Solar Photoelectro-Fenton: A Very Efficient and Low Cost Electrochemical Advanced Oxidation Process for Water Remediation

摘要

This lecture reviews the characteristics of the solar photoelectro-Fenton process and the main results obtained in our facilities upon its application at laboratory and small pilot plant scale for the degradation of environmentally-relevant organic pollutants usually found in waters. This electrochemical advanced oxidation process is based on the removal of organic matter by ·OH formed from (i) water oxidation at the anode and (ii) in the bulk from Fenton's reaction between H2O2 generated at the cathode and added Fe2+, along with the synergistic action of UV radiation from sunlight that photolyzes generated Fe(lll)-carboxylate complexes. The mineralization of several herbicides, pharmaceutical residues and dyes in different electrolytic systems is examined using both, small tank reactors directly exposed to sunlight and pre-pilot flow plants with a filter-press electrochemical reactor coupled to a tilted planar glass compartment or a compound parabolic collector as solar photoreactors. Comparative results obtained with cells equipped with Pt and boron-doped diamond anodes, alone or coupled, and a carbon-polytetrafluoroethylene gas (O2 or air) diffusion cathode, are presented. It is demonstrated that solar photoelectro-Fenton has greater mineralization current efficiency and is much less expensive than other electrochemical advanced oxidation processes like anodic oxidation, electro-Fenton and photoelectro-Fenton with artificial UVA light tested with the same electrodes. The efficacy of the treatments is discussed for several model contaminants in terms of: (i) the abatement of the total organic load of aqueous solutions, (ii) the decay kinetics of contaminants and (iii) the evolution of their aromatic intermediates, generated carboxylic acids and final inorganic ions released, which leads to the proposal of the most plausible reaction pathways.