Common methods in capacitive deionization (CDI) for selective removal are derived from membrane separation mechanism or size-based intercalation mechanism. In this study, based on the electrochemical activity of bismuth (Bi) material to chloride ions (Cl⁻) and inertness to sulfate ions (SO₄²⁻), Bi electrode is used as anode in CDI to selectively remove Cl⁻ ions from mixed NaCl and Na₂SO₄ solution. Through the reaction with Bi, Cl⁻ ions are stored in bismuth oxychloride (BiOCl). Results show that Bi electrode exhibits selectivity for Cl⁻ over SO₄²⁻ with a selectivity coefficient of more than 1.5 in solutions with mole ratio of Cl⁻ to SO₄²⁻ larger than 1. The selectivity coefficient is greatly dependent on the mole ratio of Cl⁻ to SO₄²⁻ and increases when the ratio rises. In solution with a fixed Cl⁻/ SO₄²⁻ mole ratio, higher applied voltage and prolonged time result in higher Cl⁻ ion removal capacity, but not necessarily better selectivity. The highest selectivity coefficient of 4.5 is achieved in 8.5 mM NaCl and 1.1 mM Na₂SO₄ mixed solution at voltage of 1.6 and 2.0 V after charging for 1 h. These results demonstrate that Bi electrode can selectively remove Cl⁻ ions from mixed solution with a relatively lower concentration of SO₄²⁻ ions, which provides new insights into ion separation and selective removal by CDI.

选择性去除的电容性去离子（CDI）的常用方法是从膜分离机制或基于尺寸的插层机制中衍生出来的。在这项研究中，基于铋的电化学活性（Bi）的材料，以氯离子（CL ^- ）和惰性至硫酸根离子（SO ₄ ^2- ），铋电极被用作阳极CDI以选择性地除去Cl ^-从混合离子NaCl和Na ₂ SO ₄溶液。通过与铋，氯反应^-离子存储在氯氧化铋（的BiOCl）。结果表明，双电极，用于氯展品选择性^-在SO ₄ ^2-具有大于1.5的有Cl的摩尔比的解决方案的选择性系数^-以SO ₄ ^2-大于1的选择性系数是极大地依赖于氯的摩尔比^-为SO ₄ ^2-和当该比率上升增大。在具有固定Cl溶液^- / SO ₄ ^2-的摩尔比，在更高的氯更高的施加电压和时间的延长结果^-离子清除能力，但不一定更好的选择性。在8.5 mM NaCl和1.1 mM Na ₂ SO _4中达到4.5的最高选择性系数充电1小时后，混合溶液的电压为1.6和2.0V。这些结果表明，铋电极可以选择性除去Cl ^-从混合溶液用SO的相对较低的浓度离子₄ ^2-离子，它提供了新的见解通过CDI离子分离和选择性去除。