Study Of The Degradation Of Sulfonamides In Aqueous Solution By Iron Catalyzed Calcium Peroxide

In recent years,due to the excessive use of antibiotics,a large number of antibiotics are directly discharged and accumulated in the water environment and soil,so the problem of environmental pollution about antibiotics has been widely concerned.In this study,sulfonamides a class of antibiotics were regarded as target pollutants to carry out.The research was based on Fenton oxidation method for water and soil resource remediation.The optimization for the Fenton oxidation system by computer simulation and addition of chelating agent were investigated.In this thesis,the degradation efficiency of sulfanilamide(SA)oxidized by three different oxidants,sodium percarbonate(Na2CO3·1..5H2O2,SPC),sodium persulfate(Na2S2O8,SPS)and calcium peroxide(CaO2,CP)under the catalysis of Fe2+ or Fe3+ were discussed.The amount of catalyst,the amount of oxidant and the initial pH of the solution were acted as factor variables.SA degradation efficiency was response.The response surface methodology was used to optimize the conditions of three factor variables on the degradation of SA,then obtained the best conditions and best values of S A removal.The effects of anions,cations and natural organic matter in the actual wastewater on the degradation of SA were investigated.The effects of various chelating agents on the degradation of sulfadiazine(SDZ)were further investigated.The effects of chelating agents on Fenton system and the generation of active free radicals were surveyed.The possible degradation pathway and toxicity of SDZ intermediates were inferred.The specific research conclusions were as follows:(1)SPC,SPS and CP had certain degradation effects on SA under Fe2+ or Fe3+ catalysis.Compared with other Fenton systems,Fe3+/CP had the best degradation ability on SA.3.0 mM CP catalyzed by 3.0 mM Fe3+ could remove 94.65%SA.(2)Based on three variable parameters,such as the amount of Fe3+,the amount of CP and the initial pH value of solution,the Box-Behnken factor was used to design the model,then the experimental values and computer simulation were used to obtain the response surface of the variable and the corresponding quadratic regression equation.The optimum conditions were[Fe3+]0＝2,96 mM,[CP]0＝2.33 mM and[pH]0=6.45.The presence of a certain amount of HCO3-in the actual water quality could inhibit the degradation efficiency of SA under optimal conditions.(3)Under the Fe3+/CP system,various chelating agents could promote the degradation of SDZ.The promotion effect of cysteine(L-cys)was higher than that of other chelating agents in 1.5 mM Fe3+ and 2.0 mM CP system.Under the addition of 0.5 mM L-cys,the degradation efficiency of SDZ increased from 2.14%to 66.43%.It was found that L-cys could promote the conversion of Fe3+ and Fe2+ and reduce the consumption of iron ions.(4)It can be found by electron paramagnetic resonance spectroscopy that OH and ·O2-coexist in the L-cys/Fe3+/CP system,and OH played a leading role in the degradation of SDZ.(5)The main intermediates of SDZ degradation were detected by LC-MS.The degradation pathway of SDZ was speculated.The toxicity and biological characteristics of the solution were estimated according to the degradation intermediates.After the degradation of SDZ in the L-cys/Fe3+/CP system,the overall toxicity of the solution decreased.