Efficient removal of aqueous ciprofloxacin antibiotic by ZnO/CuO-bentonite composites synthesized via carbon-bed pyrolysis of bentonite and metal co-precipitation

Antibiotics are of emerging concern due to their widespread use, lack of adequate treatment, and for their potential to threaten human health and the environment. Here, a facile fabrication approach for synthesizing ZnO/CuO-bentonite composites was investigated via carbon-bed pyrolysis of bentonite followed by ZnO/CuO co-precipitation. Sorbents were synthesized using a range of bentonite pyrolysis temperatures, metal oxide contents, and ZnO:CuO mass ratios. The ZnO/CuO-bentonite composites exhibited diverse functional groups, excellent mesoporosity, and high specific surface area (135.0 m 2  g −1 , four times that of pyrolyzed bentonite-only control). Ciprofloxacin removal was maximized at a bentonite pyrolysis temperature of 450 °C, a total metal oxide content of 25 %, and a Zn/Cu ratio between 95:5 and 93:7, and this material had an observed experimental CIP adsorption of 451 mg g −1 and a calculated maximum adsorption capacity of 1249.3 mg g −1 . This excellent CIP sorption ability was attributed to its abundant surface active sites and multiple sorption mechanisms, including hydrogen-bond interaction, ion exchange, and electrostatic interaction. These results illustrate that ZnO/CuO-bentonite composite sorbents have excellent potential for use in environmental remediation and water treatment applications.