Coupling of solar photoelectro-Fenton with a BDD anode and solar heterogeneous photocatalysis for the mineralization of the herbicide atrazine Benjamín R. Garza-Campos a , Jorge Luis Guzmán-Mar a , Laura Hinojosa Reyes a , Enric Brillas b , Aracely Hernández-Ramírez a , Edgar J. Ruiz-Ruiz a,⇑ a Universidad Autónoma de Nuevo León, Facultad de Ciencias Químicas, Av. Pedro de Alba, Ciudad Universitaria, San Nicolás de los Garza, Nuevo León, Mexico b Laboratori d’Electroquímica dels Materials i del Medi Ambient, Departament de Química Física, Facultat de Química, Universitat de Barcelona, Martí i Franqués 1-11, 08028 Barcelona, Spain highlights  Uniform and adherent TiO 2 films prepared onto glass spheres by sol–gel dip-coating.  Very low removal of atrazine by solar photocatalysis with TiO 2 catalyst.  Atrazine partly mineralized by solar photoelectro-Fenton using a BDD/BDD cell.  Faster and greater mineralization by coupled solar photoelectro-Fenton-solar photocatalysis.  Atrazine mineralization inhibited by cyanuric acid formation with maximum 65% conversion. article info Article history: Received 13 August 2013 Received in revised form 15 October 2013 Accepted 16 October 2013 Available online 11 November 2013 Keywords: Anodic oxidation Atrazine Solar heterogeneous photocatalysis Solar photoelectro-Fenton abstract Here, the synergetic effect of coupling solar photoelectro-Fenton (SPEF) and solar heterogeneous photocatalysis (SPC) on the mineralization of 200 mL of a 20 mg L 1 atrazine solution, prepared from the commercial herbicide Gesaprim, at pH 3.0 was studied. Uniform, homogeneous and adherent ana- tase-TiO 2 films onto glass spheres of 5 mm diameter were prepared by the sol–gel dip-coating method and used as catalyst for SPC. However, this procedure yielded a poor removal of the substrate because of the low oxidation ability of positive holes and Å OH formed at the catalyst surface to destroy it. Atrazine decay was improved using anodic oxidation (AO), electro-Fenton (EF), SPEF and coupled SPEF-SPC at 100 mA. The electrolytic cell contained a boron-doped diamond (BDD) anode and H 2 O 2 was generated at a BDD cathode fed with an air flow. The removal and mineralization of atrazine increased when more oxidizing agents were generated in the sequence AO < EF < SPEF < coupled SPEF-SPC. Organics were destroyed by Å OH formed from water oxidation at the BDD anode in AO, along with Å OH formed from Fen- ton’s reaction between added Fe 2+ and generated H 2 O 2 in EF. In SPEF, solar radiation produced higher amounts of Å OH induced from the photolysis of Fe(III) species and photodecomposed intermediates like Fe(III)-carboxylate complexes. The synergistic action of sunlight in the most potent coupled SPEF-SPC was ascribed to the additional quick removal of several intermediates with the oxidizing agents formed at the TiO 2 surface. After 300 min of this treatment, 80% mineralization, 9% mineralization current effi- ciency and 1.93 kW h g 1 TOC energy cost were obtained. The mineralization of atrazine was inhibited by the production of cyanuric acid, which was the main byproduct detected at the end of the coupled SPEF-SPC process. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Advanced oxidation processes (AOPs) are environmentally friendly chemical, photochemical, photocatalytic, electrochemical and photoelectrochemical technologies based on the production of Å OH to remove toxic and/or biorefractory organic pollutants from wastewaters (Malato et al., 2009; Martínez-Huitle and Brillas, 2009; Ahmed et al., 2011). The high standard reduction potential of Å OH (E°( Å OH/H 2 O) = 2.8 V vs SHE) confers to this radical a great oxidizing power for the non-selective destruction of most organics giving dehydrogenated or hydroxylated derivatives, which can be 0045-6535/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.chemosphere.2013.10.044 ⇑ Corresponding author. Tel.: +52 8183294000x3432. E-mail address: edgar.ruizrz@uanl.edu.mx (E.J. Ruiz-Ruiz). URL: http://www.uanl.mx (E.J. Ruiz-Ruiz). Chemosphere 97 (2014) 26–33 Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere