Yuanzineng kexue jishu (Nov 2024)
Preparation of Novel Silica-based Zirconium Pyrophosphate Ion-exchanger and Its Adsorption Performance for Cs+
Abstract
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+.
Keywords
