Reduced Degradation of Chlorobenzene in Cosolvent Solution Using Nanoscale Zerovalent Iron with Microwave Irradiation

Abstract

Chlorobenzene (CB) in aqueous solution is effectively degraded using nanoscale zerovalent iron (ZVI) particles suspended in the solution as the dielectric media with microwave irradiation. When nonaqueous CB is flushed out of groundwater from the contaminated soil, a cosolvent (e.g., methanol or ethanol) is usually added to aid the process. However, the cosolvent in the aqueous solution may interfere with the decomposition of dechlorination using ZVI. Results of this study confirm that if the CB aqueous solution is treated with nanoscale ZVI particles irradiated with microwave, the cosolvent will lower the contact between ZVI particles and water molecules, thus reducing the CB degradation rate. When 250-W microwave (MW) energy was applied to the CB aqueous solution containing methanol (a cosolvent) for 150 s, increasing methanol fraction in the CB solutions impaired the CB degradation rate. CB removal efficiencies are 65.4% for 0% MeOH, 53.7% for 40% MeOH, 32.2% for 60% MeOH, and 2.7% for 100% MeOH. Although the microwave radiation improved active sites on the iron particle surface, the presence of methanol suppressed adsorption of CB on iron particle surfaces thus lowering CB removal efficiency. Overall, reductive dechlorination of chlorinated organic solvents by nanoscale ZVI particles is a surface-mediated reaction; presence of a cosolvent reduces the effectiveness of dechlorination even in the presence of microwave radiation.