Comparative study of photocatalytic activities of Zn5(OH)8Cl2•H2O and ZnO nanostructures in ciprofloxacin degradation: Response surface methodology and kinetic studies

Zinc hydroxide chloride monohydrate (Zn-5(OH)(8)Cl-2 center dot H2O) and zinc oxide (ZnO) nanostructures were synthesized by simple precipitation and pyrolysis methods, respectively and characterized by means of various instrumental methods. Their photocatalytic efficiencies as two potential photocatalysts for photodegradation of a clinical wastewater, ciprofloxacin (CIP), were probed and compared. The results indicated that in comparison with Zn-5(OH)(8)Cl-2 center dot H2O nanoplates, the photodegradation was 1.4 times faster when using ZnO nanoparticles as well as higher removal percentage. The optimum pH obtained was 8 that it is typically found for hospital wastewater. Analysis of variance (ANOVA) exhibited high R-2 values, high F-values, very low P-values, and nonsignificant lack of fit values demonstrating good correlation between experimental and predicted values of the response for both catalysts. Kinetic studies identified first order model as a suitable model for description of photodegradation processes for both nanosized Zn-5(OH)(8)Cl-2 center dot H2O and ZnO. The chemical oxygen demand (COD) removal of 43.30 and 56.30% were obtained after 24 h for Zn-5(OH)(8)Cl-2 center dot H2O nanoplates and ZnO nanoparticles, respectively. Ultra-performance liquid chromatographymethod coupled with tandem mass spectrometry (UPLC-MS/MS) for the determination of CIP degradation products has been used. Taken together, ZnO nanoparticles were more efficient in CIP removal due to some properties as in higher surface area and lower band gap. (C) 2017 Elsevier B.V. All rights reserved.