Silver research

• Vinka Oyanedel-Craver• Assistant Professor

• University of Rhode Island• Department of Civil and Environmental

Engineering

Silver nanoparticles

Disinfectant properties of silver can be used to add biocide properties to different materials and/or prevent biofilm growth

Goal of study

• Inputs• Silver nanoparticles (nAg) and silver ions (Ag+)• Amount of silver•Water chemistry•Materials (clay and burn-out)

• Outcomes•Microbiological removal effectiveness• Desorption of silver• Biofilm development

Ceramic filters•Clays: Indonesia, Tanzania,and Nicaragua•Combustible material: sawdust, rice husk•Silver: Colloidal silver (nAg) and silver nitrate (Ag+)

•Silver release•Bacteria removal•Biofilm

formation

Materials

Methods

Experimental Setup

a) A schematic diagram of the tracer, bacteria and virus transport experimentsb) One-dimensional ceramic filter discc) Permeameter chamber

a)b)

c)

Experimental Setup

• A schematic diagram of the tracer, bacteria transport experiments• One-dimensional ceramic filter disc

c)

Silver release

EPA silver standard in drinking water 100 microgram/L

nAg

Control range

Control range

Ag+

• Silver impregnated disks have higher bacterial removal than controls

• Performance of nAg slightly superior than Ag+

• Performance better at higher concentration

• Sig. difference between clays

• No difference in burn-out

Viable bacteria inside the ceramic materials as function of

silver concentration and clay material

• Sig. difference between clays (Nicaragua)

• No difference in water chemistries

Recommendations

• Ag+ not used above 0.03 mg/g• Health consequences• Loss of silver

• Increase nAg used to 640 mg/filter• If hard water is used, increase more

Future Research

• Investigate• Chlorine effect on sorption of silver• Various methods of application• Alternative disinfectants