Desalination 199 (2006) 474–476

Presented at EUROMEMBRANE 2006, 24–28 September 2006, Giardini Naxos, Italy.

High-productive, nanostructured polyaniline membranesfor gas separation

Yogesh Guptaa*, Richard Wakemana, Klaus Hellgardtb aDepartment of Chemical Engineering, Loughborough University, Loughborough (Leics.), LE11 3TU, UK

email: y.gupta@lboro.ac.ukbDepartment of Chemical Engineering and Chemical Technology, Imperial College of Science,

Technology and Medicine, London, UKTel. +44 1509-222533; Fax +44 1509-223923

Received 21 October 2005; accepted 2 March 2006

1. Introduction

Polyaniline membranes have been studiedfor gas separation applications by a number ofresearchers [1–5]. The application potential forgas-selective polyaniline membranes has beenlimited, since there are no reports where a suffi-ciently thin skin (<1 µm) has been generated toachieve commercially significant gas transportrates. Thinness is desirable as the gas flux isinversely proportional to the thickness of amembrane.

2. Results and discussion

In this work, we have developed a novelmethod to make reproducible defect free self-supported polyaniline films with thicknessesbetween 2 and 6 µm, and ultra-thin polyanilinenanomembranes with a selective layer thicknessas low as 300 nm supported on a porous polyvi-nylidene difluoride (PVDF) structure. Thesemembranes were tested with various gases toevaluate permeabilities, flux and ideal separation

factors. In particular, the effect of film/mem-brane thickness on gas transport rate and separa-tion efficiency is investigated.

The gas transport rate measured for variousgases through different thicknesses of polyanilinemembranes are plotted in Fig. 1. The gas flux,observed for ultra-thin polyaniline membranessupported on PVDF was significantly higher.

The gas transport rate increased almost lin-early with decreasing polyaniline film thicknessfor the thicker membranes. In the followingTable 1, the ideal separation factors obtainedfor self-supported polyaniline membranes and

*Corresponding author.Fig. 1. Flux and ideal separation factors various gasesthrough polyaniline films.

0.01

0.1

1

10

100

1000

10000

100000

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5Membrane thickness (µm)

Flux

(106 m

3 /m2 h

bar

)

N2O2CO2H2

doi:10.1016/j.desal.2006.03.1990011-9164/06/$– See front matter © 2006 Published by Elsevier B.V.

Y. Gupta et al. / Desalination 199 (2006) 474–476 475

ultra-thin polyaniline membranes supported onPVDF supported structure achieved for variousgas pairs during this work were compared to thevalues obtained by other researchers. The high-est selectivities aA/ B (ideal) were obtained for thegas pairs H2/N2 (348.3), H2/O2 (69.526), H2/CO2

(8.623), CO2/O2 (8.060) and CO2/N2 (40.392)in the case of self-supported undoped polya-niline films, which are considerably higher thanthose obtained by other researchers. The resultsobtained during this work were reproducible forboth self-supported and ultrathin polyanilinefilms.

3. Conclusion

A novel method to make reproducibledefect free self-supported polyaniline filmswith thicknesses between 2 and 6 µm, andpolyaniline nanomembranes with a selectivelayer thickness as thin as 300 nm supported ona porous poly-vinylidene difluoride (PVDF)structure is developed. For dense polyaniline

membranes, ideal separation factors for all gaspairs tested were independent of the membranethickness. The selectivities, aA/ B (ideal), for thegas pairs H2/N2 (348.4), H2/O2 (69.5), H2/CO2

(8.6), CO2/O2 (8.1), CO2/N2 (40.4) and O2/N2

(5.0), achieved for self-supported undopedpolyaniline films are considerably higher thanthose obtained by other researchers. Idealseparation factors for polyaniline nanomem-branes were similar to those obtained for self-supported polyaniline films. Gas transport ratesfor various gases, observed for the dense poly-aniline nanofilms supported on polyvinylidenedifluoride were of the order of 105 times higherthan those reported for self-supported polya-niline membranes.

References

[1] M.R. Anderson, B.R. Mattes, H. Reiss andR.B. Kaner, Conjugated polymeric films forgas separations, Science, 252 (1991) 1412–1415.

Table 1A comparison of published selectivity data for polyaniline membranes with the results in this work.

*Self-supported membrane. **Supported membranes.

Researcher PH2/PCO2

PH2/PO2

PH2/PN2

PCO2/PO2

PCO2/PN2

PO2/PN2

Anderson et al. (1991)* 7.32 21.84 206.71 2.98 28.25 9.46 Anderson et al. (1994)* 5.02 24.60 164.00 4.90 32.66 6.66 Rebattet et al. (1995)* 7.78 30.63 195.10 3.93 25.05 6.36 Wang et al. (1999)* 6.08 29.00 265.45 4.76 38.63 9.15 Illing et al. (2001)* 5.07 16.78 164.11 3.30 32.33 9.78 Wang et al. (2004)**

(film thickness: 0.178 mm)2.29 9.85 75.17 4.28 32.72 7.60

This work Self-supported PAni films*

(film thickness: 4.007 mm)8.62 69.52 348.42 8.06 40.39 5.01

PAni/PVDF films**(separation layer thickness: 0.6 mm)

5.28 16.51 95.22 3.12 18.01 5.76

476 Y. Gupta et al. / Desalination 199 (2006) 474–476

[2] J.A. Conklin, T.M. Su, S.-C. Haung andR.B. Kaner, Gas and liquid separation applica-tion of polyaniline, in: Handbook of Conduct-ing Polymers, 2nd edition, Marcel Dekker, NY,1998, 945 pp.

[3] M.R. Anderson, An investigation of conductingpolymer materials as gas separation membranes,Dissertation, University of California, LA, 1992.

[4] S. Kuwabata and R. Charles, Investigation of thegas transport properties of polyaniline, J. Membr.Sci., 91 (1994) 1–12.

[5] M.-J. Chang, Y.-H. Liao, A.S. Myerson andT.K. Kwei, Gas transport properties of poly-aniline membranes, J. Appl. Polym. Sci., 62(1996) 1427–1436.