Study On The Oxidation Of Carbamazepine Via Catalytic Activation Of Peroxymonosulfate By Layered Double Cobalt Oxides

In recent years,with the development of industry and society,more and more wastewater have been produced from the pharmaceutical and chemical industry and municipal wastewater system.These wastewaters often contain toxic and persistent organic pollutants.If they are discharged into the water environment without treatment,they will pose a great threat to human health and environment.How to efficiently remove these organic pollutants has drawn more and more attention.Sulfate radical oxidation technology has received extensive attention because it can be applied at a wide pH range,possesses high oxidation capacity,and can thoroughly degrade organic pollutants.However,the release of active meta during the catalytic process restricts the application of this technology.To acquire a stable and efficient catalyst to activate peroxymonosulfate(PMS)for the degradation of pollutants we propose to use layered metal oxides to fix the active components,i.e.,cobalt and iron.The stability mechanism of the catalyst was studied;free radicals in the activation process were identified;key mechanisms underlying the activation reactions were investigated;and effects of environmental conditions on the degradation of pollutants were studied.The results are as follows:1.Cobalt-based catalysts can activate PMS to degrade organic pollutants,however the dosage of the catalyst needed is rather high.To minimum the dosage of the catalyst,we synthesized a highly efficient cobalt-iron-aluminum layered double hydroxide(LDH),by which the active site of the catalyst could be largely increased.In this study,Co2FeAl-LDH was synthesized to active PMS for carbamazepine(CBZ)degradation.Effects of proportion of cobalt and iron of the catalyst,PMS concentration,catalyst dosage,CBZ concentration,initial solution pH,anions in water and humic acid on the catalytic performance were systematically studied.EPR experiment and free radical quenching experiment indicate that the main active free radical was SO4·-,and the possible reaction mechanism of Co2FeAl-LDH on PMS activation and CBZ degradation is proposed.This study provides new ideas for the development of highly efficient heterogeneous catalysts for PMS activation and to pollutants degradation.2.An important issue for applying transition metal catalyst is the leaching of heavy metals during the degradation process,which could cause secondary pollution to the water environment.In order to reduce the leaching of cobalt,we further heat-treated Co2FeAl-LDH to obtain Co2FeAl-LDO.The cycle experiment and metal leaching experiment prove that the calcination of Co2FeAl-LDH greatly improves the stability of the catalyst and reduces the leaching of metal.By investigating the effect of metal compositions on the catalytic performance,the synergy of cobalt,iron,and aluminum was explored.The catalytic performance of Co2FeAl-LDO under different conditions(different PMS concentration,catalyst dosage,CBZ concentration,initial solution pH,co-existed anion,humic acid concentration,and degradation of other pollutants in the environment)were systematically studied.The EPR experiment and free radical quenching experiment prove that the main active free radical was SO4·-,and the reaction mechanism was studied.Through the degradation intermediates of CBZ,a possible reaction pathway of Co2FeAl-LDO on PMS activation and CBZ degradation was proposed.This study provides a method to prepare an efficient,easily separated,and stable catalyst that can be used to activate PMS to degrade organic pollutants.