Optimization of the electro-Fenton and solar photoelectro-Fenton treatments of sulfanilic acid solutions using a pre-pilot flow plant by response surface methodology

► Quicker degradation of sulfanilic acid by solar photoelectro-Fenton than electro-Fenton. ► The same optimized current density, Fe2+ content and pH for both processes by CCRD. ► Description of TOC, energy cost and current efficiency by response surface methodology. ► Fe(III)-carboxylate complexes as main by-products after electro-Fenton. ► Photolysis of these complexes by UV irradiation of sunlight in solar photoelectro-Fenton.