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Electrochemical nitrate removal with simultaneous magnesium recovery from a mimicked RO brine assisted by in situ chloride ions.
Journal of Hazardous Materials ( IF 12.2 ) Pub Date : 2020-01-13 , DOI: 10.1016/j.jhazmat.2020.122085
Xuejiao Ma 1 , Miao Li 2 , Chuanping Feng 3 , Zhen He 4
Affiliation  

Electrochemical reduction is effective to remove nitrate but byproducts such as ammonia and nitrite would need chloride addition for indirect oxidation to nitrogen gas. Herein, electrochemical nitrate reduction was investigated to remove nitrate from a mimicked reverse osmosis (RO) brine containing chloride that eliminates the need for external chloride addition. Both Cu/Zn and Ti nano cathodes exhibited the best performance of nitrate removal with >97 % removal in either Na2SO4 or NaCl electrolyte, although with different products. Complete nitrate reduction to nitrogen gas was realized in the RO brine whose complex composition decreased the electrode efficiency, for example from 71.4 ± 0.2%-49.4 ± 0.3 % with the Cu/Zn cathode after 5 cycles of operation. Magnesium was recovered at the same time of nitrate removal and the purity of Mg(II) could reach 96.8 ± 2.0 % after proper pH pre-treatment. In a preliminary adsorption study, a key byproduct - chlorate was reduced by 49.8 ± 2.7 % after 3-h adsorption by 100 g L-1 activated carbon. These results have demonstrated the simultaneous electrochemical nitrate removal and resource recovery from a complex water like a RO brine and provided new information such as byproduct management and electrode deterioration.

中文翻译:

在原位氯离子辅助下,从模拟的RO盐水中去除硝酸盐中的电化学硝酸盐并同时回收镁。

电化学还原可有效去除硝酸盐,但副产品(例如氨和亚硝酸盐)需要添加氯化物才能间接氧化为氮气。本文中,研究了硝酸盐的电化学还原,以从含有氯化物的模拟反渗透(RO)盐水中去除硝酸盐,从而消除了添加外部氯化物的需要。Cu / Zn和Ti纳米阴极均显示出最佳的硝酸盐去除性能,在Na2SO4或NaCl电解质中的去除率> 97%,尽管产品不同。在RO盐水中,硝酸盐完全还原为氮气,其复杂的组成降低了电极效率,例如,经过5个操作循环后,使用Cu / Zn阴极电极效率从71.4±0.2%-49.4±0.3%降低。在适当的pH预处理后,同时去除了硝酸盐的同时回收了镁,Mg(II)的纯度可达到96.8±2.0%。在初步的吸附研究中,用100 g L-1活性炭吸附3小时后,关键副产物氯酸盐减少了49.8±2.7%。这些结果证明了从复杂的水中(如RO盐水)中电化学硝酸盐的同时去除和资源回收,并提供了新的信息,例如副产物管理和电极劣化。
更新日期:2020-01-13
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