One-pot electro-synthesis of ZrO 2 –ZnO/HY nanocomposite for photocatalytic decolorization of various dye-contaminants N. Sapawe a , A.A. Jalil a,⇑ , S. Triwahyono b a Institute of Hydrogen Economy, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM, Johor Bahru, Johor, Malaysia b Ibnu Sina Institute for Fundamental Science Studies, Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM, Johor Bahru, Johor, Malaysia highlights  A new one-pot electrolysis method of Si with Zr and Zn catalyst was introduced.  1 wt% EGZrO 2 –1 wt% EGZnO/HY exhibited superior performance for MB decolorization.  High decolorization percentage (>80%) of MG, CR, and MO were achieved. graphical abstract article info Article history: Received 4 December 2012 Received in revised form 27 March 2013 Accepted 28 March 2013 Available online 11 April 2013 Keywords: EGZrO 2 –EGZnO/HY Electrochemical HY zeolite Photodecolorization Methylene blue Dyes abstract A highly photoreactive electrogenerated catalyst (EGZrO 2 –EGZnO/HY) was prepared by a facile one-pot electrochemical method. The restructuring of the aluminosilicate protonated Y zeolite (HY zeolite) frame- work presumably occurred during electrolysis via dealumination accompanied by the insertion of Zr and Zn ions resulting from anodic dissolution to form a new active species, Si coordinated with Zr and Zn in the HY framework. The photoactivity of the photocatalyst was examined by photodecolorization of methylene blue (MB) under varying pH, catalyst dosage, and initial concentrations of MB. An amount of 0.60 g L 1 1 wt.% EGZrO 2 –1 wt.% EGZnO/HY was found to be the optimum dosage for 10 mg L 1 MB, which gave almost complete photodecolorization of methylene blue after 1 h under visible light at pH 11 and room temperature. The photocatalytic reaction followed pseudo first-order kinetics which were rationalized in terms of the Langmuir–Hinshelwood model, and provided nearly complete mineral- ization. After five cycling runs, the catalyst was still stable and showed no leaching effect. High decolor- ization percentage (>80%) of other dyes such as malachite green (MG), Congo red (CR), and methyl orange (MO) were also obtained. Ó 2013 Elsevier B.V. All rights reserved. 1. Introduction There are several methods for the removal of organic pollutants, particularly dyes, that have been reported, including chemical and biological oxidation [1], adsorption [2], coagulation and floccula- tion [3], electrochemical [4], ion exchange [5], and membrane separation [6]. However, these methods have their own limitations as they are time-consuming, expensive, commercially unattractive, and generate secondary wastes [7]. Advanced oxidation processes (AOPs) using semiconductors such as TiO 2 , ZnO, WO 3 , Fe 2 O 3 , CuO, ZrO 2 , and CdS as photocatalysts are an essential technique in wastewater treatment because they can convert a wide range of harmful dyes into non-toxic products, CO 2 and water at ambient temperatures [8–14]. The most popular metal oxide used is TiO 2 , but ZnO has also attracted much attention due to its band gap energy, which is similar to TiO 2 (3.20 eV); it also demonstrates high photosensitivity and stability when degrading various pollutants [9,10]. In parallel, mixed metal oxides such as TiO 2 –ZrO 2 , Ag–ZnO, Fe 2 O 3 –TiO 2 , Sn–ZnO and Ag–TiO 2 can also ex- hibit better performance and enhance the photocatalytic activity [9,11,15–17]. 1385-8947/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.cej.2013.03.121 ⇑ Corresponding author. Tel.: +60 7 5535581; fax: +60 7 5536165. E-mail address: aishah@cheme.utm.my (A.A. Jalil). Chemical Engineering Journal 225 (2013) 254–265 Contents lists available at SciVerse ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej