Lonic resins come in two types: anion (negatively charged ions) and cation (positively charged ions). Anion resins react with negatively charged ions such as sulfate .cation resins react with positively charged ions such as calcium ions and magnesium ions.ion resins resemble small beads and are placed in tanks that raw water is passed through. Resin beds are usually several feet thick. Demineralization is a process that passes raw water through both aninon and cation exchange resins. Effluent from this process is essentially pure water