Application of novel betaine-type polyampholytes for recovery of transition metal ions

Novel linear and crosslinked betaine-type polyampholytes based on acrylic acid and ethyl 3-aminocrotonate have been synthesized by Michael addition reaction followed by radical polymerization. The polyampholytes used abbreviation as GRO-AA, GROEA-AA, GROGLY-AA (where GRO, GROEA and GROGLY are poly-betaines modified by ammonia, ethanolamine, and glycine) contain amine, hydroxyl, and hydroxyl groups in various combinations and are able to form complexes with transition metal ions. It is found. that the lengthening of alkyl groups in order GRO-AA, GROMA-AA, GRODMA-AA, GROISO-AA, GRODIISO-AA (where NA, DMA, ISO, DIISO are poly-betaines modified by methylamine, dimethylamine, isopropylamine, and diisopropylamine) leads to a decrease of the absorption capacity due to steric hindrance caused by alkyl group. It is shown, that binding ability of GRO-AA, GROEA-AA and GROGLY-AA was evaluted with 9 metal ions (Cu2+; Ni2+, Co2+, Fe3+, Pb2+, Cd2+, Al3+, Sr2+, Zn2+). The titration of linear polyampholytes by metal ions in aqueous solution leads to precipitation of polymer-metal complexes and simultaneously to a decrease of p H values of the solution owning to replacement of protons by metal ions. Absorption of metal ions by the poly-betaine hydrogel is accompanied by a gradual shrinking of gel specimen due to constant migration of metal ions deeply into the gel interior. Thus novel water-soluble and water swelling polymer betaines can potentially be applied for the purification of wastewater from metal ion pollutants