Modulating porosity and hydrophilicity of granular adsorbent by water-soluble polymers to enhance lithium extraction from ultrahigh Mg/Li ratio brine

The development of granular adsorbents with high adsorption capability and high cycle stability is of great significance for the application in efficiently extracting lithium from salt lake brine. Herein, the structure of granular aluminum-based adsorbents was regulated by adding water-soluble polymer PEG. The results showed that the molecular weight of PEG was closely related to the pore structure and surface hydrophilicity of the granular adsorbents. With the decrease of the molecular weight of PEG, the specific surface area, the average surface pore size, and the hydrophilicity of granular adsorbents increase. The optimized adsorbent PSF-PEG600@AD formed a complex pore structure with surface macropores and internal mesopores as well as excellent hydrophilicity. The mechanical strength and wear resistance are enhanced. This unique porous structure and surface hydrophilicity enable PSF-PEG600@AD rapid adsorption equilibrium in the old brine of Qarhan salt lake with a Mg/Li ratio of 323 within 4 h. The adsorption capacity remains as high as 99.02 % after 10 static adsorption-desorption cycles, showing excellent cyclic stability. This study guides a direction in preparing high-performance granular adsorbents with adjustable pore structure and surface properties.