Novel LIS-doped mixed matrix membrane absorbent with high structural stability for sustainable lithium recovery from geothermal water

Lithium-ion sieves (LIS) have gained significant interest in lithium recovery from geothermal water. However, the severe loss and low recyclability of the powder adsorbents restrict their practical application. Here, the symmetric mixed matrix membranes adsorbents of LIS (MMMs-LIS) were prepared after doping the dopamine-modified LIS into polysulfone (PSf) matrix by breath figure approach with the characters of low thickness, high exposure area of H2TiO3 (HTO) and high structural stability. The hydrophilic dopamine (DA) would probably promote the condensate water droplets to penetrate PSf matrix and make the smaller HTO/DA preferably emerge on the pore surfaces, accelerating the intercalation of Li+ into the vacancies of HTO on the premise of the strengthened interfacial interaction between HTO/DA and PSf matrix. Therefore, the well-designed MMMs processed a comparable Li+ adsorption capacity of 25.01 mg·g−1 and an equilibrium adsorption time of 45 min to powdery HTO during the dynamic adsorption process at 298.15 K (C0 = 25.78 mg·L−1, pH = 12.0). Moreover, Ti4+ loss rate of HTO in MMMs decreased from 10.5% down to 1.1% after the first desorption and then gradually alleviated after multiple cycles until stabilized at 2.3%, indicating the excellent structural stability. These results suggest the great potentials of MMMs for highly efficient and sustainable lithium recovery from geothermal water.