title: Mechanistic Features of the TiO2 Heterogeneous Photocatalysis of Arsenic and Uranyl Nitrate in Aqueous Suspensions Studied by the Stopped-Flow Technique.
abstract: The dynamics of the transfer of electrons stored in TiO2 nanoparticles to As(III) , As(V) , and uranyl nitrate in water was investigated by using the stopped-flow technique. Suspensions of TiO2 nanoparticles with stored trapped electrons (etrap (-) ) were mixed with solutions of acceptor species to evaluate the reactivity by following the temporal evolution of etrap (-) by the decrease in the absorbance at λ=600 nm. The results indicate that As(V) and As(III) cannot be reduced by etrap (-) under the reaction conditions. In addition, it was observed that the presence of As(V) and As(III) strongly modified the reaction rate between O2 and etrap (-) : an increase in the rate was observed if As(V) was present and a decrease in the rate was observed in the presence of As(III) . In contrast with the As system, U(VI) was observed to react easily with etrap (-) and U(IV) formation was observed spectroscopically at λ=650 nm. The possible competence of U(VI) and NO3 (-) for their reduction by etrap (-) was analyzed. The inhibition of the U(VI) photocatalytic reduction by O2 could be attributed to the fast oxidation of U(V) and/or U(IV) .
authors.affiliation: Gerencia Química, Comisión Nacional de Energía Atómica, Av. Gral. Paz 1499, 1650, San Martín, Prov. de Buenos Aires, Argentina.|Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Av. Rivadavia 1917, 1033, Ciudad Autónoma de Buenos Aires, Argentina.
authors.forename: Jorge M
authors.initials: JM
authors.lastname: Meichtry
authors.affiliation: Gerencia Química, Comisión Nacional de Energía Atómica, Av. Gral. Paz 1499, 1650, San Martín, Prov. de Buenos Aires, Argentina.|Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Av. Rivadavia 1917, 1033, Ciudad Autónoma de Buenos Aires, Argentina.
authors.forename: Ivana K
authors.initials: IK
authors.lastname: Levy
authors.affiliation: Chemistry Department, Faculty of Science, Helwan University, Ain Helwan, Cairo, Egypt.
authors.forename: Hanan H
authors.initials: HH
authors.lastname: Mohamed
authors.affiliation: Institut für Technische Chemie, Leibniz Universität Hannover, Callinstrasse 3, 30167, Hannover, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Dillert
authors.affiliation: Institut für Technische Chemie, Leibniz Universität Hannover, Callinstrasse 3, 30167, Hannover, Germany.|Laboratory for Nanocomposite Materials, Department of Photonics, Faculty of Physics, Saint-Petersburg State University, Ulianovskaia str. 3, Peterhof, Saint-Petersburg, 198504, Russia.
authors.forename: Detlef W
authors.initials: DW
authors.lastname: Bahnemann
authors.affiliation: Gerencia Química, Comisión Nacional de Energía Atómica, Av. Gral. Paz 1499, 1650, San Martín, Prov. de Buenos Aires, Argentina. litter@cnea.gov.ar.|Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Av. Rivadavia 1917, 1033, Ciudad Autónoma de Buenos Aires, Argentina. litter@cnea.gov.ar.|Instituto de Investigación e Ingeniería Ambiental, Universidad Nacional de General San Martín, Campus Miguelete, Av. 25 de Mayo y Francia, 1650, San Martín, Prov. de Buenos Aires, Argentina. litter@cnea.gov.ar.
authors.forename: Marta I
authors.identifier: http://orcid.org/0000-0002-0312-0177
authors.initials: MI
authors.lastname: Litter
keywords: arsenic; heterogeneous catalysis; photocatalysis; stopped flow; uranium