| Some biomass, such as bacteria, epiphyte and algae et al, can adsorb heavy metals strongly from wastewater. The biosorption using biomass is better than traditional chemical or physical methods in treatment of wastewater including heavy metals. The source of material acting as biosorbents is abundant very much, such as waste biomass including bacteria, fungus and algae et al produced in fermentation industry. It can display good economic and environmental benefit, e.g., decreasing producing cost of biosorbent and treatment cost of waste biomass, if they are used as biosorbentSaccharomyces cerevisiae producing in beer factory can adsorb many heavy metals. In this study, Cd2+ and Cu2+ are adsorbed by the free Saccharomyces cerevisiae cultured in lab. The dynamic process, the isotherm adsorption and effects of pre-treatment, pH, coexisting ions and biomass et al, on free Saccharomyces cerevisiae, are researched. Saccharomyces cerevisiae is immobiliazed in alginate. The mechanical characteristic is evaluated. The dynamic process, isotherm adsorption, factors of effect on biosorption and recycle on immobilised beads are also studied. Results are carried out as follows:The biomass capacity for Cd2+of is equal to sludge from medical industry but about three times compared with activated carbon as usual sorbent. It can be developed as a heavy metal removal agent more suitably. Some pre-treatment, such as HC1 or abrasive treatment, can greatly decrease the sorption performance for Saccharomyces cerevisiae.The sorption dynamics of dead free Saccharomyces cerevisiae is quick and independent on metabolic activity. The equilibrium biosorption time for Cd2+ and Cu2+ is 2 and 3 hours, respectively. The equations including Elovich equation, Parabola diffused equation, Double-invariable equation, Two-stage dynamic equation, and Langmuire dynamic equation, are fitted for simulating the dynamic process of Cd 2+and Cu2+biosorption, in which the best equation is Two-stage dynamic equation for Cd 2+and Elovich equation for Cu 2+, respectively, by the evaluation of their correlation coefficients.The pH value in solution can aifect the biosorption performance for Cd2+ and Cu2+. The maximum biosorption capacity of unit biomass is reached at pH 4, and the lower or higher pH will make against their biosorption. At optimum pH value and fixed Cd2+ and Cu2+ initial concentration , the total biosorption capacity and removal rate for Cd2+ and Cu2+ is increased ,but the biomass capacity is decreased contrarily, while the biomass is added gradually.At invariable biomass, the biosorption capacity of unit biomass will increase with the increasing of the Cd2+and Cu2+ initial concentration simultaneously. When the heavy metal initial concentration is lower 5 mg/L, the removal rate is rising with the increase of initial contrentration. But if it is higher 5 mg/L, the removal rate is degressive on contrary. All of these indicate that the adsorption sites on heavy metal on surface of Saccharomyces cerevisiae are limited. The isothermadsorption process of Cd2+ and Cu2+ biosorption by Saccharomyces cerevisiae can be simulated by Linear equation, Langmuir equation and Freundlich equation. But the Langmuir equation is best. Contrast to the maximum biomass capacity, 13.95mg/g for Cd and 7.67mg/g for Cu, from experiment, the variance of maximum biomass capacity, 13.96mg/g for Cd and 8. 01 for Cu, according to Langmuir equation, is 0.4% for Cd2+ and 4.03%for Cu2+, respectively.The biosorption of Cd2+ and Cu2+ by Saccharomyces cerevisiae is a physical-chemical process concentrating on chelation, which is affected by metals in solution. The coexisting ions K+, Ca2+, Na+ and Mg2+ have no obvious impact on biosorption of Cd2+ and Cu2+ by statistic analysis at low concentration. But when the concentration of any K+, Ca2+, Na+or Mg2+ ion is higher 5 mg/L, they can affect the removal of Cu2+and Cd2+. The impact sequence on biosorption is K+ |
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