Effect of buffer on direct lithium extraction from Tibetan brine by formed titanium-based lithium ion sieves

Abstract

The adsorption performance of titanium-based lithium ion sieves for Li⁺ through H⁺–Li⁺ exchange is greatly limited by the pH value of brine. To improve the adsorption capacity of HTO-P (formed titanium-based lithium ion sieves) for Li⁺, the adsorption characteristics and dynamic performance in Tibetan brine–NaHCO₃ (NaHCO₃ as a buffer added into the brine used) were studied. The addition of NaHCO₃ reduces the aggregation of H⁺ and maintains the pH value at ∼7.5, which also accelerates the mass transfer rate of Li⁺ in the initial adsorption stage. Compared with Tibetan brine, the equilibrium adsorption capacity and recovery ratio of HTO-P for Li⁺ in Tibetan brine–NaHCO₃ increase by 60% and 70%, respectively, and the adsorption equilibrium time is shortened by one-third. Moreover, the dynamic saturated adsorption capacity of HTO-P for Li⁺ reaches 14.25 mg g⁻¹ in Tibetan brine–NaHCO₃. This work provides a basis for the direct lithium adsorption and extraction process from salt lake brines.