Journal of Water Process Engineering 3 (2014) 18–25 Contents lists available at ScienceDirect Journal of Water Process Engineering journa l h om epage: www.elsevier.com/locate/jwpe Petrochemical wastewater treatment by electro-Fenton process using aluminum and iron electrodes: Statistical comparison Reza Davarnejad a,∗ , Mohsen Mohammadi a , Ahmad Fauzi Ismail b a Department of Chemical Engineering, Faculty of Engineering, Arak University, Arak 38156-8-8349, Iran b Department of Gas Engineering, Faculty of Chemical and Natural Resources Engineering, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor, Malaysia a r t i c l e i n f o Article history: Received 21 May 2014 Received in revised form 1 August 2014 Accepted 7 August 2014 Keywords: COD Electro-Fenton Optimization Petrochemical wastewater a b s t r a c t Petrochemical manufacturing wastewaters often contain a high concentration of biodegradable com- pounds that possess either toxicity or activity inhibition to the biological unit. In this paper, a comparison between aluminum and iron plate electrodes on COD and color removal from Petrochemical wastewaters by electro-Fenton process was studied. The experiments were conducted to evaluate the effects of reac- tion time, current density, pH, H 2 O 2 /Fe 2+ molar ratio, and H 2 O 2 of petrochemical wastewater (PW) (ml/l) on the performance of the process. Response surface methodology (RSM) was employed to assess indi- vidual and interactive effects of the five main independent parameters on the COD and color removal. The results show that COD and color removal efficiencies of iron electrode (67.3% and 71.58%, respectively) were more than those of aluminum electrode (53.94% and 67.35%, respectively). © 2014 Elsevier Ltd. All rights reserved. 1. Introduction The production stages of a petroleum industry, such as extrac- tion and refining, are potentially responsible for generating large volumes of effluent to be discarded in the environment [1–3]. The waste generated in oil refineries contains many different chemi- cal compositions, depending on the complexity of the refinery, the existing processes and the type of oil used [1,4]. The physical–chemical and bioremediation methods utilized for the degradation of these compounds have shown various opera- tional problems, such as: partial degradation of the effluent, toxic intermediates production, energy consumption and secondary phases generation that impose extra cost in the process [5–7]. The traditional Fenton process, one of the advanced oxidation processes (AOPs), is widely used as a suitable treatment method for highly concentrated wastewaters due to its effectiveness in producing hydroxyl radicals [8,9]. Applicability of traditional Fen- ton process is limited by its acidic pH requirements, the formation of iron sludge and high cost of hydrogen peroxide [8,10]. Electro- chemical advanced oxidation processes (EAOPs) based on Fenton’s reaction chemistry are eco-friendly methods that have recently received much attention for wastewaters remediation [10]. The ∗ Corresponding author. Tel.: +98 9188621773; fax: +98 86 34173450. E-mail addresses: R-Davarnejad@araku.ac.ir, reza davarnejad@yahoo.com.ph, redavarnejad@yahoo.com (R. Davarnejad). most popular EAOP is the electro Fenton (E-Fenton) process [11] which can proceed by the following chain reactions [11–13]: H 2 O 2 + Fe 2+ → Fe 3+ + OH • + OH - (1) Hydroxyl radicals are also generated at the surface of a high- oxygen overvoltage anode from water oxidation: H 2 O → H + + OH • + e - (2) Also the produced ferric ion from Eq. (1) can be reduced to ferrous ion by electrochemical regeneration of Fe 2+ ions on the cathode surface: Fe 3+ + e - → Fe 2+ (3) Since iron and aluminum electrodes have not been compared in detail for the treatment of petrochemical wastewaters, it is the purpose of this study is to compare the treatment of petro- chemical wastewaters by electro-Fenton using aluminum and iron electrodes. The response surface methodology (RSM) is an excellent tool for optimization and statistical analysis [14]. It allows consid- erable reduction of experiments number and a rapid interpretation [11,15]. Furthermore, it is possible to study a large number of fac- tors and to detect the possible interactions between them [15,16]. The RSM is a useful statistical method for the optimization of chemical reactions and/or industrial processes and widely used for experimental design [17]. In this paper, Optimizations of E-Fenton was carried out by the RSM which was used to develop a mathemat- ical technique to describe the effects of main independent variables http://dx.doi.org/10.1016/j.jwpe.2014.08.002 2214-7144/© 2014 Elsevier Ltd. All rights reserved.