Research On Degradation Of Sulfamethoxazole By Activating Persulfate With Supported Perovskite Catalyst

In recent years,trace amounts of antibiotics have been detected where there are water sources in the environment,even in drinking water.Therefore,it is urgent to adopt efficient and stable removal technology to control the antibiotic pollution in the environment.The advanced oxidation technology based on sulfate radicals has great potential in the removal of antibiotics due to its unique properties.In this study,sulfamethoxazole(SMX)was used as the target pollutant,and the B-site Ni-doped perovskite catalyst LaCo1-xNixO3(x=0,0.2,0.4,0.6,0.8,1)based on LaCoO3 was prepared by the sol-gel method.to activate PMS to catalyze the degradation of SMX.Based on the problems exposed by the optimal perovskite catalyst in this system,a series of optimized materials were still prepared by the sol-gel method in this paper.The main conclusions are as follows:(1)In the study of perovskite catalyst LaCo1-xNixO3(x=0,0.2,0.4,0.6,0.8,1)activated PMS to degrade SMX,the doping of B as Ni significantly improved the degradation performance of SMX,among which LaCo0.8Ni0.2O3(LCN82)had the best catalytic performance.The SMX degradation efficiency of 99.21%could be reached in 18 min of reaction.In the LCN82/PMS system,the degradation efficiency of SMX could reach more than 97%when the pH was between 3.02 and 10.02,indicating that it had a wide pH range.In addition,the anions(HCO3-,HPO42-,SO42-)and NOM(HA)in natural water bodies both inhibited the degradation of SMX,however,Cl-showed a slight promotion effect.Free radical quenching experiments showed that SO4·-,·OH and 1O2 co-degraded SMX in the LCN82/PMS system,and 1O2 played a major role.LCN82 could still maintain high degradation performance after being recycled for three times.However,the leaching of Co ions could reach 4.09 mg/L.The leached Co ions had a higher catalytic degradation of SMX.However,the kinetic constant of the LCN82/PMS system was 3.49 times that of the Co2+/PMS system.This also showed that the heterogeneous phase in the system was also involved.Therefore,it is very important to improve the leaching of metal ions from the catalyst in the reaction system.(2)In the study of optimizing the stability of the LCN82 perovskite catalyst,the doping of Sr at the B site has achieved the performance of high-efficiency degradation of SMX,and the SMX degradation efficiency of 99.02%could be reached after 6 min of reaction.However,the inhibitory effect of metal leaching was not obvious.Therefore,the catalyst should have good stability while ensuring high efficiency,the supported perovskite catalyst ZrO2-La0.5Sr0.5Co0.8Ni0.2O3(Z@LSCN82)could meet this requirement.The Z@LSCN82/PMS system reacted for 30 min to almost completely degrade SMX.In addition,the leaching of Co ions was only 0.303 mg/L,while Ni ions was not leached.In the leached Co2+/PMS system,only 36.99%of SMX was degraded in 30 min,which verified its heterogeneous system.Co and Ni on the surface of the catalyst jointly participate in the activation of the active sites of PMS,and the valence conversion of Co2+/Co3+and Ni2+/Ni3+improved the activation ability of PMS.The pH of the reaction solution could reach 97%or more SMX degradation efficiency between 3 and 10,and it had a wide pH range.The anions(Cl-,HCO3-,HPO42-)and NOM(HA)in natural waters both inhibited the degradation of SMX.Free radical quenching experiments and EPR experiments proved that SO4·-,·OH and 1O2 exist in the Z@LSCN82/PMS system to co-degrade SMX,and SO4·-plays a major role.In addition,the catalyst could still maintain high degradation performance after being recycled for 3 times.In the process of catalytic degradation of SMX,8 intermediate products were mainly produced by the hydrolysis and hydroxylation of sulfonamides under the attack of SO4·-,·OH and 1O2.In addition,the toxicity of the intermediate product was proven to be less than that of SMX.