1 2 3 Citric Acid - Modified Fenton ’ s Reaction for the Oxidation of Chlorinated Ethylenes 4 in Soil Solution Systems

28 Fenton’s reagent, a solution of hydrogen peroxide and ferrous iron catalyst, is used for an 29 in-situ chemical oxidation of organic contaminants. Sulfuric acid is commonly used to 30 create an acidic condition needed for catalytic oxidation. Fenton’s reaction often involves 31 pressure buildup and precipitation of reaction products, which can cause safety hazards 32 and diminish efficiency. We selected citric acid, a food-grade substance, as an acidifying 33 agent to evaluate its efficiencies for organic contaminant removal in Fenton’s reaction, 34 and examined the impacts of using citric acid on the unwanted reaction products. A series 35 of batch and column experiments were performed with varying H2O2 concentrations to 36 decompose selected chlorinated ethylenes. Either dissolved iron from soil or iron sulfate 37 salt was added to provide the iron catalyst in the batch tests. Batch experiments revealed 38 that both citric and sulfuric acid systems achieved over 90% contaminant removal rates, 39 and the presence of iron catalyst was essential for effective decontamination. Batch tests 40 with citric acid showed no signs of pressure accumulation and solid precipitations, 41 however the results suggested that an excessive usage of H2O2 relative to iron catalysts 42 (Fe/H2O2 < 1/330) would result in lowering the efficiency of contaminant removal by 43 iron chelations in the citric acid system. Column tests confirmed that citric acid could 44 provide suitable acidic conditions to achieve higher than 55% contaminant removal rates. 45