Optimization of silver ion release from silver-ceramic porous media for household level water purification

Abstract

A novel method has been developed to produce zerovalent silver nanopatches in a porous ceramic tablet using only clay, sawdust, water, and silver nitrate as precursors. When placed in 10 L of water, the silver nanopatches (2 to 3 nm diameter per patch) are gradually oxidized to produce silver ions, which diffuse out of the tablet into the bulk solution. The objective of this work is to optimize the silver-ceramic design to increase the rate of silver ion release from the tablet to further improve disinfection kinetics. To meet this objective, ceramic tablets were fabricated in different ways and tested for silver ion release into water over 8 to 24 h periods. Silver addition had an approximately linear effect on silver ion. Grinding the tablet into different particle sizes (4-60 mesh) had the most significant effect on silver release. However, if this ground fraction is compartmentalized into a fabric bag, silver levels produced in the water drop back to levels comparable to the single tablet form. Based on these results, 1 and 2 cm ceramic cubes were manufactured and represented a reasonable compromise between silver release and usability. Disinfection experiments on these silver-ceramic cubes resulted in effective disinfection of E. coli in laboratory experiments.