Unravelling the fouling behavior of cation exchange membrane (CEM) by waste salt containing decyltrimethylammonium chloride during membrane electrolysis

With the implementation of the zero liquid discharge (ZLD) process for industrial wastewater treatment, the generation of large quantities of industrial waste salts has become a growing concern. The presence of organic contaminants, however, limits the reuse of NaCl waste salts for ion exchange membrane electrolysis, and the fouling behavior during the electrolysis process needs to be investigated. In this study, decyltrimethylammonium chloride (DTAC)-containing salt was employed as a model industrial waste salt to evaluate the fouling of cation exchange membrane (CEM) during ion exchange membrane electrolysis involving waste salt reuse. Additionally, this study examined the effect of membrane cleaning on the properties of fouled CEMs. Results indicated that higher DTAC concentrations in the feed solution significantly exacerbated CEM fouling, forming a dense DTAC fouling layer on the membrane surface. This layer led to a marked increase in cell voltage and resistance. Electrochemical impedance spectroscopy (EIS) analysis further revealed that the DTAC fouling layer could hinder or completely obstruct the transmembrane migration of ions, particularly at elevated DTAC concentrations. Moreover, membrane cleaning proved effective in mitigating contamination during the electrolysis process. Notably, NaOH cleaning demonstrated superior performance compared to water cleaning, effectively removing most DTAC from fouled CEMs. This study provides valuable insights into organic fouling mechanisms and membrane cleaning strategies for the reuse of NaCl waste salts in ion exchange membrane electrolysis.