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Bacterial Adsorption Of Pt (4 +)

Posted on:2003-10-23Degree:MasterType:Thesis
Country:ChinaCandidate:H B HuFull Text:PDF
GTID:2190360092971195Subject:Microbiology
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The biosorption process of metals by microbe is a physico-chemical interaction between metals and the charged surface groups of micro-organisms, including living or dead microbial cells and derived microbial products. It has been known for a few decades and has received more attention in recent years because of its potential application in environmental prelection and recovery of precious metals. The recovery of precious metals using the ability of adsorbing metals of microorganisms has been considered as an economical alternative of conventional technologies of metal recovery from industrial solution. The screen and identification of strain XP05, some characteristics of Pt4+ biosorption by the dead XP05 biomass and its immobilized biomass as biosorbent were reported in this thesis.The strain XP05, showed relatively strong ability of absorbing Pt4+, was screened from bacterial strains of different sources, and identified as Citrobacter freudii.Biosorptive capacities of Pt4+ by XP05 biomass harvested at various culture ages were compared. The results indicated that XP05 biomass cultured for 24h had relatively strong absorptive ability, and could be gotten in most biomass.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 is a rapid process, within the first 8min, reaching 78.1% of the maximum biosorptive capacity and equilibrium after 60 min. The biosorptive capacity of XP05 rose with increasing temperature in the rage of 10~75癈. The content of the biomass and Pt4+ initial concentration in the solution also affected the biosorption process. The biosorptive capacity reached 64.4mg/g under the conditions of 225 Pt4+mg/L, 2.0g biomass/L, pH 2.0 and 30癈 for 60 min, the process of biosorption fitted to Langmiur model of adsorption isotherm. During the process of Pt4+biosorption by the XP05 biomass, the pH value of the solutiondid not change. Cu2+, Ca2+, Co2+, Au3+, Pb2+and Al3+could inhibit the biosorption of Pt4+ by XP05 biomass. Platinum was adsorbed from the treatment solution of waste platinum catalyst with 61.3% efficiency and the biosorptive capacity was 30.65mg/g.Six methods immobilizing biomass were compared, in which the method immobilizing XP05 biomass with gelatin-alginate sodium as entrapment material was considered to be the optimal. The biosorption of immobilized XP05 biomass was also a rapid process. The optimum pH value of Pt + biosorption was 1.5, and its biosorptive capacity rose with increasing temperature in the rage of 10~75C. The content of the biomass and Pt4+ initial concentration in the solution also affected the biosorption process. The experimental data could be fitted to Freudlich model of adsorption isotherm.The biosorptive capacity reached 35.2mg/g under the conditions of 250 Pt4+mg/L, 2.0g biomass/L, pH 1.5 and 30 癈 for 60 min.The Pt4+ adsorbed on immobilized XP05 biomass could be desorbed by various chemical agents. The results indicated that 98.7% of Pt4+ on immobilized biomass could be desorbed with 0.5mol/L HC1.The characteristics of dynamic biosorption and desorption of immobilized biomass in packed-bed reactor were researched. The saturation uptake was 24.66mgPt/g under the conditions of flow rate 1.15mL/min, pH 1.5, 50mg Pt4+/L and 1.85g biomass(dry weight). Adsorptive efficiency of Pt4+ by the immobilized XP05 biomass was above 78% for 4 cycles of adsorption and desorption.TEM and XPS showed that XP05 biomass was able to adsorb and reduce Pt4+ to Pt?particle. IR spectrum analysis indicated that and -NF^ groups on the cell wall of XP05 biomass were involved in process of adsorbing Pt4+.The properties of Pt4+ biosorption by XP05 biomass and the characterization of TEM, IR and XPS indicated that the mechanism adsorbing Pt4+ by XP05 was a process of surface complex reaction along with the oxidation and reduction between Pt4+ in solution and functional groups on the biomass surface. Amidogen played the important role in the biosorption of Pt4+ b...
Keywords/Search Tags:Curobacter freudii, biosorption, Platinum, immobilization
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