Simultaneous Degradation, Dehalogenation, and Detoxification of Halogenated Antibiotics by Carbon Dioxide Radical Anions

Despite the extensive application of advanced oxidation processes(AOPs)in water treatment,the efficiency of AOPs in eliminating various emerging contaminants such as halogenated antibiotics is constrained by a number of factors.Halogen moieties exhibit strong resistance to oxidative radicals,affecting the dehalogenation and detoxification efficiencies.To address these limitations of AOPs,advanced reduction processes(ARPs)have been proposed.Herein,a novel nucleophilic reductant—namely,the carbon dioxide radical anion(CO_(2)^(·-))—is introduced for the simultaneous degradation,dehalogenation,and detoxification of florfenicol(FF),a typical halogenated antibiotic.The results demonstrate that FF is completely eliminated by CO_(2)^(·-),with approximately 100%of Cland 46%of Freleased after 120 min of treatment.Simultaneous detoxification is observed,which exhibits a linear response to the release of free inorganic halogen ions(R^(2)=0.97,p<0.01).The formation of halogen-free products is the primary reason for the superior detoxification performance of this method,in comparison with conventional hydroxyl-radical-based AOPs.Products identification and density functional theory(DFT)calculations reveal the underlying dehalogenation mechanism,in which the chlorine moiety of FF is more susceptible than other moieties to nucleophilic attack by CO_(2)^(·-).Moreover,CO_(2)^(·-)-based ARPs exhibit superior dehalogenation efficiencies(>75%)in degrading a series of halogenated antibiotics,including chloramphenicol(CAP),thiamphenicol(THA),diclofenac(DLF),triclosan(TCS),and ciprofloxacin(CIP).The system shows high tolerance to the pH of the solution and the presence of natural water constituents,and demonstrates an excellent degradation performance in actual groundwater,indicating the strong application potential of CO_(2)^(·-)-based ARPs in real life.Overall,this study elucidates the feasibility of CO_(2)^(·-)for the simultaneous degradation,dehalogenation,and detoxification of halogenated antibiotics and provides a promising method for their regulation during water or wastewater treatment.

Screening of indicator pharmaceuticals and personal care products in landfill leachates: a case study in Shanghai, China

Identifying potential sources of pharmaceuticals and personal care products(PPCPs)in the environment is critical for the effective control of PPCP contamination.Landfill leachate is an important source of PPCPs in water;however,it has barely been involved in source apportionment due to the lack of indicator-PPCPs(i-PPCPs)in landfill leachates.This study provides the first systematic framework for identifying i-PPCPs for landfill leachates based on the wide-scope target monitoring of PPCPs.The number of target PPCPs increased from<20 in previous studies to 68 in the present study.Fifty-nine PPCPs were detected,with median concentrations in leachate samples ranging from below the method quantification limit(MQL)to 41μg/L,and 19 of them were rarely reported previously.A total of 29 target compounds were determined to be PPCPs of high concern by principal component analysis according to multiple criteria,including occurrence,exposure potential,and ecological effect.Coupled with source-specificity and representativeness analysis,erythromycin,gemfibrozil,and albendazole showed a significant difference in their occurrence in leachate compared to other potential sources(untreated and treated municipal wastewater and livestock wastewater)and correlated with total PPCP concentrations;these were recommended as i-PPCPs for leachates.Indicator screening procedure can be used to develop a sophisticated source apportionment method to identify sources of PPCPs from adjacent landfills.

Enhanced carbon tetrachloride degradation by hydroxylamine in ferrous ion activated calcium peroxide in the presence of formic acid

Hydroxyl radicals(HO*)show low reactivity with perchlorinated hydrocarbons,such as carbon tetrachloride(CT),in conventional Fenton reactions,therefore,the generation of reductive radicals has attracted increasing attention.This study investigated the enhancement of CT degradation by the synergistic effects of hydroxylamine(HA)and formic acid(FA)(initial[CT]=0.13 mmol/L)in a Fe(il)activated calcium peroxide(CP)fenton process.CT degradation increased from 56.6%to 99.9%with the addition of 0.78 mmol/L HA to the CP/Fe(II)/FA/CT process in a molar ratio o f 12/6/12/1.The results also showed that the presence of HA enhanced the regeneration of Fe(II)from Fe(III),and the production of HO*increased one-fold when employing benzoic acid as the HO*probe.Additionally,FA slightly improves the production of HO*.A study of the mechanism confirmed that the carbon dioxide radical(C02·),a strong reductant generated by the reaction between FA and HO*,was the dominant radical responsible for CT degradation.Almost complete CT dechlorination was achieved in the process.The presence of humic acid and chloride ion slightly decreased CT removal,while high doses of bicarbonate and high pH inhibited CT degradation.This study helps us to better understand the synergistic roles of FA and HA for HO·and C02·^-generation and the removal of perchlorinated hydrocarbons in modified Fenton systems.