新型硅基焦磷酸锆离子交换剂的制备及其对Cs^(+)的吸附性能研究

Preparation of Novel Silica-based Zirconium Pyrophosphate Ion-exchanger and Its Adsorption Performance for Cs^(+)DIAO

放射性废液中放射性Cs^(+)的高效去除和回收对于降低废物处置成本、促进资源循环利用具有重要意义。本文采用溶胶-凝胶共沉淀和高温处理相结合的新方法,合成了一种成本低廉的新型无机离子交换树脂硅基焦磷酸锆,采用SEM、FT-IR、XRF、XRD等手段对新树脂进行了表征,并通过静态吸附实验及柱实验系统测定了在弱酸性溶液中其对Cs^(+)的吸附性能。结果显示,Cs^(+)在该树脂上的吸附过程符合准二级动力学模型,吸附在6 h内达到平衡。在0.001 mol/L HNO3溶液中,该树脂对Cs^(+)的静态吸附容量可达2.7 mg/g。树脂对Cs^(+)的吸附具有良好的选择性,Cs^(+)与高放废液中其他共存金属离子的分离因子均大于1.5。此外,柱实验结果显示树脂颗粒柱负载的Cs^(+)可以被2.0 mol/L NH4NO3有效洗脱回收。

Efficient removal and recovery of radioactive Cs^(+)from high-level liquid waste(HLLW)is of great significance for reducing disposal cost and promoting nuclear resource recycling.Due to the significant selectivity for Cs^(+),zirconium pyrophosphate possesses great potential to uptake Cs^(+)from HLLW,whereas the micro-crystalline structure and fine powder morphology limits its industrial application with column separation.In this study,a new method combining sol-gel and high-temperature treatment was developed,and a novel silica-based zirconium pyrophosphate resin was prepared by this method.The prepared resin was characterized using scanning electron microscopy(SEM),Fourier transform infrared(FT-IR)spectra,X-ray fluorescence(XRF),X-ray diffraction(XRD),N2 adsorption/desorption isotherms and the universal testing machine,and its adsorption performance for Cs^(+)in weakly acidic solution was determined using both batch-type and dynamic column experiments in terms of the kinetics,equilibrium capacity and selectivity.The characterization results indicate the successful fabrication of silica-based zirconium pyrophosphate resin with excellent physical and chemical stability.Batch-type experiments demonstrate that Cs^(+)adsorption on the resin is equilibrated within 6 h,and the adsorption kinetics could be described by a pseudo-second-order model.Due to the competing adsorption of H+,the adsorption rate of Cs^(+)exhibits a decrease as the concentration of HNO3 increasing from 0.001 mol/L to 2.0 mol/L.The adsorption capacity of Cs^(+)increases significantly with the increase of initial Cs^(+)concentration,and the adsorption of Cs^(+)on the resin can be well fitted with Langmuir model.This implies that the adsorption process of Cs^(+)by the resin is a homogeneous single-layer adsorption process.The maximum adsorption capacity of silica-based zirconium pyrophosphate resin for Cs^(+)is determined to be 2.7 mg/g with batch-type experiment in 0.001 mol/L HNO3.More importantly,the resin exhibits high selectivity for Cs^(+)uptake over 8 co-existing metal ions in simulated HLLW,and the separation factor of Cs^(+)towards other coexisting ions is more than 1.5.Furthermore,the column experiment results indicate that the Cs^(+)adsorbed on the resin could be eluted effectively by 2.0 mol/L NH4NO3,and the desorption efficiency is greater than 80%.This demonstrates that the resin can serve as the stationary phase in columns for the efficient removal and recovery of Cs^(+).