Photocatalytic Reduction of Nitrates and Combined Photodegradation with Ammonium

Abstract

Bare titania and metal-promoted TiO2 catalysts were employed in the treatment of nitrates, which are ubiquitous pollutants of wastewater. The results show that the process can be carried out under visible light (from a white light LED lamp) and, in the best case, 23.5% conversion of nitrate was obtained over 4 h with full selectivity towards N2 by employing 0.1 mol% Ag/TiO2 prepared by flame spray pyrolysis. Moreover, the performance was worse when testing the same catalysts with tap water (11.3% conversion), due to the more complex composition of the matrix. Finally, it was found that photoreduction of nitrate can be effectively performed in combination with photo-oxidation of ammonium without loss in the activity, opening up the possibility of treating highly polluted wastewater with a single process. The latter treatment employs the two contaminants simultaneously as electron and holes scavengers, with very good selectivity, in a completely new process that we may call Photo-Selective Catalytic Reduction (Photo-SCR).

Photocatalytic Removal of Water Emerging Pollutants in an Optimized Packed Bed Photoreactor Using Solar Light

“…This way allows for the reusing of the catalytic materials from the treated effluent stream and the continuous operation, which are critical factors from an industrial point of view and scale-up [35,36]. Nevertheless, most of the current photocatalytic tests are only performed in batch photoreactors [37][38][39][40][41][42]. This experiment stage is the first step of catalyst testing.…”