Photocatalytic Removal of Escherichia Coli by ZnO Activated by Ultraviolet-C Light from Aqueous Solution

There is a great interest in photocatalytic oxidation of contaminants, using ZnO, in recent years. The main objective of this research was to study photocatalytic disinfection of E. coli bacteria as water microbial pollution index, using nano particles of ZnO and a UV lamp in a batch reactor. In this study, the contaminated water sample was prepared through adding 102 and 103 E. coli bacteria per ml of raw water. The contaminated water entered the photocatalytic oxidation reactor and removal efficiency of E. coli bacteria in different conditions were studied, including pH (5.5, 7, and 9), time (10, 20, 30, 40, 50 and 60 mins), dose of nano particles ZnO (0.2,0.4,0.8 and 1 gr/l), number of bacterium (102 and 103 per milliliter) and voltage of UV-C lamp, 27 volts. Characterizations of ZnO nano particles were determined using scanning electron microscope equipped with Energy Dispersive X-ray Analysis (EDX) system and X-ray diffraction (XRD) method. Photocatalytic process efficiency is enhanced by increasing reaction time and dose of nano particles ZnO in the presence of UV lamp irradiation. The results show that the best conditions for removal of 102 and 103 bacteria per milliliter are obtained from condition including pH of 7, reaction time of 30 mins, 0.8 gr/l doses of nano particles ZnO and 27-volt-UV lamp. The results indicate that the increase of reaction time and dose of nano particles ZnO, in the presence of radiation UV lamp, have the most significant effect on photocatalytic efficiency. Based on the results, photocatalytic can be promising method for removal of E. coli bacterium from drinking water.