Activation Of Peroxymonosulfate By Silver-based Catalytic Material For The Degradation Of P-nitrophenol Wastewater

Advanced oxidation technology based on sulfate radical（SR-AOPs）is currently one of the simplest and most efficient methods in the treatment of organic wastewater.The activation of peroxymonosulfate（PMS）by multiphase transition metal materials has become a hot spot of research by scholars.As a transition metal,Ag has excellent photosensitivity,conductivity and catalytic activity.It is often used as a catalyst in the field of photocatalysis,but rarely used in SR-AOPs.Therefore,p-nitrophenol（PNP）was used as substrate to study the performance and mechanism of activated PMS degradation of organic pollutants by silver-based nanomaterials in this paper.The main research contents are as follows:（1）The performance and mechanism of silver oxides activated PMS to degrade PNP was investigated.Ag₂O and Ag O catalytic materials were prepared by wet chemical method and according to degradation experiments,the first-order kinetic constant of Ag₂O/PMS system is0.071 min^-1,which is much lower than that of Ag O/PMS system(0.076 min^-1).Through the catalyst reuse experiment and the XRD and FT-IR characterization of the used materials,it is found that Ag₂O material is unstable and the surface is easily oxidized to Ag O by PMS,while the structure of Ag O is relatively stable.The mechanism of the two systems was further investigated,and it was confirmed that the degradation of organic pollutants in the Ag₂O/PMS system was mainly achieved by SO₄^-·generated during the oxidation process of Ag（Ⅰ）/Ag（Ⅱ）.In the Ag O/PMS system,PNP can be degraded not only by direct oxidation of Ag（Ⅱ）at high valance,but also through SO₄^-·and OH·generated during the reaction of Ag（Ⅱ）-Ag（Ⅰ）-Ag（Ⅱ）with PMS.（2）The performance and mechanism of silver-copper oxide activated PMS to degrade PNP was investigated.Ag₂Cu₂O₃（ACO-60）catalytic material was synthesized by co-precipitation method.The design of silver-based bimetal structure further improved the activity and stability of Ag₂O.In the activity experiment,it was found that ACO-60/PMS system had a good removal effect on PNP,and its first-order reaction rate constant was 0.312 min^-1.In addition,the system has the best degradation effect on PNP under weak acid and alkaline conditions,which is beneficial to the treatment of actual organic wastewater.The excellent stability and reusability of ACO-60 were confirmed by cycling experiment and the XRD characterization of used catalyst.SO₄^-·were identified as the main active substances in ACO-60/PMS system by radical quenching and EPR test,and the degradation pathway was realized by the redox reaction of Ag（Ⅰ）/Ag（Ⅱ）,Cu（Ⅱ）/Cu（Ⅰ）and Cu（Ⅰ）/Cu（Ⅱ）to generate free radical.In addition,the synergistic effect between Ag and Cu species was further discussed.It was found that the high activity of ACO-60 catalytic material was caused by the internal Cu（Ⅱ）-O-Ag（Ⅰ）bond,which promoted the reduction of Cu（Ⅱ）to Cu（Ⅰ）and increased the electron transfer rate,thus generating more active substances to degrade PNP.Based on the above research results,it is found that silver-based catalysts can effectively activate PMS to degrade PNP,which provides a foundation for the application of silver-based nanomaterials in advanced oxidation technology to treat organic wastewater.