Efficient disinfection of Escherichia coli in water by silver loaded alumina

The catalytic inactivation of Escherichia coli (E. coli) in water by silver loaded alumina as catalyst was investigated. Ag/Al2O3 and AgCl/Al2O3 catalysts exhibited high bactericidal activity at room temperature in water with no need for any light or electrical power input. Dissolved oxygen which can be catalyzed to reactive oxygen species (ROS) was found to be essential for the strong bactericidal activities of the catalysts. Decomposition of the cell wall leading to leakage of the intracellular component and the complete lysis of the whole cell were directly observed by transmission electron microscopy (TEM). The resultant change in cell permeability was confirmed by potassium ion leakage. The different morphological changes between E. coli cells treated with the catalysts and Ag+ were also observed. The formation of ROS involved in the bactericidal process by AgCl/Al2O3 was confirmed by addition of catalase and OH scavenger. Higher temperature and pH value were found to have positive effect on the bactericidal activity of AgCl/Al2O3. All these results indicated that the bactericidal effect of the catalyst was a synergic action of ROS and Ag+, not an additive one. A possible mechanism is proposed.