ZnO-functionalized fly-ash based zeolite for ciprofloxacin antibiotic degradation and pathogen inactivation

Abstract

There is an increasing need for photocatalytic materials capable to remove pollutants and to deactivate microorganisms for a wide range of applications. Here we report the preparation of fly ash-based zeolite material in which ZnO was incorporating using an alkaline hydrothermal method. The zeolitic materials were used to functionalized glass substrates through spin-coating technique and characterized by X-ray diffraction, emission spectroscopy, electrophoretic light scattering, and UV–Vis diffuse reflectance, among other techniques. The surface characteristics of the coatings were determined by scanning electron microscopy and water contact angle. The photocatalytic activity of ZnO-functionalized fly-ash based zeolite was assessed by tracking the degradation of the antibiotic ciprofloxacin (CIP) and its antimicrobial capacity by means of the inactivation of the bacteria Staphylococcus aureus and Escherichia coli under UVA (365 nm) irradiation. The results showed the formation of a sodalite zeolite structure with a band gap of 3.2 eV and photoinduced hydrophilicity. The ZnO-modified fly ash material was able to completely photodegrade CIP in less than 20 min irradiation with 365 nm UVA light, while its non-modified precursor, even displaying a high adsorption capacity was unable to remove the antibiotic after 120 min. The ZnO-zeolitic materials and coatings were able to inactivate bacteria with reductions in the number of viable colonies > 99.9 for S. aureus and > 99.0% for E. coli after 60 min of irradiation, even on specimens previously allowed to grow a mature biofilm. The zeolitic material also proved a low cytotoxicity to human fibroblast cultures.