Synthesis and Antibacterial Properties of ZnO/Clinoptilolite and TiO 2 /ZnTiO 3 /Clinoptilolite Powders

The purpose of this study was to estimate the antimicrobial activity of ZnO/clinoptilolite and ZnTiO3/clinoptilolite samples in solid media (agar plates) against Gram-negative Escherichia coli ATCC 25922 and Gram-positive Staphylococcus aureus ATCC 25923. Samples of clinoptilolite rich tuff (from Beli Plast deposit in Eastern Rhodopes, Bulgaria) treated with oxalic acid were obtained. The ZnO and TiO2/ZnTiO3 were additionally incorporated into the clinoptilolite samples. The structure, morphology and elemental composition of the pre-treated clinoptilolite samples were characterized by XRD, SEM and EDX analysis. The antibacterial activity was investigated by exposing Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in nutritive media to the ZnO, TiO2/ZnTiO3, ZnO/clinoptilolite and TiO2/ZnTiO3/clinoptilolite samples. A strong bactericidal action of both samples against E. coli and S. aureus was observed. Moreover, the TiO2/ZnTiO3/clinoptilolite sample exhibited a strong antibacterial effect in the presence of E. coli (11 mm), while another sample (ZnO/clinoptilolite) showed strong antibacterial effect against S. aureus (15 mm).