Preparation of modified carbon paste electrodes from orange peel and used coffee ground. New materials for the treatment of dye-contaminated solutions using electro-Fenton processes

• The electrochemical performance of CPE is improved by organic activated carbons modifiers. • CPE modified with organic carbons resulted in alternative cathodes to produce H 2 O 2 . • The H 2 O 2 generation is increased by MCPE with a higher EA and faradaic current. • MOPE can be used to study reactions with lower capacitive requirements. • Low electric resistance and high capacitance improves Fenton efficiency using MSPE. From an environmental perspective, there is interest in using agroindustrial waste not only in transforming it into activated carbon for adsorption applications, but also in exploring its use to prepare carbonaceous electrodes for advanced electrochemical oxidation processes. In this context, modified carbon paste electrodes were prepared and characterized using activated carbon obtained from orange peel and spent coffee ground agroindustrial waste and studied as alternative cathode materials for the production of hydrogen peroxide by means of the 2e- reduction of oxygen in slightly acidic medium. In this way, electrochemical experiments using different ratios of graphite:activated carbon:binder, allowed to obtain not only the best ratio for the electrochemical response of the electrodes (35:35:30), but also to optimize the production of hydrogen peroxide from dissolved oxygen via cathodic reduction. The performance of these materials for wastewater treatment was assessed by means of electro-Fenton experiments in which the discoloration of a model dye contaminant was employed. From these experiments it was observed that the electrode modified with spent coffee ground activated carbon has the largest efficiency of the materials surveyed, reaching 99% discoloration within two hours. This effect was explained by the combination of high capacitive and low faradaic currents.