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Modification of polysulfone ultrafiltration membranes for HNO3 treatment: time influence
Desalination 200 (2006) 294–296
Modification of polysulfone ultrafiltration membranes for HNO3 treatment: time influence M.V. Martínez de Yuso, R. de Lara, M.I. Vázquez, J. Benavente* Grupo de Caracterización Electrocinética y de Transporte en Membranas e Interfases, Dpto. Física Aplicada I, Facultad de Ciencias, Universidad de Málaga, E-29071 Málaga, Spain email: [email protected] Received 28 October 2005; accepted 3 March 2006
1. Introduction Modification of membrane transport parameters as a result of aging, fouling and cleaning agents are extensively reported in the literature [1–3]. A previous study showed that age strongly reduced membrane permeation, but acidic nitric treatment clearly increases it, with a maximum effect after 24 h acidic immersion [4]. In this work, chemical surface modifications caused by immersion of a polysulfone membrane for ultrafiltration processes in 1 M HNO3 solution at different time instances are studied by means of X-ray photoelectron spectroscopy (XPS).
XPS spectra were obtained using a Physical Electronics PHI 5700 spectrometer with a nonmonochromatic MgKa radiation as excitation source (300 W, 15 kV, 1253.6 eV), and they were recorded at a given take-off-angle f = 45° by a concentric hemispherical analyzer operating in the constant pass energy mode at 29.35 eV. Under these conditions the Au 4f7/2 line was recorded with 1.16 eV full width at half maximum (FWHM) at a binding energy of 84.0 eV [5]; charge referencing was done by setting the C–C peak at 284.6 eV. The pressure in the analysis chamber was maintained lower than 5 ´ 10–6 Pa. Membranes were irradiated for a maximum time
2. Experimental A commercial polysulfone ultrafiltration membrane (PSU) kindly submitted by PRIDESA (Barcelona, Spain) was studied. Some samples were chemically treated by immersion in 1 M HNO3 solution during different times: 0, 12, 24, 48 and 72 h. These membranes will hereafter named as PSU-X, where X represents the treatment time. *Corresponding author.
Table 1 Effect of the nitric acid treatment on atomic concentration percentage of the elements present on the surface of the polysulfone samples Sample
C1s (%)
O1s (%)
N1s (%)
S1s (%)
PSU-0h PSU-12h PSU-24h PSU-48h PSU-72h
78.7 74.2 74.1 70.3 71.2
16.2 19.3 18.6 21.6 22.5
4.2 5.3 6.6 7.5 5.8
0.9 1.2 0.7 0.6 0.5
Presented at EUROMEMBRANE 2006, 24–28 September 2006, Giardini Naxos, Italy. 0011-9164/06/$– See front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.desal.2006.03.332
M.V. Martínez de Yuso et al. / Desalination 200 (2006) 294–296
of 15–20 min to minimize X-ray induced sample damage [6]. PHI ACCESS ESCA-V6.0 F software package was used for acquisition and data analysis [7]. Atomic concentration percentages of the membrane surface characteristic elements were determined from the measured spectral regions by taking into account the corresponding area sensitivity factor [8].
295
to the HNO3 treatment. Relative atomic concentrations (A.C.%) of the elements present on the surface of the PSU-X samples are indicated in Table 1. The presence of nitrogen in sample PSU-0h is associated to impurities due to environmental contamination or rests of the chemical used for membrane manufacture [6,9] but its percentage increases as a result of nitric acid treatment; O percentage increases as a result of both treatment and time. Fig. 1 shows a comparison of C1s, O1s and N1s spectra for the different studied samples, and some differences can be observed when the different spectra are compared.
3. Results and discussion A chemical study of the surface of the chemically treated polysulfone samples was carried out by XPS in order to establish possible chemical modifications of the membrane surface associated
18000
25000
(b)
O1s
(a)
C1s
Intensity (a.u.)
Intensity (a.u.)
20000 15000 10000
12000
6000
5000 0 295
290
285
0 540
280
535
B.E. (eV)
530
525
B.E. (eV)
18000 (c)
Intensity (a.u.)
N1s 15000
12000
9000 410
405
400
395
B.E. (eV)
Fig. 1. C1s (a), O1s (b) and N1s (c) spectra for the different samples: PSU-0h (solid line), PSU-12h (o), PSU-24h (´ ), PSU-48h (Ñ), PSU-72h (+).
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M.V. Martínez de Yuso et al. / Desalination 200 (2006) 294–296
XPS analysis of the PSU-X surfaces after treatment with 1 M HNO3 solution at different time instances seems to indicate the oxidative degradation of the polysulfone (depending on the treatment time) but no nitration of the back bone polymer seems to occur.
[4]
References
[7]
[1] [2] [3]
A.E. Childress and M. Elimelesh, J. Membr. Sci., 119 (1996) 253. A. Kulkarni, D. Mukherjee and W.N. Gill, J. Membr. Sci., 114 (1996) 39. J. Pieracci, J.V. Crivello and G. Belfort, J. Membr. Sci., 202 (2002).
[5]
[6]
[8] [9]
J. Benavente and M.I. Vázquez, J. Colloid Interface Sci., 273 (2004) 547–555. D. Brigs and M.P. Seah, Practical Surface Analysis: Auger and X-ray Photoelectron Spectroscopy, John Wiley & Sons, Chischester, England, 1995. M.J. Ariza, P. Prádanos, R. Rico, E. RodriguezCastellón and J. Benavente, Surf. Interface Anal., 35 (2003) 360. Multitechnique ESCA Software Reference Manual for the PC-ACCESS SoftwareVersion 6.0, Physics Electronics, Minneapolis, 1995. A.P. Pijpers and R.J. Meier, Chem. Soc. Rev., 28 (1999) 233. J.T.F. Keurentjes, J.G. Harbrecht, D. Brikman, J.H. Hanemaaijer, M.A. Cohen and H. van´t Riet, J. Membr. Sci., 47 (1989) 333.
Modification of polysulfone ultrafiltration membranes for HNO3 treatment: time influence M.V. Martínez de Yuso, R. de Lara, M.I. Vázquez, J. Benavente* Grupo de Caracterización Electrocinética y de Transporte en Membranas e Interfases, Dpto. Física Aplicada I, Facultad de Ciencias, Universidad de Málaga, E-29071 Málaga, Spain email: [email protected] Received 28 October 2005; accepted 3 March 2006
1. Introduction Modification of membrane transport parameters as a result of aging, fouling and cleaning agents are extensively reported in the literature [1–3]. A previous study showed that age strongly reduced membrane permeation, but acidic nitric treatment clearly increases it, with a maximum effect after 24 h acidic immersion [4]. In this work, chemical surface modifications caused by immersion of a polysulfone membrane for ultrafiltration processes in 1 M HNO3 solution at different time instances are studied by means of X-ray photoelectron spectroscopy (XPS).
XPS spectra were obtained using a Physical Electronics PHI 5700 spectrometer with a nonmonochromatic MgKa radiation as excitation source (300 W, 15 kV, 1253.6 eV), and they were recorded at a given take-off-angle f = 45° by a concentric hemispherical analyzer operating in the constant pass energy mode at 29.35 eV. Under these conditions the Au 4f7/2 line was recorded with 1.16 eV full width at half maximum (FWHM) at a binding energy of 84.0 eV [5]; charge referencing was done by setting the C–C peak at 284.6 eV. The pressure in the analysis chamber was maintained lower than 5 ´ 10–6 Pa. Membranes were irradiated for a maximum time
2. Experimental A commercial polysulfone ultrafiltration membrane (PSU) kindly submitted by PRIDESA (Barcelona, Spain) was studied. Some samples were chemically treated by immersion in 1 M HNO3 solution during different times: 0, 12, 24, 48 and 72 h. These membranes will hereafter named as PSU-X, where X represents the treatment time. *Corresponding author.
Table 1 Effect of the nitric acid treatment on atomic concentration percentage of the elements present on the surface of the polysulfone samples Sample
C1s (%)
O1s (%)
N1s (%)
S1s (%)
PSU-0h PSU-12h PSU-24h PSU-48h PSU-72h
78.7 74.2 74.1 70.3 71.2
16.2 19.3 18.6 21.6 22.5
4.2 5.3 6.6 7.5 5.8
0.9 1.2 0.7 0.6 0.5
Presented at EUROMEMBRANE 2006, 24–28 September 2006, Giardini Naxos, Italy. 0011-9164/06/$– See front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.desal.2006.03.332
M.V. Martínez de Yuso et al. / Desalination 200 (2006) 294–296
of 15–20 min to minimize X-ray induced sample damage [6]. PHI ACCESS ESCA-V6.0 F software package was used for acquisition and data analysis [7]. Atomic concentration percentages of the membrane surface characteristic elements were determined from the measured spectral regions by taking into account the corresponding area sensitivity factor [8].
295
to the HNO3 treatment. Relative atomic concentrations (A.C.%) of the elements present on the surface of the PSU-X samples are indicated in Table 1. The presence of nitrogen in sample PSU-0h is associated to impurities due to environmental contamination or rests of the chemical used for membrane manufacture [6,9] but its percentage increases as a result of nitric acid treatment; O percentage increases as a result of both treatment and time. Fig. 1 shows a comparison of C1s, O1s and N1s spectra for the different studied samples, and some differences can be observed when the different spectra are compared.
3. Results and discussion A chemical study of the surface of the chemically treated polysulfone samples was carried out by XPS in order to establish possible chemical modifications of the membrane surface associated
18000
25000
(b)
O1s
(a)
C1s
Intensity (a.u.)
Intensity (a.u.)
20000 15000 10000
12000
6000
5000 0 295
290
285
0 540
280
535
B.E. (eV)
530
525
B.E. (eV)
18000 (c)
Intensity (a.u.)
N1s 15000
12000
9000 410
405
400
395
B.E. (eV)
Fig. 1. C1s (a), O1s (b) and N1s (c) spectra for the different samples: PSU-0h (solid line), PSU-12h (o), PSU-24h (´ ), PSU-48h (Ñ), PSU-72h (+).
296
M.V. Martínez de Yuso et al. / Desalination 200 (2006) 294–296
XPS analysis of the PSU-X surfaces after treatment with 1 M HNO3 solution at different time instances seems to indicate the oxidative degradation of the polysulfone (depending on the treatment time) but no nitration of the back bone polymer seems to occur.
[4]
References
[7]
[1] [2] [3]
A.E. Childress and M. Elimelesh, J. Membr. Sci., 119 (1996) 253. A. Kulkarni, D. Mukherjee and W.N. Gill, J. Membr. Sci., 114 (1996) 39. J. Pieracci, J.V. Crivello and G. Belfort, J. Membr. Sci., 202 (2002).
[5]
[6]
[8] [9]
J. Benavente and M.I. Vázquez, J. Colloid Interface Sci., 273 (2004) 547–555. D. Brigs and M.P. Seah, Practical Surface Analysis: Auger and X-ray Photoelectron Spectroscopy, John Wiley & Sons, Chischester, England, 1995. M.J. Ariza, P. Prádanos, R. Rico, E. RodriguezCastellón and J. Benavente, Surf. Interface Anal., 35 (2003) 360. Multitechnique ESCA Software Reference Manual for the PC-ACCESS SoftwareVersion 6.0, Physics Electronics, Minneapolis, 1995. A.P. Pijpers and R.J. Meier, Chem. Soc. Rev., 28 (1999) 233. J.T.F. Keurentjes, J.G. Harbrecht, D. Brikman, J.H. Hanemaaijer, M.A. Cohen and H. van´t Riet, J. Membr. Sci., 47 (1989) 333.