Novel Metal Ion Removal Method Using Protonated Hydrogel

Abstract

SummaryHydrogels based on copolymers of N‐[3‐(dimethylamino)propyl] acrylamide (DMAPAA), N,N‐dimethylacrylamide (DMAA) and N,N’‐methylenebis(acrylamide) (MBAA) were prepared as selective metal ion removal media. MBAA was used as a crosslinking agent for the DMAPAA and DMAA monomers. Polymerization mixtures were polymerized to create cylindrical shapes. The hydrogels were protonated when they were swelled in water and exhibited higher pH value inside than surrounding water because of Donnan effect. The pH value of the hydrogel could be changed by the concentration of DMAPAA monomers at the preparation. Metal ion removal experiments were carried out by swelling the hydrogels in metal ion aqueous solutions. The metal ions diffused in to the hydrogels to produce metal hydroxide in the hydrogel. The hydrogel with metal hydroxide in them were easily separated from the solution. The removal ratio of the metal increased with increasing the swelling time. The removal amount of the metal in the hydrogel was increased with the concentration of the metal ions in the solution. The selective removal of a certain metal ion from the mixed metal ion solutions was attained by controlling the pH value of the hydrogel. The results obtained here suggest the possibilities of the novel metal ion removal method replacing the coagulation and/or adsorption methods.