Copper-Resistant Bacterium Isolation,Biosorption Characteristics And Mechanism

Conventional physical and chemical methods for removing Cu2+ from aqueous solutions are usually expensive and not effective.In this thesis,on the basis of the biosorption,the main target of this study was to isolate copper-resistant strains from slagheap and operate biosorption experiments.The biosorption characteristics under different environmental conditions were investigated.And the biosorption mechanisms were studied by means of SEM,EDS,FTIR.Finally,the isothermal model and dynamic model were used to analyze the adsorption process.The main conclusions are as follows:(1)The copper-resistant strain was screened from slagheap and the minimum inhibitory concentration of Cu2+ was 200 mg/L.According to the colonial morphology,16 S rDNA analysis and physiological-biochemical characteristic,the strain was identified as Citrobacter freundii and named as Citrobacter freundii JPG1.(2)The experiment of Cu2+ adsorption by live and dead cells showed that the optimum conditions was pH=5.0(6.0),biosorbent dose=0.5 g/L and agitation speed=150 r/min.Under the optimum conditions,at the concentration of 60 mg/L,the adsorption capacity and rate of live cells were 19.6 mg/g and 17.76% and that of dead cells were 23.6 mg/g and 21.38%,respectively.SEM,EDS and FTIR analysis indicated biosorption mechanisms of live cells and dead cells.As for the live cells,the biosorption process included extracellular biosorption and intracellular accumulation.And Cu2+ were adsorbed on the bacterial surface through coordinating with hydroxyl,amine and carboxyl groups.As for the dead cells,the biosorption process only included extracellular biosorption.And Cu2+ were adsorbed on the bacterial surface through coordinating with amide groups,hydroxyl,amine and phosphonate groups.(3)The experimental biosorption data of live cells were fitted towards the models both Langmuir and Freundlich well and the coefficients of correlation R2>0.9,while R2 of dead cells were around 0.8.For the Langmuir isotherm,the affinity constant b for dead biomass was 0.056 much higher than that of live cells(0.011)and the RL value was 0.3623 for live cells and 0.1004 for dead cells.For the Freundlich isotherm,the n and KF values were 1.4687 and 1.0254 for live cells and 1.6473 and 2.002 for dead cells,which all showed that the biosorption capacity of dead cells higher than that of live biomass.(4)The pseudo first and second-order model showed that the data of biosorption kinetics both of live and dead biosorbents were fitted the pseudo second-order adsorptive model better,the qe were 25.36 and 31.82 mg/g,respectively.In addition,the biosorption process of dead cells within 60 min,while it required approximately 90 min for the live cells.It also indicated the biosorption process included extracellular biosorption and intracellular accumulation for live cells.Finally,the desorption ability of live and dead cells was studied at different pH value.At pH=1.0,the desorption rates of live cells was 62.68% and 81.05% for dead cells,which was higher than that of live cells at all.