Synthesis and adsorption properties of H4Ti5O12@CNTion sieves

In this study, H4Ti5O12@CNT ion sieves with an encapsulated structure were fabricated by combining pretreated carbon nanotubes (CNTs) as a template and carbon source, C16H36O4Ti as a titanium source, and CH3COOLi as a lithium source. By characterizing and analyzing the pretreated and untreated CNTs, numerous COOH and OH functional groups were introduced into the pretreated CNTs, which improved their dispersion in aqueous solutions and ethanol and facilitated the adsorption of lithium ions. The ion sieves prepared with the precursor roasted at 700 °C showed the best adsorption performance. Moreover, the structural integrity of the ion sieves was not affected by acid washing. For the first adsorption cycle, the ion sieves had a lithium‐ion saturated adsorption capacity of 32.32 mg/g. After five adsorption–desorption cycles, the adsorption capacity only decreased by 5.1% to 30.68 mg/g, which shows that they had good cycling stability. In this study, H4Ti5O12@CNT composite nanotubes with an encapsulated structure were prepared for use as ion sieves by combining pretreated CNTs as a template and carbon source, C16H36O4Ti as a titanium source, and CH3COOLi as a lithium source; roasting them together at different temperatures; and then washing them with hydrochloric acid to remove the lithium. Roasting and acid washing to remove the lithium were performed at different temperatures and the sample roasted at 700 °C showed the best adsorption performance. Characterization of the specific surface area, scanning electron microscopy, and transmission electron microscopy showed that the structure of the ion sieves was relatively stable and acid washing did not affect their structural integrity. In the first adsorption cycle, the saturation adsorption capacity of the ion sieves was 32.32 mg/g. After five adsorption–desorption cycles, it remained at 30.68 mg/g, exhibiting a reduction of only 5.1%. Therefore, the ion sieves had excellent cycling stability.