Water treatment for color and COD removal by electrochemical oxidation on boron-doped diamond anode
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ORIGINAL PAPER
Water treatment for color and COD removal by electrochemical oxidation on boron-doped diamond anode Hanene Akrout & Latifa Bousselmi
Received: 9 February 2012 / Accepted: 12 October 2012 # Saudi Society for Geosciences 2012
Abstract The electrochemical oxidation of synthetic wastewater which contains biazo dye [amido black (AB)] on boron-doped diamond anode, “BDD anode,” was experimentally investigated to determine the influence of several operative parameters on the performance of the process. The study focalized on the effect of studied parameters on discoloration process and the degradation of the aromatic part of the dye molecule. Two distinct pathways with two different kinetics were observed. The decrease of pH improves the discoloration rate and the degradation of aromatic byproducts after 90 min of electrolysis. The increase of current density has a considerable effect on discoloration and a little less effect on the aromatic derivative degradation. Hypochlorite electrogenerated from chloride addition exceptionally accelerates the discoloration, but it does not degrade aromatic derivatives as efficiently. It was observed that nitrates addition generates under electrolysis other derivates of AB as different colors than the dye one. The current efficiency depends very little on the initial pH; however, higher energy consumptions are obtained. Keywords Water treatment . Electrochemical oxidation . COD . Color removal . Azo dye . Efficiency
Introduction Important quantities of synthetic dyes are discharged in the environment from industrial effluents. The presence of these pollutants in water systems can cause serious health risks. H. Akrout (*) : L. Bousselmi Wastewater Treatment Laboratory, Water Researches and Technologies Centre (CERTE), BP 273, 8020, Soliman, Tunisia e-mail: [email protected] L. Bousselmi e-mail: [email protected]
Eco-friendly technologies are developed in order to reduce water consumption and environmental risk. Instead of traditional methods, electrochemical technologies are considered highly efficient and environmentally friendly. They can generate the powerful oxidizing agent (°OH). Dyes are commonly characterized from their chromophore group and aromatic derivative. The majority of dyes are azo (–N 0N-) compounds. During electrochemical degradation, azo dyes can generate more toxic and carcinogenic by-products (Brown and Devito 1993). Ricardo et al. (2010) showed that the electrochemical oxidation of organic contaminants on boron-doped diamond (BDD) anodes can reach a great efficiency comparing to other anodes used. Several papers discussed the effect of different parameters and operating conditions on the performance of electrochemical oxidation process (Martinez-Huitle and Brilllas 2009; Canizares et al. 2006; Regina Costa et al. 2009; Muruganathan et al. 2007; Özcan et al. 2008; Sakalis et al. 2006). Concerning pH effect, the results obtained by many authors are different from one study to another (MartinezHuitle and Brilllas 2009; Canizares e
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