Towards Water Disinfection Using Silver Nanoparticle-Modified Ceramic Membranes

Abstract for: AICHE Student Conference, Salt Lake City, UT,
November 6 ? November 9, 2015

Towards Water Disinfection
using Silver Nanoparticle-Modified Ceramic Membranes

Michael F.
Desmarais¹, Vinka Oyanedel-Craver², Geoffrey D. Bothun¹

¹Department
of Chemical Engineering, University of Rhode Island, Kingston, RI

²Department
of Civil & Environmental Engineering, University of Rhode Island, Kingston,
RI

Every year, more than 840, 000
people die globally from water related diseases. To address this challenge,
particularly in developing countries, effective low-cost technologies are
needed for water disinfection. A promising approach is to integrate these
technologies within household water treatment and storage (HWTS) systems, such
as ceramic filters made with indigenous materials. Previous work has shown that
HWTSs with clay filters can achieve partial water disinfection when the filters
are treated with colloidal silver ? the colloidal silver deactivates the bacteria
and leads to an approximate 2-log reduction in bacteria concentration. While
effective, (1) ceramic filters made from clay exhibit large variability in
porosity and pore size, which make it difficult to predict flux and biofouling
behavior, and to determine mechanisms of bacterial reduction. Furthermore, (2)
colloidal silver is often physically-adsorbed onto the filters, making it
difficult to control the spatial organization within the filters and causing it
to leach out.

To address these limitations, the
first goal of this project is to determine flux and evaluate
fouling layer growth using well-defined ceramic membranes with and without physically-adsorbed
silver nanoparticles (AgNPs; 95 nm diameter coated with polyvinylpyrrolidone,
or PVP). The ceramic membranes were composed of a zirconia (ZrO₂)
support layer with a titania (TiO₂) active layer with a pore size of
1.4 µm. Membrane permittivity was measured by dead-end filtration with and
without AgNPs in the absence and presence of E. Coli. Inlet and outlet
samples were colonized on agar plates to compare the bacterial reduction
between the trials with and without AgNPs. For both membranes the results were
comparable, indicating that the bacteria that passed through the membranes were
not deactivated by AgNPs. This result suggests that AgNPs either inhibit bacteria
contained within the biofilm that make direct contact with the AgNPs on the
membrane surface, but they do not deactivate bacteria in the permeate, or that
proper adherence of AgNPs to the ceramic surface was not achieved. The
membranes were also examined by scanning electron microscopy (SEM) and energy
dispersive x-ray spectroscopy (EDS) to observe the biofilms and silver
distribution.

The second goal of this project is
to examine a new templating method for forming AgNPs on the same membrane surfaces.
In this method, AgNPs were formed on ceramic membranes coated with polydopamine
through the reduction of silver nitrate at reaction times of 15, 30, 90, and
180 min. For all samples, noticeable coloration differences were observed when
compared to ceramics without AgNPs confirming AgNP formation. Preliminary
results for the polydopamine method are promising and show that AgNPs can be
formed on the surface of ceramic membranes. Additional experiments are being
conducted to determine the optimal conditions for AgNP formation and to
evaluate the membrane flux and fouling behavior.