均匀设计法优选低温等离子体改性阳离子交换膜耐氯氧化性能

Optimization of the Chlorine Oxidation Resistance of Low-temperature Plasma Modified Cation Exchange Membrane by Uniform Design

利用离子交换膜构建双膜三室电积生产金属钴是一种新的绿色湿法冶金工艺。目前市场上普通的非均相阳离子交换膜应用于该工艺时易被阳极生产的次氯酸氧化而造成膜性能下降,影响工艺效果,因此提高离子交换膜的耐氯性能是该工艺的核心技术。通过均匀试验设计,对阳离子交换膜进行低温等离子体改性,选用聚偏氟乙烯(PVDF)为接枝溶液,以期在膜表面产生高键能的含氟键官能团保护层,改善离子交换膜的耐氯氧化性能。利用活性氯浸泡法模拟实际应用中的强氧化环境,以氯离子泄漏率为表征指标,利用软件SPSS 23对均匀试验数据进行回归分析,得到实验数据显著性回归方程(R2=0.972);通过对方程系数进行t检验,挑选出影响最为显著的四个因素——等离子体放电电流强度、放电时长、接枝浓度、接枝时长;最后采用反演结合等值线图方法对方程进行寻优,预测得到的优化改性参数为:放电电流6A,放电时长5min,接枝液浓度8%,接枝时长60min。最终的验证试验表明,改性后离子交换膜的氯离子泄漏率较原膜降低了57.56%,膜的耐氯氧化性能大幅提高。

Using ion exchange membrane to build a double membrane three-compartment electrode is a new green hydrometallurgical process to produce metallic cobalt.Currently,ordinary heterogeneous cation exchange membrane used in the market on this process is easy to be oxidized by hypochlorous acid produced by the anode which results in the membrane performance degradation and affects the process effect.Therefore,improving the chlorine resistance of the ion exchange membrane is the key technology of the process.The cation-exchange membrane was modified by low temperature plasma and immersed into the polyvinylidene fluoride（PVDF）graft coating solution by homogeneous design experiment in this paper.It is expected to improve the resistance to chlorine oxidation of ion exchange membranes by for ming high-energy,fluorine-containing functional groups on the membrane surface protective layer.Strong oxidizing environment was simulated through active chlorine immersion method and the leakage rate of chloride ion was used as characterization indicator.The regression equation is obtained by utilizing software SPSS 23 to regression analyze the data of uniform design and R2=0.972,the equation is significant.Through the t test of the coefficient,the four most influential factors are selected：discharge current intensity of plasma,discharge time,grafting concentration and grafting duration.Finally,combining the inversion with the contour map method to optimize the equation.The final prediction parameters of optimal modified test are the discharge current of 6 A,the discharge time of 5 min,the grafting liquid concentration of 8%,and the grafting time of 60 min.Verification tests showed that chloride ion leakage rate of modified ion exchange membrane was 57.56%,higher than that of the original membrane,and the resistance to chlorine oxidation of the membrane was improved substantially.