Removal And Recovery Of U(Ⅵ) From Low Concentration Aqueous By The Modified Asperillus Niger

With the rapid development of nuclear technology and nuclear industrial activities, the contamination of radionuclide to water resources continues to accelerate, particularly the harm of radioactive uranium(VI) to the environment, ecology and life organism which has attracted more and more attentions. Aspergillus niger is a potential and inexpensive biosorbent that it derives from a wealth of sources, can be cultured easily, has no secondary pollution and is more stable in physical and chemical properties, etc. Then, it has an important significance and broad prospects in terms of waste water purification. In order to develop an economical, efficient, environmentally friendly and new biosorbent to treat wastewater containing low concentration of uranium(VI), this paper choose the raw biomass of Aspergillus niger(RAN) and the modified biomass of Aspergillus niger as the adsorbents for the adsorption of the low concentration of uranium(VI) from aqueous solution.The study prepared modified Aspergillus niger by modifying and grafting RAN with ethylenediamine and amidoxime. The effects of the solution p H, reaction time, initial uranium(VI) concentration, adsorbent dosage and reaction temperature on the adsorption of low concentration uranium(VI) from aqueous solution were investigated in a batch system. Meanwhile, the experiment to study the interference of other metal ions to uranium(VI) adsorption was carried out and the selective adsorption of the two modified biosorbents for uranium(VI) adsorption was investigated.The results show that the adsorption rate of the adsorption of the low concentration of uranium(VI) on the ethylenediamine modified Aspergillus niger(EMAN) and amidoxime modified Aspergillus niger(AMAN) reached 99.25% and 98.15%, respectively. And the optimum conditions were obtained, which p H was 5.0 for both modified biosotbents, the equilibrium time was 150 min for EMAN, and 180 min for AMAN. The results show that by contrast with RAN, the adsorption capacities of EMAN and AMAN for the low concentration of uranium(VI) increased by 28.9% and 27.3%, respectively.The results show that uranium(VI) adsorption processes of EMAN and AMAN are better followed the pseudo second-order kinetic model. It was also found that the absorption rate is relatively rapid at the initial stage and then the process reaches equilibrium.The results show that uranium(VI) adsorption processes onto EMAN and AMAN can be better followed Langmuir isotherm model, indicating that the adsorption processes onto the biosorbents are mainly chemical adsorption and in the form of monolayer coverage.Thermodynamic parameters obtained(Gibbs free energy change ΔGθ, enthalpy ΔHθ and entropy changes ΔSθ) show that the biosorption of uranium(VI) on both EMAN and AMAN is spontaneous, endothermic reaction process. The characterization results of EMAN and AMAN by fourier transform infrared spectroscopy(FTIR) and scanning electron microscopy(SEM) indicate that that biosorption of uranium(VI) on EMAN and AMAN mainly due to the binding interaction between uranium(VI) with surface hydroxyl groups(-OH), amino(-NH2) and amidoxime(=N-OH) groups.