Seol Yongkoo, Javandel Iraj
Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
Chemosphere. 2008 Jun;72(4):537-42. doi: 10.1016/j.chemosphere.2008.03.052. Epub 2008 May 9.
Fenton's reagent, a solution of hydrogen peroxide and ferrous iron catalyst, is used for an in situ chemical oxidation of organic contaminants. Sulfuric acid is commonly used to create an acidic condition needed for catalytic oxidation. Fenton's reaction often involves pressure buildup and precipitation of reaction products, which can cause safety hazards and diminish efficiency. We selected citric acid, a food-grade substance, as an acidifying agent to evaluate its efficiencies for organic contaminant removal in Fenton's reaction, and examined the impacts of using citric acid on the unwanted reaction products. A series of batch and column experiments were performed with varying H2O2 concentrations to decompose selected chlorinated ethylenes. Either dissolved iron from soil or iron sulfate salt was added to provide the iron catalyst in the batch tests. Batch experiments revealed that both citric and sulfuric acid systems achieved over 90% contaminant removal rates, and the presence of iron catalyst was essential for effective decontamination. Batch tests with citric acid showed no signs of pressure accumulation and solid precipitations, however the results suggested that an excessive usage of H2O2 relative to iron catalysts (Fe2+/H2O2<1/330) would result in lowering the efficiency of contaminant removal by iron chelation in the citric acid system. Column tests confirmed that citric acid could provide suitable acidic conditions to achieve higher than 55% contaminant removal rates.
芬顿试剂是一种过氧化氢和亚铁催化剂的溶液，用于对有机污染物进行原位化学氧化。硫酸通常用于营造催化氧化所需的酸性条件。芬顿反应常常涉及压力积聚和反应产物沉淀，这可能会导致安全隐患并降低效率。我们选择食品级物质柠檬酸作为酸化剂，以评估其在芬顿反应中去除有机污染物的效率，并研究使用柠檬酸对有害反应产物的影响。进行了一系列批次实验和柱实验，改变过氧化氢浓度以分解选定的氯代乙烯。在批次试验中，添加了来自土壤的溶解铁或硫酸铁盐以提供铁催化剂。批次实验表明，柠檬酸体系和硫酸体系的污染物去除率均超过90%，并且铁催化剂的存在对于有效去污至关重要。用柠檬酸进行的批次试验未显示压力积聚和固体沉淀的迹象，然而结果表明，相对于铁催化剂，过氧化氢的过量使用（Fe2+/H2O2<1/330）会导致柠檬酸体系中铁螯合去除污染物的效率降低。柱实验证实，柠檬酸可以提供合适的酸性条件，实现高于55%的污染物去除率。
