Bactericidal allophanic materials prepared from allophane soil: II. Bactericidal activities of silver/phosphorus–silver-loaded allophanic specimens

Bactericidal activities against Escherichia coli and Staphylococcus aureus in water for two sterilizing allophanic specimens prepared by loading silver or phosphorus along with silver on an allophane soil carrier, were examined in comparison to those of silver-loaded zeolite specimens. The sterilizing allophanic specimens were added to bacteria suspensions (1×106–1×107 cells of E. coli or S. aureus/1 cm3 of suspension) and stirred for a fixed period. Then bactericidal activities were evaluated from survival ratio of bacteria in liquid phase by batch method. Obvious and strong bactericidal activities of the sterilizing allophanic specimens were observed for both bacteria. These sterilizing allophanic specimens also showed immediate pronounced effects for bactericidal activity than that of silver-loaded zeolite specimens. For these allophanic specimens, it was understood that the contribution of insoluble silver in the specimens to bactericidal activity was remarkably high in comparison to those of silver-loaded zeolite specimens. Co-loading of phosphorus enhances the amount of silver loading and had a great effect in controlling silver elution from these allophanic specimens.