Treatment of Cyanide Waters by Photo-Electrocatalytic-Peroxone processJohn Wilman Rodriguez Acosta a, b, Nilson Marriaga-Cabrales b, Anna Hankin a, ca Department of Chemical Engineering, Imperial College London, South Kensington Campus, SW7 2AZb Chemical Engineering School, Universidad del Valle, Cali-Colombia, 760032c Institute for Molecular Science and Engineering, Imperial College London, SW7 2AZ, UKMaterials for Sustainable Development Conference (MATSUS)Proceedings of MATSUS Spring 2024 Conference (MATSUS24)#PhotoMat - Advances in Photo-driven Energy Conversion and Storage: From Nanoscale Materials to Sustainable SolutionsBarcelona, Spain, 2024 March 4th - 8thOrganizers: Michelle Browne, Bahareh Khezri and Katherine VillaOral, John Wilman Rodriguez Acosta, presentation 321DOI: https://doi.org/10.29363/nanoge.matsus.2024.321Publication date: 18th December 2023Wastewater generated in gold leaching processes, particularly in cyanidation treatments, still contains harmful amounts of cyanide (free and complexed with different heavy metals). In most cases, the cyanide content in these effluents exceeds the minimum concentration limits established for their discharge. Therefore, the highly toxic nature of these effluents requires adequate treatment prior to disposal. In this respect, a novel advanced oxidation technique was evaluated for the elimination of cyanide compounds, called here as photo-electrocatalytic-peroxone (PEPX), consisting of the coupling of two processes: photoelectrocatalysis (PEC) and electro-peroxone (EPX). Different parameters and operating conditions were evaluated such as the electrogeneration of hydrogen peroxide, pH, anodic and cathodic overpotential, photon flux, the presence of substrates on the photocurrent and cathodic reduction of oxygen. To interpret the interfacial phenomena that were presented, electrochemical techniques such as linear and cyclic voltammetry, chronoamperometry, open-circuit chronopotentiometry, rotating disk electrode (RDE) and electrochemical impedance spectroscopy were used. Likewise, through a response surface analysis, the effect of variables such as current density and initial substrate concentration on the free cyanide degradation capacity and on the specific energy consumption of the process was determined. With the proposed process, 100% of the CN- ion was degraded using 0.086 mA/cm2 and 94 ppm initial concentration, with the additional degradation of CNO- (29.4%) and a specific energy consumption of 4.68 kW-h L-1. Furthermore, in the treatment of cyanide wastewater from mining activities, the complete degradation of the metal cyanide complexes (copper and iron) and the total precipitation of their metals as hydroxides and oxy-hydroxides were evident. 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