Antibacterial Inactivation of Escherichia coli after TiO2-Fe3O4-Bentonite Photocatalytic Treatment

Abstract

TiO 2 -Fe 3 O 4 –Bentonite photocatalytic material has been developed to inactivate of Escherichia coli. The syntheses of the TiO 2 -Fe 3 O 4 based photocatalyst have been carried out by sol-gel method. The bentonite used for porous support was obtained from Pacitan, Indonesia. The photocatalyst material will capture energy of UV radiation followed by the electron excitation and oxidation-reduction reactions. Because of the processes, the various types of pollutants and microorganisms can be decomposed and reduced. The electron excitation will induce the formation of hydroxyl radical and O 2 . These radicals are responsible to decompose the cell wall of bacteria and further damage the bacteria’s cytoplasmic membrane. Decomposing of cytoplasmic membrane causes lipid peroxidation in the membrane, and then losing their viability. It is followed by the death of bacterial cell. This study conducted a series of Escherichia coli inactivation by using photocatalyst material of TiO2-Fe 3 O 4 -Bentonite which was irradiated with UV light. The photocatalytic inactivation of Escherichia coli was conducted in a reactor under ultraviolet (325 nm) exposing. The photocatalytic degradation was observed for 5 hours to determine the optimum initial bacteria concentration, intensity of UV light and also photocatalyst concentration. The inactivation kinetic was approached by Chick-Watson and Hom kinetic models. The colonies calculations were conducted by Total Plate Count. The optimum condition was achieved for 300 minutes process to reach 7 bacterial log reduction units for an average bacterial inoculum size of 3.8 × 10 4 CFU/ml. All disinfection experiments showed a non-linear bacterial inactivation kinetic profile, which is started with shoulder lag followed by a log reduction and the tailing curve. The inactivation kinetics of Escherichia coli using TiO 2 -Fe 3 O 4 -Bentonitephotocatalytic material system satisfactorily obeyed the Hom kinetic model.