The recovery of boron from salt lake brines has become an effective way to meet the increasing demand, particularly in China. In this study, nine commercially available monohydric alcohols with different structures were selected for boron extraction from a salt lake brine with high magnesium content. Passing through the optimization, isodecanol was finally selected for the detailed study on boron recovery from brine due to its moderate viscosity, lower solubility water entrainment and high extraction efficiency. Parameter effects on boron extraction were systematically studied, including equilibrium pH, organic concentration, phase ratio, temperature, and salting-out effect. A McCabe–Thiele diagram was established to determine the boron extraction and stripping stages. An organic solution containing 2.5 mol L−1 isodecanol was used for a simulated three-stage counter-current extraction test under optimized extraction conditions, and the boron extraction reached 99.07%. A simulated four-stage counter-current stripping test was carried out with water with the stripping efficiency of 98.71%. In total the boron recovery reached 97.79%. Additionally, the mechanism of boron extraction by isodecanol was investigated using both slope analysis method and Fourier transform infrared spectroscopy (FTIR). The stoichiometric ratio of isodecanol to boron required to form boric acid ester was found to be 1.268. These results indicate that the extraction system has great potential for commercial application in boron recovery from salt lake brines with high magnesium content.
NdFeB waste serves not only as a crucial resource for the recovery of rare earth elements (REEs) but also as an underutilized source of gallium (Ga). In this work, to simultaneously extract REEs and Ga from NdFeB waste, an efficient and novel method was developed, which involved the process of leaching, reduction, solvent extraction, precipitation, and calcination. Initially, the Pr, Nd, and Ga were co-leached with 5 mol/L HCl and liquid-solid ratio (mL/g) of 5:1 at 90 °C for 150 min, resulting in the leaching rate of Pr, Nd, and Ga were 98 %, 99 %, and 98 %, respectively. Secondly, to mitigate the interference of Fe (III) on the extraction process, Fe (III) was reduced to Fe (II) completely using Fe powder for 10 min, given that the excess iron powder factor was 1.2. Then, the tributyl phosphate (TBP) was chosen as the extractant for Ga due to its high selectivity. Under the optimal conditions, three-stage counter-current extraction achieved an extraction efficiency of 99 % for Ga, with the addition of 10 % isodecanol to eliminate the third phase. The gallium was completely stripped by water at a phase ratio (O/A) of 2:1. Subsequently, di-2-ethylhexylphosphoric acid was selected as the Pr and Nd extractant because of its high separation ability between REEs and Fe (II). The extraction efficiency of Pr and Nd achieved more than 99 % through three-stage counter-current extraction and the entire stripping of Pr and Nd was realized by 1.8 mol/L HCl. Additionally, a significant amount of Fe (II) in the raffinate was treated via adding oxalic acid to obtain FeC 2 O 4 ⋅ 2H 2 O. Finally, the Ga 2 O 3 and Nd 2 O 3 (PrO 2 ) were prepared from the stripping solution. According to the whole process, the yield of Ga, Pr, and Nd was 93.4 %, 97 %, and 98 %, with the purity of Ga 2 O 3 and Nd 2 O 3 (PrO 2 ) being 98.6 % and 98.4 %, respectively. The results suggested that the stepwise recovery of REEs and Ga from NdFeB waste can be achieved.
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