Granulation and Molding of Nb-Doped H2TiO3 Spherical Lithium-Ion Sieve for Efficient Lithium Recovery From Aqueous Solution: Adsorption Performance and Mechanism

Abstract

The granulation and molding of titanium-based lithium-ion adsorbents are of great significance for their industrial application. In this work, Nb-HTO spherical particle lithium-ion sieve adsorbent material was prepared by the phase transformation method with PVC and PAN polymers as the bonding agents. The spherical lithium-ion sieve fabricated by the granulation method exhibit high porosity, excellent structural stability and good hydrophilicity. Notably, these particles preserve distinct microporous and small mesoporous architectures, with a maximum BET specific surface area of 78.417 m²/g. The equilibrium adsorption capacity value calculated by the quasi-second-order kinetic model (q_e,cal = 26.9 mg/g) is closer to the experimental measurement value (q_e,exp = 27.4 mg/g), indicating that the adsorption process is mainly controlled by chemical adsorption. Under different temperature conditions, the ∆G^ϴ values of the adsorption reactions were all negative, while the ∆H^ϴ values were all positive. This indicates that the adsorption process of Li⁺ by the Nb-HTO-2% spherical lithium-ion sieve for granulation is a spontaneous endothermic reaction. In the brine of the Xitaijini'er Salt Lake (containing Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺), the Nb-HTO spherical lithium ion sieve exhibited a relatively high adsorption capacity for Li⁺ (8.27 mg/g), with a distribution coefficient of 166.8 mL/g, verifying its excellent adsorption selectivity in a mixed alkali metal ion system. After five cycles of adsorption/desorption experiments, the adsorption capacity of the spherical particle composite adsorbent stabilized at 25.35 mg/g, and the titanium loss rate remained at 0.007%, indicating that the granulated Nb-HTO possesses high structural stability and cycling performance. The granulated Nb-HTO has excellent performance in lithium ion adsorption and separation and is a highly promising material for lithium recovery.