Bactericidal activity of a Ce-promoted Ag/AIPO4 catalyst using molecular oxygen in water

The catalytic inactivation of Escherichia coli in water by a cerium (Ce)-promoted silver-loaded aluminum phosphate (Ag/ AIPO(4)) catalyst using molecular oxygen was investigated. With optimum Ce content, the Ag(Ce)/AIPO(4) catalyst exhibited strong bactericidal activity. The process of decomposition of the cell wall and cell membrane was directly observed by TEM. The different morphological changes of E coli cells treated with the Ag(Ce)/AIPO(4) catalyst and those treated with Ag+ suggested that the Ag+ eluted from the catalyst surface did not play an important role during the bactericidal process. Results of DMPO spin-trapping measurements by electron spin resonance (ESR) indicated the formation of the reactive oxygen species (ROS) center dot OH and center dot O-2(-), which caused the considerable bactericidal activity. The formation of H2O2 acted as an important intermediate; this was confirmed by addition of catalase as the scavenger. A possible catalytic oxidation bactericidal mechanism using molecular oxygen was proposed for the Ag(Ce)/AIPO(4) catalyst.