Zeppilli Marco, Yaqoubi Hafsa, Dell'Armi Edoardo, Lai Agnese, Belfaquir Mustapha, Lorini Laura, Papini Marco Petrangeli
Department of Chemistry, University of Rome Sapienza, Piazzale Aldo Moro 5, Rome, 00185, Italy.
Department of Chemistry, Ibn Tofail University, Laboratory of Advanced Material and Process Engineering, Campus Universitaire, BP. 242, Kenitra, Morocco.
Environ Sci Ecotechnol. 2023 Jul 26;17:100309. doi: 10.1016/j.ese.2023.100309. eCollection 2024 Jan.
Electro-bioremediation offers a promising approach for eliminating persistent pollutants from groundwater since allows the stimulation of biological dechlorinating activity, utilizing renewable electricity for process operation and avoiding the injection of chemicals into aquifers. In this study, a two-chamber microbial electrolysis cell has been utilized to achieve both reductive and oxidative degradation of tetrachloroethane (TeCA). By polarizing the graphite granules cathodic chamber at -650 mV vs the standard hydrogen electrode and employing a mixed metal oxide (MMO) counter electrode for oxygen production, the reductive and oxidative environment necessary for TeCA removal has been established. Continuous experiments were conducted using two feeding solutions: an optimized mineral medium for dechlorinating microorganisms, and synthetic groundwater containing sulphate and nitrate anions to investigate potential side reactions. The bioelectrochemical process efficiently reduced TeCA to a mixture of -dichloroethylene, vinyl chloride, and ethylene, which were subsequently oxidized in the anodic chamber with removal efficiencies of 37 ± 2%, 100 ± 4%, and 100 ± 5%, respectively. The introduction of synthetic groundwater with nitrate and sulphate stimulated reductions in these ions in the cathodic chamber, leading to a 17% decrease in the reductive dechlorination rate and the appearance of other chlorinated by-products, including -dichloroethylene and 1,2-dichloroethane (1,2-DCA), in the cathode effluent. Notably, despite the lower reductive dechlorination rate during synthetic groundwater operation, aerobic dechlorinating microorganisms within the anodic chamber completely removed VC and 1,2-DCA. This study represents the first demonstration of a sequential reductive and oxidative bioelectrochemical process for TeCA mineralization in a synthetic solution simulating contaminated groundwater.
电生物修复为从地下水中去除持久性污染物提供了一种很有前景的方法，因为它可以刺激生物脱氯活性，利用可再生电力进行工艺操作，并避免向含水层中注入化学物质。在本研究中，采用了双室微生物电解池来实现四氯乙烷（TeCA）的还原和氧化降解。通过将石墨颗粒阴极室相对于标准氢电极极化至-650 mV，并采用混合金属氧化物（MMO）对电极来产生氧气，建立了去除TeCA所需的还原和氧化环境。使用两种进料溶液进行了连续实验：一种是用于脱氯微生物的优化矿物培养基，另一种是含有硫酸根和硝酸根阴离子的合成地下水，以研究潜在的副反应。生物电化学过程有效地将TeCA还原为顺式二氯乙烯、氯乙烯和乙烯的混合物，随后它们在阳极室中被氧化，去除效率分别为37±2%、100±4%和100±5%。引入含有硝酸根和硫酸根的合成地下水刺激了阴极室中这些离子的还原，导致还原脱氯速率降低17%，并在阴极流出物中出现了其他含氯副产物，包括顺式二氯乙烯和1,2-二氯乙烷（1,2-DCA）。值得注意的是，尽管在合成地下水运行期间还原脱氯速率较低，但阳极室内的好氧脱氯微生物完全去除了VC和1,2-DCA。本研究首次证明了在模拟受污染地下水的合成溶液中，TeCA矿化的顺序还原和氧化生物电化学过程。
