Catalytic reduction of nitrate with Pd-In2O3.

This work presents a novel catalyst preparation method and the optimization of operation conditions for an effective NO3- conversion with a high selectivity and stability that guarantee water quality for human consumption. Catalytic reduction of NO3- and NO2- was carried out with Pd supported on In2O3 under mild operation conditions (25 °C, 1 atm) with H2 and CO2 as reducing and acidifying agents, respectively. The catalyst was used in batch experiments showing the suppression of NO2- accumulation and low NH4+ selectivity at acid pH. Long-term experiments were carried out with Pd on γ-Al2O3 spheres covered with In2O3. This catalyst presented a high stability during more than 700 h. A concentration of NO3- below 50 mg/L was achieved, producing less than 0.5 mg/L of NH4+ as reaction by-product by a strict limitation of the H2 fed and controlling several operating conditions.