685 Research Article Received: 1 November 2014 Revised: 19 December 2014 Accepted article published: 26 December 2014 Published online in Wiley Online Library: 21 January 2015 (wileyonlinelibrary.com) DOI 10.1002/jctb.4626 Coated nickel foam electrode for the implementation of continuous electro-Fenton treatment Elvira Bocos, a David Pérez-Álvarez, b Marta Pazos, a Maria Carmen Rodríguez-Argüelles b and Maria Ángeles Sanromán a* ABSTRACT BACKGROUND: Electro-Fenton technology has already demonstrated its ability to degrade organic pollutants. In this treatment hydroxyl radicals are formed due to the reaction of the iron catalyst along with in situ electrogenerated H 2 O 2 . However, one of the main limitations of this system is the iron released in the treated effluent. Therefore, retention of iron is required, and in this study, the use of a new cathode in which the iron is fixed on nickel foam is proposed as a solution to the electro-Fenton treatment in continuous processes. RESULTS: The retention of iron was ensured by its fixation on nickel foam using chitosan, an eco-friendly polymer, as coating agent. Different chitosan coatings were tested to optimize the manufacturing process of the new cathode. It was concluded that the best electrode for the electro-Fenton treatment of different dyes (Poly R-478 and Lissamine Green B) was obtained using a half-coating electrode cover with iron–chitosan of medium molecular weight. Furthermore, its reusability was positively evaluated in successive cycles. Finally, a continuous treatment using a fluidized bed reactor was successfully performed for the treatment of dye Lissamine Green B. CONCLUSION: Summarizing, this new cathode is a suitable alternative for the treatment of coloured wastewater by continuous electro-Fenton treatment. © 2014 Society of Chemical Industry Keywords: dyes; electro-Fenton process; chitosan; iron; nickel foam INTRODUCTION Water bodies are essential for living organisms; however, it is well known that they suffer daily the discharge of large quantities of pollutants as a result of the release of effluents by a large number of industries. This pollution can have different sources which makes treatment by conventional processes difficult since most of the contaminants are highly persistent organic compounds. In this context, the textile industry consumes large volumes of water, releasing in their fabrication process important quantities of chemical substances, especially dyes, 1 with the consequent pollution of this source. They provide colour to the effluents and given their high resistance to degradation by light, water, and chemical products, are most responsible for the recalcitrance of these effluents, causing important environmental problems. Thus, textile wastewater affects adversely the ecosystem and reduces the assimilative capacity of the environment. Over recent years, the treatment of these coloured effluents has attracted the attention of many researchers who have focused their studies on a number of technologies such as physical adsorption, 2 biodegradation, 3 chemical methods, 4 photocatalytic degradation 5 and electrochemical processes. Among these tech- nologies advanced oxidation processes (AOPs) have been widely used during recent years, attracting the interest of the scientific community. The electro-Fenton process has been widely used over the past decade to treat various organic contaminants. 6 The electro-Fenton technology is based on the continuous electro-generation of H 2 O 2 at a suitable cathode fed with O 2 or air (0.15 vvm), along with the addition of an iron catalyst to the polluted solution to produce oxidant (•OH) in the bulk by Fenton’s reaction. 7 Moreover, in the electro-Fenton process Fe 2+ can be regenerated from the reduction of Fe 3+ at the cathode. Several researchers have focused their efforts on improvement of the key variables involved in this technology such as electrode material, initial pH and Fenton’s reagents. 8 – 13 In relation to the last one, a huge amount of research has been carried out on the development of a heterogeneous catalyst able to provide the iron necessary in the release after the treatment, 12,14,15 avoiding the iron sludge generated at the end of the treatment and its release after treatment. During the past years, numerous studies have focused their efforts on study of the effect of the cathode electrode, since hydroxyl radical production can be increased by optimization of its conductivity and specific surface. 12 In this way, gas-diffusion ∗ Correspondence to: Maria Ángeles Sanromán, Department of Chemical Engi- neering, University of Vigo, 36310 Vigo, Spain. E-mail: sanroman@uvigo.es a Department of Chemical Engineering, University of Vigo, 36310 Vigo, Spain b Department of Inorganic Chemistry, University of Vigo, 36310 Vigo, Spain J Chem Technol Biotechnol 2016; 91: 685–692 www.soci.org © 2014 Society of Chemical Industry