Enhanced-oxidation of sulfanilamide in groundwater using combination of calcium peroxide and pyrite

Abstract

Fenton reaction using hydrogen peroxide (H2O2) has been widely applied to achieve the in-situ chemical oxidation of contaminated soil and groundwater. However, injecting and transporting H2O2 to a contaminated zone consumes the chemical through reactions with other substances and self-decomposition. Additionally, Fe(II), an activator for the Fenton reaction, scavenges hydroxyl radicals, greatly reducing its activity. Therefore, this study proposes a novel oxidation system combining calcium peroxide (CaO2) and pyrite for the degradation of oxidizable contaminants in groundwater. CaO2 is an oxygen releasing compound, and pyrite is a natural mineral that provides Fe(II). The individual applications of CaO2 and pyrite cannot generate OH radicals and oxidize the target pollutant, sulfanilamide. However, the combination of pyrite and CaO2 oxidized well sulfanilamide even in mild pH and 1.0 wt% of pyrite. Moreover, H2O2 and OH radicals are the dominant oxidants in the reaction. A speciation analysis shows the oxidation of pyrite in this combined system. Furthermore, this system oxidized 80% of 0.1 mM sulfanilamide, whereas only 30% was oxidized by conventional Fenton reaction, indicating that this combined system is effective and applicable to remediate groundwater. This study provides an alternative oxidation process to achieve in-situ chemical oxidation.