Catalytic reduction of nitrate in water over Pd-Cu/γ-Al2O3 catalyst

The increase of nitrate concentration in ground water has stimulated to intensive research on denitrification. Catalytic reduction of nitrate by a solid Pd-Cu bimetallic catalyst presents one of the most promising approaches for removal of nitrate from water. In this work, the catalytic reduction of nitrate in aqueous solution by powder catalyst and ceramic membrane in a batch reactor was investigated. The nitrate reduction was studied as a function of the initial concentration and the H-2 flux. The results demonstrated that Pd-Cu/gamma-Al2O3 can effectively remove nitrate, the total nitrogen removal efficiency is 81 %. The reduction activity of nitrate and the formation of ammonium are mainly controlled by the diffusion limitation and the mass transfer of the reactants. Under the condition of diffusion controlled or the intensification of the mass transfer, and a good reaction condition, the Pd-Cu/gamma-Al2O3 can reduce the amounts of ammonium while retaining higher reactivity. The ceramic membrane catalyst can create a high effective gas/liquid/solid interface, and shows higher selectivity as compared with the powder catalyst. The selectivity for nitrogen was improved from 73.4% to 89.4%. The catalytic reduction of nitrate by ceramic membrane shows a promising method for nitrate reduction, especially for the small-scale application in the rural area.