Modification of commercial acetate membranes with titanium dioxide to
apply in dinking water treatment
F. Silva1, R. Bergamasco1, M.T. Pessoa de Amorim2, C. Tavares3
1 Department
of Chemical Engineering, University of Maringá, Av. Colombo, 5790
Maringá Brazil
2 Department of Textile Engineering, University of Minho, Campus de Azúrem, 4800058 Guimarães, Portugal
3 Department of Physics, University of Minho, Campus de Azúrem, 4800-058
Guimarães, Portugal
(E-mail : mtamorim@det.uminho.pt)
Abstract
The modification of organic membranes with titanium dioxide has been applied to
avoid the membrane fouling. In this paper is studied the immobilization of titanium
dioxide onto commercial acetate membranes of different porosity is done by
deposition of titanium dioxide films at room temperature by pulsed-frequency
reactive magnetron sputtering from a high purity Ti target in Ar/O 2/N2 atmosphere.
The characterization of the modified membranes is done by SEM, FTIR and the
contact angle. All these membranes will be applied in drinking water treatment.
Keywords. Titanium dioxide - immobilization – membranes - characterization.
INTRODUCTION
Fouling is a major constraint during separations using membranes. Its occurrence leads to a decline
in the membrane permeability and can occur either by the deposition of a new layer onto the membrane
surface (cake filtration) or by intermediate, total or internal porous blocking (Hermia, 1982), besides
mechanisms as spacer clogging and adsorptive fouling. These several modes of porous blocking are due to
the size and shape of the solid/solute in relation to the distribution of the membrane pore sizes.
Fouling is a complex phenomena depending on specific interactions of that particular membrane solution
and also on a number of parameters. Previously, attempts have been made to relate fouling to flux decline
resulting from an increase in flow resistances (Jiraratananon and Chanachai, 1996).
Chemical modification of membrane surface using the deposition of titanium dioxide technique on its
surface is of special interest. It aims to reduce the hydrophobic interactions between membrane surface and
water solutes, the main cause of fouling (Morão et al., 2005). This technique improves the membrane
performance in terms of fouling reduction and permeates flux (Luo, 2005; Bae and Tak, 2005). Besides this,
it is possible to use the photocatalytic properties of titanium dioxide, largely applied in degradation of
pathogenic contaminants (Kim et al., 2003). The application of the modified membranes in a laboratorial pilot
has been tried with success. (Silva F et al, 2010)
METHODS
Cellulose acetate microfiltration membrane of pore diameter 0.45, 0.8 and 3 µm was purchased from
Advantec. The immobilization of titanium dioxide onto membranes has been made by deposition of titanium
dioxide films at room temperature by pulsed-frequency d.c reactive magnetron sputtering from a high purity
Ti target in Ar/O2/N2 atmosphere with cathode current of 0.3 A and a deposition time of 5 hours. The
conditions of titanium dioxide deposition can be obtained in C. J. Tavares et al. Ft-IR spectra were obtained
using a Nicolet Avatar 360 spectrophotometer using an ATR. The resolution of each spectrum was 8cm -1
and the number of co added scans was 30. Contac angle measurements were carried out in OCA 20, Data
physics Instruments GmbH, Filderstadt apparatus using distilled water. SEM study was carried using Nano
SEM, model FEI Nova 200, FEG/SEM.
RESULTS
The Ft-IR spectra of the unmodified and modified membranes with titanium dioxide are shown in figure 1. All
the modified membranes show a most intense band of the characteristic peaks of the C=O at 1740 cm-1
a
Figure 1. (a)FT-IR spectrum of the unmodified
membrane and (b) FT-IR spectrum of the modified
membrane
The contact angle of the modified membranes is
always larger than its of the unmodified
membranes.
The TiO2 particles were revealed by SEM (figure
not show) at the surface of the membranes and
also inside of the pores.
CONCLUSION
The modification of the commercial acetate cellulose membranes with TiO 2 immobilization films at room
temperature by pulse- frequency dc reactive magnetron sputtering allows an increase of the hydrophilitcity of
the membrane as the measurements of the contact angle and the Ft-IR spectrum indicates. The experiments
of the hydraulic permeability, fouling, and life time of these membranes will be presented in another paper.
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