An adsorptive desalination and disinfection method for salt water includes providing a volume of salt water to be desalinated and disinfected; passing the volume through a first filter cartridge assembly configured to disinfect and remove cations from the volume, wherein the first filter cartridge assembly comprises an anionic sorbent comprising the polymer impregnated iron (III)-tannate amphoteric sorbent configured to exhibit anionic behavior, and passing the volume through a second filter cartridge assembly configured to disinfect and remove anions from the volume, wherein the second filter cartridge assembly comprises a cationic sorbent comprising the polymer impregnated iron (III)-tannate amphoteric sorbent configured to exhibit cationic behavior. The volume has particulate removed through settling and filtering prior to passing through the filter cartridges in embodiments. The method also includes passing the volume through a third filter cartridge assembly configured to remove any additional trace metal ions and further disinfect the volume.