This study explores the possibility of using iron-loaded sepiolite, obtained by recovering iron from polluted water, as a catalyst in the electro-Fenton oxidation of organic pollutants in textile effluents. The removal of iron ions from aqueous solution by adsorption on sepiolite was studied in batch tests at iron concentrations between 100 and 1,000 ppm. Electro-Fenton experiments were carried out in an electrochemical cell with a working volume of 0.15 L, an air flow of 1 L/min, and 3 g of iron-loaded sepiolite. An electric field was applied using a boron-doped diamond anode and a graphite sheet cathode connected to a direct current power supply with a constant potential drop. Reactive Black 5 (100 mg/L) was selected as the model dye. The adsorption isotherms proved the ability of the used adsorbent. The removal of the iron ion by adsorption on sepiolite was in the range of 80-100 % for the studied concentration range. The Langmuir and Freundlich isotherms were found to be applicable in terms of the relatively high regression values. Iron-loaded sepiolite could be used as an effective heterogeneous catalyst for the degradation of organic dyes in the electro-Fenton process. Successive batch processes were performed at optimal working conditions (5 V and pH 2). The results indicate the suitability of the proposed combined process, adsorption to iron remediation followed by the application of the obtained iron-loaded sepiolite to the electro-Fenton technique, to oxidize polluted effluents.

The aim of this work was to improve the ability of the electro-Fenton process using Fe alginate gel beads for the remediation of wastewater contaminated with synthetic dyes and using a model diazo dye such as Reactive Black 5 (RB5). Batch experiments were conducted to study the effects of main parameters, such as voltage, pH and iron concentration. Dye decolourisation, reduction of chemical oxygen demand (COD) and energy consumption were studied. Central composite face-centred experimental design matrix and response surface methodology were applied to design the experiments and to evaluate the interactive effects of the three studied parameters. A total of 20 experimental runs were set, and the kinetic data were analysed using first-order and second-order models. In all cases, the experimental data were fitted to the empirical second-order model with a suitable degree for the maximum decolourisation of RB5, COD reduction and energy consumption by electro-Fenton-Fe alginate gel beads treatment. Working with the obtained empirical model, the optimisation of the process was carried out. The second-order polynomial regression model suggests that the optimum conditions for attaining maximum decolourisation, COD reduction and energy consumption are voltage, 5.69 V; pH 2.24 and iron concentration, 2.68 mM. Moreover, the fixation of iron on alginate beads suggests that the degradation process can be developed under this electro-Fenton process in repeated batches and in a continuous mode.

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BACKGROUND:The exploration of new technology based on electro-Fentonlike process bears advantageous and unique environmental implications however the scaling up that permits the operation in continuous mode is a decisive stage to be researched. RESULTS:A new metal-organic composite, manganese-alginate (Mn-AB), was synthesized. It was characterized by scanning electron microscope and the results showed that manganese was uniformly distributed on the surface of alginate beads. A comparative study by the decolorization of Reactive Black 5 demonstrated that the best performance was obtained by heterogeneous electroFenton using Mn-AB as catalyst. In addition, the operation in four successive batches and continuous mode, showed a high activity and stability of the developed catalyst Mn-AB without operational problems and maintained particle shapes throughout the oxidation process. The ability of Mn-AB catalyst for the degradation of other pollutants (imidacloprid, di-2-ethylhexyl phthalate, 4-nitrophenol) was confirmed by identification of several reaction intermediates using LC-MS and GC-MS. This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1002/jctb.4446 This article is protected by copyright. All rights reserved. Accepted Article CONCLUSION:The efficiency of this new Fenton-like catalyst developed in this study was successfully ascertained. The results validate an adequate heterogeneous electro-Fenton-like process to remediate continuously organic pollutants in aqueous medium. Keywords:Heterogeneous electro-Fenton, di-2-ethylhexyl phthalate, imidacloprid, 4-nitrophenol, Reactive Black 5. IntroductionOrganic substances have been widely produced in the worldwide and are applied in different industries including tanneries and dyeing, plastic, petrochemical, etc.The disposal of these substances has become a global concern because of the environmental problems caused by some of these persistent pollutants due to their direct discharge in aqueous effluent. This problem demands a solution and the removal of these recalcitrant organic compounds from wastewater is an issue of extreme importance 1,2 .Among the different organic substances, compounds like dyes, pesticides, plasticizers and phenols have attracted substantial attention from the scientific community due to the important environmental problems that they presently generate 3,4 . Dyes usually have complex aromatic molecular structures and they generate toxic effects to microbial organisms and fish due to their carcinogenic and mutagenic properties. Even in small quantities their presence in the water reduces the light penetration and photosynthesis 5 . It is outstanding the negative effect that azo dyes cause in the environmental because they represent 60-70% of the world production and their occurrence in wastewaters entail...