Sodium Activation of Silano-Phosphonate Modified Mesoporous TiO2 Leading to Improved Rare-Earth Element Extraction

Due to their presence in most modern electronic devices and as waste products in the nuclear cycle, a great deal of interest has been generated in the acquisition and/or recycling/removal of rare-earth elements (REE). Here, we present a simple one-pot route for the preparation of dimethylphosphatoethyltriethoxysilane (SiP) functionalised mesoporous TiO2 particles. The resistance of TiO2 to strong bases allowed for the use of NaOH to activate the phosphonate head group of the functionality, significantly improving its efficiency. Levels of 92.6 mg/g Ce3+ were extracted from water, which is double the previously reported value for the extraction of REEs with this type of extractant. SiP-TiO2 (Na) was also used to separate completely the Ce3+ from aqueous solutions containing Sr2+ and Cs+. Finally, the nanocomposite separated Ce3+ from other homovalent REEs, for example, Yb3+ (1:1.4 separation ratio).