Study On Degradation Characteristics And Mechanism Of Three Typical Organic Pollutants By Combination Of Ultraviolet Peroxides

In recent years,PPCPs have been widely used by people,resulting in their widespread distribution in the environment and frequent detection in water bodies.As a typical anti-inflammatory drug,diclofenac sodium（DCF）has refractory and bioaccumulative effects,and is often discharged into the natural water body with the effluent from the sewage treatment plant,which seriously endangers human health and the ecological environment.The physicochemical properties of norfloxacin（NFX）and diclofenac sodium are similar,but NFX entering the environment can induce a large number of drug-resistant bacteria,affecting the microbial population structure and destroying the original ecological balance.Aniline is an important amine compound with high toxicity and"triad"effect,and is listed as one of the 129 substances controlled by the US EPA.The removal of three pollutants is of great significance to the ecological environment and public health.Calcium peroxide（CaO₂）,as a new environmentally friendly material,not only releases O₂ in water,but also releases H₂O₂.It was originally widely used in aquaculture and agricultural cultivation,and has been gradually introduced into the field of environmental restoration in recent year and played a unique advantage.The degradation characteristics of CaO₂ on DCF,NFX and aniline under ultraviolet（UV）catalytic activation were investigated.Firstly,the degradation of three target pollutants by separate CaO₂,UV alone and UV/CaO₂ was investigated.Then,the effects of CaO₂ dosage,initial pH of solution and water matrix（Cl^-,NO₃^-,HCO₃^-）on the degradation of three pollutants were studied.Finally,the types and changes of oxidizing active substances in the UV/CaO₂ system were investigated.In addition,in order to investigate the effect of UV/CaO₂ and UV/H₂O₂ on pollutants,the degradation kinetics of the two systems and the difference of active substances under the same conditions were studied.The results showed that UV/CaO₂ had the best removal effect on aniline,NFX and DCF when the initial pH of the solution was 6 and CaO₂=1g/L,and the removal rates were 100%,98%and 91%,respectively.When the CaO₂ concentration is within a certain concentration range,the removal rate of contaminants will increase with the increase of the concentration;when the initial pH of the solution is raised to 8,the removal rates of UV/CaO₂ to aniline,NFX and DCF can be reduced to 95%,40%and 44%,respectively;the order of the effects of three inorganic anions on the removal of organic pollutants in the water matrix is:NO₃^->HCO₃^->Cl^-,where under UV/CaO₂ system the effect of Cl^-on the degradation of three pollutants is different,the degradation of aniline is not affected by Cl^-,but the removal of NFX and DCF can be slightly promoted and inhibited by Cl^-;HCO₃^-and NO₃^-can inhibit the degradation of aniline,NFX and DCF.The mechanism of action of UV/CaO₂ system was studied by adding quenchers.The results showed that the oxidizing active substance which plays a major role in the degradation of three pollutants in this system is·OH.The study found that,unlike UV/H₂O₂ technology,UV/CaO₂technology is affected by the initial pH of the solution.UV/CaO₂ can degrade pollutants under circumneutral pH conditions,so no need to add acid to adjust pH,so a new method for the removal of organic contaminants under circumneutral pH conditions is provided for the water treatment field.