Journal of Hazardous Materials 163 (2009) 711–716 Contents lists available at ScienceDirect Journal of Hazardous Materials journal homepage: www.elsevier.com/locate/jhazmat Electrochemical removal of phenol from oil refinery wastewater O. Abdelwahab a,∗ , N.K. Amin b , E-S.Z. El-Ashtoukhy b a Environmental Division, National Institute of Oceanography and Fisheries, Kayet Bay, El-Anfushy, Alexandria, Egypt b Chemical Engineering Department, Faculty of Engineering, Alexandria University, Alexandria, Egypt article info Article history: Received 8 January 2008 Received in revised form 12 May 2008 Accepted 4 July 2008 Available online 12 July 2008 Keywords: Electrocoagulation Phenol Removal Wastewater abstract This study explores the possibility of using electrocoagulation to remove phenol from oil refinery waste effluent using a cell with horizontally oriented aluminum cathode and a horizontal aluminum screen anode. The removal of phenol was investigated in terms of various parameters namely: pH, operating time, current density, initial phenol concentration and addition of NaCl. Removal of phenol during elec- trocoagulation was due to combined effect of sweep coagulation and adsorption. The results showed that, at high current density and solution pH 7, remarkable removal of 97% of phenol after 2 h can be achieved. The rate of electrocoagulation was observed to increase as the phenol concentration decreases; the max- imum removal rate was attained at 30 mg L -1 phenol concentration. For a given current density using an array of closely packed Al screens as anode was found to be more effective than single screen anode, the percentage phenol removal was found to increase with increasing the number of screens per array. After 2h of electrocoagulation, 94.5% of initial phenol concentration was removed from the petroleum refin- ery wastewater. Energy consumption and aluminum Electrode consumption were calculated per gram of phenol removed. The present study shows that, electrocoagulation of phenol using aluminum electrodes is a promising process. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Treatment of industrial wastewaters is a problem of major con- cern nowadays. More strict regulations are being imposed, which persevere on the need to develop and employ treatment tech- nologies capable to deal with the hazardous pollutants present in many industrial waste streams [1]. Wastewater containing pheno- lic compounds presents a serious discharge problem due to their poor biodegradability, high toxicity and ecological aspects [2]. Phe- nols are widely distributed as environmental pollutants. They exist in different concentrations in wastewaters disposed from many industrial processes, including coking, synthetic rubber, plastics, paper, oil refineries, petrochemical, ceramic, steel, conversion pro- cesses and phenolic resin industries [3,4]. Phenols are considered as priority pollutants since they are harmful to organisms at low con- centrations and many of them have been classified as hazardous pollutants because of their potential harm to human health [3]. Due to the high toxicity of phenols, they are subjected to specific Abbreviations: c.d, current density; COD, chemical oxygen demand; EC, elec- trocoagulation; E.Consumption, energy consumption; Al Consumption, aluminum electrode consumption. ∗ Corresponding author. Tel.: +20 121093161. E-mail address: olaabdelwahab53@hotmail.com (O. Abdelwahab). regulations, and their industrial use is increasingly avoided by sub- stituting them with harmless compounds [5]. The Environmental Protection Agency (EPA) calls for lowering phenol content in the wastewater to less than 1 mg L -1 [6]. Wastewaters containing phenols and other toxic compounds need careful treatment before discharge into the receiving bodies of water. Biological treatment, activated carbon adsorption, solvent extraction, chemical oxidation and electrochemical methods are the most widely used methods for removing phenol and phenolic compounds from wastewaters [7–12]. Such problems as high cost, low efficiency, and generation of toxic by-products are associated with the above methods [13]. Biological and electrochemical meth- ods have little or no harmful effects on the environment, because these techniques do not involve the use of harmful reagents. On the other hand, electrochemical reactions are more or less independent of the condition of the wastewater and can proceed as long as a current is supplied to the electrode [14]. Electrocoagulation is the process utilizing “sacrificed” anodes to form active coagulant which is used to remove pollutant by precip- itation and flotation in situ. Compared with traditional chemical coagulation, electrocoagulation has, in theory, the advantage of removing the smallest colloidal particles; the smallest charged par- ticles have a greater probability of being coagulated because of the electric field that sets them in motion. It has also the advantage of producing a relatively low amount of sludge [15]. EC process 0304-3894/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2008.07.016