Search

The development of effective methods for the abatement of some harmful pollutants from waste waters and from hydric resources is a challenging task. Nitrogen containing compounds, such as inorganic ammonia, nitrites and nitrates are harmful contaminants for drinking water, inducing acute and/or chronic diseases, especially affecting infants and children. Furthermore, when released in waste waters they contribute to eutrophication, or possibly contaminate ground water. This is particularly relevant in agriculturally intensive zones and in the case of some relevant industrial processes involving e.g., nitration reactions. In the present paper, we review existing or innovative processes, mainly based on photocatalytic steps for the abatement of inorganic N-containing compounds from waste waters and for drinking water treatment, focusing on selectivity towards innocuous N2.

Several N-containing organic compounds of anthropic origin, namely dyes, pesticides/herbicides and pharmaceuticals, are responsible of water pollution, due to their high solubility in water and low adsorption in soil, leading to a high mobility in the aquifer. Besides pesticides and dyes, widely recognized as water pollutants, environmental contamination by pharmaceuticals is an emerging issue, since both drugs and their metabolites may act as water pollutants, and most of water potabilization plants do not treat them. Removal of such species by physico-chemical methods (adsorption and coagulation; sedimentation; filtration; use of membranes and chlorination) suffers from several drawbacks, including high operating costs, and formation of secondary pollutants that are then released in the environment. Nonetheless, currently employed biological methods do not allow removing nonbiodegradable pollutants. Advanced oxidation processes (AOPs), which imply the in situ production of highly reactive species (i.e., H2O2, OH, O− 2 , O3 under relatively mild experimental conditions, allow the degradation (and eventual mineralization to CO2 and H2O) of refractory organics into readily biodegradable compounds and may be used either before or after biological treatments. This review addresses the most common catalytic and photocatalytic AOPs that can be adopted for the removal of some N-containing compounds of different origin and nature.