Removal of Perchlorate from Water and Wastewater by Catalytic Hydrogen Gas Membrane Systems
DEPUTY DIRECTOR OF DEFENSE RESEARCH AND ENGINEERING ARLINGTON VA STRATEGIC ENVIRONMENTAL RESEARCH AND DEVELOPMENT PROGRAM
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Year I work explored several methods for the reduction of perchlorate in water by 1 molecular hydrogen gas in the presence of catalysts, 2 elemental or zero-valent metals, 3 an indirect electrochemical system, 4 a catalytic mono-membrane, and 5 a catalytic dual-membrane system. More than 150 experiments were conducted to screen the best catalysts using gaseous or atomic hydrogen as the reducing agent. Appendix A summarizes catalysts and catalytic systems studied throughout the project period ending December 2005. Results showed that the extent and the rate of perchlorate reduction varied among the systems studied. Overall, two methods stood out as the most promising processes the catalytic dual-membrane system and the indirect electrochemical system using a titanium electrode. These two methods were studied further during Year II. For the catalytic dual-membrane system, it was found that perchlorate was removed completely at a rapid to moderately rapid rate. A total of 18 metallic catalysts from the first, second, and third rows of the periodic table were studied. In terms of the gross reaction rate constant, Ti titanium and Co cobalt from the first row and Sn tin from the second row were the most promising, with a rate constant of 9.5 M-hr-1. In terms of specific rate constant, i.e., rate constant per mass of catalyst, the following are the most promising catalysts Sc scandium and Cr chromium from the first row, Mo molybdenum and Cd cadmium from the second row, and Pt platinum from the third row. The specific rate constant of the above metallic catalysts was 10 microM-hr-1-mg-1 catalyst. In summary, we have discovered that Ti, Sn, Cr, Mo, Cd, and Pt are the most promising metallic catalyst for the reduction of perchlorate in dilute aqueous solutions.
- Inorganic Chemistry