Oxygen solubility modeling in aqueous solutions

Abstract

Oxygen dissolved in the aqueous phase (O/sub 2/)/sub aq/ is an important oxidant in many industrial processes, ranging from pressure leaching and heap leaching of metals from minerals to the bleaching of wood fibers in the pulp and paper industry. Frequently, (O/sub 2/)/sub aq/ is a prime agent promoting corrosion of metals in aqueous systems. This study presents a general solubility model for estimating oxygen solubility in aqueous inorganic solutions over a wide range of conditions. These include changes in oxygen partial pressure P(O/sub 2/) (atm), variations in the process temperature T (K), and changing concentrations C/sub t/ of dissociated inorganic solute I. The model is based on a thermodynamic analysis showing that the concentration c/sub aq/ of (O/sub 2/)/sub aq/ in pure water is dependent upon P(O/sub 2/) and T via an equation of the form c/sub aq/=P(O/sub 2/)f(T), where f(T) is a T-dependent function related to the chemical potential, entropy, and partial molar heat capacity of the gaseous oxygen (O/sub 2/)/sub g/ and dissolved (O/sub 2/)/sub aq/ species. In the presence of a single I, this equation is modified by a /spl phi/-factor such that the new oxygen solubility, (c/sub aq/)/sub I/, becomes (c/sub aq/)/sub I/=/spl phi/c/sub aq/=/spl phi/P(O/sub 2/)f(T), where /spl phi/ is an I-dependent function of C/sub I/. Inorganic solutes of similar stoichiometry, composed of a common anion and having cations from the same group in the Periodic Table, tend to exhibit a similar /spl phi/-factor and (c/sub aq/)/sub I/ value, provided all concentrations, c/sub aq/, (c/sub aq/)/sub I/, and C/sub I/, are reported in molal (m) units (mol/kg H/sub 2/O). Methods for incorporating the effect of multiple I on /spl phi/ are presented and discussed.