Experiments On The Treatment Of Sulfonamides In Water By The Electrochemical And Persulfate Synergetic Method

In recent years,new pollutants are frequently detected in surface water and groundwater,mainly including medicines and personal care products,which have the characteristics of low concentration,high toxicity and difficult removal.Among them,sulfa antibiotics(SAs)is one of the antibiotic with highest detection rate.SAs pollution can cause harm to human health,micro-organisms and aquatic animals in the environment.Therefore,looking for effective ways to remove antibiotic contamination in water is one of the hot issues in water treatment.Electrochemical and persulfate synergistic method is a new advanced oxidation method with the advantages of rapid reaction,strong oxidizing ability and high removal rate.The technology has shown good prospects,but the activation method of persulfate is still a difficult problem,and the research on the mechanism is less.The subject adopts electrochemical and peroxydisulfate synergistic method to treat sulfa antibiotics in water,using Fe2+ and AC as the peroxodisulfate activators,respectively,and self-formulated sulfamethoxazole(SMX)water as the treated water sample.At first,the effectiveness of electrochemical(EC)and PS synergistic system for the treatment of SMX under the presence of different activators was explored,and the effects of various reaction factors and coexisting ions on the treatment effect were analyzed.Then the mechanism of oxidation reaction was studied,and the kinetic analysis of the reaction was carried out.Finally,the kinetic model of the reaction was established.When Fe2+ was used as PS activator,the removal efficiency of SMX in five conditions was investigated.The removal rate of SMX by EC/Fe2+/PS system was 89.4%,which was higher than the sum of EC(50.45%)and Fe2+/PS(23.28%),indicating that there is synergistic effect between electrochemistry and Fe2+ activated persulfate method.The effects of various factors on the treatment of SMX by EC/Fe2+/PS system were studied.Acidic condition is favorable for the oxidative degradation of SMX,when pH is 3,the removal efficiency is the best.Fe2+concentration and plate spacing have the best value,too high or too low are not conducive to SMX degradation.To a certain extent,increasing the concentration of PS,electrolyte concentration and current density can increase the removal rate of SMX.The presence of Cl-,HCO3-and CO32-in water can inhibit the oxidation and degradation of SMX in different degrees.These ions have scavenging effects on free radicals or participate in the complexation of iron ions.NO3-in aqueous solution is relatively stable,no significant effect on the treatment effect.When using AC as PS activator,there is synergistic effect between the electrochemical and AC activated persulfate method.In the treatment of SMX by EC/AC/PS system,the increase of SMX concentration resulted in the increase of intermediate products,and the competition with pollutants leads to the decrease of oxidative degradation efficiency.As with the EC/Fe2+/PS system,acidic conditions favor the degradation of SMX,but the optimum pH value was 5 when AC act as activator.The increase of AC concentration,PS concentration and current density can all improve the treatment effect,but the effect of the treatment effect is not obvious when the condition number reaches a certain level.There is an optimum plate spacing of 9 cm.After repeated use of AC for 4 times,its activity remained high,and the removal rate of SMX by EC/AC4/PS system still exceeded 80%.The effect of coexisting anions on the treatment of SMX in the EC/AC/PS system was similar to that of the EC/Fe2+/PS system,but the degree of inhibition was smaller than that of the latter.The free radical test shows that SO4-· plays a leading role in acid conditions.By scanning the absorption spectrum before and after the reaction of the solution,it is found that the structure of SMX benzene ring is gradually destroyed,and the system has a good removal effect on SMX.According to the data analysis,electrochemical and persulfate synergistic method treatment of SMX followed first-order reaction kinetics;After further kinetic analysis,the kinetic model of EC/Fe2+/PS system was obtained Ct = C0 exp(-8.9921*10-4[Fe2+]0.4383[PS]0.7747[Na2SO4]0.3382 C0.4095 D0.8573).The order of the influence degree of each factor to the reaction is plate spacing>PS concentration>Fe2+ concentration>current density>electrolyte concentration.In EC/AC/PS system,the reaction kinetic model was obtained Ct = C0 exp(-1.100*10-3[AC]0.4471[PS]0.6397 C0.5658 D0.8405 t).The order of the influence degree of each factor to the reaction is plate spacing>PS concentration>current density>AC concentration.The dynamic model is well fitted to the actual value.The results show that the electrochemical synergistic persulfate method can effectively oxidize sulfonamide antibiotics in water,and the treatment effect is good.It provides an efficient and environmentally friendly treatment for removing sulfonamides from water.The obtained reaction kinetic model provides a theoretical basis for the application of the method to practical process.