Application of acrylate gel having poly(ethylene glycol) side chains to recovery of gold from hydrochloric acid solutions

Hydrogel beads were synthesized from radical polymerization of poly(ethylene glycol) monoacrylate (PEGA) and poly(ethylene glycol) diacrylate (PEGDA), and applied for the recovery of Au(III) from hydrochloric acid solutions. The acrylate hydrogels had poly(ethylene glycol) units as side chain, and retained water as much as 70% of their dry-weight. Due to a strong interaction between Au(III) and poly(ethylene glycol) units in the hydrogel structure, the metal was adsorbed into the hydrogel beads with the percent adsorption of more than 90% irrespective of the acid concentration. The adsorption was well correlated with the Freundlich isotherm equation, and the adsorbed amount of Au(III) reached as high as 121 mg-Au/g-dry gel at maximum. Moreover, selective separation of Au(III) was attained since other heavy metals such as Cu(II), Zn(II), Fe(III) and Al(III) were excluded from the hydrogel beads. The present hydrogel beads were preferable in treating dilute acid solutions to avoid the hydrolysis of ester group in the gel structure at high acidities.