Degradation Mechanism Of Sulfamethoxazole In Livestock And Poultry Wastewater By Copper-based Fenton

With the development of large-scale and intensive breeding mode,livestock and poultry breeding wastewater has become the main source of pollution for the input of antibiotics into the environment.If the antibiotics in wastewater are directly discharged into the environment without treatment,the original ecological environment will be changed and the corresponding resistance genes will be screened out.Finally,it harms human health through the enrichment of the food chain.The existing water treatment technology in livestock and poultry breeding plants can’t degrade antibiotics well.At the same time,the existence of antibiotics will reduce the degradation efficiency of conventional pollutants in the traditional process,and even lead to the collapse of the biological treatment unit.Therefore,in order to make up for the low degradation efficiency of antibiotics in livestock and poultry breeding wastewater by traditional process,it is urgent to study new technology to degrade antibiotics in livestock wastewater from the source.This paper is based on the degradation of sulfamethoxazole（SMZ）by copper Fenton（Cu-H₂O₂）.The mechanism of Cu-H₂O₂ degradation of SMZ was mainly studied.To investigate the effect of Ca SO₃ on Cu-H₂O₂ system degradation of SMZ at low copper concentration.The effect of coexisting ions in wastewater on SMZ degradation efficiency of Cu-H₂O₂ system was investigated.Research shows,the optimal reaction conditions for the degradation of SMZ in Cu-H₂O₂ system are pH=7,Cu²⁺:H₂O₂=1:125,SMZ=1 mg/L,reaction temperature T=25℃,stirring intensity r=350 r/min,and the removal rate of SMZ reaches95.2%after 180 min of reaction.In addition,the reaction system has a certain degradation efficiency for different kinds of antibiotics.The oxidation efficiency of Cu-H₂O₂ system has a strong correlation with the reaction p H.The degradation efficiency of SMZ in the reaction system under neutral and weak alkaline conditions is significantly higher than that under acidic conditions.Based on the above studies,chemical probes,alcohol inhibitors and UV full spectrum analysis showed that the active species of Cu-H₂O₂ system were·OH and Cu（Ⅲ）,in which Cu（Ⅲ）was the main active species.The p H value of the reaction system has a significant effect on the amount of·OH and Cu（Ⅲ）,and the amount of·OH generated by the Cu-H₂O₂ system under acidic conditions is much greater than that generated by the reaction system under alkaline conditions.The quenching experiment of 2,9-dimethyl-1,10-phenanthroline（NCP）proved that Cu（Ⅰ）is the key to produce active species.Visual Minteq 3.0 software simulation further proved that the main catalytic action in Cu-H₂O₂ system is not Cu²⁺but some new ecological copper ion complexes.The analysis of the products from the degradation of SMZ by the Cu-H₂O₂ system shows that the degradation of SMZ by the Cu-H₂O₂ system is not a complete mineralization reaction,but through a series of oxidation,demethylation and ring-opening reaction processes to degrade SMZ into relative Intermediate product with smaller molecular weight and simpler structure.In order to study the effect of sulfite enhanced degradation of SMZ by copper based Fenton like system at low copper concentration,the degradation efficiency under different conditions was analyzed,result representation:when Cu²⁺=0.02 mmol/L,the oxidation capacity of Cu-H₂O₂ system with low concentration of copper ions is limited,and the degradation efficiency is only 50.9%after 180 min reaction.When the molar ratio of Cu²⁺:H₂O₂:Ca SO₃ was 1:125:10,the degradation efficiency of SMZ reached 35.2%after 15 min.Free radical inhibitor experiments and UV full spectrum analysis showed that the addition of Ca SO₃ did not change the composition of active species in the reaction system,but it could accelerate the rate of Cu（Ⅲ）generation in the same time.The coexistence of Zn²⁺in the livestock and poultry breeding wastewater has a certain strengthening effect on the Cu-H₂O₂ system degradation reaction process of SMZ.This may be due to the certain catalytic effect of Zn²⁺complex on hydrogen peroxide.When the concentration of Cl^-is less than 5 m M,the degradation efficiency of SMZ in Cu-H₂O₂ system can be improved.This is because the addition of Cl^-can form Cu（Ⅲ）-Cl_n with Cu（Ⅲ）and reduce the activation energy required by the reaction system.However,the presence of HCO₃^-significantly inhibits the degradation efficiency of Cu-H₂O₂ system for SMZ due to the strong complexation ability of HCO₃^-and Cu²⁺occupying the catalytic site.