ENVR 175 |
| This study tested alumina-supported Pd-In bimetallic catalysts for nitrate reduction with hydrogen in a continuous-flow packed-bed reactor. The goal was to assess the role that solution conditions have on the product distribution of catalytic nitrate reduction. Experimental results showed that nitrate at an influent concentration of 1 mM was reduced below the regulatory MCL of 0.71 mM by the addition of hydrogen, with no accumulation of nitrite or nitrous oxide. The final products were ammonia and nitrogen. Ammonia production increased with increases in pH, hydrogen and sulfide concentrations, and decreased by addition of dissolved oxygen. Sulfide was shown to completely foul the catalyst bed. Regeneration with NaOCl and NaHCO3 was able to restore nitrate reduction to near its pre-fouled level, but high ammonia production and low levels of nitrous oxide were observed. Ammonia production from the fresh and regenerated sulfide-fouled catalyst was 32.1±0.5 and 82.3±1.9% of nitrate reduced (on a molar basis), respectively. These results indicate that influent pH and hydrogen levels can be optimized to reduce ammonia production and that reduced sulfur species should be removed from nitrate-contaminated source waters before they come in contact with Pd-In catalysts. |
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Advances in Abiotic Transformation Processes for Micropollutants in Drinking Water and for Sourcewater Protection
8:30 AM-12:10 PM, Wednesday, April 9, 2008 Morial Convention Center -- Rm. 237, Oral
Division of Environmental Chemistry |