Removal of heavy metal ions from aquatic solutions by membrane chromatography

Abstract

Polyvinylalcohol membranes were prepared by a solvent casting technique. Metal-complexation ligand, i.e. monochlorotriazinyl-dye Cibacron Blue F3GA was then attached. These membranes with a high water content of 119%, and containing 8.7 mmol Cibacron Blue F3GA/m(2) were used in the adsorption/stripping of some selected heavy metal ions [Cu(II), Hg(II), Pb(II) and Cd(II)] from aquatic solutions containing varying initial concentration of metal ions. Adsorption rates were very high, and equilibrium was achieved in about 10 min. The non-specific adsorption of heavy metal ions on the plain membranes was low [0.63 mmol/m(2) for Cu(II), 0.75 mmol/m(2) for Hg(II), 0.94 mmol/m(2) for Pb(II) and 1.22 mmol/m(2) for Cd(II)]. The maximum adsorptions of heavy metal ions onto the Cibacron Blue F3GA-attached affinity membranes for non-competitive conditions were 16.9 mmol/m(2) for Hg(II), 19.2 mmol/m(2) for Cu(II), 25.8 mmol/m(2) for Pb(II), 32.4 mmol/m(2) for Cd(II). The observed order in adsorption was found to be Cd(II) > Pb(II) > Cu(II) > Hg(II). Different behavior was observed for competitive adsorption. The order of affinity was Cu(II) > Cd(II) > Hg(II) > Pb(II). Regeneration of polyvinylalcohol membranes was done by using 0.1 M HNO3 in 30 min. Heavy metal ions could be repeatedly adsorbed and stripped without significant decrease in adsorption capacity. The experimental data of adsorption from solutions containing metal ions were found to correlate well with Langmuir isotherm equation