Effect of Carbon Dioxide in Seawater on Desalination: A Comprehensive Review

Abstract

The two main methods of removing salt from ocean water currently in use for large scale applications are: distillation using thermal desalination and membrane reverse osmosis separation. A detailed knowledge of the CO₂ solubility in the seawater at the conditions prevailing in the system is required for the modeling of CO₂ release in the multi‐stage flash distillers. The measurement of the solubility of CO₂ in pure water has been extensively studied in the literature, whereas there is a lack of saline solutions studies. Several studies have investigated the solubility of CO₂ in seawater under different temperatures and pressures without covering the conditions that prevailed in the desalination plants for example low pressures and high temperatures. The gas solubility can be theoretically estimated by considering the ionic strength and the salting‐out parameter in the low‐pressure regime, i.e., near atmospheric pressure. The measurements of gas solubility can be made as a function of the seawater temperature and salinity at low pressure where effect of pressure can be considered negligible. Alkaline scale formation causes fouling in the MSF plants and it is known that the rate of formation of calcium carbonate and magnesium hydroxide in seawater depends on a number of parameters such as temperature, pH, concentration of bicarbonate ions, rate of CO₂ release, concentration of Ca²⁺ and Mg²⁺ ions, and total dissolved solids. This review shows an overview of the carbon dioxide solubility in the high concentrated saline water, carbonate equilibriums in the seawater and the various correlations used to characterize the CO₂‐seawater system.