Enhanced degradation of monochlorobenzene in groundwater by ferrous iron/persulfate process with cysteine

Abstract

Monochlorobenzene (MCB) pollution in the groundwater has attracted extensive attention due to its high toxicity and refractory. Ferrous-activated persulfate process (Fe2+/PS) is feasible to degrade MCB; however, the slow redox cycle of Fe2+/Fe3+ and the narrow valid pH range limit its application. In this study, cysteine (Cys) cooperating with the Fe2+/PS process (Fe2+/Cys/PS) can be employed to enhance the MCB degradation owing to its reduction and complexation ability, in which the effects of Cys, Fe2+, PS concentrations, and the value of pH were evaluated. Existences of sulfate radicals (SO4−) and hydroxyl radicals (HO) were confirmed by radical scavenger tests and Electron paramagnetic resonance (EPR) studies, in which HO was mainly responsible for MCB degradation in Fe2+/Cys/PS process. According to the aforementioned results, a potential mechanism and a plausible pathway of MCB degradation were proposed. The Fe2+/Cys complex can be repeatedly reused in practical applications. Likewise, the excellent performance of Fe2+/Cys/PS process in the degradation of MCB was also observed in the real groundwater. In summary, the novel Fe2+/Cys/PS process might provide a potentially effective technique for remediation of organic-contaminated groundwater.