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

Abstract

The extraction properties of mono-hydroxy alcohols (2-butyl-1-octanol, 2-ethyl-1-hexanol, 1-octanol) and dihydroxy 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 mxylene.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.