Removal of chlorinated organic compounds from ground water by AOP in a bubble column photochemical reactor

氯化挥发性有机化合物(CVOCs)，如三氯乙烯(TCE)和四氯乙烯(PCE)，已被广泛用作金属脱脂和干洗的工业溶剂。由于地下储水罐泄漏和处置不当，许多土壤和地下水供应受到污染。在处理难降解和不可生物降解的化合物时，所谓的高级氧化工艺(AOPS)是有效的，因为它在臭氧和/或H_2O_2等复合氧化剂中使用紫外光产生极强的氧化剂--OH自由基。然而，在地下水中常见的碳酸盐、腐殖质和硝酸盐等自由基清除剂的存在下，AOPS的效率会降低。在本研究中，我们设计了一种新型的AOP反应器，通过减少OH自由基清除剂和紫外线吸收剂，可以提高UV/H_2O_2工艺的效率。这是通过构建UV-鼓泡塔反应器(UV-BCR)来实现的，在该反应器中，污染气体(经过气提或土壤蒸气提取)可以被吸收到无清除剂的环境中，在那里它可以进行氧化。然后，根据化学工程和光化学原理，结合数学模型，对UV-BCR的性能进行了分析和预测。

Chlorinated Volatile Organic Compounds(CVOCs), such as trichloroethylene(TCE) and tetrachloroethylene(PCE) have been widely used as industrial solvents for degreasing metals and for dry cleaning. Many soils and groundwater supplies have become contaminated as a result of leaking underground storage tanks and improper disposal practices. In the treatment of the refractory and non-biodegradable compounds the so-called Advanced Oxidation Processes(AOPs) are effective, because of the production of the extremely powerful oxidants -OH radicals, with the use of UV light in a combination win oxidants such as ozone and/or H_2O_2. The efficiency of AOPs is however reduced in the presence of radical scavengers, such as carbonates, humic material and nitrates usually found in groundwater. The AOPs for on-site destruction and detoxification of CVOC-contaminated groundwater has been needed.In this study, we designed the novel type AOP reactor that could improve the efficiency of the UV/H_2O_2 process due to the reduction of OH radical scavengers and UV absorbers. This was achieved by constructing the UV-bubble column reactor(UV-BCR) in which the polluted gas (after air stripping or soil vapor extraction) could be absorbed into the scavenger free environment where it can undergo the oxidation. Later, the performance of the UV-BCR was analyzed and predicted based on the chemical engineering and photochemical principles coupled with the mathematical modeling.