Activation of persulfate and hydrogen peroxide by using sulfide-modified nanoscale zero-valent iron for oxidative degradation of sulfamethazine: A comparative study

Abstract In this study, sulfide-modified nanoscale zero-valent iron (S-nZVI) was employed to activate persulfate (PS) and hydrogen peroxide (H 2 O 2 ) for the removal of sulfamethazine (SMT). The potential influencing factors, such as oxidant concentration, SMT concentration, Fe/S molar ratio and initial pH, were examined. The removal of SMT in the S-nZVI/PS system increased with the increasing PS concentration, while there was an optimum H 2 O 2 concentration in the S-nZVI/H 2 O 2 system. The S-nZVI/H 2 O 2 system showed much stronger oxidative capacity than the S-nZVI/PS system under the same fitting condition. Moreover, the S-nZVI/PS system was more susceptible to the molar ratio of Fe/S in S-nZVI, and a higher SMT removal was achieved under conditions of Fe/S ≥ 40. Nevertheless, the S-nZVI/PS system was efficient over a wide pH range of 3–9, while the efficient pH in the S-nZVI/H 2 O 2 system was confined to just 3. In addition, the SMT removal by the S-nZVI/PS system was further examined in simulated groundwater and it was found that the influence of groundwater components on the removal of SMT was insignificant over the pH range of 5–8, but a notable negative effect was observed at pH 9.