Fluoroquinolone ciprofloxacin removal from synthetic and real wastewaters by single and combined electrochemical advanced oxidation processes. A review

Abstract

Ciprofloxacin (CIP) is a widely prescribed fluoroquinolone antibiotic detected in the aquatic environment fostering the emergence of bacteria and posing risks the human health and ecosystem integrity. The present comprehensive critical review deals with CIP removal from synthetic and real wastewater by electrochemical advanced oxidation processes (EAOPs) up to 2024. Lower performance was obtained in real wastewaters than synthetic ones because their components scavenged-generated oxidizing agents. Anodic oxidation (AO) has been developed with active dimensionally stable anodes (DSA) and the non-active potent boron-doped diamond (BDD) one, where CIP solutions in chloride medium reached a maximal of 75 % mineralization. A more rapid CIP degradation and up to 96 % mineralization have been found for homogeneous electro-Fenton (EF) with Pt and Fe²⁺ catalyst. Heterogeneous Fenton with functionalized iron cathodes and solid iron catalysts, and heterogeneous EF-like with non-ferrous catalysts gave worse results. Novel modified EF processes with dual cathodes for direct.^•OH production after H₂O₂ electrogeneration allowed up to 96 % mineralization. Photoelectro-Fenton (PEF) with UVA light and solar PEF (SPEF) can yield overall mineralization by the rapid photolysis of final Fe(III)-carboxylate species formed. Photoelectrocatalysis (PEC) with new photoanodes like FTO/Ni–ZnO under UVA light yielded 87 % mineralization. Hybrid AO, EF, PEF, and PEC processes with persulfate, O₃, ultrasounds, or photocatalysis were more powerful than their single EAOPs. The characteristics and performance of each method, the generation of oxidants (^•OH, O₂^•−, and/or ¹O₂), its reusability, and the by-products produced are discussed. The loss of toxicity of the treated solutions by EAOPs is finally detailed.