Synthesis and characterization of acrylamide and 2-hydroxyethyl methacrylate hydrogels for use in metal ion uptake studies

Two series of novel hydrogels consisting of different molar ratios of monomers were prepared for specialty applications as sorbents for some common metal ions. The hydrogels, comprising acrylamide (AAm) and 2-hydroxyethyl methacrylate (HEMA), were prepared in a 1:1 water–acetone solvent system using fixed concentration of the initiator system comprising ammonium persulphate (APS) and N,N,N,N-tetramethylethylene diamine (TEMED) and were in situ crosslinked using two different crosslinkers [ethylene glycol dimethacrylate (EGDMA) and N,N-methylene bisacrylamide (N,N-MBAAm)]. In the reaction scheme employed to prepare hydrogels, only [HEMA] was changed over five concentrations. Hydrogels were further functionalized by partial saponification with 0.5 M NaOH. The hydrogels were characterized by FTIR, SEM and water uptake, and were used as adsorbents for Cu2+, Fe2+ and Cr6+ ions. The metal ion sorption was observed in the order: Fe2+ > Cu2+ > Cr6+. From the results obtained we can tailor some hydrogels for specific metal ion separation and enrichment, as the selectivity for these ions is significantly different.