Temperature and pressure dependent solubility of oxygen in water: a thermodynamic analysis

A thermodynamic analysis of the temperature dependent equilibrium between oxygen solubility (activity) in purl water and oxygen partial pressure P-O2 was undertaken. Experimental oxygen solubility sources were used to determine a set of self consistent Values for the chemical potential, entropy and partial molar heat capacity of dissolved oxygen. These were combined with established thermodynamic data for gaseous oxygen to develop a single thermodynamic equation describing the relationship between gaseous oxygen fugacity, dissolved oxygen activity, temperature and the equilibrium constant k. This equation was consistent with k values calculated from published experimental solubility data for temperatures from 273 to 616 K and pressures to 60 atm, encompassing the conditions encountered during oxygen leaching operations. Within these ranges, it was shown that the gas fugacity and dissolved oxygen activity coefficients were sufficiently close to unity that the k-equation may be used to relate the molal concentration c(aq) of dissolved O-2 for any combination of temperature T (K) and P-O2 (atm), c(aq) = P-O2{0.046T+203.357Tln(T/298) - (299.378+0.092T)(T-298)-20.591x103 / (8.3144)T} The significance of the difference in heat capacity between gaseous and dissolved oxygen was discussed, leading to suggestions for incorporating the effects of dissolved mineral solutes into the oxygen solubility equation. (C) 1998 Elsevier Science B.V.