Chromatographic Study on Boron Isotopic Fractionation at High Pressure

Abstract

Boron isotopic fractionation factor (S) between boron adsorbed onto kaolin clay and boron in aqueous solution was determined by break-through column chromatography at 25.0 MPa at 5 and 25°C. The S values obtained were 1.0021 at 5°C and 1.0011 at 25°C, and were smaller than those obtained by the batch method performed at the atmospheric pressure at room temperature. Theoretical calculations estimate that more than 90% of boron in the clay phase was taken up as B(OH)3-form at high pressures. Combining the present S values with preliminarily obtained one at 12.0 MPa, it is likely that S value decreases with increasing pressure, which suggests that the difference of the partial isotopic molar volumes between 10B(OH)3 and 11B(OH)3 is larger than that of the volumes between 10B(OH)4 − and 11B(OH)4 −.