Photocatalytic abatement of ammonia in nitrogen-containing effluents

Abstract

The photocatalytic abatement of aqueous ammonia, the major nitrogen-containing compound in livestock manure, was investigated employing (i) a batch reactor equipped with an immersion UVA lamp, containing aqueous suspensions of different commercial TiO2 powders and (ii) a 40L prototype plug flow photo-reactor, suitable for the photocatalytic treatment of real swine and bovine manure, consisting of 9 vertical elements connected in series, internally coated with a TiO2 film, each one centrally housing a UVA lamp. A preliminary systematic investigation performed with the first photo-reactor evidenced that ammonia conversion and the selectivity toward the main oxidation products (N2, NO2− and NO3−) depend on the amount of dissolved O2, on pH and on the photocatalyst's amount and structural features. Extremely promising results, in terms of both ammonia conversion (up to the 88%) and selectivity to nitrogen gaseous species (99%), were achieved when the prototype photo-reactor was fed with suitably pre-treated manure. The TiO2-based photocatalytic treatment can thus be considered an effective remediation technology for the abatement of nitrogen-containing pollutants in surface and groundwater, originating from large-scale animal husbandries.