Peroxymonosulfate Activation By Metal Nanomaterials For Degradation Of Organic Contaminants

In the field of global environment,the hotspot issues are water quality and toxicity caused by chemical pollutants.As typical organic pollutants,bisphenol A,rhodamine B（Rh B）and tetracycline（Tet）are harmful to human health.Advanced oxidation processes of peroxymonosulfate（PMS）can produce·SO₄^-and·OH which remove chemical contaminants efficiently.PMS can be activated by metal ions.However,the traditional metal oxides have poor stability and leaching of active components,resulting in problems like catalyst deactivation and secondary pollution.At the same time,there are still blind spots in the efficient removal mechanism of pollutants in PMS system.Therefore,it is of great practical significance to study the highly stable and active PMS oxidation catalyst and its action mechanism.This work highlights nano bimetallic oxide catalyst to improve the stability of the catalyst and activate PMS to remove pollutants.Meanwhile,the reaction mechanism of pollutant removal regulation was clarified.The main research contents are as follows:（1）Co_xMn_y catalyst was prepared by a co-precipitation method,the preparation conditions were studied:The optimal ratio of cobalt manganese bimetallic oxide（Co_xMn_y）catalyst is 4/1,the optimal calcination temper ature in muffle furnace is400℃,the optimal calcination temperature is 3 h,and the optimal sedimentation time is 4 h.Compared with Co O_x and Mn O_x single component catalysts,Co_xMn_ycomposite catalyst effectively promoted the activation of PMS to degrade BPA.Within 3 minutes,the degradation efficiency of BPA with 30 ppm can reach 100%.Co_xMn_y catalyst also showed good catalytic degradation performance for organic pollutants such as Rh B and Tet.（2）The physical–chemical properties of catalyst were characterized and analyzed.It was found that the structural size of the Co_xMn_y composite catalyst was significantly reduced and the amorphous structure was enhanced compared with the Co O_x and Mn O_x single component catalysts.At the same time,the Co-O-Mn composite bond in the Co_xMn_y composite catalyst enhanced the defective structure of the catalyst and induced more oxygen vacancies and the formation of surface Mn⁴⁺species.（3）Free radical scavenger experiment and electron spin resonance（EPR）were used to explore the mechanism of BPA activation and degradation by PMS.The analysis showed that the catalysts of Co O_x,Mn O_x and Co_xMn_y activate PMS into active oxygen species like ¹O₂,·O₂^-,·SO₄^-and·OH.The structural defects of Co_xMn_ycatalyst significantly promoted the formation of ¹O₂ and improve the degradation efficiency of BPA.The degradation of BPA in Co_xMn_y/PMS system mainly followed non-free radical path.The intermediate products of BPA degradation were analyzed by gas chromatography-mass spectrometry（GC-MS）,and three possible reaction paths were speculated.