Thermodynamics of the oxidation of dissolved organic contaminants in shuttle orbiter humidity condensates

Abstract

A condensing heat exchanger has been used to collect humidity condensates during two space shuttle missions. Analyses of the reclaimed waters indicate the presence of short chain ' alcohols, carboxylic acids and other hydrophilic low molecular weight organics which originate as airborne contaminants consequent to human metabolism and materials outgassing. To better understand aqueous phase oxidation processes proposed for the mineralization of these dissolved organics, the thermodynamics of combustion of the predominant species to CO 2 (aq) and H 2 O( ) have been examined. The relationships between temperature, ΔH, ΔS, and ΔG for the mineralization reactions have been derived for nine of the most significant contaminants and fitted to a fourth degree polynomial with excellent results. These data were then used to calculate values of the three aforementioned thermodynamic properties as functions of reaction temperature for the complete oxidation of the two humidity condensates. The results indicate that the enthalpy of combustion will result in only minor heating of the aqueous phase.

Electrochemical oxidation process for water condensates recycling in a shuttle orbiter

“…8. For the tests carried out at higher current intensity, a noticeable increase in the NO 3 2 concentration was initially noted up to a rather stable value (see Fig. 9).…”

“…During manned space missions the accumulated hygiene and condensate water must be reclaimed on board a spacecraft, otherwise the high purity water produced by the fuel cell (as a valuable by-product) during the electrical energy generation is not sufficient to maintain the water balance [3]. Nowadays, the energy needed to support long-term or permanently manned International Space Station (ISS) missions is provided by solar panel arrays, which exploit the high intensity of UV irradiation.…”