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

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 center dot-) and hydroxyl radicals (HO center dot) were confirmed by radical scavenger tests and Electron paramagnetic resonance (EPR) studies, in which HO center dot 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.