Solar photoelectro-Fenton degradation of the herbicide 4-chloro-2-methylphenoxyacetic acid optimized by response surface methodology

► The herbicide MCPA is quickly mineralized by solar photoelectro-Fenton. ► A CCRD allowed the optimization of current, Fe2+ content and solution pH. ► TOC, MCE and energy consumption are described by response surface methodology. ► Generated hydroxyl radical destroys MCPA and its aromatic oxidation by-products. ► UV light of solar irradiation photolyzes the Fe(III)-carboxylate complexes produced.