A convenient one-step synthesis of mesoporous ZrO₂/SBA-15 and its uranium adsorption properties

Mesoporous ZrO₂/SBA-15 materials were prepared for the first time by a one-step method using ZrO₂ as zirconium source and their uranium (U(VI)) adsorption behavior were studied. The influence of ZrO₂ content on the structure, morphology and hydrothermal stability of the obtained ZrO₂/SBA-15 was investigated. It was found that the structural order of ZrO₂/SBA-15 decreased with increasing ZrO₂ content. The hydrothermal stability of SBA-15 was improved by loading of ZrO₂. Furthermore, the effects of pH, initial U(VI) concentration, contact time, temperature and ZrO₂ content on the U(VI) adsorption capacity were studied. The results demonstrated that the U(VI) adsorption capacity decreased with increasing ZrO₂ content and temperature. The adsorption process was found to be well fitted to the Langmuir and pseudo-second-order model. The calculated maximum adsorption capacities were 326 and 294 mg·g^-1 for 0.4ZrO₂/SBA-15 and 0.8ZrO₂/SBA-15 samples at 283 K, respectively. Furthermore, the analysis of thermodynamic parameters (ΔG, ΔH, and ΔS) revealed that the process of U(VI) adsorption onto ZrO₂/SBA-15 was feasible, spontaneous and exothermic. (author)