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

Polyhydroxyethylmethacrylate (PHEMA) microbeads carrying Cibacron Blue F3GA (22.3 mu mol 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 the se 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. Adso rption of these metal ions onto the Cibacron Blue F3GA-immobilised microbea ds from single solutions were 81.86; 75.62; 69.87; and 102.48 mu mol g(-1) for Pb(II), Cd(II), Cu(II) and Zn(II), respectively. When the heavy metal i ons competed tin the case of the adsorption from their mixture) the amounts of adsorption were 2.00 and 5.88 mg g(-1) fbr Cu(II) and Pb(II), respectiv ely. Under competitive conditions the affinity of Cd(II) and Zn(TT) was neg ligible. Therefore, it was of great importance to know the stability consta nts of Cibacron Blue F3GA-metal ion complexes. The formation constants of d ye-metal ion complexes have been investigated applying the method of Ruzic [18]. The calculated values of stability constants were 1.88 x 10(5) l mol( -1) for Pb(II)-dye; 3.10 x 10(5) l mol(-1) for Cu(II)-dye; 1.85 x 10(4) l m ol(-1) for Zn(II)-dye and 5.15 x 10(4) l mol(-1) for Cd(II)-dye complex. PH EMA microbeads carrying Cibacron Blue F3GA can be regenerated by washing wi th a solution of nitric acid (0.1 M). The maximum desorption ratio was as h igh as 99%. These PHEMA microbeads are suitable for repeated use for more t han three adsorption-desorption cycles without considerable loss of adsorpt ion capacity. (C) 2001 Elsevier Science B.V. All rights reserved.