Performance And Mechanism Of Peroxymonosulfate Activation By Cobalt Sulfides For Organic Pollutants Degradation

In recent years,the control of refractory organic pollutants has become one of the research hotspots in the field of water treatment.The unique advantages of advanced oxidation process based on peroxymonosulfate or persulfate（PMS or PS）,such as strong oxidizing property,convenient operation,and no need for external energy,have attracted extensive attention of researchers.And,a variety of heterogeneous catalytic materials have been developed rapidly.Among them,metal sulfides have redox properties and acid-base functions,which can effectively activate PMS to degrade organic pollutants.But there are problems such as limited catalytic activity,low mineralization efficiency,and metal ions leaching.In this study,to overcome these problems,sulfur vacancies（SVs）and bimetallic active sites were used to regulate and optimize the catalytic performance of catalysts.And,the performance and mechanism of PMS activation was systematically studied.On this basis,fixed-bed experiments were used to explore the application of heterogeneous PMS activation system degradation of organic wastewater.This study provides a new insight for cobalt sulfides activated PMS to degrade organic wastewater.The main research conclusions and innovations are as follows:（1）The performance and mechanism of the synergistic activation of PMS by trace Fe³⁺and CoS₂ for organic pollutants degradation were studied.The experimental results showed that the CoS₂/Fe³⁺/PMS system exhibited excellent removal efficiency（above 90%）and higher mineralization efficiency for methylene blue（MB）,diclofenac sodium（DCF）,sulfamethoxazole（SMX）and bisphenol A.conversion rate（50.82%～88.16%）.Mechanistic studies revealed that the catalytic activity was related to the synergistic effect between trace Fe³⁺and SVs on the surface of CoS₂.singlet oxygen（¹O₂）was the main reactive oxygen species,which was attributed to the oxidative decomposition of PMS as the dominant reaction mechanism.The addition of Fe³⁺was beneficial to optimize the distribution of SVs and promote the oxidative decomposition of PMS,thereby producing a large amount of ¹O₂.The combined contribution of sulfate radicals（SO₄·^–）and hydroxyl radicals（·OH）enhanced the degradation and mineralization efficiency of pollutants.The above studies revealed the synergistic mechanism of trace Fe³⁺and CoS₂ in the activation of PMS.（2）On the basis of the above studies,the efficiency and mechanism of SVs-rich CoS@Fe S-1 heterogeneous catalysts for activating PMS to degrade organic pollutants were further developed.The experimental results showed that the removal efficiency of SMX,DCF,MB and Rhodamine B（Rh B）by CoS@Fe S-1 activated PMS was over 95%,and the mineralization efficiency was 46.07%～66.87%.Mechanistic studies showed that the synergistic effect of heterojunction and SVs was beneficial to adjust electron density and reduce the adsorption energy of CoS@Fe S-1 to PMS,promote the enrichment of O₂ by SVs on CoS@Fe S-1 to further generate ¹O₂.Meanwhile,the delocalized electrons made it easier for Co²⁺to reduce PMS to form SO4·-/·OH.The above studies proposed the mechanism of SVs synergistic heterojunction activation of PMS to degrade organic pollutants.（3）According to the above study on catalytic system,a treatment system of CoS@Fe S-1/PMS oxidation system continuous flow fixed bed reactor for the degradation of organic wastewater was carried out.The test results showed that the degradation efficiency of SMX was 77%～90%after continuous operation for 15 h.Rh B degradation efficiency was78%～100%after running for 11 h.The feasibility of CoS@Fe S-1/PMS oxidation system for the effective treatment of practical refractory organic pollutant wastewater has been preliminatively verified.