Removal Of Bisphenol AF And Methyl Orange From Water By Potassium Ferrate Catalyzed By Cuprous Sulfide

With the development of industry,different kinds of new persistent organic pollutants are emerging constantly.These pollutants are so difficult to degrade that they remain in the environment for a long time and eventually pass to human through the food chain,posing a great threat to human health.Potassium ferrate,a water treatment agent,has attracted much attention because of its high efficiency and environment-friendly attributes.In recent years,methods to enhance the treatment efficiency of potassium ferrate have been widely studied in order to solve the problems of large dosage,long acting time and difficulty in achieving complete mineralization when potassium ferrate is used alone.In this paper,copper sulfide(Cu2S)was used to strengthen potassium ferrate(K2FeO4)to produce strong oxidizing intermediate products to enhance the oxidation efficiency of K2FeO4 to degrade persistent organic pollutants(POPs).The main research contents and conclusions were as follows:The influencing factors of degradation of organic pollutants in Cu2S/K2FeO4 system were studied,including Cu2S initial concentration,K2FeO4 initial concentration,reaction temperature,initial pH value of solution,HA and common inorganic anions in solution,etc.The results show that the degradation effect of Cu2S/K2FeO4 system on organic pollutants will increase first and then decrease with the increase of Cu2S concentration.The excessive concentration of Cu2S hasa significant difference in the impact on different organic compounds:the degradation of BPAF will be severely inhibited,but the degradation of MO will be slightly enhanced.The increase of K2FeO4 initial concentration will enhance the degradation effect of organic pollutants,but the high concentration of K2FeO4 will aggravate the self-consumption among oxidized species.The increase of reaction temperature will enhance the effective collision and increase the removal rate,but the high temperature will increase the self-consumption of high-priced iron,resulting in the reduction of removal rate.Cu2S/K2FeO4 system has the best strengthening effect under the pH value of 6-8.The presence of HA,CO32-and PO42-will restrain the degradation of organic matter,while NO3-significantly restrain the degradation of BPAF,but has only a slight effect on the degradation of MO.The strengthening effect of Cu2S on the degradation of BPAF by K2FeO4 was studied.The results show that the strengthening effect of Cu(Ⅰ)is related to the contact surface area,and Cu(Ⅰ)can transfer electrons with Fe(VI)to produce strongly oxidizing Fe(Ⅴ)and Fc(Ⅳ).The strengthening effect of S2-in the system is related to its form of existence.As an electron donor,S2-slowly released by insoluble sulfide can transfer electrons with Cu(Ⅱ)to form Cu(Ⅰ),and with Fe(Ⅲ)to form Fe(Ⅱ).Cu(I)and Fe(Ⅱ)can continue to transfer electrons with Fe(Ⅵ)to form intermediate valence irons.In addition,the experiment of radical quenching show that hydroxyl radical(·OH)with strong oxidization existes in the system,but the species that contribute the most to oxidation are the intermediate valence irons.Experiment of the degradation of methyl orange(MO)in Cu2S/K2FeO4 system show that,in addition to the strengthening effect of Cu(Ⅰ)and S2-,the-SO3-group of MO may contributes to the degradation of MO itself by electron transfer with Fe(VI)to generate the intermediate valence irons.The experiment of radical quenching shows that there may be sulfate radical(SO4·-)in the system,which is speculated to be caused by SO32-with Fe(Ⅵ)in the aerobic environment.Studies on the degradation of target pollutants in micro-polluted water show that Cu2S/K2FeO4 system is still more rapid and efficient than K2FeO4 system alone,and may have oxidative degradation effect on the other organic matters and microbial metabolites in micro-polluted water.