Barium Sulfate Solubility in Aqueous Solutions Containing Chlorides or Nitrates

Electrolyte fluids produced during operation in geothermal wells and in natural gas or oil reservoirs involve temperature and composition variations. Crystallization fouling (or scaling) on the surface of industrial equipment happens due to these changes in the thermodynamic state. For this purpose, an experimental apparatus was designed and built to measure the solubility of sparingly soluble salts below the boiling point of water at ambient pressure. This work sheds light on the equilibrium properties of aqueous solutions containing barium sulfate (BaSO4) by reporting its 195 measurements of solubility in a wide range of temperatures and ionic strengths at ambient pressure, of which 143 new solubilities were determined. The equilibrium solubility of BaSO4 was measured and discussed in pure water or in solutions containing chlorides MCl (M = Na, Mg, K, Ca) or nitrates MNO3 (M = Na, K) at three temperatures (298.1, 323.1 and 368.1 K) at electrolyte molalities of up to 2 mol/kg water. The experimental solubility results of BaSO4 were compared with those reported in the literature for an electrolyte solution under the same conditions. The extended UNIQUAC model of Thomsen and Rasmussen was used as a reference to the experimental results of BaSO4 solubility. The experimental results indicated that generally the solubility of BaSO4 increases as a function of temperature until it reaches a maximum at around 373.1 K. It has been discovered that the addition of another electrolyte to the system can cause BaSO4 solubility to increase. A few exceptions are observed: KCl and CaCl2 beyond a certain value at 298.1 and 323.1 K cause BaSO4 solubility to decrease. Nitrate salts have a higher impact on solubility compared to chloride salts. The effect seems to be related to the anion. The cation has slightly less impact on solubility. The results presented in this work can facilitate better performance of thermodynamic models, further enabling safe operation and cost reduction for future sustainable energy production.