Recovery of boron from unacidified salt lake brine by solvent extraction with 2,2,4-trimethyl-1,3-pentanediol

The recovery of boron from salt lake brine using 2,2,4-trimethyl-1,3-pentanediol was investigated. Factors affecting boron recovery, including pH, concentrations of extractant and H3BO3, phase ratio(O/A), and temperature, were investigated. Increasing pH initially resulted in high extraction rate, but there was a limitation, as further increasing pH resulted in rapid formation of B[OH]4- having a low capacity to complex with TMPD, and therefore lower boron extraction. Boron recovery increased as the TMPD and O/A increased. The combination of pH <7, O/A=1 & n(TMPD/H3BO3)=2:1 was ideal for boron recovery, resulting in extraction efficiency of >85%. To investigate extraction mechanism, slope ratio method was combined with Raman and infrared spectroscopy to characterize the structure of complex. Furthermore, under optimal conditions, a three-stage extraction and two-stage stripping process was performed, resulting extraction and stripping efficiency were 97.12% and 88.98%, respectively. The results reveal a promising strategy of boron recovery from SL brine without acidification.