Interaction of oxidants in siderite catalyzed hydrogen peroxide and persulfate system using trichloroethylene as a target contaminant

In situ chemical oxidation (ISCO) is an effective method used for the remediation of soil and groundwater. Both mineral catalyzed hydrogen peroxide (H2O2) process, which produces hydroxyl radicals (HO center dot), and mineral catalyzed persulfate process, which produces sulfate radicals (SO4-center dot), have significant potential to oxidize a considerable range of organic contaminants. In this study, siderite catalyzed H2O2 and persulfate process was studied to investigate the interaction mechanism of this system with the use of trichloroethylene (TCE) as a target contaminant. The use of certain amounts of soluble iron ions rather than siderite to degrade TCE revealed that ferrous ions played an important role in the catalytic activity. The degradation of TCE in siderite catalyzed H2O2 and persulfate systems with different H2O2 and persulfate concentrations was in accordance with first-order kinetics reactions. In the siderite catalyzed H2O2 system, 49.3% of TCE was removed in 30 h. However, in the siderite catalyzed H2O2 and persulfate system, 100% of TCE was removed in 24 h. Increasing the H2O2 or persulfate dosage, which means more Ha or SO4-center dot generation, can yield a higher TCE removal efficiency, it was concluded that both Ha and SO4-center dot were effective radicals for oxidizing TCE. By further studying the remaining oxidants, the faster oxidant decomposition rate in the siderite catalyzed H2O2 system than in the siderite catalyzed H2O2 and persulfate system revealed that the addition of persulfate slowed the decomposition of H2O2, which reduced the loss of HO center dot and enhanced the TCE removal efficiency. (C) 2013 Published by Elsevier B.V.