Study On Degradation Effect And Mechanism Of Chlortetracycline

BackgroundAs a broad-spectrum antibiotic,Chlortetracycline(CTC)can exist in the environment for a long time due to continuous emission and cause potential threat to the ecological environment and human health.The high concentration of CTC wastewater discharged from pharmaceutical and livestock plants is the main source.Traditional treatment cannot degrade CTC effectively,resulting in the generation and spread of drug resistance and posing great challenges to public health.Thus,developing technology high concentration wastewater of CTC is a practical problem to be solved urgently.Hydrodynamic cavitation(HC)is a new technology,which has many advantages,such as low cost,high efficiency,simple operation and no secondary pollution,and has been applied in organic sewage sludge degradation,water disinfection,material grinding and other fields.The feasibility of application of HC in the treatment of high concentration wastewater of CTC,and the degradation effect and mechanism of treatments are the focus of this paper.ObjectivesThe extend of degradation,cavitation effect and degradation products of high concentration wastewater of CTC were investigated by using HC combined with H2O2 and Fenton oxidation technology,aiming to explore a rapid and efficient technology for high concentration CTC wastewater.This study evaluated ecological risk of CTC in water samples and cost of different treatments,providing reference for the practical application of the screening technology.MethodsBased on HPLC and UHPLC-MS,the effects of HC instrument parameters,cavitation time and the extend of degradation of CTC by HC and HC combination with H2O2,Fenton were studied,and the degradation pathways as well as intermediates of different degradation methods of CTC were speculated.In addition,ecological risks of water samples of CTC by different treatment methods based on chronic toxicity data of organic pollutant of ECOSAR were used to evaluate the above methods.The efficiency and cost of the treatment method were estimated by calculation of cavitation yield.Results1.In terms of degradation rate,the extend of degradation was best at inlet pressure of 2.0 bar by using HC alone.Under this inlet pressure,the effect of cavitation time on CTC was limited,and the degradation rates of CTC at 5 min and 30 min were 51.02%and 59.58%,respectively.Under the combined of HC and concentration of 4.0 mM H2O2,the degradation rates at 5 min and 30 min were 89.70%and 93.81%,respectively.The degradation rate of CTC in 30 min was 88.89%by HC combined with Fenton oxidation.3.The degradation of CTC by using HC alone occurred ring-opening,C-N bond breaking,demethylation,dehydroxylation and desaturation,and six degradation products were generated.The degradation of CTC by using HC combined with H2O2 occurred glycine binding and C-C double bond cleavage,and 13 degradation products were produced.4.Ecological risk of water samples of CTC in 30min by HC had high risk to green algae,daphnia and fish.Ecological risk of water samples of CTC had a high risk to green algae and daphnia,and a middle risk to fish by using HC combined with H2O2.Put degradation rate and energy consumption into consideration,the cost of HC combined H2O2 treatment of CTC is the lowest.Conclusions1.Considering the degradation rate and energy consumption,HC combined with H2O2 is the best method to treat CTC.The degradation rate of CTC was 93.81%at 30min,and cost was 0.165 CNY/L.2.HC combined with H2O2 is a rapid and effective pretreatment technique of high concentration CTC,and can be used for primary treatment in pharmaceutical factories.