Mercury removal from synthetic solutions using poly(2-hydroxyethylmethacrylate) gel beads modified with poly(ethyleneimine)

Abstract

In this study, the Hg 2+ adsorption–desorption properties of poly(ethyleneimine) (PEI)-attached poly(2-hydroxyethylmethacrylate) (PHEMA) beads were investigated. Spherical PHEMA beads with an average size of 150–200 μm were obtained by suspension polymerization of 2-hydroxyethylmethacrylate conducted in an aqueous dispersion medium. Owing to the reasonably rough character of the bead surface, PHEMA beads had a specific surface area of 14.8 m 2/g. PEI chains could be covalently attached onto the PHEMA beads with equilibrium binding capacities up to 50 mg PEI/g beads. PEI-attached PHEMA beads were utilized as adsorbent in the adsorption–desorption of Hg 2+ ions from synthetic solutions. The adsorption process was fast; 90% of adsorption occurred within 45 min and equilibrium was reached at around 1 h. The maximum Hg 2+ adsorption capacity obtained was 1.67 mmol/g at a pH of about pH 5.0. Adsorption behavior can be described at least approximately by the Langmuir equation. The metal-chelating beads can be easily regenerated by 0.1 M HNO 3 with higher effectiveness. Adsorption of heavy metal ions from artificial wastewater was also studied. The adsorption capacities were 1.32 mmol/g for Hg 2+, 0.34 mmol/g for Ni 2+ and 0.42 mmol/g for Cu 2+.