Selective reduction of nitrate to N2 using ilmenite as a low cost photocatalyst

This work assesses the feasibility of using natural ilmenite as catalyst in NO3- photo-reduction with oxalic acid as reducing agent. The experimental set-up includes a magnetically stirred batch reactor equipped with a medium pressure Hg UV-lamp (30 W/m(2)). Experiments were carried out under N-2 atmosphere at 25 degrees C, using 1-2 times the stoichiometric amount of C2O42- to reduce NO3- to N-2. The reduction of NO3- to N-2 via NO2- is, by far, the main route. Concurrently, the generation of NOx (g) via NO3- and NO2- reduction is also observed. The complete NO3- and C2O42- removal and a selectivity towards N-2 > 93 % is achieved by using the stoichiometric C2O42- dose after 210 min, without the generation of undesirable NH4+. The residual NO2- concentration was lower than 0.5 mg N/L. Besides, doubling the C2O42- dose allowed the complete removal of nitrogen from the aqueous phase with a N-2 selectivity > 97 %.