Improved Performance of Cation Exchange Membranes Coated with Chitosan

Abstract

Desalination with electrodialysis is used to obtain fresh water from saltwater brines. However, removal of the salt can be inefficient at low ionic concentrations because of the drastic increase of voltage required under those conditions, leading to limited adoption of this process. In this study, a commercially available cation exchange membrane was successfully coated with chitosan with different degrees of deacetylation. Higher degrees of deacetylation led to increased hydrophilicity of the membrane surfaces and possibly improved the wetting of the surface with the salt solutions. The base membrane and membranes coated with varying degrees of deacetylation were tested to determine how standard electrodialysis metrics such as limiting current density (LCD), ionic flux, and current utilization were affected to evaluate the effects of membrane hydrophilicity. Higher hydrophilicity improved the NaCl flux, current efficiency, and voltage requirements at low NaCl concentrations. Our strategy provides a simple method to control the membrane hydrophilicity, leading to improved performance.