Decolorization and mineralization of an azo reactive dye using loaded nano-photocatalysts on spacer fabric: Kinetic study and operational factors Seyed Majid Ghoreishian a , Khashayar Badii b, *, Mohammad Norouzi c , Abosaeed Rashidi d , Majid Montazer e , Mahsa Sadeghi f , Maedeh Vafaee g a Young Researchers and Elites Club, South Tehran Branch, Islamic Azad University, Tehran, Iran b Department of Environmental Researches, Institute for Color Science and Technology (ICST), Tehran, Iran c Young Researchers and Elites Club, Science and Research Branch, Islamic Azad University, Tehran, Iran d Department of Textile Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran e Department of Textile Engineering, Amirkabir University of Technology, Tehran, Iran f Department of Textile Engineering, South Tehran Branch, Islamic Azad University, Tehran, Iran g Department of Chemical Engineering, Semnan University, Semnan, Iran 1. Introduction The discharge of textile wastewater containing various organic and mineral pollutants such as dyes and pigments into natural streams and rivers causes serious environmental problems. In fact, most of the dyes owing to their conjugated aromatic compounds and complicated chemical structure are toxic to the aquatic living organisms [1–5]. Among the broad range of the dyes used in textile industry, reactive dyes due to their favorable characteristics such as low energy consumption in the dyeing process, color brightness and water fastness, have found extensive application and they constitute almost 50% of the annual worldwide production of the dyes [6]. Some reactive dyes, such as RBB which are composed of one or more azo bonds (–N 55 N–) and aromatic rings are categorized as xenobiotic compounds. Additionally, because the fixation efficien- cy of azo dyes is estimated to fall in the range of 60% to 90%, their loss in the dyeing process causes environmental concerns [7–9]. The conventional methods for wastewater decolorization such as chemical, physical or biological methods only transform dyes from aqueous to another phase, which consequently results in secondary pollution [10–17]. Therefore, post-treatments of the solid wastes, which are costly operations, are required [18,19]. Currently, advanced oxidation processes (AOPs) have been developed as alternative methods for decolorization of dyes and other contaminated wastewaters. The main purpose of AOPs is to transfer all organic compounds to water, carbon dioxide and Journal of the Taiwan Institute of Chemical Engineers 45 (2014) 2436–2446 A R T I C L E I N F O Article history: Received 21 January 2014 Received in revised form 9 April 2014 Accepted 12 April 2014 Available online 16 May 2014 Keywords: Decolorization Textile wastewater Azo reactive dye 3-Dimensional fabric Kinetics study A B S T R A C T In this study, the photocatalytic decolorization and mineralization of Remazol Black B (RBB), an azo reactive dye, in aqueous solutions was investigated using UV/H 2 O 2 /ZnO, UV/H 2 O 2 /TiO 2 and UV/H 2 O 2 / ZnO:TiO 2 systems. ZnO and TiO 2 nanoparticles were loaded on 3-dimensional polyethylene terephthalate fabrics (spacer fabrics). Morphology of the spacer fabrics and the presence of the nanoparticles were studied by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), respectively. Furthermore, the effects of key operational parameters on the efficiency of the decolorization were investigated. These parameters included initial pH value, initial hydrogen peroxide concentration, initial dye concentration, the loaded nanoparticle ratio and the presence of anions (sulfate, chloride and bicarbonate). Zero-, first- and second-order reaction kinetics were evaluated. Complete decolorization and high efficient mineralization with 90% total organic carbon (TOC) reduction were achieved at 120 min treatment in the case of ZnO:TiO 2 under optimum condition. The results proved that the novel heterogeneous photocatalytic process is capable of decolorizing and mineralizing azo reactive dyes in textile wastewater. ß 2014 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +98 2122969777/+98 2122543290. E-mail address: badii@icrc.ac.ir (K. Badii). Contents lists available at ScienceDirect Journal of the Taiwan Institute of Chemical Engineers jou r nal h o mep age: w ww.els evier .co m/lo c ate/jtic e http://dx.doi.org/10.1016/j.jtice.2014.04.015 1876-1070/ß 2014 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.