Preparation Of β-cyclodextrin Modified Mesoporous Silica Material (SBA-15-CD) And Experimental Study On U(Ⅵ) Removal

As one of the radionuclides and the main fuel of nuclear reactors,uranium poses a serious threat to the environment through most processes and activities related to the nuclear fuel cycle,including mining,milling and spent nuclear reprocessing.Dissolved uranium mainly exists in the form of UO₂²⁺,which is both radioactive and chemically toxic,and can accumulate through the food chain and eventually cause potential harm to human health.The adsorption method has attracted much attention because of its advantages such as simple operation and high processing efficiency.In this study,β-CD was used to modify mesoporous silica SBA-15,and a new adsorbent（SBA-15-CD）was synthesized by post-grafting method;the solution pH,dosage,adsorption time,and temperature were discussed.The influence of other factors on adsorption,and the FTIR and XPS analysis were used to study the adsorption mechanism of modified materials on U（Ⅵ）.The results obtained are as follows:（1）β-cyclodextrin-modified mesoporous silica material（SBA-15-CD）was synthesized using triethoxy（3-isocyanatopropyl）silicon as a cross-linking agent and post-grafting method.The appearance of particulate matter on the SBA-15-CD modified by the introduction ofβ-CD indicates that the grafting was successful,and the main structure of the parent material was not damaged during the functionalization process.Both the specific surface area and pore volume of SBA-15-CD are smaller than those of pure SBA-15,but the average pore size is increased.（2）The results of SBA-15-CD adsorption experiments on U（Ⅵ）show that the optimal adsorption pH is 5,the optimal dosage is 0.20g/L,and the adsorption equilibrium time is 30min;the adsorption process is in compliance with quasi-secondary The kinetic model and Langmuir isothermal model,the maximum adsorption capacity of SBA-15-CD reached 330.0mg/g at 30℃,which was significantly better than the unmodified SBA-15.The thermodynamic analysis shows that the adsorption process is a spontaneous endothermic reaction,and the degree of chaos in the system increases after adsorption.After four cycles of adsorption process,the removal rate of U（Ⅵ）by SBA-15-CD can still reach 94%,indicating that the modified material has good recyclability.（3）The results of FTIR spectra before and after adsorption show that the intensity of the C=O stretching vibration peak in SBA-15-CD-U weakens and shifts to the right,the bending vibration peak of the Si-OH bond basically disappears,and-NH-and The superimposed characteristic peaks of-OH are shifted;the binding energy shown in the high-resolution N 1s spectrum is negatively shifted from 400.5 eV to 400.3 eV;after adsorption of U（Ⅵ）,COO-can be observed in the O 1s spectrum Both the and CO groups transition to lower binding energies.In summary,U（Ⅵ）can be well adsorbed on SBA-15-CD,and its reaction is mainly the complexation with hydroxyl,ester and amino groups on the surface of the material.