Lithium solvent extraction from weak alkaline brine by 2-hydroxy-5-nitro-4-alkoxy-benzophenone and TRPO

Solvent extraction of lithium by β-diketones from alkaline brine has been known to be an efficient process. However, its relatively high working pH, consequently the high alkaline consumption and substantial dissolution loss in raffinate, limit its industrial application. Herein, a novel lithium extractant, i.e., 2-hydroxy-5-nitro-4-n-octoxy-benzophenone (referred to as N531), was proposed, which can extract lithium at relatively lower pH with remarkable low alkaline consumption and dissolution loss. Exactly, the pH corresponding to half lithium extraction is 8.5, and the Li/Na separation factor is ~500. The extractant concentration in the raffinate varied from 0.8 to 9.3 mg L⁻¹, depending on the pH and salinity. An application case was given to extract lithium from the raw brine of Zabuye salt lake, indicating that N531 is a commercially prospective extractant to extract lithium from alkaline brine.