Use of biopolymers and acrylamide-based hydrogels for sorption of Cu2+, Fe2+ and Cr6+ ions from their aqueous solutions

Hydrogels of two important biopolymers (dextrin and starch) with different acrylamide monomers viz., acrylamide, N-isopropyl acrylamide and 2-acrylamido-2-methylpropanesulfonic acid and crosslinked with N,N-methylene bisacrylamide were used as sorbents for three transition metal ions. These hydrogels have high water absorption capacity and also have ion exchange groups. The hydrogels have been used to extract Fe2+, Cu2+ and Cu6+ ions from their aqueous solutions. Sorption of these ions has been studied as a function of nature of backbone polymer and crosslinker concentration used in the synthesis of these hydrogels. Effect of functionalization of hydrogels by partial hydrolysis with 0.5 M NaOH on metal ion uptake has also been studied, and it results in appreciable uptake of Cu2+ ions and Fe2+ ions but in total rejection of Cr6+ ions. These results are of interest for the development of hydrogel-based technologies for water purification and metal ions separation and enrichment.