NUMERICAL-SIMULATION OF IODINE SPECIATION IN RELATION TO WATER DISINFECTION ABOARD MANNED SPACECRAFT .1. EQUILIBRIA

Elemental iodine (I-2) is currently used as the drinking water disinfe ctant aboard the Shuttle Orbiter and will also be incorporated into th e water recovery and distribution system for the International Space S tation Alpha. Controlled release of I-2 is achieved using the Microbia l Check Valve (MCV), a flow-through device containing an iodinated pol ymer which imparts a bacteriostatic residual concentration of approxim ate to 2mg/L to the aqueous stream. During regeneration of MCV caniste rs, I-2 concentrations of approximate to 300mg/L are used. Dissolved i odine undergoes a series of hydrolytic disproportionation and related reactions which result in the formation of an array of inorganic speci es including: I-, I-3(-), HOI, OI-, IO3-, HIO3, I2OH-, I2O-2, and H2OI +. Numerical estimation of the steady-state distribution of inorganic iodine containing species in pure water at 25 degrees C has been achie ved by simultaneous solution of the multiple equilibrium expressions a s a function of pH. The results are reported herein.