Industrial reverse osmosis (RO) membranes suffer from rapid degradation due to chlorine and have limited ability to reject specific ions. Novel lyotropic liquid crystal (LLC) membranes developed by the Gin Group consist of highly ordered porous systems with unique ion selectivity properties and higher levels of chlorine resistance. The project goal was to conclusively demonstrate that LLC membranes have ion selectivity properties distinctly different from current commercial membranes. Salt solutions of increasing ionic size and charge were tested with three commercial reverse osmosis and nanofiltration membranes to investigate whether ionic rejection in each membrane was primarily due to size exclusion, charge exclusion, or a combination of both mechanisms. Results were compared to previously gathered LLC membrane data. Results indicate that LLC membranes have a linear size exclusion mechanism not found in commercial membranes.