E-pH Diagram of Fe-N-H<sub>2</sub>O System and its Application in Nitrite

Reduction product of nitrite by Spherical sponge iron (SSI) was investigated through static state experiment combined with E-pH diagram of Fe-N-H2O system. In a certain range of pH and redox potential, the speciation of iron include Fe0, Fe2+, Fe3+, Fe(OH) 2 and Fe(OH) 3 , and the speciation of N was NO 2 , NO 3 -, N 2 , NH 4 + or NH 3 as the initial speciation of N was nitrite. pH in solution increased to above 10 in 6min because of rapid erosion battery reaction of zero-valent iron. Moreover, the E value in solution declined quickly to the minimum and then increased slightly because of dissolution of oxygen from atmosphere. It was suggested that ammonium was the finial product during the reduction of nitrite by SSI. Nitrite removal from wastewater was related with escape of ammonia, which was gas state of ammonium, when the water solution was alkaline.