Abstract: Water, as an important natural resource, is an indispensable resource for human life and production. Industrial water usage accounts for a large proportion of the total water consumption in the country, with the steel industry being one of the water-intensive industrial processes. The production of steel from raw materials requires a large amount of water, so the full utilization of the wastewater generated in the steel industry process is of great practical significance. For the nanofiltration concentrated wastewater generated in the steelmaking process, selective electrodialysis can not only greatly remove Cl- to obtain water for slag flushing, but obtain a high-purity and concentrated NaCl solution. In this study, selective anion and cation exchange membranes are replaced in the membrane stack, with the anion exchange membrane playing a key role in the system by separating Cl- and SO42-. The effects of different operating modes, voltages, volume ratios, and temperatures on the separation efficiency of Cl- and SO42- are explored, and pilot-scale long-term verification experiments are conducted. The experimental results indicate that constant voltage operation mode is more suitable for deep separation of Cl- and stable membrane operation. Under different voltages, membranes exhibit a high SO42- rejection rate, exceeding 97%, and reduces Cl- concentration below 1000 mg/L in the diluted chamber, resulting in a mass ratio of SO42- to Cl- greater than 10. Pilot-scale selective electrodialysis operated under 20 V at room temperature for 2 months demonstrates that the selective electrodialysis method has strong adaptability to fluctuations in wastewater concentration. It can effectively remove Cl- ions, stabilizing the concentration of Cl- in the desalination chamber to below 1000 mg/L. The mass ratio of SO42- to Cl- exceeds 10 by far, achieving a sulfate retention rate of over 94.5%. The energy consumption remains relatively stable, ranging from 0.254 to 0.278 kW?h/kg NaCl.

Key words: waste liquid of in iron and steel industry, selective electrodialysis, selective separation of monovalent anions, pilot-scale long-term operation

摘要： 钢铁工业是耗水大户，有效资源化利用钢铁生产各个环节产生的废水有助于减少水资源的消耗。针对钢铁流程产生的纳滤浓缩废液，本工作利用选择性电渗析技术，探究了不同操作模式、外加电压、体积比及温度对废液中致腐蚀离子Cl-与SO42-分离过程的影响，并进行了中试长周期验证试验。小试实验结果表明，恒压操作模式更适用于Cl-与SO42-的深度分离和膜的稳定运行，不同电压下SO42-截留率较高，可达97%以上，同时淡室中Cl-浓度下降至1000 mg/L以下，SO42-与Cl-质量比大于10。中试验证实验在室温、20 V电压下运行2个月，实验发现选择性电渗析对浓度波动的废水原料具有较强的适应性，同时可稳定脱除Cl-，使淡室中Cl-浓度下降至1000 mg/L以下，SO42-与Cl-的质量比远大于10，SO42-截留率可达94.5%以上，单位能耗变化较小，维持在0.254~0.278 kW?h/kg NaCl。

关键词: 钢铁工业废水, 选择性电渗析, 单价阴离子选择性分离, 中试长周期运行