Sulfur dioxide transport through aqueous solutions: Part I. Theory

Expressions are derived for the steady state flux of sulfur dioxide through films of water and neutral and alkaline salt solutions. A local equilibrium approximation yields and analytical expression for the flux through water and neutral salt solutions. To account for deviations from local equilibrium, the conversion from sulfur dixoxide (aq) to sulfur containing ions (and vice versa) is assumed frozen near the boundaries of the film (x = 0, x = 1). The thickness of the boundary layer near x = 1 is pH dependent, indicating an increasing deviation from equilibrium flux in increasingly alkaline solutions. Strong nonequilibrium behavior can be realized under some conditions for a film of concentrated sodium hydroxide operating as a liquid membrane and in conventional scrubbers.