DEVELOPMENT OF CATALYSTS FOR A SELECTIVE NITRATE AND NITRITE REMOVAL FROM DRINKING-WATER

The increasing nitrate concentration of ground water has stimulated intensive research on the denitrification of drinking water. At present nitrate is removed either by physicochemical or biological methods. The application of catalysts in the purification of drinking water was not examined. We found that nitrate and nitrite can be reduced with hydrogen on noble metal catalysts. Products of the reaction are gaseous nitrogen and dissolved ammonia, which is un-desired in drinking water. Here we describe the development of a supported palladium catalyst, which reduces nitrite to nitrogen with a selectivity of 99.9 %. After activation with a second metal, e.g. copper, this catalyst shows nitrate removal activity, but also a higher formation of ammonia. The addition of palladium catalysts to the palladium-copper catalysts and hydrogen limitation reduce the ammonia formation of the nitrate reduction. After complete removal of 100 mg/l nitrate, less than 0.5 mg/l ammonia were formed, so that the application of the catalysts in the purification of drinking water seems possible.