CELLULOSE ACETATE MEMBRANES MODIFIED WITH BIOCIDAL SILVER BASED GRAPHENE OXIDE
NANOCOMPOSITE
Patricia Fernanda Andrade1, Andreia Fonseca de Faria1, Ana Carolina Mazarin de Moraes1, Maria do Carmo
Gonçalves1, and Oswaldo Luiz Alves1
Affiliations: 1Institute of Chemistry, University of Campinas (UNICAMP). Campinas, Brazil
Abstract
One of the multiple approaches to prevent biofouling is membrane functionalization with bioactive
nanomaterials. In this study, the antibacterial activity of cellulose acetate (CA) membranes was achieved by
embedding graphene oxide decorated with silver nanoparticles (GOAg) into the polymeric matrix (CA-GOAg).
The CA-GOAg membranes were investigated by field emission scanning electron microscopy (FESEM) and
transmission electron microscopy (TEM).
Keywords: Biofouling, nanocomposites, membranes, cellulose acetate.
INTRODUCTION
Biofilms are defined as complex agglomerates of cells which are surrounded by an exopolysaccharide
extracellular polymeric matrix (EPS)1. The biofilm structure plays an important role in microbial communities,
since it provides a support for microbial growth, protection against hazardous substances, optimal environment
for exchange of genetic material between cells, and sometimes can also act as a source of nutrients2.
Therefore, the biofilm formation has led to several industrial problems, thus causing mechanical blockage in
fluid systems, increase in energy consumption, and corrosion in metallic surfaces 3. In this study, we
demonstrate that the GOAg nanocomposite incorporation into cellulose acetate membranes can prevent biofilm
formation. Even though the water permeability was slightly decreased, the functionalization with GOAg
nanocomposite has been shown to impart a strong antibacterial activity to the membranes, as evaluated against
the Gram-negative Escherichia coli.
METHODS
Cellulose acetate (CA) membranes were prepared using the wet phase-inversion method. First, cellulose
acetate was dissolved in acetone. After complete dissolution, pre-synthesized GO and GO-Ag nanoparticles
were dispersed in DI water and slowly dispersed in the CA solution through sonication. The final solution
composition was of 11% CA, 67% acetone, and 22% water (wt%). The nanomaterials (GO and GOAg) were
introduced aiming to reach 0.1, 0.25, and 0.5% in relation to the polymer mass. The GOAg nanocomposite and
the membranes morphologies were respectively examined in a transmission electron microscope, operating at
120 kV (Zeiss Libra 120), and in a field emission scanning electron microscope (JEOL JSM-6340), operating at
a 3 kV accelerating voltage.
RESULTS AND DISCUSSION
Figure 1 shows the CA, CAGO 0.5%, and CA-GOAg 0.5% membrane morphologies investigated by
FESEM. The FESEM images were obtained for the membrane surfaces and cross-sectional areas. No
significant differences on the CA, CA-GO and CA-GOAg membrane surface morphologies were observed by
FESEM images (Figures 1a, 1b, and 1c). The formation of asymmetric “finger-like” and also “sponge-like”
structures was detected in the cross-section images for all CA membranes (Figure 1d). However, a
predominance of the sponge-like structure in the CA-GO and CA-GOAg membranes was observed (Figures 1e
and 1f). Figure 2 shows TEM images of GOAg sheets dispersed in the polymeric matrix, where yellow arrows
show the AgNPs (black dots) attached onto the GO nanosheets and incorporated in the CA matrix. Although we
could not visualize the AgNPs anchored on GO sheets in the FESEM images, the TEM images presented that
the GOAg nanocomposite was well distributed and adhered to the cellulose acetate matrix. The results obtained
herewith highlight the potential application of GOAg as an effective antibacterial nanocomposite to prevent
biofouling in nanofiltration and microfiltration membranes.
ACKNOWLEDGMENT
The authors would like to thank CNPq, FAPESP, CAPES and INOMAT for financial support.
REFERENCES
1.
Drenkard, E. Microbes Infect, 5, 1213, 2003.
2.
Hall-Stoodley, L., Costerton, J.W. and Stoodley, P. Nat Rev Micro, 2, 95,2004.
3.
Chmielewski, R.A.N. and Frank, J.F., Compr Rev Food Sci Food Saf, 2, 22, 2003.
Figure 1. FESEM micrographs of pure CA (a, d), CA-GO (0.5 wt%) (b, e), and CA-GOAg (0.5 wt%) membranes (c, f):
surfaces (a, b and c) and cross-sections (d, e and f).
Figure 2. (a) FESEM micrograph of the CA-GOAg (0.5 wt%) membrane cross-sections, and (b, c) TEM images of the
membrane ultrathin sections, showing the presence of the GO-Ag nanocomposites into the polymeric matrix. The yellow
arrows indicate the AgNPs supported on GO sheets.