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Halonitromethanes (HNMs), a representative nitrogen-containing disinfection byproduct, have gained significant concerns due to their higher cytotoxicity and genotoxicity. UV/chlorination is considered a promising alternative disinfection technology for chlorination. This study aimed to investigate the HNMs formation from benzylamine (BZA) during UV/chlorination. The experimental results revealed that the yields of HNMs initially raised to a peak then dropped over time. Higher chlorine dosage and BZA concentration promoted the formation of HNMs, whereas alkaline pH inhibited their formation. The presence of bromine ion (Br - ) not only converted chlorinated-HNMs (Cl-HNMs) to brominated (chlorinated)-HNMs Br (Cl)-HNMs) and brominated-HNMs (Br-HNMs) but also enhanced the total concentration of HNMs. Besides, the calculated cytotoxicity index (CTI) and genotoxicity index (GTI) of HNMs were elevated by 68.97% and 60.66% as Br - concentration raised from 2 to 6 µM. The possible formation pathways of HNMs from BZA were proposed based on the intermediates identified by a gas chromatography/mass spectrometry (GC/MS). In addition, the formation rules of HNMs in actual water verified the results in deionized water during UV/chlorination. The results of this study provide basic data and a theoretical basis for the formation and control of HNMs, which is conducive to applying UV/chlorination., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

LED-UV 265 /chlorine is a promising alternative disinfection technology that emits mono-wavelength light for high germicidal efficiency. Halonitromethanes (HNMs) are highly cytotoxic and genotoxic disinfection byproducts that can be formed during LED-UV 265 /chlorine disinfection. Thus, this work aimed to investigate the HNMs formation from glycine (Gly) during LED-UV 265 /chlorine disinfection. The results indicated that the concentrations of chlorinated-HNMs (Cl-HNMs) increased first and then decreased as the reaction proceeded. Besides, the effects of operating parameters (UV intensity, free chlorine dosage, and pH) and coexisting ions (Cu 2+ and Br - ) on HNMs formation were investigated. It was found that the formation concentrations of Cl-HNMs increased with the increase of LED-UV 265 intensity and free chlorine dosage but decreased with increased pH. The presence of Cu 2+ promoted the formation of Cl-HNMs. The total concentration of HNMs (at 3 min) with adding 1.5 mg/L Cu 2+ was 30.90% higher than that without Cu 2+ . Notably, nine species of HNMs were detected after adding Br - , and the total concentrations of HNMs were enhanced. Moreover, Cl-HNMs were gradually transformed into brominated (chlorinated)-HNMs and brominated-HNMs as Br - concentration increased. According to the findings, the possible formation mechanism of HNMs from Gly during LED-UV 265 /chlorine disinfection was deduced. Finally, it was demonstrated that the formation laws of HNMs from Gly in real water samples were basically consistent with those in simulated water. Insights obtained in this study help to comprehend the HNMs formation from Gly and provide strategies for controlling the production of HNMs during LED-UV 265 /chlorine disinfection., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Bromide ion (Br - ) is known as a prevalent component in water environments, which exhibits significant impacts on halonitromethanes (HNMs) formation. This study was performed to explore and compare the formation, toxicity, and mechanisms of HNMs from poly(diallyl dimethyl ammonium chloride) (PDDACl) in the absence and presence of Br - in the UV/monochloramine (UV/NH 2 Cl) disinfection process. The results showed that chlorinated HNMs were found in the absence of Br - , while brominated (chlorinated) HNMs and brominated HNMs were found in the presence of Br - . Furthermore, the peaks of total HNMs were promoted by 2.0 and 2.4 times, respectively when 1.0 and 2.0 mg L -1 Br - were added. Also, the peaks of total HNMs were enhanced with the increase of the NH 2 Cl dosage, which were reduced with the increase of pH. It should be noted that Br - induced higher toxicity of HNMs, and the cytotoxicity and genotoxicity of HNMs with the addition of 2.0 mg L -1 Br - were 78.0 and 3.7 times those without the addition of Br - , respectively. Meanwhile, both the reaction mechanisms of HNMs produced from PDDACl were speculated in the absence and presence of Br - . Finally, different HNMs species and yields were discovered in these two real water samples compared to those in simulated waters. These findings of this work will be conducive to understanding the significance of Br - affecting HNMs formation and toxicity in the disinfection process., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Microplastic (MP) pollution in aquatic systems has attracted increasing attention in recent years. MPs will inevitably encounter aging process in the environment. However, research on the effects of aged MPs on freshwater ecosystems remains limited. This study compared the properties of pristine and aged polystyrene (PS) MPs of different sizes (20 nm, 200 nm, 2000 nm) and determined the effects of aging on the toxicity of PS MPs to typical freshwater cyanobacteria, Microcystis aeruginosa. Aging process induced significant changes to the properties of the MPs, especially their microstructures and surface functional groups. Aging process also influenced zeta potential, which could further affect stability and toxicity of PS MPs. After 96 h exposure, increase of algal growth and photosynthetic activity was observed in the treatment of pristine 200 nm, aged 20 nm and aged 200 nm PS MPs. In addition, pristine 20 nm, pristine 200 nm, pristine 2000 nm, aged 20 nm and aged 200 nm PS MPs were adsorbed on algal cell surface, which could influence the cell permeability. Pristine PS MPs promoted microcystin synthesis and release, which could do harm to drinking water safety and freshwater ecosystems. However, there was no significant increase in aged PS MPs treatments. Furthermore, the increased 13 C content of algal cells in all pristine PS MPs treatments indicated that M. aeruginosa assimilated more CO 2 and generate more energy to resist the stress of pristine PS MPs when compared with aged PS MPs. These results indicate that aging process did not necessarily enhance the toxicity and biological risk of PS MPs to freshwater ecosystems. Findings of this study fill the knowledge gap in understanding the effects and risks of aged MPs on freshwater ecosystems., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Chlorinated-halonitromethanes (Cl-HNMs) including chloronitromethane (CNM), dichloronitromethane (DCNM), and trichloronitromethane (TCNM) are nitrogenous disinfection by-products, which have high cytotoxicity and genotoxicity to human. This study aimed to investigate the degradation kinetic modeling and mechanism of Cl-HNMs under monochloramine activated by ultraviolet of 254 nm (UV/NH 2 Cl) treatment. The first-principle kinetic model of UV/NH 2 Cl process was developed to simulate Cl-HNMs degradation. Of note, the second-order rate constants of Cl-HNMs reacting with HO• (∼10 8  M -1  s -1 ), Cl• (k Cl•,CNM or DCNM  = ∼10 10  M -1  s -1 , k Cl•,TCNM  = ∼10 2  M -1  s -1 ), Cl 2 • - (k Cl•,CNM or DCNM  = ∼10 9  M -1  s -1 , k Cl•,TCNM  = ∼10 1  M -1  s -1 ), ClO• (∼10 5 -10 6  M -1  s -1 ) and CO 3 • - (∼10 6 -10 7  M -1  s -1 ) were obtained by the first-principle kinetic model. Overall, Cl-HNMs degradation under UV/NH 2 Cl treatment was successfully predicted by the kinetic model under various conditions. It was found that UV (>60%) was dominant in Cl-HNMs degradation, followed by HO• (3.8%-24.5%), reactive chlorine species (RCS, 0.9%-28.8%) and CO 3 • - (0-26.1%). Among the contributions of RCS, Cl• and Cl 2 • - were main radicals in the degradation of CNM and DCNM, while ClO• was responsible for the abatement of TCNM. The minimum EE/O values under UV/NH 2 Cl treatment were approximately 30% lower than those under UV treatment. Finally, the possible degradation pathways were proposed, including hemolytic/heterolytic cleavage of Cl-HNMs by UV irradiation, hydrogen abstraction/electron transfer of CNM and DCNM and adduct reaction of TCNM by free radicals. This study based on the kinetic model is beneficial to predict and control the concentrations of Cl-HNMs under UV/NH 2 Cl treatment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

UV/chlor(am)ine are efficient for achieving multiple-barrier disinfection and maintaining residuals, while bromide (Br - ) has notable impacts on the formation and toxicity of halonitromethanes (HNMs) during UV/chlor(am)ine disinfection. This study investigated the effects of Br - on HNMs formation and toxicity alteration during UV/chlor(am)ine disinfection of nitrate containing humic acid (HA) water. Results reveal that the maximum concentration of HNMs during UV/chlorine disinfection was 12.03 μg L -1 with 0.2 mg L -1 Br - , which was 22.5% higher than that without Br - , and the predominant species of HNMs were converted from trichloronitromethane (TCNM) to dibromonitromethane (DBNM) and tribromonitromethane (TBNM). However, the maximum concentration of HNMs during UV/chloramine disinfection was 3.69 μg L -1 with 0.2 mg L -1 Br - , which was increased by 26.0% than that without Br - , and the predominant species of HNMs were converted from dichloronitromethane (DCNM) to bromochloronitromethane (BCNM) and DBNM. Notably, the HNMs species and yields during UV/chloramine disinfection were less than those during UV/chlorine disinfection, primarily due to the higher concentrations of HO· and reactive chlorine/bromine species in UV/chlorine. Also, in the ranges of the Br - :Cl 2 molar ratio from 0 to 0.32 and pH from 6.0 to 8.0, the Br - :Cl 2 molar ratio of 0.16 and acidic pH contributed to the HNMs formation during UV/chlorine disinfection, and a high Br - :Cl 2 molar ratio and neutral pH contributed to the HNMs formation during UV/chloramine disinfection. Note that the incorporation of Br - significantly improved the calculated cytotoxicity (CTI) and genotoxicity (GTI) of HNMs formed, and the calculated CTI and GTI of HNMs formed during UV/chloramine disinfection were 28.19 and 48.90% of those during UV/chlorine disinfection. Based on the diversity of nitrogen sources, the possible formation pathways of HNMs from nitrate containing HA water were proposed during UV/chlor(am)ine disinfection in the presence of Br - . Results of this study indicated that UV/chloramine can reduce the formation and toxicity of HNMs efficiently., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier Ltd.)

The degradation of chloroquine phosphate (CQP), an anti-COVID-19 drug, was investigated in a UV-activated persulfate system (UV/PS). The second-order rate constants of CQP with hydroxyl radicals (HO·) and sulfate radicals (SO 4 - ·) were determined using a competition kinetics experiment, and the effects of persulfate concentration, pH, and inorganic anions on the degradation of CQP were also systematically studied. Furthermore, a kinetic model was established to predict the concentration of CQP and major free radicals to explore its mechanism of influence. The results showed that the degradation efficiency of CQP could reach 91.3% after 10 min under UV/PS, which was significantly higher than that under UV, sunlight, or PS alone. At pH=6.9, the second-order rate reaction constants of CQP with HO· and SO 4 - · were 8.9×10 9 L·(mol·s) -1 and 1.4×10 10 L·(mol·s) -1 , respectively, and the main active species was SO 4 - ·. The degradation rate of CQP increased with increasing concentrations of PS and decreased with the addition of HCO 3 - and Cl - . The removal efficiency of CQP was inhibited under stronger alkaline conditions. N -de-ethylation, cleavage of the C-N bond, and hydrogen abstraction were proposed as the principal pathways of CQP degradation based on LC-MS analysis. The mineralization rate of CQP could be improved by increasing PS concentration and pH values. This study could be helpful for the treatment of anti-COVID-19 pharmaceutical wastewater.

The UV/Cl 2 process is commonly used to achieve a multiple-barrier disinfection and maintain residuals. The study chose methylamine as a precursor to study the formation of high-toxic halonitromethanes (HNMs) in the presence of bromide ions (Br - ) during UV/Cl 2 disinfection. The maximum yield of HNMs increased first and then decreased with increasing concentration of Br - . An excessively high concentration of Br - induced the maximum yield of HNMs in advance. The maximum bromine incorporation factor (BIF) increased, while the maximum bromine utilization factor (BUF) decreased with the increase of Br - concentration. The maximum yield of HNMs decreased as pH value increased from 6.0 to 8.0 due to the deprotonation process. The BUF value remained relatively higher under an acidic condition, while pH value had no evident influence on the BIF value. The maximum yield of HNMs and value of BUF maximized at a Cl 2 :Br - ratio of 12.5, whereas the BIF value remained relatively higher at low Cl 2 :Br - ratios (2.5 and 5). The amino group in methylamine was first halogenated, and then released into solution as inorganic nitrogen by the rupture of C-N bond or transformed to nitro group by oxidation and elimination pathways. The maximum yield of HNMs in real waters was higher than that in pure water due to the high content of dissolved organic carbon. Two real waters were sampled to verify the law of HNMs formation. This study helps to understand the HNMs formation (especially brominated species) when the UV/Cl 2 process is adopted as a disinfection technique., (Copyright © 2022. Published by Elsevier B.V.)

Using MXene as substrate, CoOOH@MXene with different mass content of CoOOH were prepared and used to active peroxymonosulfate (PMS) for the sulfamethoxazole (SMX) degradation. The sample characterizations demonstrated the successful preparation of CoOOH@MXene. CoOOH@MXene possessed much higher BET surface area (183.82 m 2 /g) than CoOOH (85.36 m 2 /g) and MXene (6.89 m 2 /g) due to the good dispersibility of CoOOH particles on MXene. Due to its large surface area, 1.3CoOOH@MXene displayed the best catalytic performance for the degradation of SMX. With 0.2 g/L of 1.3CoOOH@MXene and 0.5 mM of PMS, 20 μM of SMX was completely eliminated in 10 min. The degradation followed pseudo-first-order kinetic model well, with rate constants of 0.33 min -1 for 1.3CoOOH@MXene and 0.054 min -1 for CoOOH. Influencing factors of initial pH, catalyst dosage, PMS concentration, SMX concentration, and co-existing anions on SMX degradation were assessed systematically. Recycling tests verified the excellent reusability and stability of the catalyst. Quenching experiments and electron paramagnetic resonance analysis substantiated that 1 O 2 played a leading role. Moreover, the intermediates were identified, and degradation pathways and activation mechanism of CoOOH@MXene for PMS were proposed. This work may highlight the application of MXene with transition metals in PMS activation., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Cupric oxide (CuO) is able to catalyze the reactions among disinfectant, extracellular polymeric substances (EPS) and bromide (Br - ) in copper pipes, which may deteriorate the water quality. This study aimed to investigate the metabonomic and transcriptomic modulations of HepG2 cells caused by the CuO-catalyzed formation of disinfection byproducts (DBPs) from EPS. The presence of CuO favored the substitution reactions of chlorine and bromine with EPS, inducing a higher content of total organic halogen (TOX). In addition, DBPs were shifted from chlorinated species to brominated species. A total of 182 differential metabolites (DMs) and 437 differentially expressed genes (DEGs) were identified, which were jointly involved in 38 KEGG pathways. Topology analysis indicates that glycerophospholipid and purine metabolism were disturbed most obviously. During glycerophospholipid metabolism, the differential expression of genes GPATs, AGPATs, LPINs and DGKs impacted the conversion of glycerol-3-phosphate to 2-diacyl-sn-glycerol, which further affected the conversion among phosphatidylcholine, phosphatidylserine and phosphocholines. During purine metabolism, it was mainly the differential expression of genes POLRs, RPAs, RPBs, RPCs, ENTPDs and CDs that impacted the transformation of RNA into guanine-, xanthosine-, inosine- and adenosine monophosphate, which were further successively transformed into their corresponding nucleosides and purines. The study provides an omics perspective to assess the potential adverse effects of overall DBPs formed in copper pipes on human., (Copyright © 2022. Published by Elsevier Ltd.)

Halonitromethanes (HNMs) is a typical class of nitrogenous disinfection byproducts with high toxicity. The effect of Br - on the formation and transformation of HNMs from dimethylamine (DMA) during the ultraviolet (UV)/chlorine disinfection has been investigated in current study. Results reveal that only chloronitromethane, dichloronitromethane and trichloronitromethane (TCNM) could be found during the UV/chlorine disinfection. Whereas in the presence of Br - , nine species of HNMs could be observed simultaneously. When Br - concentration increased from 0 to 15.0 mg L -1 , the predominant species of HNMs were gradually changed from TCNM to dibromonitromethane and tribromonitromethane, which contributed to 23.37% and 31.07% of total HNMs concentration at 15 mg L -1 Br - , respectively. The presence of Br - not only shifted the chlorinated-HNMs (Cl-HNMs) towards brominated-HNMs (Br-HNMs) but also affected the dominant species and total concentration of HNMs. When Br - concentration was 4.0 mg L -1 , the formation of HNMs decreased with the increase of pH from 6.0 to 8.0 and increased with the increase of free chlorine and DMA. When free chlorine concentration rose from 0.25 to 1.1 mmol L -1 , Br-HNMs were shifted to Br(Cl)-HNMs and then to Cl-HNMs. According to the findings, possible formation and transformation pathways of HNMs from DMA were proposed in the presence of Br - during the UV/chlorine disinfection. Finally, it was proved that the effect of Br - on the trend of HNMs in real water was similar to that in deionized water, but higher HNMs concentrations and delayed peak time were observed in real water. This study can provide the scientific evidence and fundamental data for the applications of UV/chlorine disinfection in the treatment of water containing Br - ., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The synthesis of environmental-friendly metal-free photocatalysts has great significance in photocatalytic technology. In this work, we firstly report the successful synthesis of in situ epitaxial growth of g-C 3 N 4 on carbon dots through a facile thermal polymerization technique. Characterization and density functional theory (DFT) calculations were conducted to clarify the structure engineering and the electronic/chemical properties of the in-plane interconnected carbon dots/g-C 3 N 4 (C-CN) heterostructures. With the optimal carbon dots content, the C-CN exhibited 3.2 times higher degradation rate for sulfadiazine (SDZ) than that of g-C 3 N 4 . Besides, the C-CN heterostructures displayed excellent stability and reusability in five consecutive cycles. The enhanced photocatalytic activity was related to the narrowed band gap and the local electronic density of valance band and conduction band orbitals of the unique plane heterostructures, corroborated by the spectroscopic characterizations and theoretical calculations. Photogenerated holes dominated the degradation of SDZ, while OH showed a negligible contribution. Moreover, DFT calculation succeeded to predict that the atoms with high Fukin index (f 0 ) on SDZ molecule were more vulnerable to radicals attack. SDZ degradation pathway mainly included smiles-type rearrangement, SO 2 extrusion, ring hydroxylation and SN bond cleavage processes. The eco-toxicity assessment revealed the generation of less toxic intermediates after photocatalysis. Our findings not only afford a new technique for constructing g-C 3 N 4 -based in-plane heterostructures with high and stable photocatalytic efficiency, but also highlight the feasible application of metal-free photocatalysts in environmental remediation., (Copyright © 2019 Elsevier Inc. All rights reserved.)

The vacuum ultraviolet (VUV) process, which can directly produce hydroxyl radical from water, is considered to be a promising oxidation process in degrading contaminants of emerging concern, because of no need for extra reagents. In this study, the influencing factors and mechanism for degradation of diethyl phthalate (DEP) by the VUV process were investigated. The effects of irradiation intensity, inorganic anions, natural organic matter (NOM), and H 2 O 2 dosage on the performance of VUV process were evaluated. The results showed that DEP could be more efficiently degraded by the VUV process compared with ultraviolet (UV)-254-nm irradiation. The presence of HCO 3 - , NO 3 - and NOM in the aqueous solutions inhibited the degradation of DEP to a different degree, mainly by competing hydroxyl radicals (HO • ) with DEP. Degradation rate and removal efficiency of DEP by VUV process significantly enhanced with the addition of H 2 O 2 , while excess H 2 O 2 dosage could inhibit the DEP degradation. Moreover, based on the identified seven oxidation byproducts and their time-dependent evolution profiles, a possible pathway for DEP degradation during the VUV process was proposed. Finally, the ecotoxicity of DEP and its oxidation byproducts reduced overall according to the calculated results from Ecological Structure Activity Relationships (ECOSAR) program. The electrical energy per order (EE/O) was also assessed to analysis the energy cost of the DEP degradation in the VUV process. Our work showed the VUV process could be an alternative and environmental friendly technology for removing contaminants in water.

Low-pressure (LP) UV treatment after chlorine disinfection was associated with enhanced formation of trichloronitromethane (TCNM), a halonitromethane disinfection by-product (DBP), due to the chlorination of tryptophan. Evidence was found that the concentration of TCNM from tryptophan increased quickly to the maximum for the first instance. Moreover, the increase of TCNM under UV exceeded 10 times than under dark. Then, it was found to have an obvious decrease in the formation of TCNM, even finally hardly disappear. In order to elucidate reasons for this phenomenon, the effects of light intensity, initial tryptophan concentration, free chlorine concentration, pH, and tert-butanol (TBA) on the formation of TCNM were investigated under UV/chlorine treatment. Finally, the effects of tryptophan on the formation of TCNM and the direct photodegradation of TCNM under LP UV irradiation were studied for analyzing the possible pathways of TCNM formation from amino acid. Since amino acids are very common in water sources, further research into chemical oxidation of these species by LP UV and chlorine is recommended. It can help us to find the precursors of TCNM formation and reduce the risk of TCNM formation for drinking water and wastewater utilities.

Advanced oxidation processes (AOPs) have been widely used for the destruction of organic contaminants in the aqueous phase. In this study, we introduce an AOP on activated peroxymonosulfate (PMS) by using ascorbic acid (H 2 A) to generate sulfate radicals (SO 4 •- ). Sulfate radicals, hydroxyl radicals (HO • ), and ascorbyl radicals (A •- ) were found using electron spin resonance (ESR). But we found A •- is negligible in the degradation of microcystin-LR (MCLR) due to its low reactivity. We developed a first-principles kinetic model to simulate the MCLR degradation and predict the radical concentrations. The MCLR degradation rate decreased with increasing pH. The scavenging effect of natural organic matter (NOM) on SO 4 •- was relatively small compared to that for HO • . Considering both energy consumption and MCLR removal, the optimal H 2 A and PMS doses for H 2 A/PMS process were determined at 1.0 × 10 -6 M and 1.6 × 10 -5 M, respectively. In addition, we determined the toxicity using the protein phosphatase 2A (PP2A) test and the results showed that MCLR was readily detoxified and its oxidation byproducts were not hepatotoxic. Overall, our work provides a new type of AOP and a promising, efficient, and environmental-friendly method for removing microcystins in algae-laden water.

In this study, the degradation of 2-methylisoborneol (2-MIB) and geosmin (GSM) was evaluated by electrochemical oxidation (EO) using boron-doped diamond (BDD) electrode. Both 2-MIB and GSM could be degraded efficiently in sulfate electrolyte compared to inert nitrate or perchlorate electrolytes, implying that in-situ generated persulfate may be responsible for contaminants degradation. The observed linear relationship between 2-MIB (GSM) degradation rates and persulfate generation rates further proved that the in-situ generated persulfate enhanced 2-MIB (GSM) degradation. Moreover, a divided electrolytic cell was employed to investigate the effect of cathodic reactions on contaminants degradation and persulfate generation, and results confirmed that both anodic and cathodic reactions participated in 2-MIB (GSM) degradation. High current density and low solution pH were found to be favorable for 2-MIB and GSM degradation. The degradation intermediates were identified and the possible pathways of 2-MIB and GSM degradation were proposed. This study indicated that the EO process with BDD anode could be considered as a potential alternative for the removal of 2-MIB and GSM., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The degradation kinetics and mechanism of the antiepileptic drug oxcarbazepine (OXC) by UV-activated persulfate oxidation were investigated in this study. Results showed that UV/persulfate (UV/PS) process appeared to be more effective in degrading OXC than UV or PS alone. The OXC degradation exhibited a pseudo-first order kinetics pattern and the degradation rate constants (k obs) were affected by initial OXC concentration, PS dosage, initial pH, and humic acid concentration to different degrees. It was found that low initial OXC concentration, high persulfate dosage, and initial pH enhanced the OXC degradation. Additionally, the presence of humic acid in the solution could greatly inhibit the degradation of OXC. Moreover, hydroxyl radical (OH•) and sulfate radical (SO4 (-)••) were identified to be responsible for OXC degradation and SO4 (-)• made the predominant contribution in this study. Finally, major intermediate products were identified and a preliminary degradation pathway was proposed. Results demonstrated that UV/PS system is a potential technology to control the water pollution caused by emerging contaminants such as OXC.

Eight commonly occurring polybrominated diphenyl ethers (PBDEs), including BDE 28, 47, 99, 100, 153, 154, 183, 207, and 209, were investigated in water samples from seven major inflowing rivers of Lake Chaohu to determine the distribution characteristics, potential sources and inputs to the lake. The sum of 8 BDE congeners (Σ8PBDEs) had a concentration varied from 0.31 to 84 ng L(-1), with those of BDE 209, BDE 47, BDE 99, and BDE 153 being 0.31-83, <0.012-0.36, <0.012-1.3, and <0.012-0.77 ng L(-1), respectively. These levels were in the high range of the global PBDEs concentrations in the water environments. The highest concentrations of Σ8PBDEs were detected in the western rivers, of which the main pollution sources were strongly related to human activities in urban centers, such as automobile-derived wastes. A sewage treatment plant was likely an important source of the lower brominated BDEs input to one western river. The correlation analyses (all p<0.05) between PBDEs and DOC, TN, TP, and EC, suggested that the distributions and sources of PBDEs in rivers might also be related with the soil erosion by heave floods. Σ8PBDEs input to Lake Chaohu from the rivers outlets was estimated at 344 kg yr(-1) during the flood season. BDE 209 was the dominant contributor with an input of 340 kg yr(-1), followed by BDE 99 (1.3 kg yr(-1)), BDE 47 (0.83 kg yr(-1)) and BDE 153 (0.60 kg yr(-1))., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Effects of algae Nitzschia hantzschiana, Fe(III) ions, humic acid, and pH on the photochemical reduction of Hg(II) using the irradiation of metal halide lamps (lambda > or = 365 nm, 250 W) were investigated. The photoreduction rate of Hg(II) was found to increase with increasing concentrations of algae, Fe(III) ions, and humic acid. Alteration of pH value affected the photoreduction of Hg(II) in aqueous solution with or without algae. The photoreduction rate of Hg(II) decreased with increasing initial Hg(II) concentration in aqueous solution in the presence of algae. The photochemical kinetics of initial Hg(II) and algae concentrations on the photoreduction of Hg(II) were studied at pH 7.0. The study on the total Hg mass balance in terms of photochemical process revealed that more than 42% of Hg(II) from the algal suspension was reduced to volatile metallic Hg under the conditions investigated.

Simultaneously photocatalytic reduction of Cr(VI) and oxidation of bisphenol A (BPA) in aqueous solution in the presence of Fe(III)-OH complexes were investigated under a 250 W metal halide lamp (lambda>or=365 nm). Synergy effect of the simultaneous photocatalytic oxidation and reduction of both pollutants was achieved. The effects of initial pH value, initial concentration of BPA, Cr(VI) and Fe(III) were preliminarily investigated. The results showed that both photocatalytic reduction of Cr(VI) and degradation of BPA could occur simultaneously in the Fe(III)/Cr(VI)/BPA ternary system, and the rates of photocatalytic reduction of Cr(VI) and the oxidation of BPA were more rapid at a low pH range of 2.0-3.0. The increase of the initial concentration of Fe(III) was favorable to both photocatalytic reduction of Cr(VI) and oxidation of BPA. The reduction efficiency of Cr(VI) decreased with increasing initial concentrations of Cr(VI) and BPA, but the degradation efficiency of BPA was not changed obviously at different Cr(VI) concentrations.

In this thesis, the photochemical reduction of hexavalent chromium Cr(VI) in the presence of algae, Chlorella vulgaris, was investigated under the irradiation of metal halide lamps (lambda = 365 nm, 250 W). The affecting factors of photochemical reduction were studied in detail, such as exposure time, initial Cr(VI) concentration, initial algae concentration and pH. The rate of Cr(VI) photochemical reduction increased with algae concentration increasing, exposure time increasing, initial Cr(VI) concentration decreasing and the decrease of pH. When pH increased to 6, the rate of Cr(VI) photochemical reduction nearly vanished. When initial Cr(VI) concentration ranged from 0.4 to 1.0 mg L(-1) and initial algae concentration ranged from ABS(algae) (the absorbency of algae) = 0.025 to ABS(algae) = 0.180, According to the results of kinetic analyses, the kinetic equation of Cr(VI) photochemical reduction in aqueous solution with algae under 250 W metal halide lamps was V0 = kC(0)(0.1718)A(algae)(0.5235) (C0 was initial concentration of Cr(VI); A(algae) was initial concentration of algae) under the condition of pH 4.

Ferrate is multi-function agent in water treatment and shows great oxidizing ability and excellent purifying effect. This experiment evaluated the performance of ferrate for arsenic removal. Experimental results show that the best rate of ferrate and arsenic (III) is 15:1, the efficiency of As removal can be achieved 98%, and the residual concentration of As3 + is < 0.05 mg/L. The optimum pH is 5.5 to approximately 7.5. The oxidative and coagulation time is 10 min and 30 min respectively. The salinity and hardness did not interfere with removal arsenic. This method is easy, very effective comparing with ferric method and KMnO4-Ferric method.