Some characteristics of Ag＋ biosorption and bioreduction by Lactobacillus sp. A09 biomass were reported. The optimum pH value of Ag＋ biosorption by strain A09 was 4.5. Temperature(6～ 50 ℃ ) did not affect the biosorption. The biosorptive efficiency (91％ ) and biosorptive capacity(Ag＋ 125 mg· g－ 1 dry weight biomass ) were achieved under the conditions of Ag＋ 100 mg· L－ 1, biomass 800 mg· L－ 1, pH 4.5 and 30 ℃ for 24 h contact. TEM analysis indicated that A09 biomass could reduce Ag＋ to Ag0 as Ag particles on the surface of cells. IR spectroscopy showed that － CO2－ and － HN－ C=O on the surface of cells may involve in the precession for adsorbing Ag＋ .
The strain XP05 with relatively strong ability of absorbing Pt4+ was screened from bacterial strains of different sources.and was identified as Citrobacter freudii.The properties of Pt4+ adsorption by dead XP05 biomass were investigated.The optimum pH value of Pt4+ biosorption by the dead XP05 biomass was 2.0. The biosorption was a rapid process,reaching 78.1% of the maximum biosorptive capacity at the first 8 minutes and equilibrium after 60 min of the adsorption.The biosorptive capacity of the biomass rose with increasing temperature in the rage of 10～75℃.The content of the biomass and Pt4+ initial concentration in the solution also affected the biosorption process.The biosorptive capacity with 64.4 mg/gwas achieved under the conditions of 225 Pt4+ mg/L,2g biomass/L,pH 2.0 and 30℃ for 60 minutes of the adsorption.During the process of Pt4+ biosorption by dead XP05 biomass,the pH value of the solution was not changed.Cu2+?Ca2+?Co2+?Au3+?Pb2+ and Al3+ inhibited the biosorption.The adsorptive efficiency and capacity of Pt4+ by the biomass from the treatment solution containing 111.76 mg Pt4+/L of waste platinum catalyst were 61.3% and 30.65 mg/g.respectively.
