Abstract: Saccharomyces cerevisiae waste biomass procured from the beer brewery, was used as the adsorbent for Pd²⁺. The physico-chemical properties of adsorbing Pd²⁺by the biomass were investigated. The results indicate that the adsorption of Pd²⁺by the biomass was affected by adsorption time, pHvalue, adsorbent concentration and Pd²⁺initial concentration in the solution. The biosorption is a rapid process, the capacity of the adsorption after 45 min reached the maximum, and 92.0% of the maximal capacity was obtained at the first 3 min of the adsorption. The optimum pH value was 3.5. In the range of 5-60 ℃, the biosorption was not affected by temperature. The isotherMOf the adsorption of Pd²⁺by the biomass followed Langmuir and Freundich models under the conditions of initial Pd²⁺mass concentration(30-300 mg/L) and biomass mass concentration(2g/L). Biosorptive capacity of 94.5 mg/g was obtained under the conditions of pH=3.5, mass ratio of an initial Pd²⁺to biomass being 0.2 and at 30 ℃ for 60 min of the adsorption. Palladium was removed from the treated solution of waste palladium catalyst with 32.2 mg/g of biosorptive capacity. The results of X-ray photoelectron spectrometer analysis indicate that the biomass could adsorb Pd²⁺ions from the aqueous solution. The observation in the transmission electron microscope shows that without the extra-electron donor, the waste biomass of Saccharomyces cerevisiae could adsorb and reduce Pd²⁺ions in the solution to microbial Pd⁰particles, which could become well-formed palladium crystals, as well as Pd²⁺ions adsorbed on the γ-Al₂O₃could be reduced to Pd⁰particles by the biomass.

Key words: Saccharomyces cerevisiae waste biomass, Palladium, Biosorption, Enzyme-independent bioreduction