Research On The Performance And Mechanism Of Degradation Of PPCPs Pollutants By UV/SPC Oxidation System

Pharmaceuticals and personal care products?PPCPs?are widely detected in surface waters and are of concern because of their potential health and ecological threats.PPCPs have been frequently detected in surface waters such as rivers and lakes in recent years.Therefore,it is particularly necessary to develop new and efficient treatment technologies.Photo-assisted Fenton(Fe²⁺/Fe³⁺/H₂O₂)oxidation is a effective method to remove organic pollutants in water.However,traditional photo-assisted Fenton technology has many disadvantages,such as excessive consumption of iron salt and H₂O₂,and suitable pH value.The range is relatively narrow?2.5³.5?,and it is easy to produce secondary pollution caused by iron sludge.In addition,it should be pointed out that H₂O₂ is not easy to transport and preserve,and it has poor stability and easy decomposition when it is added,so that the treatment cost is increased.Therefore,this study constructed a photo-assisted Fenton system based on percarbonate?SPC?,and studied the performance and mechanism of the degradation of organic sunscreens.In this study,2-hydroxy-4-methoxybenzophenone?BP-3?and Sulfamethoxazole was used as a model compound to study the degradation performance and mineralization ability of photo-assisted/SPC system for contaminant,and through steady-state free radical quenching.Exclusion experiments and paramagnetic resonance spectroscopy were used to study the degradation mechanism of model compounds in oxidative systems.The main findings and results are as follows:?1?Steady-state degradation kinetics Experimental studies have shown that contaminant has higher degradation efficiency in UV/SPC system than single illumination and SPC system alone.pH significantly affects the degradation efficiency of UV/SPC system.When the pH is increased,the degradation efficiency is decreased.However,under partial neutral conditions,the degradation efficiency is still high.With the increase of SPC dosage,the degradation efficiency increases gradually.However,excessive SPC doping has little effect on the photolysis rate constant k value.Overall,the system is more efficient at low pH and higher SPC dosage.?2?Based on the UV/SPC system,the conditions for oxidative degradation of contaminant were optimized.The degradation of sulfamethoxazole was studied under the conditions of pH=3 and SPC dosage of 50 mmol·L^-1.Free radical quenching experiments and paramagnetic resonance spectroscopy indicated that the degradation of contaminant in UV/SPC system was mainly related to·OH.The second-order rate constant of BP-3 and·OH reaction was 1.37×10¹00 M^-1s^-1,which was close to the diffusion control rate(10¹00 M^-1s^-1).At the same time,the effect of dissolved components in water environment on the oxidation efficiency of UV/SPC system was studied.It was found that dissolved organic matter?DOM?in water had a significant effect on the reaction.As the concentration of DOM increases,the degradation efficiency of the system will gradually decrease.As the concentration of Cl^-increases,the degradation of BP-3 is first promoted and then inhibited;the degradation of sulfamethoxazole is continuously inhibited;The presence of Br^-leads to a decrease in the degradation efficiency of BP-3 in the UV/SPC system,which is related to the fact that Br^-is a good quencher for·OH.