Catalytic Reduction of High Concentration Nitrate-Bearing Industrial Wastewater for Ammonium Recovery

The concept of NH₄⁺/NH₃ production from wastewater treatment for subsequent recovery and reuse has gained much attention in the past few years. The conversion of NO₃^– present in wastewater into NH₄⁺/NH₃ through catalytic reduction is a sustainable approach for resource utilization from wastewater. In the present work, the application of this technique to industrial wastewater with a high NO₃^– concentration is proposed. A good activity of Pd–Cu catalysts supported on carbon black was observed at high NO₃^– concentrations. Complete NO₃^– conversion was achieved in water with an initial concentration of 1000 mg/L and a catalyst concentration of 0.93 g/L in a stirred reactor. Furthermore, an improvement in catalytic activity was obtained when the reactor was operated without pH control, resulting in an increase in NH₄⁺ formation to 184 mg/L. Additionally, in successive 8-h reaction cycles with a reaction medium equivalent to that of industrial wastewater, a progressive decrease in catalytic activity was observed, which may be associated with a noticeable decrease in the Pd⁰/Pdⁿ⁺ species ratio.