Kinetics of oxidative degradation/mineralization pathways of the antibiotic tetracycline by the novel heterogeneous electro-Fenton process with solid catalyst chalcopyrite

TLDR: In this article, the degradation of solutions of the antibiotic tetracycline (TC) has been studied by a novel electrochemical advanced oxidation process, consisting in electro-Fenton (EF) process using chalcopyrite as heterogeneous catalyst.

Abstract: The degradation of solutions of the antibiotic tetracycline (TC) has been studied by a novel electrochemical advanced oxidation process, consisting in electro-Fenton (EF) process using chalcopyrite as heterogeneous catalyst. In fact, chalcopyrite powder was the source of Fe 2+ and Cu 2+ ions instead of a soluble catalyst salt used in conventional EF. Experiments were performed in an undivided cell equipped with a Pt or boron-doped diamond (BDD) anode and a carbon felt cathode, where TC and its oxidation intermediate products were destroyed by hydroxyl radicals ( OH) formed both, in the bulk solution from electrochemically induced Fenton’s reaction (Fe 2+ and H 2 O 2 ) and Fenton’s-like reaction (Cu + and H 2 O 2 ), and at the anode surface from water oxidation. The effects of operating parameters such as applied current, chalcopyrite concentration and anode material were investigated. TC decay followed pseudo-first-order reaction kinetics. The absolute rate constant for TC oxidation by OH was found to be 3.2 × 10 9  M −1  s −1 , as determined by the competition kinetic method. EF process using chalcopyrite as heterogeneous catalyst showed to be more efficient than conventional EF, achieving almost total mineralization of the TC solution (98% of total organic carbon removal) after 360 min under optimum operating conditions. A plausible mineralization pathway for mineralization of TC aqueous solution by OH was proposed based on the identification of different oxidation by-products. Moreover, toxicity tests pointed out that this heterogeneous EF process was able to detoxify the TC solutions.