Removal of Acid Brown 14 in aqueous media by electrocoagulation: Optimization parameters and minimizing of energy consumption J. Basiri Parsa ⁎, H. Rezaei Vahidian, A.R. Soleymani, M. Abbasi Department of Applied Chemistry, Bu-Ali Sina University, Hamadan 65178, Iran abstract article info Article history: Received 5 October 2010 Received in revised form 16 May 2011 Accepted 17 May 2011 Available online 8 June 2011 Keywords: Electrocoagulation Water treatment Acid Brown 14 Energy consumption Electrocoagulation (EC) has been employed for the removal of Acid Brown 14 (AB14) from water by a bench scale (BS) and pilot scale (PS). In order to find the best condition of the process, the influence of various parameters such as anode materials, pH, supporting electrolyte, current density and stirring speed were investigated. Energy consumption was considered as the main criterion of process evaluation and optimum conditions were found. The effect of anode surface covering and its position were studied. At the optimum conditions by the BS reactor after 18 min, 91% and 87% of the dye and COD content of the solution have been removed, respectively. Ultimately EC process using a pilot scale (PS) reactor was performed. By this apparatus after about 200 min, 80% and 64% of the dye and COD content were removed, respectively. Kinetic trend of color and COD removal for both of the BS and PS reactors were obtained. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Wastewaters generated by textile industries are known to contain considerable amount of toxic aromatic dyes especially azo dyes. The colored wastewater released into the ecosystem is a dramatic source of esthetic pollution and perturbation in the aquatic life [1,2]. There are many processes to remove pollutants from effluents such as adsorption, precipitation, chemical degradation, photo degradation, biodegrada- tion, chemical coagulation and EC. Adsorption and precipitation processes are very time-consuming and costly with low efficiency. Chemical degradation by oxidative agents such as chlorine is the most important and effective method, but it produces some very toxic products such as organochlorine compounds. Photo-oxidation by UV/H 2 O 2 or UV/TiO 2 needs additional chemicals and therefore causes a secondary pollution. Although biodegradation process is cheaper than other methods, it is less effective because of the toxicity of dyes that has an inhibiting effect on the bacterial development. But EC is a simple, reliable and coast effective method for the treatment of wastewater without any need for additional chemicals and no sensitivity to toxicity [2]. In this technique, the amount of generated sludge is lower than chemical coagulation as another beneficial characteristic [3]. The EC has been used for treatment of municipal wastewater and effluents containing algae, phosphate, sulfide, sulfate, sulfite, fluoride and heavy metals ions such as; Fe 2+ , Ni 2+ , Cu 2+ , Zn 2+ , Pb 2+ , Cd 2+ [4–9]. The main aim in coagulation process is the conversion of light suspends solids or solved pollutant to the heavier agglomeration for rapid precipitation and separation from target media. In the chemical coagulation process, the coagulant chemicals such as; Al 2 (SO 4 ) 3 , FeSO 4 , Fe 2 (SO 4 ) 3 , FeCl 3 , are introduced directly to the media. But EC involves the in situ generation of coagulants by electrolytic oxidation of an appropriate sacrificial anode upon application of a direct current. The generated metal ions hydrolyze in the electro chemical cell to produce metal hydroxide ions and neutral M(OH) n . The coagulated pollutants are removed by sedimentation, filtration or flotation from the waste [10,11]. Iron and aluminum have been widely used as electrode materials in EC systems according to the literature, because they are cheap and very effective [12]. The proposed mechanism for generation of coagulant by using of Al as anode is presented below [3]: Mechanism 1: Anode : Al ðSÞ →Al 3þ ðaqÞ þ 3e À ð1Þ In bulk : Al 3þ ðaqÞ + 3H 2 O→AlðOHÞ 3 + 3H þ ðaqÞ ð2Þ Cathode : 3H þ ðaqÞ þ 3e À →3=2H 2ðgÞ ð3Þ Mechanism 2: Anode : Al ðSÞ →Al 3þ ðaqÞ þ 3e À ð4Þ Cathode : 3H 2 O þ 3e À →3=2H 2ðgÞ þ3OH À ðaqÞ ð5Þ In bulk : Al 3þ ðaqÞ þ 3OH À ðaqÞ →AlðOHÞ 3 ð6Þ Desalination 278 (2011) 295–302 ⁎ Tel.: +98 811 8282807; fax: +98 811 8257407. E-mail address: parssa@basu.ac.ir (J.B. Parsa). 0011-9164/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.desal.2011.05.040 Contents lists available at ScienceDirect Desalination journal homepage: www.elsevier.com/locate/desal