Adsorption Of The Rare Earth Ions By Microorganism And Their Interactions

ABSTRACT:Two adsorption or accumulation bacteria strains were screened from soil by dilution-plate method and identified as Agrobacterium and Nocardia.The studies on the conditions of adsorping La³⁺and Ce³⁺by R and 782 strains indicate that the optimum conditions of adsorping La³⁺and Ce³⁺by R strains are at initial concentration of La³⁺15mg/L,initial concentration of Ce³⁺.10mg/L, bacteriumage 36h,temperature 30℃,rotation speed 150rpm,pH 6.8,biomass 15mg/50mL,biosorption of time 2 hour;the optimum conditions of adsorping La³⁺ and Ce³⁺by 782 strains are at initial concentration of La³⁺and Ce³⁺15mg/L, bacteriumage 36h,temperature 30℃,rotation speed 150rpm,pH 6.8,biomass 15mg/50mL,biosorption of time 2 hour.On the optimum conditions of adsorpting La³⁺and Ce³⁺,the max La³⁺,Ce³⁺adsorption capacity of 35.34 mg/g,31.74 mg by R strian and that of 37.22 mg,43.19mg/g by 782 strains.Results of two bacteria selective adsorption of rare earth ions tests show that the selective adsorption capacity of R and 782 is not obvious.Comparing the biosorping capacity of living and non-living bacteria,the capacity of adsorption by living R strains is higher than that of non-living;782 strains has no difference between living and non-living bacteria.Desorption and pretreatment test of R and 782 strains indicate that desorption rate all can reach 80%by joining the Sodium citrate, potassium oxalate and EDTA.Preatreatment by acid of R and 782 strains can decrease the biosorption capacity.The biosorption capacity on La3+ and Ce3+ of 782 strains by alkali pretreatment increase by 1.18%,0.53%.Biosorption kinectic results of 2 strains showed that the biosorption involved two phases.The first phase was very quick and took place in the initial fifteen minutes, adsorption capacity is greatly improved.The other was a very slow process and the adsorption uptake capacity increased very slowly.After forty five minutes,the adsorption equilibrium reached.This biosorption systems were better described by the pseudo-second kinetic model(R²ï¼ž0.99).Both of the Langrnuir and Freundlich adsoption isotherms were studied,which indicated that the Langmuir model well fitted this experimental data.The tests on the effect of rare earth ions on 2 strains growth,were carried out.The results show that it can extend the stable phase of strains,postpone the Decline phase and inhibit the mycelium pellet expansion by adding 30μmol/L La³⁺and Ce³⁺.In the preence of rere earth ions,R and 782 strains are all able to secrete red pigment;The concentrations of La³⁺and Ce³⁺which R strains could endure arrived at 80mg/L and 120mg/L,782 strains arrived at 100 mg/L and 120 mg/L.It's also found the rare earth ions have some impact on the protein expression of R and 782 strains,which mainly manifested in the difference of protein expression quantities,especially R strains.