Lithium adsorption performance of a three-dimensional porous H2TiO3-type lithium ion-sieve in strong alkaline Bayer liquor

Abstract

Removing lithium from the Bayer liquor for ensuring good alumina product quality demands a special lithium ion-sieve (LIS) with good stability in a strong alkaline medium. In this study, a three-dimensional porous H₂TiO₃-type LIS (porous-HTO) prepared by a polystyrene (PS) colloidal microspheres template was applied to adsorb Li⁺ from the strong alkaline Bayer liquor. XRD and SEM results confirm the fine stability of porous-HTO in strong alkaline medium, and the regeneration tests show that more than 64 mg g⁻¹ lithium adsorption capacity still remains even after 5 cycles of lithiation–delithiation in the simulation Bayer liquor. The lithium adsorption processes of porous-HTO and bare H₂TiO₃-type LIS (bare-HTO) both fit the pseudo-second-order model, but the adsorption capacity and the adsorption rate of the porous-HTO are much better than those of the bare-HTO. For porous-HTO, the adsorption rate constant is 0.02357 g mg⁻¹ h⁻¹ and the equilibrium adsorption capacity is 76.3 mg g⁻¹, while for bare-HTO, the adsorption rate constant is 0.009682 g mg⁻¹ h⁻¹ and the equilibrium adsorption capacity is only 44.8 mg g⁻¹. The lithium selectivity tests demonstrate that the coexisting ions including Na⁺, K⁺, AlO₂⁻, SiO₃²⁻ in the simulation Bayer liquor have low influence on lithium adsorption. The simulation Bayer liquors with Li⁺ ions of 56.00, 30.00 and 5.00 mg L⁻¹ are all reduced to below 1.00 mg L⁻¹ by virtue of one-time-adsorption of porous-HTO at various solid to liquid ratios of 1.0, 0.5 and 0.1 g L⁻¹, respectively.