Degradation of sulfanilamide by Fenton-like reaction and optimization using response surface methodology

Excess sulfonamides are discharged into the environmental system due to the abuse of antibiotics, which threatens the ecological environment and human health. In this study, the ferric and ferrous as well as calcium peroxide (CP), sodium percarbonate (SPC) and sodium persulfate (SPS) have been used to build Fenton-like system for the sulfanilamide (SA) removal. Compared with other Fenton-like system, the Fe³⁺/CP system exhibited better degradation capacity and 94.65% SA was removed with 3.0 mM CP and 3.0 mM Fe³⁺. A response surface and corresponding quadratic regression equation were obtained by using a three-level Box-Behnken factorial design with the initial pH value and the dosage of Fe³⁺ and CP as the model parameters. Depended on the result of the response surface, the optimum conditions of the removal of SA in Fe³⁺/CP system could be obtained: [Fe³⁺] = 2.96 mM, [CaO₂] = 2.33 mM and [pH] = 6.45. Besides that, the influences of Na⁺, Mg²⁺, Cl^-, HCO₃^-, NO₃^- and HA on SA removal were also investigated under the optimum condition. The results revealed that the high concentration of HCO₃^- was able to inhibit degradation of SA while other ions and HA have little effect on SA degradation. These results provided a novel strategy to evaluate the catalyst/oxidant system by combining experiment and computer simulation in wastewater treatment.