On the biosorption effect of lead ions on the nonliving baker's yeast from solution

The given paper is to present our study on the effect of biosorption of lead ions on the nonliving baker's yeast with the adsorption conditions and the biosorption mechanism analyzed by using such instruments as AAS(atomic absorption spectra),SEM(scanning electron microscope)/EDS(energy dispersive analysis system of X-ray).The results of our study show that the adsorptive quantity should be defined as functions of the solution pH,contact time,baker's yeast concentration,salt concentration and the initial concentration of lead ions.Our experiments also indicate that the best adsorption parameters and quantitative analysis of Pb2+ by dried waste beer yeast revealed that at optimum conditions(pH = 4.0-5.5;Pb2+,the initial concentration = 1.0 mmol/L;biomass dose = 4.0 g/L,T=30 ℃,with the highest metal uptake values being 45.07 mg/g and 92.45%.The kinetic analysis of the different temperatures proves that the biosorption process of baker's yeast to Pb2+ should be a fast one and the low temperature tends to slow down the sorption equilibrium.Furthermore,our experimental results come into perfect conformity with the Langmuir isotherms at different temperatures,by which the maximum biosorption capacities of lead ions onto baker's yeast prove to be 71.53 mg/g,72.10 mg/g and 75.82 mg/g at 10 ℃,20 ℃ and 30 ℃,respectively.And,finally,SEM/EDS analysis found that baker's yeast cell surface tends to absorb large amounts of Pb2+ covered with a layer of particles containing Pb2+.Such a phenomenon would become serious with the increase of initial Pb2+ ions concentration,which proves that,as a consequence,nonliving baker's yeast turns to have a high biosorption capacity for Pb2+ ions.