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首页> 外文期刊>Separation and Purification Technology >Indirect electrochemical reduction of perchlorate and nitrate in dilute aqueous solutions at the Ti-water interface
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Indirect electrochemical reduction of perchlorate and nitrate in dilute aqueous solutions at the Ti-water interface

机译：在Ti-水界面间接稀释高浓度水溶液中的高氯酸盐和硝酸盐

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Perchlorate and nitrate are contemporary contaminants in drinking water. In most perchlorate containing surface or ground waters, nitrate was also present at significant concentrations. The present study investigated the removal of perchlorate and nitrate at the Ti-water interface by indirect electrochemical reduction process. Results indicated that perchlorate and nitrate could be reduced readily at the surface of a Ti anode simultaneously. Upon the application of an anodic current at the Ti electrode, Ti species such as Ti(III) or Ti(II) were generated. These multivalent Ti species are strong reducing agent that can reduce perchlorate and nitrate ion. The dominant end product of the indirect electrochemical reduction was chloride or nitrite. However, when these two anions were co-existing, the nitrite concentration was negligible. The reduction for both anions followed typical Langmuir-Hinshelwood kinetics; zero-order and first-order reaction at high and low concentrations, respectively. The first-order reaction rate constant was in the range of 10~ 5 s~(-1). Perchlorate and nitrate at initial concentration of 200 and 1000 ppm individually were reduced to final concentration of <20 and <200 ppb, respectively, over a short reaction time of 6-8 h. The reaction mechanism was studied with the aid of surface analysis of the solid end products (e.g., TiO2 particles) remaining on the Ti electrode using XPS and SEM/EDX. It was observed that doping of chlorine and nitrogen atoms onto the solid TiO2 particles contributed partially to imbalance of the total Cl and N mass in the system. Additionally, formation of volatile chlorine and hypochlorite species brought mass imbalance to total chlorine.
机译：高氯酸盐和硝酸盐是饮用水中的当代污染物。在大多数含高氯酸盐的地表水或地下水中，硝酸盐的含量也很高。本研究研究了通过间接电化学还原工艺去除钛-水界面处的高氯酸盐和硝酸盐。结果表明，在钛阳极的表面上，高氯酸盐和硝酸盐可以很容易地被还原。在Ti电极上施加阳极电流后，会生成Ti物种，例如Ti（III）或Ti（II）。这些多价钛物质是强还原剂，可以还原高氯酸根和硝酸根离子。间接电化学还原的主要最终产物是氯化物或亚硝酸盐。但是，当这两种阴离子共存时，亚硝酸盐的浓度可以忽略不计。两种阴离子的还原都遵循典型的Langmuir-Hinshelwood动力学。在高浓度和低浓度时分别发生零级和一级反应。一阶反应速率常数在10〜5 s〜（-1）范围内。在6-8小时的短时间内，分别将初始浓度为200和1000 ppm的高氯酸盐和硝酸盐分别降低至最终浓度<20和<200 ppb。借助XPS和SEM / EDX对残留在Ti电极上的固体最终产物（例如TiO2颗粒）进行了表面分析，研究了反应机理。观察到，将氯和氮原子掺杂到固体TiO2颗粒上部分地导致了系统中总Cl和N质量的不平衡。另外，挥发性氯和次氯酸盐物质的形成使总氯质量失衡。

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