Applicability of a catalytic reduction method using a palladium-copper catalyst and hydrazine for the denitration of a highly concentrated nitrate salt solution

Denitration of a highly concentrated sodium nitrate (NaNO 3 ) aqueous solution via a catalytic reduction method using a palladium-copper catalyst supported on carbon powder (Pd-Cu/C) and hydrazine (N 2 H 4 ) was investigated. It was demonstrated that nitrate ion (NO 3 − ) in a 5 mol L −1 NaNO 3 solution was completely reduced through an intermediate nitrite ion (NO 2 − ) to nitrogen compounds such as nitrogen, nitrous oxide, and ammonia. By comparing the reaction rates of NO 3 − and NO 2 − obtained using catalysts with various Pd-Cu compositions and different reductants (hydrogen (H 2 ) or N 2 H 4 ), it was determined that the catalyst with a molar ratio of Pd:Cu = 1:0.66 provides the maximum reaction rates for NO 3 − and NO 2 − using N 2 H 4 , and that not only the reactions of NO 3 − and NO 2 − but also that of N 2 H 4 were affected by the Pd-Cu composition.