An Improved Oxidation Reactor for Total Organic Carbon Measurements

Closed-loop water recycle systems for future manned space mission will required sensitive analytical methods to determine the quality of the water and insure the health and safety of the crew. As part of a NASA-funded study, we have been investigating techniques for the measurement of Total Organic Carbon (TOC) in water for use on the Space Station. The prototype system developed employs a membrane-based conductometric CO₂ sensor which provides a gravity-independent means for measuring the amount of CO₂ produced from the oxidation of organic compounds. Recently, we have been developing a system for the oxidation of organic compounds that does not require the use of chemical oxidizing agents. The reagentless oxidation reactor uses a combination of electrolytic and photolytic oxidation to convert organic compounds to CO₂. A new reactor design which incorporates a larger surface area anode and active removal of hydrogen has been tested and the oxidation efficiency for a range of organic compounds determined. Oxidation efficiencies as high as 96% to 99% can be obtained at concentrations up to ∼50 ppm C, even for difficult to oxidize organic compounds such as urea. The samples were pre-acidified and the reactor operated at approximately 60 °C. The reactor produced stable oxidation without any significant decrease in the efficiency of the reactor over time, as was observed in previous reactor designs.