Graphene quantum dots (GQDs) decorated zeolitic imidazole framework-67 (ZIF67) electrode for the in-situ oxidation of ciprofloxacin in water

Ciprofloxacin (CIP) is a biorecalcitrant pharmaceutical compound that is frequently found in wastewater and aquatic environment and has a wide range of detrimental effects on living organisms. In this study, graphene quantum dots doped zeolitic imidazole framework-67 (GQDs@ZIF67) electrodes were prepared for the direct electrochemical degradation of CIP in NaCl supporting electrolyte. The presence of GQDs improved oxidation peak current at a lower applied potential, which enhanced the direct oxidation capacity and applicability of GQDs@ZIF67 electrode for CIP degradation. Under optimal conditions ([NaCl] = 0.1 M, applied potential of 1.0 V (∼0.5 A m−2), pH = 7, and temperature = 25 °C), the CIP removal and mineralization efficiency was greater than 90 and 70%, respectively, after five consecutive cycles. The GQD@ZIF67 electrocatalytic system was effective over a broad range of initial pH. Scavenger test and EPR measurement showed that the RCSs, i.e., ClO• and Cl2•− were being generated in the GQDs@ZIF67-based electrochemical system and played the main role in CIP oxidation. The intermediates of degradation were studied, and a plausible mechanism was proposed. This research developed an innovative electrocatalytic approach for treating antibiotic-contaminated water. [Display omitted] •GQDs@ZIF67 electrode was applied in CER for CIP removal.•GQD doping improve the elctrocatalytic activity and conductivity of ZIF67.•GQDs@ZIF67 anode exhibits excellent stability and reusability.•ClO• and Cl2•− in EAOP system played important role in CIP degradation.