Surface modification and spatial optimization of pre-lithiation TiO2 ion sieves for efficient extraction of lithium

The closed pores and slow kinetics of conventional Ti-based adsorbents (HTO) hinder their industrial application in the selective adsorption of Li+ from wastewater. Herein, a surface modification and spatial optimization strategy was developed to improve the adsorption performance of HTO for Li+. The strong hydrophilicity caused by high roughness of modified HTO increases the contact area between the Li+-containing solution and the absorbent, which shortens the diffusion path of Li+ to the adsorbent surface and accelerates the migration of Li+ to the adsorbent surface. The excellent lithium affinity of N heteroatom on the surface of modified HTO promotes the conversion of hydrated Li+ into activated Li+, which can be easily captured by the adsorbent. The large specific surface area of modified HTO provides abundant absorption sites of Li+. The material with rich pores provides sufficient space to improve the adsorption capacity of Li+. The small particle size shortens the transport path of Li+ from the adsorbent surface to its interior, thereby reducing the transport resistance, which accelerates the migration of Li+ into the adsorbent and releases a large number of active sites on the surface. The experimental results show that the Li+ adsorption rate is increased from 0.37 mg·g−1·min−1 to 0.82 mg·g−1·min−1 after modification. The adsorption capacity of the adsorbent is 49.05 mg·g−1 and it remains 96.7 % after 5 cycles, indicating excellent adsorption performance and recyclability. This study provides a strategy for effective extraction of Li+ from low concentration solutions.