On Demand Electrochemical Production of Reagents to Minimize Resupply of Expendables

Abstract

The electrosynthesis of expendable reagents including acids, bases, and oxidants from simple salts or salt mixtures has been demonstrated using a variety of electrochemical cells. A five chambered electrodialytic water splitting (EDWS) cell with bipolar membranes was utilized to efficiently convert sodium sulfate, sodium chloride, potassium nitrate, and potassium chloride to conjugate acids and bases. With the same cell, selective segregation of cations and anions from mixed salt solutions occurred, resulting in relatively pure acids and bases. These results suggest that pure acids and bases can be produced from composite spacecraft brines. Chemical oxidants such as sodium and ammonium persulfate were also synthesized with high current efficiencies by the electrooxidation of salts and acids in a two chambered electrochemical cell. This demonstration of the electrosynthesis of useful reagents from simple and mixed salts provides opportunities to eliminate expendables and bring inorganic material balances nearer to closure in future manned space missions. The current technology is capable of producing reagents suitable for the pretreatment of urine, control of pH and nutrient levels in bioreactor and hydroponics solutions, hydrolysis of biomass, and treatment of acidic or basic incinerator exhaust gases.