Benzene depletion by Fe2+-catalyzed sodium percarbonate in aqueous solution

• Effective degradation of benzene is achieved by Fe2+-catalyzed SPC.
• The primary reactive oxygen species is HO in SPC/Fe2+ system.
• Fe2+-catalyzed SPC oxidation is suitable for alkalescent conditions.
• Effective Fe2+-catalyzed SPC oxidation of benzene in real groundwater is achieved.

In this study, the chemical oxidation of benzene by Fe2+-catalyzed sodium percarbonate (SPC) was conducted. The effects of various factors, such as the SPC/Fe2+/benzene molar ratio, temperature, order of the reagent addition, solution matrix including the presence of anions (Cl−, HCO3−, SO42− and NO3−) and natural organic materials (NOM), and the initial solution pH, were thoroughly investigated. The experimental results showed that benzene can be completely degraded (<0.01 mg/L) in 20 min with a SPC/Fe2+/benzene molar ratio of 10/10/1 at 20 °C, indicating the effectiveness of Fe2+/SPC oxidation for benzene removal. The degradation of benzene is significantly influenced by the SPC/Fe2+/benzene molar ratio as well as the order of the reagent addition, but less affected by the temperature. HCO3− and NOM have significant scavenging effects on benzene degradation, whereas Cl− has a slightly expediting effect at low concentration and a scavenging effect at high concentration. Meanwhile, the influences of SO42− and NO3− are negligible at the tested ionic strength ranges. The degradation of benzene was not apparently inhibited at pH 9.0. This result indicated that Fe2+-catalyzed SPC oxidation is suitable for alkalescent conditions which is superior to the conventional Fenton process. Hydroxyl radical (HO) has been confirmed as the predominant species responsible for benzene degradation by using free radical probe compounds tests, HO scavengers tests and electron paramagnetic resonance (EPR) analysis. In addition, an amazing effective Fe2+-catalyzed SPC oxidation of benzene in actual groundwater was achieved, indicating that Fe2+-catalyzed SPC oxidation is a highly promising technique for the remediation of benzene-contaminated groundwater.