Hydrophilic Granules for Efficient Lithium Recovery from Real Oilfield Brine with High Capacity and Selectivity

Facing limited lithium supply and rising demand, exploring diverse and economical lithium resources is key to easing pressure. Oilfield brine, with low land and freshwater use for lithium extraction, offers great potential. However, developing stable granular adsorbents with high adsorption capacity and selectivity for oilfield brine with an ultrahigh Na+/Li+ ratio is highly significant. Herein, hydrophilic polyacrylonitrile (PAN)/ Li1.33Mn1.67O4 (LMO)-based granules were prepared by straightforward nonsolvent-induced phase separation. Meanwhile, polyethylenimine (PEI) was modified to PAN binder and the obtained PANP-LMO granules exhibit a highly interconnected three-dimensional network. The load capacity of LMO reached up to 87%, which was helpful for excellent adsorption performance. Notably, the adsorption capacity reached 17.4 mg/g. Moreover, PANP-LMO showed enhanced selectivity toward Li+ (distribution factor Kd = 15006 mL/g) over other coexisting cations, with a separation factor of αNaLi = 12695, αMgLi = 5919, surpassing those of previously reported adsorbents. Theoretical calculations indicated that abundant amino groups from PEI effectively improved the selectivity of Li+ toward other cations. When used in Zhongyuan oilfield brine, the lithium adsorption efficiency was 98.7%, with the Na+/Li+ ratio descending to 4.5 from 2,316, the Mg2+/Li+ ratio descending to 0.1 from 19.5. This suggests that the adsorbent’s performance remained unaffected in the real brine with ultrahigh Mn+/Li+ ratio. These findings collectively indicate that PANP-LMO granules could present a competitive option for industrial processes.