Oxidative Degradation of Propachlor by Cu(II) Activated Persulfate

The development of strategies aiming to remove chloroacetanilide herbicides from contaminated groundwater and to remediate the contaminated sites is a timely and important task. The process of in situ chemical oxidation (ISCO) by persulfate (S2O82) can be accelerated by, metal ion activation to more effectively degrade the subsurface pollutants, owing to the enhancement of sulfate radicals (SO4-) generation. Copper is commonly a coexisting metal pollutant together with organic pollutants in soils and groundwater, and they also can be used as the activator of persulfate for the remediation of pesticide contaminated soils and groundwater. In this study, the oxidative degradation of propachlor by Cu2+ activated persulfate at different reaction conditions was systematically studied. The results show that Cu2+ is a more effective activator for persulfate oxidation than other reported metal ions, such as Fe2+ reported in many previous studies. The activation of persulfate by Cu2+ ions gave a long lasting and efficient degradation effect for propachlor and also posed a high mineralization rate. With fixed propachlor and persulfate concentrations, higher Cu(2+)concentration can achieve a proportionally higher degradation rate for propachlor. Comparing to the experiment carried out at 30 degrees C, a higher temperature (55 degrees C) showed the enhancement of Cu2+ activation. Based on the same other reaction conditions, 10 mg/L propachlor can be completely degraded in 32 h at 55 degrees C; while at 30 degrees C propachlor degradation rate only achieved 45.4%. The pH of the reaction system also posed a significant effect on propachlor degradation by Cu2+ activated persulfate, and the acidic condition was found to be more favorable for such metal activated degradation process. Overall, the results obtained in this study may indicate a promising technological development in remediating soils and groundwater that contain both chloroacetanilide pesticide and copper pollutants via the in situ injection of persulfate at the contaminated sites.