Abstract:

Titanium-based ion sieve adsorbents have good application prospects in the extraction of cesium from salt lake brine and the treatment of radioactive nuclear wastewater. In this paper, based on the improved sol-gel technology, trace Zn²⁺ was doped into the Ti—O lattice of Cs₂Ti₆O₁₃ to improve the cell structure, and the zinc doped titanate precursor material (CZnTO) was prepared. The precursor was subjected to acid treatment to form a zinc-doped protonated titanate (HZnTO). The prepared HZnTO was characterized by XRD, SEM, EDS, FTIR, Raman spectroscopy and XPS, which showed that the incorporation of trace amounts of Zn²⁺ did not destroy the original layered structure. Through adsorption experiments, the effects of aqueous pH, initial cesium ion concentration, adsorption time and temperature on the adsorption behavior of HZnTO were investigated. The studies found that at 288K, pH=11 and an initial Cs⁺ concentration of 3000mg/L, the adsorption of HZnTO for about 2h could achieve a saturated adsorption capacity of 323mg/g. In a low concentration solution with an initial Cs⁺ concentration of 30mg/L, HZnTO could still maintain an adsorption and removal rate of over 80%. The adsorption of Cs⁺ on HZnTO conformed to the quasi second order kinetic equation and Langmuir adsorption isotherm, indicating that the adsorption of Cs⁺ on HZnTO was chemical adsorption mainly by single molecular layer adsorption. Selective adsorption experiments and cyclic adsorption-desorption experiments showed that the selectivity of HZnTO for Cs⁺ was much higher than that of other ions. After 7 cycles of cyclic adsorption, the adsorption capacity of HZnTO could still reach 87.6% of that of the initial cycle, demonstrating a good stability.

Key words: cesium ion sieve, doping, adsorption, kinetics, thermodynamics

摘要：

钛系离子筛型吸附剂在盐湖卤水提铯、处理放射性核废水等方面具有很好的应用前景。本文基于改进型溶胶-凝胶技术，将微量Zn²⁺掺入Cs₂Ti₆O₁₃的Ti—O晶格中以改善晶胞结构，制备出锌掺杂型钛酸盐前体材料（CZnTO）。前体经过酸处理形成锌掺杂型质子化钛酸盐（HZnTO），通过X射线衍射仪、扫描电子显微镜与能谱仪、傅里叶变换红外光谱、拉曼光谱和X射线光电子能谱等表征手段对制备的HZnTO进行表征，证明微量Zn²⁺的掺入未破坏原有层状结构。通过吸附实验，考察了水相pH、初始Cs⁺浓度、吸附时间和温度等因素对HZnTO吸附行为的影响。研究表明，在288K、pH=11且初始Cs⁺浓度为3000mg/L的最优条件下，吸附2h左右，HZnTO即可达到饱和吸附容量323mg/g。在初始Cs⁺浓度为30mg/L的低浓度溶液下，HZnTO依然能保持80%以上的吸附率。HZnTO对Cs⁺的吸附符合准二级动力学方程和Langmuir吸附等温式，说明Cs⁺在HZnTO上的吸附为化学吸附，以单分子层吸附为主。选择性吸附实验和循环吸附-脱附实验表明，HZnTO对于Cs⁺的选择性远高于其他离子，循环吸附7次后，HZnTO的吸附容量依然能达到初次循环的87.6%，表现出良好的稳定性。

关键词: 铯离子筛, 掺杂, 吸附, 动力学, 热力学