Removal of fluoride by effectively using spent cation exchange resin

Spent strongly acidic cation exchange resin was effectively used for the removal of trace concentration of fluoride ions. For this purpose, the spent resins were pulverized into fine powders to be used together with inorganic coagulation agent consisting of iron, aluminum, and calcium in batchwise operation. Prior to this operation, the pulverized resins were loaded with Zr(IV) ions to develop adsorption sites which effectively and selectively adsorb fluoride ions over other coexisting anionic species such as chloride and sulfate ions. The fluoride uptake capacity of the Zr(IV)-loaded resin powder was negligibly affected by the coagulation agent. This combined process of adsorption and coagulation was proven to be used for at least six repeated cycles of adsorption followed by desorption using dilute alkaline solution without lowering the uptake capacity for fluoride ion. Quantitative removal of trace concentration of fluoride was successfully achieved from actual waste plating solution by this process.