Crude metallothionein (MT) extracts from Scchizosaccharomyces pombe entrapped in sol-gels were investigated for the removal of heavy metals such as cadmium and zinc. The sol-gel provided a robust immobilization matrix for the protein extract. Adsorption and desorption isotherms were developed for both cadmium and zinc. Both metals were recovered from the sol-gel by desorption using a 1 M NaCl solution. The adsorption kinetic studies showed that cadmium and zinc adsorption followed the Langmuir isotherm. The distribution factors for cadmium and zinc were found to be 5.43 L/mg and 2.88 L/mg, respectively. Greater than 60% of Zn2+ was also removed using MT sol-gels. The experiments demonstrated that MT has a greater capacity for Cd than polyethyleneimine immobilized in the sol-gels. The adsorption capacity of MT was found to be 588.2 mg of cadmium and 434.8 mg of zinc per gram of immobilized MT, which is significantly higher than with nonbiological chelators such as polyethyleneimine or EDTA.

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