]; Major Science and Technology Program for Water Pollution Control and Treatment in China [2017ZX07202006]; Fundamental Research Funds for the Central UniversitiesFundamental Research Funds for the Central Universities; Beijing Key Laboratory for Emerging Organic Contaminants Control This research was partly supported by the National Natural Science Foundation of China (21577033, 21777042, 51408425), the Major Science and Technology Program for Water Pollution Control and Treatment in China (2017ZX07202006), the Fundamental Research Funds for the Central Universities and Beijing Key Laboratory for Emerging Organic Contaminants Control.

Pharmaceutical and personal care products (PPCPs) have been the focus of increasing concern in recent decades due to their ubiquity in the environment and potential risks. Out-of-date PPCPs are usually discharged into municipal solid wastes (MSWs), enter the leachates in MSW landfills, and have serious adverse effects on the surrounding water environment. However, the occurrence and removal of PPCPs from landfill leachates have rarely been examined to date. This lack of knowledge makes the landfill an underestimated source of PPCPs in the environment. In this review, we collected the relevant publications of PPCPs in landfill leachates, systematically summarized the occurrence of PPCPs in landfill leachates globally, evaluated the removal performances for various PPCPs by different types of on-site full-scale leachate treatment processes, and assessed the impacts of landfill leachates on PPCPs in the adjacent groundwater. In particular, influencing factors for PPCPs in landfill leachates, including the physicochemical properties of PPCPs, climate conditions, and characteristics of landfill sites (i.e., landfill ages) as well as sociological factors (i.e., economic development), were extensively discussed to understand their occurrence patterns. Future perspectives were also proposed in light of the identified knowledge gaps. To the best of our knowledge, this is the first review regarding the occurrence and removal of PPCPs from landfill leachates worldwide., This work was partly supported by the National Natural Science Foundation of China (21777042, 21577033, 51408425), the Major Science and Technology Program for Water Pollution Control and Treatment in China (2017ZX07202006), the Fundamental Research Funds for the Central Universities, and Beijing Key Laboratory for Emerging Organic Contaminants Control.

Elimination of polycyclic aromatic hydrocarbons (PAHs) from coke wastewater is crucial to minimize the PAHs contamination levels to the environment. Knowledge about the characteristics of PAHs removal in biological treatment processes, especially hybrid systems, for real coke wastewater treatment has been very scarce. In this study, a lab-scale hybrid anaerobic–anoxic–oxic (A1/A2/O) process was used to treat highly toxic coke wastewater and operated more than 600 d at total hydraulic retention time (HRT) of 50 h, 40 h, 30 h, 20 h and internal mixed liquor recirculation ratio (R) of 3, 6, 9. Removal performance and behaviors of priority PAHs in the hybrid A1/A2/O system were investigated. The results showed that the appropriate total HRT and R from oxic reactor to anoxic reactor for organics and nitrogen removal was 40 h and 3, respectively. The concentrations of total PAHs were very high (254–488 μg/L) in the raw coke wastewater, and effectively reduced to 4.1–4.5 μg/L in the final effluent by the present system under the optimized operational conditions. Among the three treatment units, anoxic reactor made the largest contribution to the total PAHs removal. Large amounts of PAHs (415–1310 μg/g) were adsorbed to the activated sludge in the anoxic and oxic reactor, leading to a much higher load of PAHs (2535 μg/d) in the excess sludge than that in the treated coke wastewater (93 μg/d) at SRT 60 d. Therefore, the excess sludge was identified as the major emission source of PAHs in coke wastewater during the hybrid A1/A2/O process, and might pose an environmental risk if the excess sludge was not properly treated and disposed.

Synthesizing supported heterogeneous catalysts is always considered as a persistent approach for degradation of contaminants. However, the stability of these nanocomposites and improvement of process conditions influencing target pollutants degradation are still limited. Herein, on the basis of self-adhesive nature of polydopamine (PDA) and its strong electrostatic interaction with metallic ions, we synthesized a facile, stable, magnetically separable, and environmentally benign PDA decorated, reduced graphene oxide (rGO) supported Fe nanocatalyst (PDA@Fe/rGO). The effects of process variables (pH, PDA@Fe/rGO, and persulphate (PS) dose) on the degradation performance of trichloroethene (TCE), a model chlorinated organic pollutant selected in this study, were investigated. PDA not only encapsulated the host Fe/rGO magnetic particles but also exhibited high magnetization. PDA wrapping tremendously enhanced the thermal stability of nanocatalyst with just 24.1% weight loss at elevated temperature compared to solo Fe/rGO (40.2%). Moreover, TCE degradation mechanism was interpreted by ESR and radical scavenger tests, validating OH , SO4 − and O2 − radicals being responsible for TCE degradation. Considering its eminent catalytic activity, simple synthesis approach and excellent kinetics, this recyclable and improved PDA assisted Fe/rGO nanocatalyst further opens a door for practical implementation in the field of contaminated groundwater remediation.

A comprehensive characterisation of four phenolic compounds in surface water and various emission sources was conducted simultaneously in a typical industrial city upstream of the Taihu Lake watershed. The overall concentrations of the target compounds ranged from 0.15 to 2.75 μg/L in the surface water and from 0.43 to 377 μg/L in the emission sources. Relatively high concentration levels were observed in August, during which the rainy season typically occurred in the study area, indicating seasonal emission sources. The spatial distribution revealed severe phenolic-compound contamination in the northeast part of the study area. According to the relationships between the surface water and emission sources, combined-sewer overflow and surface runoff from agricultural activities were identified as seasonal emission sources that were responsible for the increased concentration levels in wet seasons. Indirect discharge of industrial wastewater was proposed as a persistent emission source responsible for the severe contamination level in the northeast region over the entire sampling period, accounting for 16.5% of the phenolic-compound load in a demonstration river section. The findings of this study are useful for identifying the sources of phenolic compounds and controlling the contamination from the main sources in a typical industrial city.

This study investigated the occurrence and distribution of pesticides in surface water (lakes, major rivers and tributaries) and potential discharge sources (fish ponds, livestock and poultry farms, and sewage treatment plants) in Wujin District (northwest of Taihu Lake), Jiangsu province, China. An analytical liquid chromatography-tandem mass spectrometry method was developed for 38 pesticides, which was applied in the monitoring of 240 surface water samples and 76 potential discharge source samples. Eleven insecticides and five fungicides with temporal and spatial variation were detected in surface water. The total pesticide concentrations in surface water in different seasons were as follows: March > August > June > November. The two most polluting and widespread pesticides were carbendazim (maximum concentration 508 ng L−1, detection rate 100%) and imidacloprid (maximum concentration 438 ng L−1, detection rate 88%). Gehu Lake (S46) and Sanshangang River (S12) were seriously polluted water bodies. Seven insecticides and four fungicides were detected in the potential discharge sources; and their composition changed significantly with the seasons. The concentrations of detected organophosphorus pesticides and neonicotinoids (e.g. acetamiprid in March and dichlorvos in November) in a few non-agricultural planting sources were far greater than those detected in surface water, and hence a few fish ponds, livestock and poultry farms, and sewage treatment plants might be the potential discharge sources of pesticides in the surrounding surface water. The estimated input flux of the studied pesticides from upstream rivers to Taihu Lake was 141.95 kg a−1. Furthermore, more attention should be paid to the medium or high aquatic ecotoxicological risk presented by the levels of organophosphorus pesticides, carbamates, and benzimidazoles.

Membrane bioreactors (MBRs) were shown contradictory results for the removal of antibiotics, such as sulfonamides (SAs), from wastewater in different studies, which highlighted the necessity for comprehensive investigation on removal mechanisms of sulfonamides in well-controlled lab-scale MBRs. In the present study, the removal performance of nine SAs by a lab-scale anaerobic/anoxic/oxic-membrane bioreactor (A1/A2/O-MBR) was studied at environmental relevant concentrations. The results showed that all the SAs were efficiently eliminated (93.9%-97.5%) in the A1/A2/O-MBR, much more efficiently than the previously reported MBR-based processes. The largest contribution to the total removal was made by the aerobic reactor (71.1%-85.3%) A small portion of SAs (7.1%-22.5%) were removed by anoxic reactor. Activated sludge in the A1/A2/O-MBR was harvested to conduct batch experiments to further study the removal and degradation kinetics of SAs under anaerobic, anoxic and aerobic conditions. The results indicated that only sulfisoxazole could be removed under anaerobic condition. Modest biodegradation of individual SAs (15-33%) was observed under anoxic condition. Under aerobic condition, most investigated SAs underwent an efficient and fast removal (68-77%) in 6h without a lag phase; while sulfisomidine and sulfamethazine were removed less efficiently (approximately 47% after 6h reaction). The aerobic and anoxic degradation of SAs fitted the first-order kinetics model well, and the obtained biodegradation rate constants (k1) were reliable to predict removal efficiencies of SAs in the anoxic and aerobic reactor of A1/A2/O-MBR based on their HRTs.

The chemical degradation performance of carbon tetrachloride (CT), one of the harmful groundwater contaminants, by H2O2/Fe(II)/formic acid (FA), sodium percarbonate (SPC)/Fe(II)/FA and calcium peroxide (CP)/Fe(II)/FA processes was investigated and compared. The results showed that under the same molar ratio of 12/12/12/1 of oxidant/Fe(II)/FA/CT (initial CT = 0.13 mM), oxidant CP performed better than SPC and H2O2 with CT removal of 88.9%, 42.5% and 12.5%, respectively. Scavenging tests and electron paramagnetic resonance (EPR) detection confirmed that in the presence of FA, carbon dioxide anion (CO2 −) was the main responsible radical for CT removal. Mass balance of chloride ions released from CT confirmed the complete mineralization of CT, and CT degradation pathways were proposed. Moreover, effects of the initial solution pH, Cl−, HCO3−, NO3− and SO42− anions were also investigated. CT could be effectively degraded among a wider pH range of 4–10 in SPC/Fe(II)/FA process, but only in acidic condition in CP/Fe(II)/FA process. HCO3− anions negatively affected CT degradation, and CP was more sensitive to HCO3− than SPC. CT degradation performance in actual groundwater demonstrated the feasibility of both SPC/Fe(II)/FA and CP/Fe(II)/FA processes, therefore providing useful information of potential alternatives for oxidant selection.

The strict environmental management has been implemented in Taihu Basin to reduce the surface water contamination; however, the effectiveness of the management actions has not been comprehensively evaluated. In the present study, 364 samples were collected during four campaigns over a span of one year from surface water, municipal wastewater treatment plants (MWWTPs), industrial wastewater treatment plants (IWWTPs), industrial enterprises, and aquaculture in a typical region in the Upper Taihu Basin. Overall concentration, temporal variation and spatial distribution of 16 PAHs in surface water and various pollution sources were evaluated and the potential pollution sources were identified. Results showed that concentrations of individual PAHs in the surface water ranged from less than the limit of quantification (LOQ) to 949 ng L−1, indicating a reduction of PAH contamination level after the implementation of environmental management actions. Influent of MWWTPs and wastewater from industrial enterprises exhibited relatively high ∑PAHs concentrations (mean: 880 ng L−1 and 642 ng L−1, respectively); these samples also exhibited a similar seasonal variation as well as composition of PAH congeners to those found in surface water, and therefore were designated as the main emission sources of PAHs in the studied region. Additional source apportionment using principal component analysis was also conducted to verify the proposed sources and diagnose other pollution sources. The findings provided a thorough understanding of PAH pollution, especially its major emission sources, in a typical region with pollution-intensive industries after the implementation of strict environmental management.

The degradation performance of trichloroethylene (TCE) by sodium percarbonate (SPC) activated with citric acid (CA) chelated Fe(II) in the presence of nonionic surfactant Tween-80 was investigated. The addition of CA successfully prevented the precipitation of iron and facilitated TCE degradation. However, Tween-80 had an inhibitory effect on TCE degradation mainly due to the competition of ∗OH between Tween-80 and TCE. The effect of SPC and Fe(II) dosage on TCE degradation was also explored and the results displayed that 87.2% of TCE could be degraded in 15 min at the SPC/Fe(II)/CA/TCE molar ratio of 3/4/2/1. Free radical probe tests confirmed that both O2-∗ and ∗OH were generated in the SPC/Fe(II)/CA system. Free radical scavenging tests implied that the degradation of TCE in the SPC/Fe(II)/CA system was mainly attributed to ∗OH, while O2-∗ was only partially involved in the degradation of TCE. In addition, TCE removal was suppressed with the raising of the initial solution pH from 3.0 to 9.0. The actual groundwater (containing Tween-80) tests confirmed that 93.2% of TCE degradation could be achieved at the SPC/Fe(II)/CA/TCE molar ratio of 30/40/10/1 and strongly demonstrated that the SPC/Fe(II)/CA process has potential for the in situ treatment of TCE contaminated groundwater in the presence of surfactant Tween-80. In conclusion, TCE degradation by Fe(II) activated SPC system in the presence of Tween-80 can be significantly enhanced with the addition of CA, and this finding offers an innovative direction for removing chlorinated organic contaminants from groundwater in contaminated site after surfactant solubilization treatment.

A persulfate/percarbonate (PS/SPC) system activated with citric acid (CA) chelated-Fe(II), which combined the benefits of sole PS and SPC systems, was conducted for phenanthrene (PHE) degradation in aqueous solution. The effects of oxidant concentration, Fe(II)-CA dosage, PS/SPC molar ratio and initial solution pH were investigated in the laboratory. The results indicated that the addition of CA could remarkably enhance PHE removal, and PHE could be degraded completely at 0.5 mM PS, 0.5 mM SPC and 0.5 mM Fe(II) with 0.1 mM CA in 60 min. PHE oxidation process was more efficient in acidic condition, which presented a two-stage degradation pattern and PHE removal followed a pseudo-first-order kinetic model in the second stage. The results of free radical probe tests, scavenging tests and EPR analysis demonstrated that OH was the predominant radical for PHE oxidation. The major degradation intermediates of PHE were identified by LC–MS, and the possible reaction mechanism and PHE degradation pathways were proposed.

Most of the calcium peroxide (CaO2) based Fenton oxidation studies focus on the individual pollutant degradation. In this study, the simultaneous oxidation of benzene, toluene, ethylbenzene, and xylene (denoted as BTEX) by CaO2 based Fenton system was demonstrated. It was observed that BTEX removal increased with increasing molar ratios of CaO2/Fe(II)/BTEX. In the case of CaO2/Fe(II)/BTEX molar ratio of 5/5/1, BTEX removal were 35% in the ultrapure water and 15% in the actual groundwater. In the case of CaO2/Fe(II)/BTEX molar ratio of 40/40/1, BTEX removal were elevated to 98% in the ultrapure water and 88% in the actual groundwater. Chelating Fe(II) agents, such as citric acid (CA), oxalic acid (OA), and glutamic acid (GA), significantly enhanced the destruction of BTEX. When the molar ratio of Fe(II)/CA, Fe(II)/GA, and Fe(II)/OA was 10/20 while fixing CaO2/Fe(II)/BTEX molar ratio of 10/10/1, the enhancements in BTEX removal were 60%, 32%, and 72%, respectively. In terms of BTEX removal, OA chelated Fe(II) was demonstrated to be most effective in the CaO2/Fe(II)/BTEX system. Based on TOC analysis, the transformation effect was confirmed. The transformation products of BTEX were determined and oxidation pathways were proposed, in which HO was mostly responsible to the parent compounds mineralization.

The enhancement effect of an environmentally friendly reducing agent, ascorbic acid (AA), on trichloroethene (TCE) degradation by Fe(III)-activated calcium peroxide (CP) was evaluated. The addition of AA accelerated the transformation of Fe(III) to Fe(II), and the complexation of Fe(III)/Fe(II) with AA and its products alleviated the precipitation of dissolved iron. These impacts enhanced the generation of reactive oxygen species (ROSs). Investigation of ROSs using chemical probe tests, electron paramagnetic resonance (EPR) tests, and radical scavenger tests strongly confirm large production of hydroxyl radicals (HO•) that is responsible for TCE degradation. The generation of Cl− from the degraded TCE was complete in the enhanced CP/Fe(III)/AA system. The investigation of solution matrix effects showed that the TCE degradation rate decreases with the increase in solution pH, while Cl−, SO42− and NO3− anions have minor impact. Conversely, HCO3− significantly inhibited TCE degradation due to pH elevation and HO• scavenging. The results of experiments performed using actual groundwater indicated that an increase in reagent doses are required for effective TCE removal. In summary, the potential effectiveness of the CP/Fe(III)/AA oxidation system for remediation of TCE contaminated groundwater has been demonstrated. Additional research is needed to develop the system for practical implementation.

Poly- and perfluoroalkyl substances (PFASs) have attracted mounting attention due to their potential harmful effects and degradation-resistant property. This study continuously monitored the concentration of PFASs for four seasons in two years in the northwest of Tai Lake Basin. The occurrence, spatiotemporal distribution, seasonal and annual variation, and source apportionment of 13 PFASs were investigated in 60 surface water sampling sites and 33 emission sources. The average concentrations of the total PFASs were 205.6 ng L−1 and 171.9 ng L−1 in 2018 and 2019, respectively. This improvement could be mainly attributed to the local industrial restructuring. Furthermore, principal component analysis and heat map-hierarchical cluster analysis were employed to analyze distribution characteristics and the possible sources of PFASs pollution. It showed that perfluorooctane sulfonate (PFOA) mainly originated from the effluents of chemical plants, while the potential source of perfluorohexane sulfonate (PFHxS) included all the three types of emission sources. Besides, two indicators were adopted to evaluate the impact of non-point sources and the result showed the effect of runoff was obvious while the effect of atmospheric deposition was weak. A systematic mass balance calculation showed that the total riverine input flux from Wujin District to Tai Lake was 126.5 kg/a.

Pharmaceutically active compounds (PhACs) have been widely reported in most megacities in China but seldom in small and median-sized cities. The aim of this study is to investigate occurrence and distribution characteristics of PhACs in a typical small and medium-sized city in China and analyze their sources. 33 PhACs and 4 chiral drugs were selected for a four-season monitoring campaign in Wujin District, Jiangsu Province, a typical small and median-sized city, in 2018. PhACs concentration level in surface water, ranging from ng L-1 to μg L-1, was lower than in large-sized cities and areas in China. Impact from agricultural sources should be concerned in the study area: (1) Significant correlation between concentrations of antibiotics and NH4-N in surface water indicated the potential impact from agricultural sources (fishponds and livestock farms); (2) Government regulating measures on livestock and poultry farms since January 2018 have effectively decreased macrolides and lincosamides emissions into surface water. As for source analysis, CF/CBZ (Caffeine/Carbamazepine) was a feasible indicator to trace untreated wastewater and enantiomeric fraction values of metoprolol (MTP) were also suggested to be helpful for identifying untreated wastewater. The results of both two indicators indicated more input of untreated wastewater to surface water in the northeast area and upstream of Wuyi Canal. To our best knowledge, this is the first study to systematically analyze PhACs in aquatic environment for a small and medium-sized city in China.

The mechanism of surfactants in surfactant-in situ chemical oxidation (S-ISCO) coupled process for trichloroethene (TCE) degradation was firstly reported. The performance of TCE solubilization and inhibition of TCE degradation in three nonionic surfactants (TW-80, Brij-35, TX-100) in PS/Fe(II)/citric acid (CA) system was compared and TW-80 was evaluated to be the optimal surfactant in S-ISCO coupled process due to the best TCE solubilizing ability and minimal inhibition for TCE degradation (only 31.8% TCE inhibition in the presence of 1 g L−1 TW-80 surfactant). The inhibition mechanism in TCE degradation was also demonstrated by comparing the strength of ROSs and PS utilization. In the presence of TW-80 (1 g L−1), over 97.5% TCE was removed at the PS/Fe(II)/CA/TCE molar ratio of 30/4/4/1, in which more than 86.7% TCE was dechlorinated. The result of scavenger experiments revealed that the dominant radicals were HO• and SO4−• in PS/Fe(II)/CA system in TW-80 containing aqueous solution, among which SO4−• performed a greater role in TCE removal. Moreover, over 85.3% TCE degradation in actual groundwater revealed the potential of PS/Fe(II)/CA process for actual groundwater remediation in containing TW-80 of TCE contaminant. This research provided a novel alternative technology for groundwater remediation with TCE contaminant when containing surfactants.

This work demonstrates the impact of hydroxylamine hydrochloride (HAH) addition on enhancing the degradation of trichloroethene (TCE) by the citric acid (CA)-chelated Fe(II)-catalyzed percarbonate (SPC) system. The results of a series of batch-reactor experiments show that TCE removal with HAH addition was increased from approximately 57 to 79% for a CA concentration of 0.1 mM and from 89 to 99.6% for a 0.5 mM concentration. Free-radical probe tests elucidated the existence of hydroxyl radical (HO•) and superoxide anion radical (O2 •-) in both CA/Fe(II)/SPC and HAH/CA/Fe(II)/SPC systems. However, higher removal rates of radical probe compounds were observed in the HAH/CA/Fe(II)/SPC system, indicating that HAH addition enhanced the generation of both free radicals. In addition, increased contribution of O2 •- in the HAH/CA/Fe(II)/SPC system compared to the CA/Fe(II)/SPC system was verified by free-radical scavengers tests. Complete TCE dechlorination was confirmed based on the total mass balance of the released Cl− species. Lower concentrations of formic acid were produced in the later stages of the reaction for the HAH/CA/Fe(II)/SPC system, suggesting that HAH addition favors complete TCE mineralization. Studies of the impact of selected groundwater matrix constituents indicate that TCE removal in the HAH/CA/Fe(II)/SPC system is slightly affected by initial solution pH, with higher removal rates under acidic and near neutral conditions. Although HCO3 − was observed to have an adverse impact on TCE removal for the HAH/CA/Fe(II)/SPC system, the addition of HAH reduced its inhibitory effect compared to the CA/Fe(II)/SPC system. Finally, TCE removal in actual groundwater was much significant with the addition of HAH to the CA/Fe(II)/SPC system. The study results indicate that HAH amendment has potential to enhance effective remediation of TCE-contaminated groundwater.

Experiments were conducted to investigate the use of graphene-oxide supported metallic nanocomposites for improving the degradation of trichloroethane (TCA) by sodium percarbonate (SPC). Two methods of production, chemical reduction (CR) and solvo-thermal (ST), were tested for preparation of single (Fe) and binary (Fe-Cu) nanocomposites supported by reduced graphene oxide (rGO). A variety of analytical techniques including N2 adsorption Brunauer-Emmett-Teller (BET), x-ray diffraction (XRD), fourier-transfrom infrared spectroscopy (FTIR), and transmisison electron microscopy (TEM) were applied to characterize the physicochemical and microstructural properties of the synthesized nanocomposites. The characterization indicated that the CR method produced nanocomposites that comprised only mesoporous structure. Conversely, both micro and mesoporous structures were present for samples produced with the ST method. The synthesized single and bimetallic composites produced from the ST method showed higher surface areas, i.e. 93.6 m2/g and 119.2 m2/g as compared to the ones synthesized via the CR method, i.e. 13.8 m2/g and 38.0 m2/g respectively. The results of FTIR and XRD analyses confirmed that the ST method produced highly crystalline nanocomposites. SEM and TEM analysis validated that metallic particles with definite morphology well distributed on the surface of rGO. X-ray photoelectron spectroscopy (XPS) analysis confirmed the homogeneity nanocomposites and occurrence of variation in copper oxidation states during degradation process. EDS mapping validate the homogeneous distribution of Cu and Fe at reduced graphene oxide surface. The Fe-Cu/rGO (ST) activated SPC system effectively degraded TCA (92%) in 2.5 h at low nanocomposite dose compared to the Fe-Cu/rGO (CR) and only Fe, for which the maximum degradation efficiencies achieved were 81% and 34%. In conclusion, excellent catalytic characteristics were observed for the ST-synthesized single and bimetallic (Fe/rGO, Fe-Cu/rGO) catalysts. These catalysts were successful in improving the degradation of TCA via activated SPC.

Complete degradation of benzene by the Fe(III)-activated sodium percarbonate (SPC) system is demonstrated. Removal of benzene at 1.0 mM was seen within 160 min, depending on the molar ratios of SPC to Fe(III). A mechanism of benzene degradation was elaborated by free-radical probe-compound tests, free-radical scavengers tests, electron paramagnetic resonance (EPR) analysis, and determination of Fe(II) and H2O2 concentrations. The degradation products were also identified using gas chromatography-mass spectrometry method. The hydroxyl radical (HO ) was the leading species in charge of benzene degradation. The formation of HO was strongly dependent on the generation of the organic compound radical (R ) and superoxide anion radical (O2 −). Benzene degradation products included hydroxylated derivatives of benzene (phenol, hydroquinone, benzoquinone, and catechol) and aliphatic acids (oxalic and fumaric acids). The proposed degradation pathways are consistent with radical formation and identified products. The investigation of selected matrix constituents showed that the Cl− and HCO3− had inhibitory effects on benzene degradation. Natural organic matter (NOM) had accelerating influence in degrading benzene. The developed system was tested with groundwater samples and it was found that the Fe(III)-activated SPC has a great potential in effective remediation of benzene-contaminated groundwater while more further studies should be done for its practical application in the future because of the complex subsurface environment.

Ethylbenzene (EB) degradation performance in (S,S)-ethylenediamine-N,N-disuccinic acid (EDDS) chelated Fe(III) activated sodium percarbonate (SPC) system was investigated in this study. The effects of various factors, such as the dosages of SPC and Fe(III), molar ratio of EDDS/Fe(III), anions (Cl−, HCO3−, SO42−, and NO3−) concentration, natural organic matters (NOM), and initial solution pH were evaluated. The results showed that the addition of EDDS remarkably improved the EB removal in Fe(III)/SPC system. Both HCO3− anions and NOM had significantly inhibitive effect, while the influence of SO42−, Cl− and NO3− could be negligible on EB degradation. The EB removal was inhibited at extremely low and high initial solution pH. Moreover, the results of free radical probe tests, scavenger tests and electron paramagnetic resonance (EPR) detection indicated that OH was the predominant species responsible for EB degradation even though both OH and O2− were generated in the SPC/EDDS–Fe(III) system. The oxidation products were analyzed and possible EB degradation pathways were proposed. In conclusion, this study provides an important insight into the application of SPC/EDDS–Fe(III) system in the removal of EB contaminant, especially for in situ remediation of BTEX-contaminated groundwater.

The reduction performance of carbon tetrachloride (CT) mediated by carbon dioxide radical anion (CO 2 − ) was investigated in this study, and CO 2 − was generated by the reaction of formic acid and sulfate radical produced in the UV/S 2 O 8 2− process. The effects of various factors including persulfate and formic acid concentrations, solution pH, and anions such as Cl − , HCO 3 − , NO 3 − , and SO 4 2− were evaluated. The experimental results showed that CT could be almost completely removed in 60 min with 1.50 mM persulfate and 2.25 mM formic acid. CT degradation efficiency was found to increase with increasing persulfate (0.75−4.50 mM) and formic acid (0.75−2.25 mM) concentrations. In the pH adjusted solutions (from pH 6–8), maximum CT degradation occurred at pH 6. Both Cl − and NO 3 − (1−100 mM), as well as HCO 3 − at high concentrations (10 and 100 mM), adversely affected CT degradation performance. The addition of methyl viologen as CO 2 − scavengers proved the presence of CO 2 − in this UV/S 2 O 8 2− /HCOOH process, and the dechlorination of CT was not complete as Cl − release rate was 80.6% after 240 min.

This study conducted a comparison of the CaO(2)-based Fenton (CaO(2)/Fe(II)) and Fenton-like (CaO(2)/Fe(III)) systems on their benzene degradation performance. The H(2)O(2), Fe(II), Fe(III), and HO(●) variations were investigated during the benzene degradation. Although benzene has been totally removed in the two systems, the variation patterns of the investigated parameters were different, leading to the different benzene degradation patterns. In terms of the Fe(II)/Fe(III) conversion, the CaO(2)/Fe(II) and CaO(2)/Fe(III) systems were actually inseparable and had the inherent mechanism relationships. For the CaO(2)/Fe(III) system, the initial Fe(III) must be converted to Fe(II), and then the consequent Fenton reaction could be later developed with the regenerated Fe(II). Moreover, some benzene degradation intermediates could have the ability to facilitate the transformation of the Fe(III) to Fe(II) without the classic H(2)O(2)-associated propagation reactions. By varying the Fe(II) dosing method, an effective degradation strategy has been developed to take advantage of the two CaO(2)-based oxidation systems. The proposed strategy was further successfully tested in TCE degradation, therefore extending the potential for the application of this technique.

β-blockers are a class of medications widely used to treat cardiovascular disorders, including abnormal heart rhythms, high blood pressure, and angina pectoris. The prevalence of β-blockers has generated a widespread concern on their potential chronic toxicity on aquatic organisms, highlighting the necessity of comprehensive studies on their environmental distribution, fate, and toxicity. This review summarizes the up-to-date knowledge on the source, global distribution, analytical methods, transformation, and toxicity of β-blockers. Twelve β-blockers have been detected in various environmental matrices, displaying significant temporal and spatial variations. β-blockers can be reduced by 0–99% at wastewater treatment plants, where secondary processes contribute to the majority of removal. Advanced oxidation processes, e.g., photocatalysis and combined UV/persulfate can transform β-blockers more rapidly and completely than conventional wastewater treatment processes, but the transformation products could be more toxic than the parent compounds. Propranolol, especially its (S)-enantiomer, exhibits the highest toxicity among all β-blockers. Future research towards improved detection methods, more efficient and cost-effective removal techniques, and more accurate toxicity assessment is needed to prioritize β-blockers for environmental monitoring and control worldwide.

In this study, an environmentally friendly complexing agent, S,S′-ethylenediamine-N,N′-disuccinic acid (EDDS), was applied in Fe(III)-mediated activation of persulfate (PS), and the degradation performance of trichloroethylene (TCE) was investigated. The effects of PS concentration, Fe(III)/EDDS molar ratio, and inorganic anions on TCE degradation were evaluated, and the generated reactive oxygen species responsible for TCE removal were identified. The results showed that nearly complete TCE degradation was achieved with PS of 15.0 mM and a molar ratio of Fe(III)/EDDS of 4:1. An increase in PS concentration or Fe(III)/EDDS molar ratio to a certain value resulted in enhanced TCE degradation. All of the anions (Cl−, HCO3 −, SO4 2−, and NO 3 − ) at tested concentrations had negative effects on TCE removal. In addition, investigations using radical probe compounds and radical scavengers revealed that sulfate radicals (SO 4 ·− ), hydroxyl radicals (·OH), and superoxide radical anions (O 2 ·− ) were all generated in the Fe(III)–EDDS/PS system, and ·OH was the primary radical responsible for TCE degradation. In conclusion, the Fe(III)–EDDS-activated PS process is a promising technique for TCE-contaminated groundwater remediation.

In this study, the application of sodium percarbonate (SPC) catalyzed by various chelated-Fe(II) to stimulate the degradation of benzene in groundwater remediation was investigated. Effective oxidation of benzene was achieved in CIT/SPC/Fe(II) and OA/SPC/Fe(II) systems. The reaction mechanism for benzene degradation in CIT/SPC/Fe(II) and OA/SPC/Fe(II) systems was elucidated by free radical probe compound tests, free radical scavenger tests and electron paramagnetic resonance (EPR) analysis. And hydroxyl radical (HO ) and superoxide anion radical ( O 2 - ) were confirmed as the predominant species responsible for benzene degradation. Besides, the effects of various factors, such as the solution characteristics including the presence of anions (Cl − , HCO 3 − , SO 4 2− and NO 3 − ), natural organic materials (NOM), and the initial solution pH on benzene degradation were also evaluated. The influences caused by SO 4 2− , NO 3 − , Cl − and NOM were negligible, but HCO 3 − anion had a slightly inhibitive effect in low concentration (1 mM) and an apparently inhibitive effect in high concentration (10–100 mM). However, the additions of CIT and OA eliminated the adverse influence of HCO 3 − and ensured a high benzene degradation efficiency at wider pH range. Finally, results obtained in actual groundwater test strongly demonstrated that Fe(II)-CIT and Fe(II)-OA catalyzed SPC systems are applicable for the remediation of benzene-contaminated groundwater in practice.

We examine quantum anomalous Hall (QAH) insulators with intrinsic magnetism displaying quantized Hall conductance at zero magnetic fields. The spin-momentum locking of the topological edge stats promises QAH insulators with great potential in device applications in the field of spintronics. Here, we generalize Haldane’s model on the honeycomb lattice to a more realistic two-orbital case without the artificial real-space complex hopping. Instead, we introduce an intraorbital coupling, stemming directly from the local spin-orbit coupling (SOC). Our dxy /d x 2–y 2 model may be viewed as a generalization of the bismuthene px /py -model for correlated d-orbitals. It promises a large SOC gap, featuring a high operating temperature. This two-orbital model nicely explains the low-energy excitation and the topology of two-dimensional ferromagnetic iron-halogenides. Furthermore, we find that electronic correlations can drive the QAH states to a c = 0 phase, in which every band carries a nonzero Chern number. Our work not only provides a realistic QAH model, but also generalizes the nontrivial band topology to correlated orbitals, which demonstrates an exciting topological phase transition driven by Coulomb repulsions. Both the model and the material candidates provide excellent platforms for future study of the interplay between electronic correlations and nontrivial band topology.

The quantification of microplastics (MPs), especially small MPs (20–100 μm), in freshwater environment and wastewaters is a great challenge due to the complexity of environmental compartment. In the present study, a novel method based on the optimization of sampling, pretreatment, and detection was developed for small MPs (20–100 μm) in freshwater and wastewaters. A customized plankton sampler was installed to efficiently collect MPs and avoid sampler clogging; a novel dual filter system simplified the pretreatment, achieving full examination for small MPs in the samples. The recoveries of small MPs at environmental abundance, which were specified for the first time, verified the feasibility of the developed method. The method was successfully applied for small MPs detection in river, municipal wastewaters and landfill leachates, demonstrating a large bias in the determination of MPs if small MPs were not involved in quantification. To the authors' knowledge, it is the first study that realized the determination of such small MPs in the high-strength wastewater, i.e. landfill leachates.

The performance of trichloroethene (TCE) degradation was significantly improved with the addition of FeS in nanoscale calcium peroxide (nCP) environment and the enhancement of HO generation in nCP/Fe(II)/FeS system was confirmed by comparison with nCP/Fe(II) and nCP/FeS systems. The role of FeS in nCP/Fe(II)/FeS system demonstrated that the majority of reactive oxygen radicals (ROSs) was generated on the catalyst surface due to the heterogeneous reaction through FeS activated nCP in one hand, and the reductive FeS could promote TCE degradation by regenerating Fe(II) from Fe(III) in the other hand. The probe as well as scavenger test results suggested that the major ROSs was HO rather than O2− . Over 91.5% TCE could be degraded at the molar ratio of 2/2/4/1 of nCP/Fe(II)/FeS/TCE, in which more than 95.5% TCE was dechlorinated. The effect of surfactants on TCE degradation was evaluated. In contrast, further investigation found that BTEX removal was inhibited with the addition of FeS. In conclusion, this study revealed the well function and fundamental synergistic mechanism of FeS. Moreover, the degradation of TCE in actual groundwater confirmed that nCP/Fe(II)/FeS technique has a great advantage and potential in TCE contaminated groundwater remediation in ISCO practice.

Trichloroethylene (TCE) is chloride organic solvent used in industrial process and frequently detected as one of contaminants in groundwater. In present study, nano zero valent iron-nickel composite (nZVI-Ni) was prepared successfully by ion exchange process and investigated as a proficient sodium persulfate (SPS) activator for the removal of TCE in Fenton-like oxidation system. The physico-chemical characteristics, structure, and surface morphology of the prepared nZVI-Ni nanocomposite was analyzed through energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), N2 adsorption-desorption, transition electron microscopy (TEM), X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS). The experimental results obtained from batch tests in lab showed that more than 95% of TCE could be removed efficiently at nZVI-Ni/SPS/TCE molar ratio of 4/4/1 within 120 min at 20 °C. Further scavenging tests were designed to examine the presence of HO , SO4 − and O2− radicals and verified the major role of HO radical in the nZVI-Ni/SPS system for the complete removal of TCE. Moreover, the generation of HO radicals in the system was confirmed through electrons paramagnetic resonance (EPR) of nZVI-Ni composite. The influence of surfactants on TCE removal was tested and the results showed that the percentage removal of TCE was recorded as 97.75%, 95.63% and 77.50% in the presence of Tween-80, BRIJ-35 and TX-100 surfactants at the nZVI-Ni/SPS/TCE molar ratio of 80/80/1, respectively. Results of TCE degradation in real groundwater revealed that nZVI-Ni can be applicable and is a promising catalyst for TCE removal in in-situ chemical oxidation (ISCO) practice. In Summary, these significant findings strongly demonstrate the feasibility and potential of nZVI-Ni activated SPS process as an alternative technique for TCE contaminated groundwater remediation.

Twenty-two Shiga toxin-producing Escherichia coli (STEC) strains and six potential surrogates (E. coli strains K12 and P1, Listeria innocua, Lactobacillus plantarum, Bifidobacterium lactis, and Enterococcus faecium) were screened in wheat flour at two water content levels of 8 and 13% (0.25 and 0.55 water activities) for survival at 6 °C and resistance to a heat treatment at 82 °C for 5 min. The results showed that the moisture content of the flour had a significant impact on the inactivation. The STEC populations were inactivated by an average of 1.7 log CFU/g and 6.0 log CFU/g at 8 and 13% moisture levels, respectively. The STEC strains linked to notorious outbreaks showed viable counts above the average STEC viable counts after storage and after the heat treatment at respective moisture levels. These strains have been incriminated in outbreaks related to food products such as hazelnuts, sprouts, “Jack in the Box” fast food, apple juice, mettwurst sausage and cookie dough. The survival after storage and heat inactivation of E. faecium NRRL-B2354 and E. coli P1 indicated the potential suitability of these bacteria as surrogates for STEC for wheat flour process validations.

Although the utilization of formic acid (FA) as a target compound for modeling the kinetic and mechanism in several Fenton processes has been previously reported, this study explored the potential of FA as an efficient hydroxyl radical (HO ) scavenger to generate reductive carbon dioxide radical (CO2 −) for carbon tetrachloride (CT) degradation in nanoscale zero valent iron (nZVI) suspension in the presence and absence of oxidant. The results showed that the presence of 3.12 mM FA enhanced CT removal from 11.4% to 85.0% within 60 min in oxygenated 0.5 g/L nZVI suspension. Meanwhile, the presence of 3.12 mM FA improved Fe2+ elution by 5 folds under pH = 3. The generation of H2O2 in oxygenated nZVI suspension was also monitored. Hence, it was hypothesized that the rapid CT degradation in nZVI/FA system was initiated by reductive CO2 − radical. In anaerobic nZVI/oxidant/FA system, CT degradation of 69.3% and 75.1% was achieved when using H2O2 or calcium peroxide (CP) as the oxidant, respectively. The addition of oxidant at 10 min reaction performed the best for CT removal as enough Fe2+ has been released after the dissolution of nZVI. These results demonstrated that a suitable dose of released Fe2+ was the key factor to enhance HO and CO2 − radical generation in nZVI/oxidant/FA system. This study provided new information about effective usage of nZVI and FA for enhancing CT degradation in heterogeneous Fenton system.

The surface properties of nanocomposites are influenced by the existence of inorganic species that may affect its performance for specific catalytic applications. The impact of different ionic species on particular catalytic activity had not been investigated to date. In this study, the surface charge (zeta potential) of graphene-oxide-supported nano zero valent iron (G-nZVI) was tested in definitive cationic (Na(+), K(+), Ca(2+) and Mg(2+)) and anionic (Br(−), Cl(−), NO(3)(−), SO(4)(2−), and HCO(3)(−)) environments. The efficiency of G-nZVI catalyst was inspected by measuring the generation of reactive oxygen species (ROS) for the degradation of 1,1,1-trichloroethane (TCA) in sodium percarbonate (SPC) system. Tests conducted using probe compounds confirmed the generation of OH(•) and O(2)(•−) radicals in the system. In addition, the experiments performed using scavenging agents certified that O(2)(•−) were primary radicals responsible for TCA removal, along with prominent contribution from OH(•) radicals. The study confirmed that G-nZVI catalytic capability for TCA degradation is notably affected by various cationic species. The presence of Ni(2+) and Cu(2+) significantly enhanced (94%), whereas Na(+) and K(+) had minor effects on TCA removal. Overall, the results indicated that groundwater ionic composition may have low impact on the effectiveness of G-nZVI-catalyzed peroxide TCA treatment.

Two carboxylic acids (formic acid (FA) and citric acid (CIT)) enhanced the Fenton process using Fe(II)-activated calcium peroxide (CP) to develop a hydroxyl radical (HO•) and carbon dioxide radical (CO(2)•(-)) coexistence process for the simultaneous redox-based degradation of three chlorinated hydrocarbons (CHs), namely carbon tetrachloride (CT), tetrachloroethene (PCE), and trichloroethene (TCE), was investigated. The experimental results showed that CT removal was increased while PCE and TCE degradation were decreased with the addition of FA to the Fe(II)/CP system. However, addition of CIT to the Fe(II)/CP/FA system enhanced the removal efficiency of all three contaminants. For example, 81.7%, 79.4%, and 96.1% of CT, PCE, and TCE, respectively, were removed simultaneously under the optimal molar ratio of 12/12/12/12/1 of CIT/CP/Fe(II)/FA/CHs. Investigations of the degradation mechanism confirmed the specific roles of HO• and the secondarily generated CO(2)•(-) radical, i.e., PCE and TCE were degraded oxidatively by HO• while CT was degraded via reductive dechlorination by CO(2)•(−). Carbonate reduced PCE and TCE degradation in actual groundwater as it consumed reactive oxygen species, whereas humic acid and neutral pH had minimal impact on contaminant removal. These results can help us better understand the synergistic effects of different carboxylic acids in the modified Fenton process for the redox-based degradation of refractory chlorinated hydrocarbons.

This study presents a performance comparison of Fe(II)-catalyzed sodium percarbonate (SPC), Fe(II)-EDDS-catalyzed SPC, and of the innovative hydroxylamine hydrochloride (HA)-Fe(II)-EDDS-catalyzed SPC for the degradation of trichloroethylene (TCE) in water. TCE degradation was greater in the Fe(II)-EDDS-catalyzed SPC system compared to the Fe(II)-catalyzed SPC system, indicating the effectiveness of adding EDDS as an enhancement factor for the removal of TCE. Moreover, TCE degradation was faster in the HA-Fe(II)-EDDS-catalyzed SPC system compared to the Fe(II)-EDDS-catalyzed SPC system, illustrating that HA can play a synergistic role in TCE degradation. Analysis of iron distribution in the three systems demonstrated that EDDS addition maintained iron in soluble form, and that the generation of soluble ferrous from ferric iron was expedited with addition of HA. Studies using nitrobenzene and carbon tetrachloride probes provided insights on the generation of hydroxyl radical (HO•) and superoxide anion radical (O2•-) in the three systems. A gradual increasing contribution of O2•- to TCE removal in Fe(II)-catalyzed SPC, Fe(II)-EDDS-catalyzed SPC, and HA-Fe(II)-EDDS-catalyzed SPC systems was verified through free-radical scavenger tests. Finally, monitoring of Cl- concentrations manifested the complete dechlorination of TCE. A possible mechanism of TCE degradation involving two pathways of HO• oxidation and O2•- reaction was proposed.

Nano zero-valent iron (nZVI) particles with higher reactivity have been recognized as more efficient catalysts than Fe(II) for the groundwater remediation. The rapid emergence of novel catalyst supports efficiently prevent the rapid aggregation of nZVI and further improve catalytic reactivity. However, the lack of ability to avoid the potential oxidation of bare nZVI-support structure in air environment hinders its wider application in the actual contaminated sites. In this study, nZVI on reduced graphene oxide (rGO) functionalized by polydopamine (PDA) (nZVI-PDA@rGO) was synthesized successfully and applied into sodium persulfate (SPS), potassium monopersulfate (PMS) and H2O2 oxidative environments to remove trichloroethylene (TCE). For comparison, nZVI supported on solely rGO was prepared. The XRD test displayed the stronger stability of α-Fe(0) in nZVI-PDA@rGO catalyst against oxidation exposed to air. Compared with nZVI-rGO, a core shell structure of nZVI-PDA@rGO was observed in TEM image obviously. The dosage tests showed nZVI-PDA@rGO had a better catalytic reactivity than nZVI-rGO for TCE removal at lower catalyst and oxidant dosages, i.e. PMS dosage: 0.3 mM, catalyst dosage: 50 mg L−1, TCE removal: 45.0% (nZVI-rGO) up to 99.6% (nZVI-PDA@rGO). TCE removal mechanisms were revealed through radical scavenger tests, demonstrating sulfate radicals played more important role in nZVI-PDA@rGO catalyzed-oxidant systems.

Fe(II) activated sodium percarbonate (SPC) process (SPC/Fe(II)) could efficiently remove sulfamethoxazole (SMX) in the aqueous phase, and has the potential in groundwater remediation. However, the degradation mechanisms, especially the degradation products and pathways till now have remained unclear. In the present study, intermediate products were identified using high resolution liquid chromatography coupled with ion trap and time-of-flight mass spectrometry (LCMS-IT-TOF). Nine intermediate products were identified, six of which have not yet been reported during the oxidation of SMX. The oxidation mechanisms involved hydroxyl substitution, the cleavage of sulfonamide bond, isoxazole ring opening and a rearrangement following the loss of the SO2-group. Based on the identified intermediate products, the degradation pathways of SMX by SPC/Fe(II) process were illustrated. Fenton's reaction after the dissolution of SPC was proposed as the main reaction mechanisms, which was checked and confirmed by radical species detection tests and radical species scavenging studies. The results showed that although both O2- and HO were present in SPC/Fe(II) system, HO was dominant in the system while O2- was seldom involved in the degradation of SMX. These findings provided useful information and supported the application of this advanced oxidation process for antibiotics elimination in the groundwater.

In this study, the degradation performance of carbon tetrachloride (CT) by sodium percarbonate (SPC) activated with Fe(II) in the presence of ethyl alcohol (EA) was investigated. The experimental results showed that CT could be readily degraded and the optimal EA/Fe(II)/SPC/CT molar ratio for CT reduction was 100/50/20/1. Superoxide radical anion ( ) and hydroxyethyl radical (

The thermally activated persulfate (PS) degradation of carbon tetrachloride (CT) in the presence of formic acid (FA) was investigated. The results indicated that CT degradation followed a zero order kinetic model, and CO2– · was responsible for the degradation of CT confirmed by radical scavenger tests. CT degradation rate increased with increasing PS or FA dosage, and the initial CT had no effect on CT degradation rate. However, the initial solution pH had effect on the degradation of CT, and the best CT degradation occurred at initial pH 6. Cl– had a negative effect on CT degradation, and high concentration of Cl– displayed much strong inhibition. Ten mmol·L–1HCO3– promoted CT degradation, while 100 mmol·L–1NO3– inhibited the degradation of CT, but SO42– promoted CT degradation in the presence of FA. The measured Cl–concentration released into solution along with CT degradation was 75.8% of the total theoretical dechlorination yield, but no chlorinated intermediates were detected. The split of C-Cl was proposed as the possible reaction pathways in CT degradation. In conclusion, this study strongly demonstrated that the thermally activated PS system in the presence of FA is a promising technique in in situ chemical oxidation (ISCO) remediation for CT contaminated site.