Zero-valent iron/activated carbon microelectrolysis to activate peroxydisulfate for efficient degradation of chlortetracycline in aqueous solution

Abstract

Tetracycline antibiotics are widely used in human and veterinary medicine; however, their gradual increase in the aquatic environment poses a serious threat to human health and ecosystems. The reactivity of peroxydisulfate (PDS) in the degradation of chlortetracycline (CTC) in aqueous solution using a zero-valent iron/activated carbon (AC) microelectrolysis method (Fe⁰–AC/PDS) was investigated by batch experiments. The results showed that the effects of different systems were as follows: Fe⁰–AC/PDS > Fe⁰/PDS > AC/PDS > Fe⁰–AC > AC > Fe⁰ > PDS. In the Fe⁰–AC/PDS system, the degradation efficiency of CTC could reach 88% under the following optimal experimental conditions: Fe⁰ dose of 0.4 g L⁻¹, PDS dose of 2 g L⁻¹, pH of 3 and initial CTC concentration of 50 mg L⁻¹. The presence of Cl⁻, HCO₃⁻ and H₂PO₄⁻ inhibited the degradation of CTC, while humic acid accelerated the degradation rate of CTC. The mineralization of CTC was evaluated from the TOC, with a value of 31.44% in 7 h. Free radical identification experiments showed that SO₄⁻˙ and O₂⁻˙ were involved in the degradation of CTC. The iron and carbon materials had good reusability, and the degradation rate of CTC was still approximately 70% after four cycles. Finally, the possible mechanism for the degradation of CTC by the Fe⁰–AC/PDS systems was discussed. Based on the above conclusions, Fe⁰–AC microelectrolysis is a new heterogeneous catalytic method for green and efficient activation of PDS and demonstrates potential applicability in the treatment of wastewater.