Recovery of boron from
unacidified salt lake brine bysolvent
extraction with 2,2,4-trimethyl-1,3-pentanediol
Xiaowu Peng a, b, Dong Shi a, b,
Yuze Zhang a, b, c, Licheng
Zhanga, b,
Lianmin
Ji a, b, Lijuan Li a, b, 11∗Corresponding author at: Qinghai Institute of Salt Lakes, Chinese
Academy of Sciences, 810008 Xining, China.
E-Mail address: lilj@isl.ac.cn
a Key Laboratory of Comprehensive and Highly Efficient Utilization of
Salt Lake Resources, Qinghai Institute of Salt Lakes, Chinese Academy of
Sciences, Xining 810008, Qinghai, China.
b Qinghai Engineering and Technology Research Center of Comprehensive
Utilization of Salt Lake Resources, Xining 810008, Qinghai, China.
c University of Chinese Academy of Sciences, Beijing 100049, China.
Abstract:In this work, the extraction of
boron from salt lake (SL) brine using 2,2,4-trimethyl-1,3-pentanediol
(TMPD) was investigated. Factors affecting boron recovery during the
solvent extraction process, including feed pH, concentrations of
extractant and H3BO3, phase ratio of
organic to brine (O/A), and temperature, were investigated. Increasing
feed pH initially resulted in a high boron
extraction
rate, but there was a limitation, as further increasing feed 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 concentration and O/A
increased. Salting-out effect experiment indicated that the addition of
magnesium chloride showed two opposite effects on boron extraction. The
combination of pH <7, O/A=1 &
TMPD/H3BO3 molar ratio=2:1 was ideal for
boron recovery, resulting in boron extraction efficiency of
>85%. To investigate the extraction mechanism, the slope
ratio method was combined with Raman spectroscopy and infrared
spectroscopy to characterize the structure of TMPD and boron complex in
organic extraction solvent. Furthermore, under the optimal conditions, a
three-stage extraction and two-stage stripping process was performed,
resulting the extraction and stripping efficiency of boron were 97.12%
and 88.98%, respectively. The results of the study reveal a promising
strategy of boron recovery from SL brine without acidification.
Key Words:Boron
recovery; TMPD; Extraction complex; Salt lake brine