Quaternized poly(1-vinylimidazole) hydrogel for anion adsorption

Poly(1-vinylimidazole) (PVIm) hydrogels were synthesized through free radical polymerization/crosslinking of 1-vinylimidazole (VIm) in aqueous solutions with azobisisobutyronitrile (AIBN) used as the initiator and N,N′-methylenebisacrylamide (MBAAm) as the crosslinking agent. To quaternize PVIm, dimethylsulfate was used as the methylating agent. Pristine and quaternized PVIm hydrogels were characterized by spectroscopic techniques. Finally, ground hydrogels were used in anion adsorption. The amount of anion adsorbed (in m-eq. anion/g polymer) and adsorption% was determined for fluoride, bromide, nitrite, nitrate, phosphate and sulfate anions using ion chromatography techniques. The amount of phosphate adsorbed on QPVIm hydrogel was the highest and the amount of fluoride adsorbed on QPVIm hydrogel was the lowest. Ion chromatographic study showed that when 1/1 mol ratio of anion to polymer (on a repeating unit basis) was used, 24.7 % of fluoride, 60.6 % of nitrite, 61.6 % of bromide, 63.0 % of nitrate, 99.3 % of phosphate and 98.2 % of sulfate were removed from the medium.