Appropriate conditions or maximizing catalytic reduction efficiency of nitrate into nitrogen gas in groundwater

This study focused on the appropriate catalyst preparation and operating conditions for maximizing catalytic reduction efficiency of nitrate into nitrogen gas from groundwater. Batch experiments were conducted with prepared Pd and/or Cu catalysts with hydrogen gas supplied under specific operating conditions. It has been found that Pd-Cu combined catalysts prepared at a mass ratio of 4:1 can maximize the nitrate reduction into nitrogen gas. With an increase in the quantity of the catalysts, both nitrite intermediates and ammonia can be kept at a low level. It has also been found that the catalytic activity is mainly affected by the mass ratio of hydrogen gas to nitrate nitrogen, and hydrogen gas gauge pressure. Appropriate operating values of H-2/NO3-N ratio, hydrogen gas gauge pressure, pH, and initial nitrate concentration have been determined to be 44.6 g H-2/g N, 0.15 atm, 5.2 (-), 100 mg L-1 for maximizing the catalytic reduction of nitrate from groundwater. (C) 2003 Elsevier Science Ltd. All rights reserved.