Solubility of BaSO4 and the Physicochemical State of Barium in Seawater

Abstract

Barium sulfate solubility in diluted Na₂SO₄–NaNO₃ solutions and seawater of 35‰ salinity at 22°C was studied in experiments. The value obtained for the thermodynamic solubility product of barium sulfate was \(L_{{{\text{BaSO}}_{4}^{0}}}^{0}\) = (7.57 ± 0.87) × 10^–11. It was shown that equilibrium concentration of dissolved barium in seawater was 30.7 μg/L and the water mass of the World Ocean was slightly undersaturated in BaSO₄. The experimental data were used to determine the values of the mean ionic activity coefficient of BaSO₄, total activity coefficient, and fractions of free Ва²⁺ ions in seawater: 0.108, 0.131, and 0.59, respectively.