Concurrent magnesium and boron extraction from natural lithium brine and its optimization by response surface methodology

Abstract

The high demand of lithium for electromobility and energy storage requires an efficient and sustainable optimization of the current extraction from natural lithium brine process. In this context, this study develops a simultaneous Mg2+ and B3+ extraction system, which could be a contribution to the elimination of precipitation stages and the generation of high purity lithium brine. This dual system composed of a dialkylphosphate ionic liquid and a 2-ethylhexanol/kerosene mixture as magnesium and boron extractors, respectively, was optimized by a mathematical and statistical method known as response surface methodology (RSM). The RSM method identified, through a small number of experiments, the interdependencies of the parameters involved in the extraction process, and calculated their optimal values to achieve the maximum extraction efficiency of Mg2+ and B3+. The optimization was performed from two approaches. The first, maximizing the extraction of Mg2+ and B3+, resulted in experimental efficiencies of 99.17% of Mg2+, 99.36% of B3+ and 23.54% of Li+; whereas the second, in which lithium co-extraction was minimized, yielded efficiencies of 83.56% Mg2+, 99.22% B3+ and 3.36% Li+, results that demonstrate the high extraction capacity of the system, as well as proving the validity of the statistical model.