Recovery of boric acid from salt lake brines by solvent extraction with 2-butyl-1-n-octanol

A systematic investigation was conducted on the extraction of boric acid from salt lake brine using 2-butyl-1-n-octanol dissolved in sulfonated kerosene. The extraction parameters, including the concentration of extractant, phase ratio and pH value of the brine, were optimized. The salting-out effects of the extraction process were investigated in the presence of AlCl3, MgCl2 and NaCl, and an empirical equation was subsequently proposed. The positive salting-out effects were observed on the extraction of boric acid in the order of AlCl3 > MgCl2 > NaCl. Thermodynamic modeling results indicate that the extraction process is exothermic. To evaluate the feasibility of the process, a multi-stage countercurrent extraction and stripping process was performed under the optimized operating conditions. The results showed an overall boric acid extraction efficiency of 99.35% and a stripping efficiency of 99.63%, and the overall boric acid recovery and the purity of the stripping solution both exceeded 98%. The results of this study reveal a potential industrial application of the boric acid extraction process.