Enhancement of benzene degradation by persulfate oxidation: synergistic effect by nanoscale zero-valent iron (nZVI) and thermal activation

The feasibility of an advanced oxidation process based upon sodium persulfate (SPS) activated simultaneously by heat (50 °C) and nanoscale zero-valent iron (nZVI) on benzene removal was investigated. The experimental results strongly showed the synergistic effect of thermal and nZVI activation to SPS and benzene removal was enhanced with the increase of SPS/nZVI/benzene molar ratio. Specifically, 94% of benzene could be removed in 1 hr at 50 °C at the SPS/nZVI/benzene molar ratio of 10/5/1. The radical scavenger tests and electron paramagnetic resonance (EPR) analysis confirmed that SO4•− was the predominant species contributing to benzene degradation. Further, the effects of the solution matrix on benzene elimination were investigated. The results indicated that benzene destruction in the thermally activated SPS/nZVI system performed better under acidic conditions, and the high concentration of both Cl− and HCO3− had adverse effects on benzene elimination. The test for the performance of benzene degradation in the actual groundwater demonstrated that benzene could be degraded entirely at SPS/nZVI/benzene molar ratio of 40/40/1 at 50 °C, indicating that the synergistic catalysis of thermal and nZVI activation to SPS is exploitable and the thermally activated SPS/nZVI system can be applicable to the remediation of benzene contaminated groundwater.

Plasma-Induced Degradation of Benzene in Aqueous Solution

Removal of benzene and effects of various parameters on the removal efficiency in the aqueous solution with plasma are studied. Results indicated that the degradation rate can be considerably raised by prolonging the discharge time, removal proceeded faster when the treatment was conducted in alkaline or acidic than in neutral media. Fe2+ shows an evident accelerated effect on the benzene elimination, and the presence of H2O2 benefited the degradation. It is demonstrated that the hydroxyl radicals were the most responsible oxidants in the benzene degradation. The major intermediate products resulted from the degradation were identified by an HPLC analysis and a degradation path way was proposed.