Comparison of removing NO3− in the polluted groundwater of in-situ leaching of uranium mine with DNB and Fe0

Removing NO₃^- in polluted groundwater of in-situ leaching uranium mine with iron powder (zero-valent iron, Fe⁰), DNB, iron powder and DNB are studied. The condition of tests include different pH of solution, dosage of iron powder, and treating time. The experimental results show that over 93% of NO₃^- in unneutralized polluted groundwater (pH value about 1.46) can be removed with 16.5 g·L^-1 iron powder in 4 days. NO₃^- in neutralized polluted groundwater (pH value about 7.62) can also be removed with 2 g·L^-1 iron powder. The removing rate of NO₃^- is enhanced with time and the highest removing rate reaches 54% in 5 days. NO₃^- in neutralized polluted groundwater can also be removed with DNB in condition of ρ(COD)/ρ(NO₃^-) equal to 1.5, 35°C, pH 5-8. The removing rate of NO₃^- is over 90% in 5 days. In certain conditions, the removing rate of NO₃^- with DNB is 30% higher than that with iron powder. The removing rate is promoted with DNB adding iron powder. Comparing to DNB, the iron powder can be used in larger range of pH of the polluted groundwater.