Photo-assisted natural chalcopyrite activated peracetic acid for efficient micropollutant degradation.

The effective activation of natural chalcopyrite (CuFeS2) on peracetic acid (PAA) to remove organic micropollutants was studied under visible light irradiation. Results showed than an effective sulfamethoxazole (SMX) degradation (95.0 %) was achieved under visible light irradiation for 30 min at pH 7.0. Quenching experiments, electron spin resonance analysis, and LC/MS spectrum demonstrated that HO• and CH3C(O)OO• were the main reactive species for SMX degradation, accounting for 43.3 % and 56.7 % of the contributions, respectively. Combined with X-ray photoelectron spectroscopy analysis, the photoelectrons generated on CuFeS2 activated by visible light enhanced the Fe3+/Fe2+ and Cu2+/Cu+ cycles on the surface, thereby activating PAA to generate HO•/CH3C(O)OO•. The removal rate of SMX decreased with the increase in wavelengths, due to the formation of low energy photons at longer wavelengths. Besides, the optimal pH for degradation of SMX by CuFeS2/PAA/Vis-LED process was neutral, which was attributed to the increasing easily activated anionic form of PAA during the increase in pH and the depletion of Fe species at alkaline conditions. Cl-, HCO3-, and HA slightly inhibited SMX degradation because of reactive species being quenched and/or shielding effect. Furthermore, the degradation efficiency of different pollutants by CuFeS2/PAA/Vis-LED was also measured, and the removal efficiency was different owing to the selectivity of CH3C(O)OO•. Finally, the process exhibited good applicability in real waters. Overall, this study provides new insight into visible light-catalyzed activation of PAA and suggests on further exploration of the intrinsic activation mechanism of PAA.

Assessment of the UV/Chlorine Process in the Disinfection of Pseudomonas aeruginosa: Efficiency and Mechanism.

UV irradiation and chlorination have been widely used for water disinfection. However, there are some limitations, such as the risk of generating viable but nonculturable bacteria and bacteria reactivation when using UV irradiation or chlorination alone. This study comprehensively evaluated the feasibility of the UV/chlorine process in drinking water disinfection, and Pseudomonas aeruginosa was selected as the target microorganism. The number of culturable cells was effectively reduced by more than 5 orders of magnitude (5-log10) after UV, chlorine, and UV/chlorine treatments. However, intact and VBNC cells were detected at 103 to 104 cells/mL after UV and chlorine treatments, whereas they were undetectable after UV/chlorine treatment due to the primary contribution of reactive chlorine species (Cl•, Cl2•-, and ClO•). After UV/chlorine treatment, the metabolic activity determined using single cell Raman spectroscopy was much lower than that after UV. The level of toxic opr gene in P. aeruginosa decreased by more than 99% after UV/chlorine treatment. Importantly, bacterial dark reactivation was completely suppressed by UV/chlorine treatment but not UV or chlorination. This study suggests that the UV/chlorine treatment can completely damage bacteria and is promising for pathogen inactivation to overcome the limitations of UV and chlorine treatments alone.

Solar irradiation combined with chlorine can detoxify herbicides.

The solar/chlorine process is an energy-efficient advanced oxidation process that can produce reactive species such as hydroxyl radical, reactive chlorine species and ozone. This study investigated the process' ability to detoxify the typical herbicides atrazine and mecoprop (methylchlorophenoxypropionic acid). Both herbicides are resistant to direct solar photolysis or chlorination alone, but they can be degraded by the solar/chlorine process effectively. Atrazine inhibited the development of Arabidopsis thaliana, but such inhibition was negligible after solar/chlorine treatment of an atrazine solution. The transformation of atrazine in the process was shown to be through hydroxylation, hydrogen abstraction and dechlorination but did not involve chlorine substitution or addition. Cl• reacts with atrazine and mecoprop with rate constants of 6.87 × 109 M-1s-1 and 1.08 × 1010 M-1s-1, respectively, while ClO• reacts with mecoprop with a rate constant of 1.11 × 108 M-1s-1. The degradation kinetics of atrazine and mecoprop by solar/chlorine was simulated by modeling, which fitted the experimental results well. Hydroxyl radicals (HO•) mainly contributed to the degradation of atrazine by solar/chlorine at pH 7 with the contribution of 65%, whereas ClO• and O3 were main species responsible for the degradation of mecoprop with the contribution of 72% and 17%, respectively. The pseudo-first-order rate constants (k's) of the two degradations increased substantially (by 28.8% for atrazine and by 198% for mecoprop) when the chlorine dosage was increased from 50 µM to 200 µM. The k's decreased with increasing pH. The presence of natural organic matter inhibited the degradation of both herbicides, while the presence of bromide enhanced their degradation. This work reveals a feasible method for the detoxifying herbicides by combining chlorine with solar radiation.

DBP alteration from NOM and model compounds after UV/persulfate treatment with post chlorination.

The UV/persulfate process is an effective advanced oxidation process (AOP) for the abatement of a variety of micropollutants via producing sulfate radicals (SO4•-). However, when this technology is used to reduce target pollutants, the precursors of disinfection byproducts (DBPs), such as natural organic matter (NOM) and organic nitrogen compounds, can be altered. This study systematically investigated the DBP formation from NOM and five model compounds after UV/H2O2 and UV/persulfate treatments followed with 24 h chlorination. Compared to chlorination alone, the yields of trichloromethane (TCM) and dichloroacetonitrile (DCAN) from NOM decreased by 50% and 54%, respectively, after UV/persulfate treatment followed with chlorination, whereas those of chloral hydrate (CH), 1,1,1-trichloropropanone (1,1,1-TCP) and trichloronitromethane (TCNM) increased by 217%, 136%, and 153%, respectively. The effect of UV/H2O2 treatment on DBP formation shared a similar trend to that of UV/persulfate treatment, but the DBP formation was higher from the former. As the UV/persulfate treatment time prolonged or the persulfate dosage increased, the formation of TCM and DCAN continuously decreased, while that of CH, 1,1,1-TCP and TCNM presented an increasing and then decreasing pattern. SO4•- activated benzoic acid (BA) to form phenolic compounds that enhanced the formation of TCM and CH, while it deactivated resorcinol to decrease the formation of TCM. SO4•- reacted with aliphatic amines such as methylamine (MA) and dimethylamine (DMA) to form nitro groups, which significantly increased the formation of TCNM in post chlorination, and the rate was determined to be higher than that of HO•. This study illuminated the diverse impacts of the structures of the precursors on DBP formation after UV/persulfate treatment, and DBP alteration depended on the reactivity between SO4•- and specific precursor.

Feasibility of the solar/chlorine treatment for lipid regulator degradation in simulated and real waters: The oxidation chemistry and affecting factors.

This work investigated the feasibility and mechanisms of solar/chlorine process in the removal of a kind of emerging contaminants, lipid regulators (gemfibrozil (GFRZ), benzafibrate (BZF), and clofibric acid (CA)), in simulated and real waters. These lipid regulators could be effectively removed by solar/chlorine treatment, and their corresponding pseudo-first-order rate constants (k') increased with increasing chlorine dosage. The degradation of GFRZ and BZF was primarily ascribed to reactive chlorine species (RCS) and ozone, while that of CA was mainly attributable to hydroxyl radical (HO) and ozone. As pH rose from 5.0 to 8.4, kozone' of GFRZ and BZF increased, while kHO' decreased. However, kRCS' of GFRZ increased by 130%, while that of BZF decreased by 43.3%. These changes resulted in slight changes in the overall k's with increasing pH. k's of GFRZ, BZF, and CA by solar/chorine treatment were inhibited by natural organic matter (NOM) while the presence of bromide enhanced the degradation of GFRZ by solar/chlorine process. The degradation of lipid regulators was still effective in a secondary wastewater effluent sample and a sand-filtered water sample, although that was inhibited due to the dissolve organic matter (DOM) contained in real waters. The acute toxicity during the degradation of GFRZ by solar/chlorine treatment was comparable to that by treatment with chlorine alone. This study demonstrated that RCS played an important role in the degradation of micropollutants by the solar/chlorine treatment and the feasibility of solar/chlorine process in the application for the degradation of organic compounds in real waters.

PPCP degradation and DBP formation in the solar/free chlorine system: Effects of pH and dissolved oxygen.

The solar/chlorine process produces multiple reactive species by solar photolysis of chlorine, which can be used as an energy-efficient technology for water treatment. This study investigated the effects of pH and dissolved oxygen (DO) on the degradation of pharmaceuticals and personal care products (PPCPs) and on the formation of disinfection byproducts (DBPs) in the solar/chlorine system. The degradation of 24 structurally diverse PPCPs was enhanced appreciably in the solar/chlorine system compared to solar irradiation and dark chlorination. The reactive species in the solar/chlorine system were identified to be hydroxyl radicals (HO), reactive chlorine species (RCS, i.e., Cl and ClO) and ozone. With increasing pH from 6 to 8, the steady-state concentrations of HO and Cl decreased from 1.23 × 10-14 M to 4.79 × 10-15 M and from 9.80 × 10-16 M to 4.31 × 10-16 M, respectively, whereas that of ClO increased from 5.30 × 10-14 M to 2.68 × 10-13 M and the exposure of ozone increased from 0.44 µM min to 1.01 µM min in 90 min. Accordingly, the removal efficiencies of 6 PPCPs decreased and 11 PPCPs increased. The decreased removal of PPCPs with increasing pH was due to the decrease in HO and Cl, while the increased removal was attributed to the increased ClO and ozone. The presence of DO enhanced the degradation of most PPCPs, indicating the role of ozone on the degradation. The formation of total organic chlorine (TOCl) and known DBPs was enhanced by 60.7% and 159.4%, respectively, in the solar/chlorine system compared to chlorination in a simulated drinking water containing 2.5 mg L-1 natural organic matter (NOM). As the pH rose from 6 to 8, TOCl formation decreased by 16.2%, while that of known DBPs increased by 58.6% in solar/chlorine. The absence of DO slightly suppressed the formation of TOCl and known DBPs. This study illustrated the significant role of RCS in the solar/chlorine system, which enhanced the degradation of micropollutants but increased the formation of chlorinated DBPs.

Comparison of the UV/chlorine and UV/H2O2 processes in the degradation of PPCPs in simulated drinking water and wastewater: Kinetics, radical mechanism and energy requirements.

The degradation of pharmaceuticals and personal care products (PPCPs) by the UV/H2O2 and UV/chlorine processes was compared at practical concentrations in simulated drinking water and wastewater. In pure water, the UV/chlorine process performed better than the UV/H2O2 process for the degradation of 16 PPCPs among the investigated 28 PPCPs under neutral conditions. Interestingly, the UV/chlorine approach was superior to the UV/H2O2 approach for the removal of all PPCPs in simulated drinking water and wastewater at the same molar oxidant dosage. The radical sink by oxidants and/or H2O was 2-3 orders of magnitude higher in UV/chlorine than UV/H2O2 in pure water. Thus, the UV/chlorine process was less affected by the water and wastewater matrices than UV/H2O2. In UV/chlorine, the concentration of ClO• was calculated to be ∼3 orders of magnitude greater than that of HO• in pure water, and the reactivities of ClO• with some PPCPs were as high as > 108 M-1 s-1. ClO• was mainly scavenged by the effluent organic matter (EfOM) with a rate constant of 1.8 × 104 (mg L-1)-1 s-1 in wastewater. Meanwhile, secondary radicals such as Br•, Br2•-, ClBr•- and CO3•- further contributed to PPCP degradation by the UV/chlorine process in wastewater, whose concentrations were at least 2 orders of magnitude higher than that in UV/H2O2. Compared with the UV/H2O2 process, the UV/chlorine process saved 3.5-93.5% and 19.1%-98.1% electrical energy per order (EE/O) for PPCP degradation in simulated drinking water and wastewater, respectively.

Kinetics and mechanisms of the degradation of PPCPs by zero-valent iron (Fe°) activated peroxydisulfate (PDS) system in groundwater.

The abatement of pharmaceuticals and personal care products (PPCPs), including carbamazepine (CBZ), acetaminophen (ACP) and sulfamethoxazole (SMX), by zero-valent iron (Fe°) activated peroxydisulfate (PDS) system (Fe°/PDS) in pure water and groundwater was investigated. The removal rates of CBZ, ACP and SMX were 85.4%, 100% and 73.1%, respectively, within 10 min by Fe°/PDS in pure water. SO4•-, •OH and O2•- were identified in the Fe°/PDS system, and O2•- was indicated to play an important role in the ACP degradation. The degradation of PPCPs increased with increasing dosages of Fe° and PDS or with decreasing pH and initial PPCP concentrations. Interestingly, the degradation of PPCPs by Fe°/PDS was significantly enhanced in groundwater compared with that in pure water, which was partially attributed to SO42- and Cl-. The first-order constants of CBZ, ACP and SMX increased from 0.021, 0.242 and 0.013 min-1 to 0.239, 2.536 and 0.259 min-1, and to 0.172, 1.516 and 0.197 min-1, respectively, with increasing the concentrations of SO42- and Cl- to 100 mg/L and 10 mg/L, respectively. This study firstly reports the unexpected enhancement of groundwater matrix on the degradation of micropollutants by Fe°/PDS, demonstrating that Fe°/PDS can be an efficient technology for groundwater remediation.

Degradation of lipid regulators by the UV/chlorine process: Radical mechanisms, chlorine oxide radical (ClO•)-mediated transformation pathways and toxicity changes.

Degradation of three lipid regulators, i.e., gemfibrozil, bezafibrate and clofibric acid, by a UV/chlorine treatment was systematically investigated. The chlorine oxide radical (ClO•) played an important role in the degradation of gemfibrozil and bezafibrate with second-order rate constants of 4.2 (±0.3) × 108 M-1 s-1 and 3.6 (±0.1) × 107 M-1 s-1, respectively, whereas UV photolysis and the hydroxyl radical (HO•) mainly contributed to the degradation of clofibric acid. The first-order rate constants (k') for the degradation of gemfibrozil and bezafibrate increased linearly with increasing chlorine dosage, primarily due to the linear increase in the ClO• concentration. The k' values for gemfibrozil, bezafibrate, and clofibric acid degradation decreased with increasing pH from 5.0 to 8.4; however, the contribution of the reactive chlorine species (RCS) increased. Degradation of gemfibrozil and bezafibrate was enhanced in the presence of Br-, whereas it was inhibited in the presence of natural organic matter (NOM). The presence of ammonia at a chlorine: ammonia molar ratio of 1:1 resulted in decreases in the k' values for gemfibrozil and bezafibrate of 69.7% and 7%, respectively, but led to an increase in that for clofibric acid of 61.8%. Degradation of gemfibrozil by ClO• was initiated by hydroxylation and chlorine substitution on the benzene ring. Then, subsequent hydroxylation, bond cleavage and chlorination reactions led to the formation of more stable products. Three chlorinated intermediates were identified during ClO• oxidation process. Formation of the chlorinated disinfection by-products chloral hydrate and 1,1,1-trichloropropanone was enhanced relative to that of other by-products. The acute toxicity of gemfibrozil to Vibrio fischeri increased significantly when subjected to direct UV photolysis, whereas it decreased when oxidized by ClO•. This study is the first to report the transformation pathway of a micropollutant by ClO•.

Comparative investigation of X-ray contrast medium degradation by UV/chlorine and UV/H2O2.

The degradation of iopamidol and diatrizoate sodium (DTZ) by UV/chlorine was carried out according to efficiency, mechanism, and oxidation products, and compared to that by UV/H2O2. The pseudo-first order rate (k') of iopamidol and DTZ was accelerated by UV/chlorine compared to that by UV and chlorine alone. k' of iopamidol and DTZ by UV/chlorine increased with increasing chlorine dosage. Both of iopamidol and DTZ could not be effectively removed by UV/H2O2 compared to that by UV/chlorine. Secondary radicals (Cl2- and ClO) rather than primary radicals (HO and Cl) were demonstrated to be mainly responsible for the enhanced removal of iopamidol and DTZ by UV/chlorine. The oxidation products of iopamidol and DTZ resulting from UV/chlorine and UV/H2O2 process were identified, and differences existed in the two systems. IO3- (the desired sink of I-) was the major inorganic product in the UV/chlorine process whereas I- was the predominant inorganic product in the UV/H2O2 process. The formation of chlorine-containing products during the degradation of iopamidol and DTZ by UV/chlorine was also observed. H-abstraction, additions, de-iodination were shared during the degradation of iopamidol by UV/chlorine and UV/H2O2. Neutral pH condition was preferred for the removal of iopamidol and DTZ by UV/chlorine. UV/chlorine could also be applied in real waters for the removal of iopamidol and DTZ.

Factors affecting the roles of reactive species in the degradation of micropollutants by the UV/chlorine process.

The UV/chlorine process is an emerging advanced oxidation process (AOP) that produces various reactive species, such as hydroxyl radicals (HO) and reactive chlorine species (RCS). The effects of the treatment conditions, such as chlorine dosage and pH, and the water matrix components of natural organic matter (NOM), alkalinity, ammonia and halides, on the kinetics and reactive species in the degradation of four micropollutants, metronidazole (MDZ), nalidixic acid (NDA), diethyltoluamide (DEET) and caffeine (CAF), by the UV/chlorine process were investigated. The degradation of MDZ and CAF was primarily attributable to HO and ClO, respectively, while that of NDA was primarily attributable to both ClO and CO3-. HO, Cl and CO3- are important for the degradation of DEET. The second-order rate constants for ClO with CAF and CO3- with NDA were determined to be 5.1 (±0.2) × 107 M-1s-1 and 1.4 (±0.1) × 107 M-1s-1, respectively. Increasing chlorine dosage slightly changed the contribution of HO but linearly increased that of ClO to micropollutant degradation. Increasing pH decreased the contribution of either HO or Cl but not that of ClO. Both NOM and bicarbonate decreased the contributions of HO and Cl, whereas NOM but not bicarbonate significantly decreased that of ClO. The contribution of either HO or Cl first rose and then fell as the molar ratio of ammonia to chlorine increased from 0 to 1:1, while that of ClO decreased. The co-presence of high concentrations of Cl- and Br- enhanced the contribution of ClBr- and BrCl.

Degradation of sulfamethoxazole by UV, UV/H2O2 and UV/persulfate (PDS): Formation of oxidation products and effect of bicarbonate.

The frequent detection of sulfamethoxazole (SMX) in wastewater and surface waters gives rise of concerns about their ecotoxicological effects and potential risks to induce antibacterial resistant genes. UV/hydrogen peroxide (UV/H2O2) and UV/persulfate (UV/PDS) advanced oxidation processes have been demonstrated to be effective for the elimination of SMX, but there is still a need for a deeper understanding of product formations. In this study, we identified and compared the transformation products of SMX in UV, UV/H2O2 and UV/PDS processes. Because of the electrophilic nature of SO4-, the second-order rate constant for the reaction of sulfate radical (SO4-) with the anionic form of SMX was higher than that with the neutral form, while hydroxyl radical (OH) exhibited comparable reactivity to both forms. The direct photolysis of SMX predominately occurred through cleavage of the NS bond, rearrangement of the isoxazole ring, and hydroxylation mechanisms. Hydroxylation was the dominant pathway for the reaction of OH with SMX. SO4- favored attack on NH2 group of SMX to generate a nitro derivative and dimeric products. The presence of bicarbonate in UV/H2O2 inhibited the formation of hydroxylated products, but promoted the formation of the nitro derivative and the dimeric products. In UV/PDS, bicarbonate increased the formation of the nitro derivative and the dimeric products, but decreased the formation of the hydroxylated dimeric products. The different effect of bicarbonate on transformation products in UV/H2O2 vs. UV/PDS suggested that carbonate radical (CO3-) oxidized SMX through the electron transfer mechanism similar to SO4- but with less oxidation capacity. Additionally, SO4- and CO3- exhibited higher reactivity to the oxazole ring than the isoxazole ring of SMX. Ecotoxicity of transformation products was estimated by ECOSAR program based on the quantitative structure-activity relationship analysis as well as by experiments using Vibrio fischeri, and these results indicated that the oxidation of SO4- or CO3- with SMX generated more toxic products than those of OH.

Molecular epidemiology demonstrates that imported and local strains circulated during the 2014 dengue outbreak in Guangzhou, China.

The dengue virus (DENV) is a vital global public health issue. The 2014 dengue epidemic in Guangzhou, China, caused approximately 40,000 cases of infection and five deaths. We carried out a comprehensive investigation aimed at identifying the transmission sources in this dengue epidemic. To analyze the phylogenetics of the 2014 dengue strains, the envelope (E) gene sequences from 17 viral strains isolated from 168 dengue patient serum samples were sequenced and a phylogenetic tree was reconstructed. All 17 strains were serotype I strains, including 8 genotype I and 9 genotype V strains. Additionally, 6 genotype I strains that were probably introduced to China from Thailand before 2009 were widely transmitted in the 2013 and 2014 epidemics, and they continued to circulate until 2015, with one affinis strain being found in Singapore. The other 2 genotype I strains were introduced from the Malaya Peninsula in 2014. The transmission source of the 9 genotype V strains was from Malaysia in 2014. DENVs of different serotypes and genotypes co-circulated in the 2014 dengue outbreak in Guangzhou. Moreover, not only had DENV been imported to Guangzhou, but it had also been gradually exported, as the viruses exhibited an enzootic transmission cycle in Guangzhou.

The improvement effects of edible bird's nest on proliferation and activation of B lymphocyte and its antagonistic effects on immunosuppression induced by cyclophosphamide.

Edible bird's nest (EBN) is regarded as an immune-enhancing food in the People's Republic of China. The aim of this study is to demonstrate the efficiency of EBN in improving the immunity of mouse both in vivo and in vitro. We observed the effects of EBN on spleen lymphocytes proliferation and activation, as well as immunoglobulin isotypes as indicators. In addition, we evaluated the content of total sIgA in the intestinal juice to assess mucosal immunity. The results showed that EBN could promote the proliferation and activation of B-cells and increase IgE, IgA, IgM, and IgG3 levels. We also found that EBN extract can promote the secretion of sIgA in the small intestine. Using cyclophosphamide (CY), we established an immunosuppressed mouse model in which we identified a reversal influence on the ratio of CD3(+)/CD19(+) cells, which indicates that EBN also protects B-cells from the damage induced by CY. We also applied polymyxin B to exclude the interference of lipopolysaccharide throughout the experiment. In conclusion, we found that EBN can reduce the intestinal immune injury induced by CY by accelerating the proliferation and activation of B-cells and enhancing antibody secretion of B-cells.

Degradation of atrazine by UV/chlorine: Efficiency, influencing factors, and products.

In this work, the degradation of atrazine by the combination of UV and chlorine (UV/chlorine) due to the formation of radicals during chlorine photolysis was systematically investigated in terms of efficiency, factors that influence the degradation kinetics, as well as oxidation products. It was found that the degradation efficiency of atrazine was enhanced by UV/chlorine compared to UV or chlorine alone. The degradation efficiency of atrazine was favorable at a lower pH, but was inhibited in the presence of natural organic matters. Meanwhile, the initial chlorine dosage, alkalinity, and chloride barely influenced the degradation efficiency under neutral pH conditions. The degradation of atrazine by UV/chlorine was inhibited in real waters (i.e., surface water and ground water) compared to in deionized water but was still more effective than UV alone. The oxidation products of atrazine resulting from de-alkylation, dechlorination-hydroxylation, alkylic-hydroxylation, alkylic-oxidation, alkylic-hydroxylation-dehydration, deamination-hydroxylation, and dechlorination-hydrogenation in UV/chlorine process were detected, which were slightly different from those formed in UV/H2O2 (commonly used UV-based advanced oxidation process). Particularly, the yields of three primary transformation products (desethyl-atrazine (DEA), desisopropyl-atrazine (DIA), and desethyl-desisopropyl-atrazine (DEIA)) were comparatively quantified in these two processes. The different trend of them formed in UV/chlorine system (DEA:DIA≈4) compared to that formed in UV/H2O2 system (DEA:DIA≈1) could be ascribed to the different reaction reactivities and mechanisms between HO• and Cl• with atrazine.