Nitrate photocatalytic reduction on TiO2: Metal loaded, synthesis and anions effect. Issue 4 (August 2020)

• Record Type: Journal Article
• Authors: Freire, Jessica M.A.; Matos, Maria A.F.; Abreu, Dieric S.; Becker, Helena; Diógenes, Izaura C.N.; Valentini, Antoninho; Longhinotti, Elisane
• Is Part Of: Journal of environmental chemical engineering. Volume 8:Issue 4(2020)
• Publication Date: 2020-08
• Subjects: Groundwater -- Denitrification -- Photocatalytic reduction -- Loaded TiO2 catalysts; Chemical engineering -- Environmental aspects -- Periodicals; Environmental engineering -- Periodicals; Chemical engineering -- Environmental aspects; Environmental engineering; Periodicals; 660.0286
• DOI: 10.1016/j.jece.2020.103844
• Languages: English
• ISSNs: 2213-2929

Abstract

Graphical abstract: Highlights: Photocatalytic reduction of NO3 − to N2 was studied over TiO2 -based catalysts. Formate oxidation at hvb + produces CO2 − that, in turn, reduces NO3 − to N2 . Inorganic anions in the medium induce activity loss of the catalysts. TiO2 loaded with Ag + showed performance improvement of c.a. 15 %. Abstract: Herein we report the study of the photocatalytic reduction of nitrate by TiO2 in presence of inorganic anions and for TiO2 loaded with Ag +, Cu 2+, Ni 2+, and Fe 3+ by following the wet impregnation method. All photocatalytic assays were performed in solution containing formic acid as scavenger of the photogenerated holes ( hvb + ). The observed dependence of the photocatalytic nitrate reduction on the concentration of HCOOH suggests this specie is oxidized at hvb + forming CO2 − radicals that, in turn, reduces NO3 − to N2 . The photocatalytic assays in presence of H2 PO4 −, SO4 2−, HCO3 −, F − and Cl − indicated the surface anionization leading to hvb + blocking and, as consequence, to the decrease of HCOOH oxidation. Indeed, impedimetric data indicated the adsorbed anions on TiO2 are mainly responsible for hindering the interaction between the electron donor (HCOOH) and the photocatalyst. Among the metal ions used for loading, only Ag + was efficient in storage the photogenerated electrons ( ecb − ) with a performance improvement of 15.5 % in respect to the neat TiO2 catalyst. Experiments carried out with groundwater samples showed an activity loss that was assigned to the catalyst poisoning by other ions, although with selectivity to N2 close to 100 %.