Studies On Adsorption Of The Rare Earth Ions By Aspergillus Niger

One adsorption or accumulation La³⁺ fungi strain A01 was screened from soil ,and identified as Aspergillus Niger by investigating the characteristic of the strain.The tests on the effect of rare earth ions on A01 growth were carried out. The results show that it can shorten the stable phase of the strain ,move up the Decline phase .The concentrations of La³⁺,Ce³⁺ and Nd³⁺ which A01 strains couldn′t grow arrived at 800mg/L,600mg/L and 800mg/L.It's also found the rare earth ions may promote the growth of A01 in some relative low concentration,and restrain it in high concentration.The studies on the conditions of adsorping La³⁺ by A01 indicate that the optimum conditions of adsorping La³⁺ is at initial concentration of La³⁺ 40mg/L ,temperature 32℃,rotation speed 200rpm, pH 7.0, biomass 4mg/50mL, biosorption of time 1.5 hour . On the optimum conditions of adsorpting La³⁺, the max adsorption capacity can reach 125.62 mg/g.From the test adsorping rare earth by A01,we can know that the adsorption capacity to Yb³⁺,Lu³⁺ and Ho³⁺ are high and are all more than 290mg/g.And the adsorption capacity to heavy rare earth elements are higher than to light rare earth elements.Results of A01 selective adsorption of rare earth ions tests show that the selective adsorption capacity of A01 is not obvious. The desorption rate are all not ideal, the highest rate can reach 75.46% by joining 0.1M HNO3.Electron microscopy revealed that La³⁺ crystal deposits at the cell surface, indicating that a precipitate formed at the cell surface.Biosorption kinectic results of A01 showed that the biosorption was very quick in the initial fifteen minutes, adsorption capacity is greatly improved. Then there 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. Both of the Langmuir and Freundlich adsoption isotherms were studied ,which indicated that the Langmuir model well fitted this experimental data.