0011-9164/09/$– See front matter © 2008 Elsevier B.V. All rights reserved Desalination 244 (2009) 144–152 NO 3 ! removal with a new delafossite CuCrO 2 photocatalyst W. Ketir, A. Bouguelia, M. Trari* Laboratory of Storage and Valorization of Renewable Energies, Faculty of Chemistry, U.S.T.H.B., BP 32, 16111 Algiers, Algeria Tel. +213 (21) 247950; Fax: +213 (21) 247311; email: mtrari@usthb@yahoo.fr Received 14 March 2007; Accepted 20 May 2008 Abstract The removal of NO 3 ! by a CuCrO 2 -mediated catalytic photoprocess was investigated under mild conditions. The delafossite CuCrO 2 exhibits an excellent chemical stability over the whole pH range and relatively a large specific surface area when elaborated by chemical means. The optical gap was found to be 1.28 eV, close to the optimal value required for terrestrial applications. The conduction band is located at !1.06 V SCE and thus lies below the NO 3 ! level leading to a thermodynamically favorable nitrate reduction under visible light. The possibility of identifying the reaction products via the intensity-potential characteristics was explored. The reaction of NO 3 ! proceeds in competition with the water reduction and seems to be the major reason in the regression of the photoactivity during prolonged testing. The complete conversion occurs in less than ~4 h with a quantum efficiency of ~2%. Keywords: Delafossite; Photoprocess; Nitrate; Water reduction 1. Introduction The development of processes for the removal of inorganic pollutants in water has been exten- sively studied [1]. Some ecological problems arise from nitrification through fertilizers and beyond a threshold concentration, NO 3 ! leads to environmental problems in both surface and groundwater. The nitrogen-based oxides coming from increasing industrial activities disturb the *Corresponding author. ecological system. The World Health Organiza- tion guidelines requires the NO 3 ! level to be less than or equal to 45 mg L !1 . Many methods have been used to lower the NO 3 ! concentration, e.g., anion exchange, activated alumina or reverse osmosis [2]. However, such techniques are expensive and often are not easy use. Photo- catalyzed reactions using semiconductor powder have been widely investigated [3–5], but only a few papers concerning denitrification have been reported [6,7]. doi:10.1016/j.desal.2008.0 .0 5 20 .