Lithium-enriched monoclinic lithium metatitanate (beta-Li2TiO3) with a high molar ratio of Li to Ti(2.11) was synthesized by a hydrothermal method. The related lithium ion-sieve (H2TiO3), obtained by acid pickling of Li2TiO3, with a specific surface area of 45.35 m(2) g(-1) and a pore volume of 0.166 cm(3) g(-1) possessed a maximum adsorption capacity of 76.7 mg g(-1) in LiOH solution (similar to 2 g L-1 of Li+ ions) at 30 degrees C for 24 h, which was much higher than those reported for other lithium ion-sieves. Adsorption isotherms and kinetic analysis indicated that the adsorption of Li+ ions onto H2TiO3 followed the Langmuir isotherm model and a pseudo-second order kinetics equation. The adsorption mechanism showed that the improvement of lithium adsorption capacity was closely related to the free hydrogen formation of beta-Li2TiO3 and HTi2 layer exposure of H2TiO3, suggesting a clear direction for designing the lithium ion-sieve with high performance.