Boron Volatilization and Its Isotope Fractionation during Evaporation of Boron Solution

Abstract

Evaporation experiments were undertaken to determine the volatility of parts-per-million concentrations of boron in water and dilute HCl in the presence and absence of equimolar mannitol and/or cesium. Multiple 10 mL aliquots prepared identically were evaporated to various extents or just to dryness and heated 10−20 min after reaching dryness under filtered air at 60 °C. Boron was only retained quantitatively in water during evaporation and after reaching dryness in the presence of equimolar mannitol and cesium. Boron was retained quantitatively in dilute HCl solution during evaporation, without mannitol or cesium. But it could be retained when the dilute HCl just reached dryness and thereafter only in the presence of equimolar mannitol. Isotopic measurements of the evaporating solutions and residues indicate that the heavier isotope, 11 B, is preferentially lost from the near- neutral and acidic solutions examined. The results are pertinent for procedures requiring preconcentration of boron.