Adsorption of heavy metal ions on polyhydroxyethylmethacrylate microbeads carrying Cibacron Blue F3GA

Abstract

Polyhydroxyethylmethacrylate (PHEMA) microbeads carrying Cibacron Blue F3GA (22.3 μmol g −1) were prepared for the removal of Pb(II), Cd(II), Cu(II) and Zn(II) ions from aqueous solutions containing different amount of these ions (10–400 mg l −1) and at different pH values (2.0–6.0). Adsorption rates were high, and adsorption equilibria were reached within 10 min. Adsorption of these metal ions onto the Cibacron Blue F3GA-immobilised microbeads from single solutions were 81.86; 75.62; 69.87; and 102.48 μmol g −1 for Pb(II), Cd(II), Cu(II) and Zn(II), respectively. When the heavy metal ions competed (in the case of the adsorption from their mixture) the amounts of adsorption were 2.00 and 5.88 mg g −1 for Cu(II) and Pb(II), respectively. Under competitive conditions the affinity of Cd(II) and Zn(II) was negligible. Therefore, it was of great importance to know the stability constants of Cibacron Blue F3GA-metal ion complexes. The formation constants of dye-metal ion complexes have been investigated applying the method of Ruzic [18]. The calculated values of stability constants were 1.88×10 5 l mol −1 for Pb(II)-dye; 3.10×10 5 l mol −1 for Cu(II)-dye; 1.85×10 4 l mol −1 for Zn(II)-dye and 5.15×10 4 l mol −1 for Cd(II)-dye complex. PHEMA microbeads carrying Cibacron Blue F3GA can be regenerated by washing with a solution of nitric acid (0.1 M). The maximum desorption ratio was as high as 99%. These PHEMA microbeads are suitable for repeated use for more than three adsorption–desorption cycles without considerable loss of adsorption capacity.