Extraction of lithium from salt lake brine containing borate anion and high concentration of magnesium

Lithium recovery from salt lake brine with a high magnesium/lithium concentration ratio from Qinghai province, China, was investigated. Li+ extraction was performed using tributyl phosphate in methyl isobutyl ketone as the extractant and FeCI3 as the coextractant. An extraction mechanism, based on cation exchange of Li+ and Mg2+ with H+ and Na+, was proposed. Boron exists as B(OH)(4)(-) in salt lake brine and is extracted into organic phase as boric acid. B(OH)(4)(-) in salt lake brine can strip H+ from the regenerated organic phase; this results in extraction of larger amounts of Li+ and Mg2+ because of electroneutrality. Based on cation exchange mechanism and neutralization of B(OH)(4)(-) with H+, the extraction behaviors of Li+ and Me+ from salt lake brine are successfully predicted. An experiment using a five-stage mixer-settler with countercurrent flow was conducted. The results showed that B(OH)(4)(-) largely favors lithium extraction from salt lake brine. (C) 2016 Elsevier B.V. All rights reserved.