Boron extraction by aliphatic mono- and di-hydroxy alcohols from a representative continental brine

The extraction properties of mono-hydroxy alcohols (2-butyl-1-octanol, 2-ethyl-1-hexanol, 1-octanol) and di-hydroxy alcohols (2-ethyl-1,3-hexanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-methyl-2,4-pentanediol) towards boron, potassium, lithium, sodium, calcium and magnesium ions were investigated as a function of pH and phase volume ratio (O/A) by considering an aqueous phase with a composition mimicking the brine from the Salar de Hombre Muerto in Argentina, in the Lithium Triangle. The mono-hydroxy alcohols are soluble in kerosene and sulfonated kerosene whereas the di-hydroxy alcohols are only soluble in mixtures of kerosene and toluene or m-xylene. No significant effect of the diluent on the extraction properties is observed. All alcohols exhibit high selectivity for boron over potassium, lithium, sodium, calcium and magnesium at acidic pH (pH = 1–5.5). A significant decrease of the extraction efficiency of boron by the mono-hydroxy alcohols is observed at pH >5.5 while no significant decrease of the extraction efficiency occurs with di-hydroxy alcohols. Finally, the best conditions to selectively extract boron from the synthetic brine with 1 mol L⁻¹ mono-hydroxy alcohols or di-hydroxy alcohols at 35 °C are pH = 5.5 and O/A = 4 when the diluent is kerosene and O/A = 2 when the diluent is a mixture of kerosene and toluene.