Optimization of Silver Ion Release from Silver-Ceramic Porous Media for Household Level Water Purification

Rekha Singh,Sydney Turner,Veronica Son,James A. Smith,Chloe Rento

doi:10.3390/w11040816

Rekha Singh, Sydney Turner + Show 3 more

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https://doi.org/10.3390/w11040816

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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.

Highlights

Consumption of microbially contaminated drinking water is one of the greatest threats to global public health
Samples were taken from the center of the ceramic tablet embedded with 3 g of silver and manufactured using the standard protocol
All the particles passed through a 20 mesh screen were used for ceramic tablet fabrication, creating various sizes of pores throughout the ceramic matrix to facilitate silver ion diffusion and release into the bulk solution

Summary

Introduction

Consumption of microbially contaminated drinking water is one of the greatest threats to global public health. The World Health Organization (WHO) estimates that consumption of unsafe water causes the deaths of over 5 million people per year. More than 1.5 million of these deaths are to children under the age of 5 [1]. Diarrheal diseases (transmitted by contaminated water) are a major contributor to these alarming numbers [2,3,4]. There are additional health burdens on children who experience cognitive impairment and stunted growth as a result of gastrointestinal infections caused by consumption of water with pathogenic organisms [5]. In many parts of sub-Saharan Africa, there is low-quality drinking water and high rates of human immunodeficiency virus (HIV) infection [6]

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