Article pubs.acs.org/est
Porous Ceramic Tablet Embedded with Silver Nanopatches for LowCost Point-of-Use Water Purification Beeta Ehdaie, Carly Krause, and James A. Smith* Department of Civil and Environmental Engineering, University of Virginia, Charlottesville, Virginia 22904, United States
Downloaded via WESTERN SYDNEY UNIV on January 10, 2019 at 20:49:16 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.
S Supporting Information *
ABSTRACT: This work describes a novel method to embed silver in ceramic porous media in the form of metallic silver nanopatches. This method has been applied to develop a new POU technology, a silver-infused ceramic tablet that provides long-term water disinfection. The tablet is fabricated using clay, water, sawdust, and silver nitrate. When dropped into a household water storage container, the ceramic tablet releases silver ions at a controlled rate that in turn disinfect microbial pathogens. Characterization of the silver-embedded ceramic media was performed using transmission electron microscopy. Spherical-shaped patches of metallic silver were observed at 1−6 nm diameters and confirmed to be silver with energy dispersive spectroscopy. Disinfection experiments in a 10 L water volume demonstrated a 3 log reduction of Escherichia coli within 8 h while silver levels remained below the World Health Organization drinking water standard (0.1 mg/L). Silver release rate varied with clay mineralogy, sawdust particle size, and initial silver mass. Silver release was repeatable for daily 10 L volumes for 154 days. Results suggest the ceramic tablet can be used to treat a range of water volumes. This technology shows great potential to be a low-cost, simple-to-use water treatment method to provide microbiologically safe drinking water at the household level.
■
INTRODUCTION 1.87 million deaths result from unsafe drinking water and poor sanitation annually.1−3 An estimated 780 million people lack access to an improved water supply.1,2 The World Health Organization (WHO) suggests that one potential solution to poor-quality household drinking water is treatment at the point of use (POU).4,5 A recent meta-analysis reported that household water interventions can be more effective in improving water quality compared to interventions at the source; however, this is dependent on the user compliance.6 Ease of use, affordability, and long-term effectiveness are key factors but also make development of POU technologies an extremely difficult design problem. Current conventional methods are labor intensive, such as fabric filtration and boiling, or dependent on variable factors such as availability of sunlight for solar disinfection. A common theme among a majority of POU methods is recontamination due to poor sanitation. Therefore, successful designs must be technologically effective with respect to removal and/or deactivation of waterborne pathogens under a wide range of water chemistries, and simple to use to ensure user compliance, long-term effectiveness, and reduce risk of recontamination.5,6 They must also be socially acceptable, scalable, and affordable, which likely requires local materials, labor, and/or ease of transport.7−9 Some of the most promising POU technologies include the application of silver as a disinfecting agent. The antimicrobial effects of silver are well-known and recent studies have shown its effectiveness against bacteria,10−14 viruses,15 and protozoa.16,17 At low levels (
