College of Environmental Science and Engineering, Hunan University, Changsha, 410082, PR China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha, 410082, PR China.
Key Laboratory of Water Pollution Control Technology, Hunan Research Academy of Environmental Sciences, Changsha, 410004, PR China.
Water Res. 2019 Jun 15;157:191-200. doi: 10.1016/j.watres.2019.03.078. Epub 2019 Mar 29.
In this study, indirect electrochemical reduction with zero-valent titanium (ZVT) as anode successfully achieved the selective nitrate removal from simulated groundwater. The maximum nitrate removal efficiency and N selectivity reached to 83.4% and 78.5% after 12 h, respectively. Experimental results demonstrated that the gaseous by-products (NO and NO) were negligible and the nitrate reduction process could be well depicted by pseudo-first-order kinetic model. Decreasing the pH value of electrolyte was favorable to electrical energy utilization efficiency and nitrate removal. The chloride ultimately showed inhibitory effects on electrochemical reduction of nitrate. During the electrochemical reaction, the ZVT lost electrons to generate the reducing agents (Ti and Ti), which could afford electrons for nitrate reduction and form the solid by-products TiOClN. A 2-stage strategy, indirect electrochemical reduction + hypochlorite treatment (pre-reduction + post-oxidation), was developed to completely remove nitrate and the long-term performance of nitrate reduction was comprehensively evaluated. The effluent nitrate steadily kept at 8.8 mg N/L during 120 h continuous operation when the influent nitrate concentration was 25.9 mg N/L. Simultaneously, nitrite concentration was lower than 0.01 mg N/L, and ammonium and Ti ions were not detected in the effluent.
在这项研究中，采用零价钛（ZVT）作为阳极的间接电化学还原成功地实现了模拟地下水中硝酸盐的选择性去除。经过 12 小时，硝酸盐去除效率和 N 选择性最高分别达到 83.4%和 78.5%。实验结果表明，气态副产物（NO 和 NO）可忽略不计，硝酸盐还原过程可用准一级动力学模型很好地描述。降低电解质的 pH 值有利于电能利用效率和硝酸盐去除。氯离子最终对硝酸盐的电化学还原表现出抑制作用。在电化学反应过程中，ZVT 失去电子生成还原剂（Ti 和 Ti），这些还原剂可以为硝酸盐还原提供电子，并形成固体副产物 TiOClN。开发了一种两阶段策略，即间接电化学还原+次氯酸盐处理（预还原+后氧化），以完全去除硝酸盐，并对硝酸盐还原的长期性能进行了全面评估。当进水硝酸盐浓度为 25.9mgN/L 时，在 120 小时的连续运行中，出水硝酸盐稳定保持在 8.8mgN/L 以下，同时，亚硝酸盐浓度低于 0.01mgN/L，出水中未检出铵离子和 Ti 离子。
