Enhanced degradation of benzene in aqueous solution by sodium percarbonate activated with chelated-Fe(II)

In this study, the application of sodium percarbonate (SPC) catalyzed by various chelated-Fe(II) to stimulate the degradation of benzene in groundwater remediation was investigated. Effective oxidation of benzene was achieved in CIT/SPC/Fe(II) and OA/SPC/Fe(II) systems. The reaction mechanism for benzene degradation in CIT/SPC/Fe(II) and OA/SPC/Fe(II) systems was elucidated by free radical probe compound tests, free radical scavenger tests and electron paramagnetic resonance (EPR) analysis. And hydroxyl radical (HO) and superoxide anion radical (O2-) were confirmed as the predominant species responsible for benzene degradation. Besides, the effects of various factors, such as the solution characteristics including the presence of anions (Cl−, HCO3−, SO42− and NO3−), natural organic materials (NOM), and the initial solution pH on benzene degradation were also evaluated. The influences caused by SO42−, NO3−, Cl− and NOM were negligible, but HCO3− anion had a slightly inhibitive effect in low concentration (1 mM) and an apparently inhibitive effect in high concentration (10-100 mM). However, the additions of CIT and OA eliminated the adverse influence of HCO3− and ensured a high benzene degradation efficiency at wider pH range. Finally, results obtained in actual groundwater test strongly demonstrated that Fe(II)-CIT and Fe(II)-OA catalyzed SPC systems are applicable for the remediation of benzene-contaminated groundwater in practice.