Cu₃P electrode catalyze degradations of metronidazole and chloramphenicol fast in high-amount Cl⁻ over broad pH

Electrochemical advanced oxidation process (AOP) is highly effective to the degradations of antibiotics, especially in the presence of large amounts of salts. In industrial waste water and river, there are always abundant chloride ions which replace the reactive oxygen species (ROS) and corrode the transition metal electrodes. Herein, hierarchical Cu₃P/Cu slices with porous structures were applied to electrocatalyze the degradations of metronidazole (MNZ) and chloramphenicol (CAP) in NaCl electrolytes assisted by peroxymonosulfate. MNZ and CAP were fully decomposed in 1 h and 2 h at pH 3.0–9.0, respectively. Apparent first-order reaction rate constant, k_obs were 0.139, 0.113, 0.096, 0.092, and 0.117 min⁻¹ with 50 mM Na₂SO₄, 50 mM, 100 mM, 150 mM, and 200 mM NaCl as electrolytes at pH 3.0 for MNZ, respectively. Small molecules, such as acetonitrile (P6, m/z = 42), acetic acid (P5, m/z = 61), and imidazol (P3, m/z = 83) were present after decompositions of MNZ with Na₂SO₄ or NaCl as electrolytes. Some derivatives, 2-(2-amino-5-nitro-1H-imidazaol-1-yl) acetic acid (P1, m/z = 183) were present at the same time. For CAP, k_obs were 0.066, 0.050, 0.051, 0.050, and 0.048 min⁻¹ with 50 mM Na₂SO₄, 50 mM, 100 mM, 150 mM, and 200 mM NaCl as electrolytes at pH 3.0, respectively. (2-hydroxy-2-(4-nitrophenyl) acetic acid (P1, m/z = 195) and p-nitrobenzoic acid (P2, m/z = 165) were remained in 2 h in NaCl. Some derivative of CAP (P7, m/z = 370) were formed by the additions of one -Cl and one -OH on to nitrobenzene groups. With Na₂SO₄ as electrolytes, only P1 (m/z = 195) remained. The study provides a new way to decompose antibiotics efficiently.