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 ( O 2 - ) 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 − , HCO 3 − , SO 4 2− and NO 3 − ), natural organic materials (NOM), and the initial solution pH on benzene degradation were also evaluated. The influences caused by SO 4 2− , NO 3 − , Cl − and NOM were negligible, but HCO 3 − 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 HCO 3 − 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.