Journal of Hazardous Materials B139 (2007) 381–390 Electrochemical treatment of Procion Black 5B using cylindrical flow reactor—A pilot plant study S. Raghu, C. Ahmed Basha ∗ Central Electrochemical Research Institute, Karaikudi 630006, Tamilnadu, India Received 24 January 2006; received in revised form 15 June 2006; accepted 15 June 2006 Available online 27 June 2006 Abstract The paper presents the results of an efficient electrochemical treatment of Procion Black 5B—a pilot plant study. Experiments were conducted at different current densities and selected electrolyte medium using Ti/RuO 2 as anode, stainless-steel as cathode in a cylindrical flow reactor. By cyclic voltammetric analysis, the best condition for maximum redox reaction rate was found to be in NaCl medium. During the various stages of electrolysis, parameters such as COD, colour, FTIR, UV–vis spectra studies, energy consumption and mass transfer coefficient were computed and presented. The experimental results showed that the electrochemical oxidation process could effectively remove colour and the chemical oxygen demand (COD) from the synthetic dye effluent. The maximum COD reduction and colour removal efficiencies were 74.05% and 100%, respectively. Probable theory, reaction mechanism and modeling were proposed for the oxidation of dye effluent. The results obtained reveal the feasibilities of application of electrochemical treatment for the degradation of Procion Black 5B. © 2006 Elsevier B.V. All rights reserved. Keywords: Advanced oxidation; Textile; Colour removal; Electro-oxidation; Ti/RuO 2 electrode 1. Introduction Water is the best resources in nature and is essential for animal and plant life. Pollution of water bodies is gradually increas- ing due to industrial proliferation and urbanization. Nowadays, the worldwide production and use of chemical compounds have increased tremendously and many of them find their way into the environment. Many of these compounds are non-biodegradable. Therefore, the major concern is to treat the wastewater before it is discharged into environment [1]. The textile and dyeing industry has drawn the attention of environmentalist of world- wide because of its high resource consumption profile in terms of water, chemicals, energy and release of highly contaminated coloured effluent at the end of process leading to intense water pollution. The existing wastewater treatment technology is often inadequate to control the colour of effluent to minimize the tox- icity of wastewater having impact on aquatic organisms [2,3]. Aerobic treatment of industrial effluents typically removes most ∗ Corresponding author. Tel.: +91 4565 227550; fax: +91 4565 227779. E-mail addresses: subraghu 0612@yahoo.co.in (S. Raghu), cab 50@rediffmail.com, basha@cecri.res.in (C.A. Basha). of the biological oxygen demand (BOD) and 60–80% of COD in wastewater [4–6]. However, these treatments are ineffective for colour removals from the textile industry wastewater because most of the synthetic dyes that are non-biodegradable. In aero- bic process, the azo bonds can be used as electron acceptor in the electron pathways. The products of the azo bond clevage are lower molecular weight aromatic amines. Although they are colourless, they cannot be further degraded under anaero- bic conditions. Therefore, various combined processes, such as anaerobic/aerobic [5], chemical/biological [7], and electrochem- ical/biological [8], processes have been under intensive study to completely mineralize organic dyes. Though all the above methods have been found to be fairly satisfactory, considering the very stringent environmental regu- lations, there is a need for more effective alternatives. Anodic oxidation of some benzene derivatives (model organic pollu- tants) at platinum and DSA (dimensionally stable anode) anode elucidate the possibilities of the electrochemical method [9]. Dimensionally stable anode (DSA) with Ru/TiO 2 as a catalyti- cally active layer coated on a titanium substrate by the thermal decomposition method has been successfully used and caused a technological revolution in the chloro-alkali industry since its invention in 1960s [10]. The first fundamental research on the 0304-3894/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2006.06.082