Competitive biosorption of Pb2+, Cu2+ and Zn2+ ions from aqueous solutions onto valonia tannin resin.

Competitive biosorption of Pb(2+), Cu(2+) and Zn(2+) on valonia tannin resin (VTR) present in binary and ternary mixture were compared with the single metal solution. The effects of the presence of one metal ion on the biosorption of the other metal ion were investigated in terms of equilibrium isotherm and biosorption yield. Experimental results indicated that the uptake capacity and biosorption yield of one metal ion were reduced by the presence of the other metal ion. The extent of adsorption capacity of the binary and ternary metal ions tested on VTR was low (18-80%) as compared to single metal ions. Comparisons between biosorption of Pb(2+), Cu(2+) and Zn(2+) ions by the biomass of VTR in the binary and ternary solution could lead to the conclusion that biosorption of Pb(2+) ions was preferential to that of Cu(2+) and Zn(2+) ions. VTR removed the target metal ions in the selectivity order of Pb(2+)>Cu(2+)>Zn(2+). The biosorption equilibrium data for the single metal solutions fitted the Langmuir model well. Results show that the pseudo-second-order equation provides the best correlation for the biosorption process in the single-ion system.