| Because of uniform regular array of pores,large specific surface areas,adjustable pore size in a certain range,and excellent hydrothermal stability,commonly prepared SBA-15 material has a wide range of applications in the catalytic,adsorption,biological macromolecule loading and other fields.However,the long pore length,small pore size and particle size,and the lack of surface active groups limits its further application to some degree.Based on these problems,preparation and modification of large SBA-15 were performed in this paper.The physical structures and chemical properties of the prepared materials were characterized by SEM,TEM,N2 adsorption-desorption,VSM,FT-IR and XRD.The main works are as follows:(1)Based on the typical synthesis method,the large-pore SBA-15 was prepared by changing the experimental conditions.By employing expanding process,the SBA-15 morphology was changed and the pore size increased from 5.48 to 20.31 nm.Compared with the typical SBA-15,the adsorption performance of uranium(VI)shows little difference.The optimum pH value is found to 6,the pseudo-2nd-order kinetic model and Langmuir isotherm can describe the adsorption behavior well.The adsorption is dominated by chemical action,and it’s a spontaneous and endothermic process.The saturated adsorption capacity of monolayer is slightly decreased from 165.02 to 157.48 mg/g.The adsorption of uranium on the material changed slightly in the presence of NaCl in the system.With 0.1 mol/L Na2CO3 solution used as eluent,the desorption rate was over 92%,the material adsorption capacity of uranium maintained at a high level after the sorbent being used for four times.(2)The magnetic large-pore SBA-15 material(M-SBA-15)was prepared and it was found that the doping of the magnetic particles didn’t change the original structure of the material.The optimum pH value is 6 and the equilibrium time is 6 h.The Langmuir isothermal and pseudo-2nd-order adsorption kinetic models can describe the adsorption process well.The adsorption is a chemical process,and the saturated adsorption capacity of monolayer is 179.86 mg/g.The adsorption process is found to be endothermic and spontaneous from the thermodynamic parameters.In the presence of different concentrations of ions,the sorbent maintains a good adsorption performance and reusability.(3)Aminated magnetic large-pore SBA-15(NH2-M-SBA-15)was obtained and the structure was maintained as origin.It was found that the optimum pH was 6 and the adsorption reached equilibrium at 6 h.The process was in accordance with the Langmuir isothermal and pseudo-2nd-order adsorption kinetics model,which was mainly controlled by chemical force,and the saturated adsorption capacity was increased to 495.05 mg/g.From the thermodynamic parameters ΔH and ΔG,it’s found that the adsorption of uranium on the material is spontaneous and endothermic,and the material shows good anti-interference ability and recyclability.(4)Phosphorylated large-pore SBA-15 material(P-SBA-15)was synthesized,and the morphology of the material did not change significantly before and after modification.The results show that the best pH value is 6.The whole adsorption process equilibrium is achieved by 15 min,and it’s in a good accordance with Langmuir isothermal and pseudo-2nd adsorption kinetics,the chemical action mainly controls the adsorption process and its saturated adsorption capacity has been greatly improved.The increasing temperature can enhance the adsorption to some extent,and the sorbent shows higher specificity for uranium adsorption. |
