离子交换膜化学反应器去除饮用水中Cr(Ⅵ)的研究

New approach to removal of chromium(Ⅵ) from drinking water by ion exchange membrane chemoreactor

构建离子交换膜化学反应器,研究其在无外加电压作用下去除饮用水中Cr(Ⅵ)的效果。结果表明,当原水Cr(Ⅵ)初始浓度为0.019 2mmol/L,补偿溶液NaCl浓度为100mmol/L,流量为2.5mL/min时,给体池Cr(Ⅵ)分离去除率为86.2%。随着给体池共存离子浓度的增加,其对Cr(Ⅵ)交换竞争作用加强,给体池Cr(Ⅵ)分离去除率逐渐降低;在相同共存离子浓度条件下,3种共存离子对Cr(Ⅵ)分离效果的影响程度依次为SO24-、NO3-、Cl-。补偿溶液NaCl浓度由1mmol/L增加至100mmol/L时,Cr(Ⅵ)分离去除率基本不变,但是Don-nan分离12 h后化学反应池Cr(Ⅵ)浓度由0.001 5 mmol/L增加至0.016 0 mmol/L。Cr2O27-离子交换过程可用一级反应动力学方程描述,离子交换反应速率常数为0.014 2 min-1。加入10 mmol/L共存离子Cl-、NO3-和SO24-后,离子交换反应速率常数分别降低至0.013 5min-1、0.010 5 min-1和0.008 9 min-1。Cr(Ⅵ)在化学反应池中浓缩富集,离子交换26 h后化学反应池Cr(Ⅵ)浓度为0.069 8 mmol/L,可通过投加硫酸亚铁还原剂和碱液将其去除。

The paper is intended to introduce a new approach to removal of chromium（ VI ） from drinking water by ion exchange membrane chemoreactor developed by the present authors. For this purpose, we have investigated the possibility to remove Cr （VI） from drinking water with no electrical potential. The results of our experiments show that the separation efficiency of Cr（ Ⅵ） from the feeding chamber can be made to reach 86.2% under the conditions of the influent Cr（ VI ） being 0.019 2 mmol/L, the NaCl concentration of 100 mmol/L in the counterion solution, the flow rate of the feed and counterion solutions of 2.5 mL/min. With the concentration increase of the accompanying anions, the competitive effect of ion exchange for Cr（ Ⅵ ） and accompanying anions would be strengthened, with the separation of Cr（ Ⅵ ） from the feed chamber dropping gradually. Under the same experimental concentrations of the accompanying anions, it can be found that the influence of the three kinds of accompanying anions on the separation process of Cr （ Ⅵ ） from the feed chamber follows the order of SO4^2- 〉 NO3^- 〉 Cl^- . If the NaCI concentration increases from 1 mmol/L to 100 mmol/L in the counterion solution, no change is likely to be found with the separation of Cr（ Ⅵ ） from the feed chamber. However, the Cr（ Ⅵ ） concentration in the chemoreactor increases from 0.001 5 mmol/L to 0.016 0 mmol/L after 12 h of Donnan dialysis. It has also been discovered that the ion exchange process of Cr2O7^2- can also be described by the first order kinetic model, with the reaction rate constant of ion exchange being 0.014 2 min^- 1. Adding the accompanying anions Cl^- , NO3^- and SO4^2- of 10 mmol/L to the feed solution, the reaction rate constant of Cr（ VI ） ion exchange is likely to drop to 0.013 5 min^-1, 0.010 5 min^-1 and 0.008 9 min-1 respectively. The Cr（ Ⅵ ） tends to get concentrated in the chemoreactor and its concentration is likely to reach 0.069 8 mmol/L after 26 h of ion exchange. And, finally, it would be removed by addition of ferrous sulfate and alkali.