Surface modification of lithium-ion sieves by silane coupling agent for improved adsorption performance

Solid-phase reaction is a promising method to synthesize lithium-ion sieves H2TiO3 (HTO) for simple production process. However, the uneven mixing of raw materials during the solid-phase reaction causes the agglomeration phenomenon. In this work, silane coupling agent (3-aminopropyl)triethoxysilane (KH550) was employed for surface modification of HTO to yield the HTO/KH550 composite by forming covalent bond. The crystallinity, composition, morphology, and porosity of HTO/KH550 were characterized by a series of techniques. The agglomeration phenomenon was well alleviated and HTO/KH550 showed increased surface area. The adsorption experiments were detailed carried out by varying the different factors. HTO/KH550 exhibited improved lithium adsorption capacity and adsorption rate constant (25.61 mg·g−1 and 0.0037 mg·g−1·h−1 vs 22.41 mg·g−1 and 0.0020 mg·g−1·h−1 of HTO) derived from surface modification by KH550. Ion exchange mechanism in the adsorption process was revealed by X-ray photoelectron spectroscopy (XPS). Selective adsorption experiments were performed and HTO/KH550 exhibited the partition coefficient (Kd) of Li+ much higher than the competing ions (Na+, Mg2+, K+, and Ca2+). Furthermore, HTO/KH550 showed excellent cyclic stability with the adsorption capacity loss of only 3.3 % after five adsorption–desorption cycles. This work is of guiding significance to synthesize surface modified lithium-ion sieves for industrial production.