Selective Extraction of Lithium Ion from Aqueous Solution with Sodium Phosphomolybdate As a Coextraction Agent

Sodium phosphomolybdate with a spatial stereo symmetry structure and stability in acid and alkali was used as a new coextraction agent for separating Li+. In addition, methyl isobutyl ketone and tributyl phosphate were used as diluent and extractant, respectively. The influence of operation conditions on separation performance of lithium ion was investigated. The single stage extraction efficiency of Li+ was 58.74% with the volume fraction of tributyl phosphate, O/A phase ratio, and molar ratio of sodium phosphomolybdate to lithium as 40%, 3.6, and 1, respectively. Then the cross-flow and saturated extraction experiments were conducted. When 0.2 mol/L LiCl + 1.8 mol/L NaCl solution was used as washing agent and O/A phase ratio was 3, the washing efficiency of Mg2+ reached up to 99.59%. When 0.26 mol/L HCl solution was used as stripping agent and O/A phase ratio was 3, the stripping efficiency of Li+ reached 98.3%. The difference in extraction efficiency was within 6.5% through 10 recyclings of the organic phase, indicating that the coextraction agent was very stable. The extraction mechanism was investigated and the binding ability of P═O in tributyl phosphate molecule followed the sequence Li+ ≫ Na+ > K+ > Mg2+.