Role of reactive oxygen species and effect of solution matrix in trichloroethylene degradation from aqueous solution by zeolite-supported nano iron as percarbonate activator

The role of reactive oxygen species (ROSs) and effect of solution matrix have been investigated for the degradation of trichloroethylene (TCE). Zeolite-supported nano iron (Z-nZVI) was synthesized as an activator to catalyze sodium percarbonate (SPC) with or without hydroxylamine, i.e. as reducing agent (RA). The probe tests confirmed the generation of OH · and O −· 2 in the Z-nZVI activated SPC system in absence of the RA, while the presence of RA significantly increased the generation of OH · and O −· 2 radicals. Scavenger tests demonstrated that OH · was the main ROS responsible for TCE degradation, whereas O −· 2 also participated in TCE degradation. From the solution matrix perspective, the experimental results confirmed significant scavenging effects of Cl − (1.0, 10.0, and 100 mmol L −1 ) and HCO 3 − (1.0 and 10.0 mmol L −1 ), whereas the scavenging effects were fairly impeded at 100 mmol L −1 concentration of HCO 3 − . On the other hand, a considerable decline in scavenging effect was observed in the presence of RA in tested Cl − and HCO 3 − concentration ranges. In addition, negligible scavenging effects of NO 3 − and SO 4 2− anions were found in all tested concentrations. The effect of initial solution pH on catalytic activity indicated a significant increase in the TCE degradation in the presence of RA even at higher pH value of 9. The results indicated that the Z-nZVI activated SPC system in presence of RA can effectively degrade chlorinated organic solvents, but it is important to consider the intensive existence of anions in groundwater.