(381o) Design of Titanium-Based Ion-Sieves Structure and Regulation of pH Value for Lithium Recovery from Brines

With the rapid development and wide application of lithium batteries, the industrial demand for lithium resources has increased dramatically, and the lithium extraction from Salt lakes is gradually becoming the main way to obtain lithium resources owing to its abundant resource reserves, simple extraction process and low environmental pollution. Titanium-based ion sieves (H₂TiO₃) with the layer structure is an excellent adsorption material for lithium extraction from brines, which has a high theoretical Li adsorption capacity, up to 142 mg(Li)/g(H₂TiO₃), and stable structure. In this work, titanium-based ion sieves (HTO powders) were synthesized via the solid-state reaction of Li₂CO₃ and TiO₂ at 750 °C under the LiCl/LiOH molten environment, where the high calcination temperature (750 °C) made the prepared HTO powders with a stable structure under acid regeneration. Because the Li⁺ adsorption mechanism on titanium-based ion sieves is based on Li⁺/H⁺ ion exchange, the influence of H⁺ content in the brine (pH value) on the Li⁺ adsorption amount is very obvious. Here, a quantitative relationship between the lithium adsorption amount on HTO ion-sieves and the pH value and lithium concentration in brine was established to optimize the lithium extraction process from brines. Then, a demonstration case of pH value regulation in the lithium extraction process was implemented from a carbonate-type brine using titanium-based ion sieves. The carbonate-type brine contains a large amount of carbonate ions, and has a good pH-buffering ability to accept the exchanged H⁺ ions of titanium-based ion sieves, enhancing lithium extraction. PVB-HTO composite particles with 1-2 mm particle size were molded using HTO powders and PVB polymers, and were filled in a fixed-bed adsorber. Dependent on the pH-buffering action in the carbonate-type brine, a favorable Li⁺ adsorption breakthrough performance was observed when the brine passed through the PVB-HTO particles packed column, having a broad prospect in industrial application.