The effect of bore fluid type on the structure and performance of polyetherimide hollow fiber membrane in gas–liquid contacting processes Gh. Bakeri a,b , A.F. Ismail a,⇑ , M. Rahimnejad b , T. Matsuura c , D. Rana c a Advanced Membrane Technology Research Centre (AMTEC), Universiti Teknologi Malaysia, 81310 Skudai, Johor, Malaysia b Faculty of Chemical Engineering, Babol Noshirvani University of Technology, Babol, Iran c Department of Chemical and Biological Engineering, University of Ottawa, Ottawa, ON, Canada K1N 6N5 article info Article history: Received 3 May 2012 Received in revised form 20 July 2012 Accepted 31 July 2012 Available online 9 August 2012 Keywords: Polyetherimide hollow fiber membrane Membrane contactor Bore fluid Absorption flux Phase inversion promoter abstract The effect of bore fluid type on the structure and performance of polyetherimide hollow fiber membranes in contactor application was investigated. Water was used as phase inversion promoter in spinning dope and water and pure NMP were used as bore fluid. SEM micrographs show that the major parts of both membranes consist of spongelike structure which is related to the high viscosity of spinning dope that reduces the diffusion of coagulant (water) into membrane sublayer and decreases the rate of phase inver- sion. In the case of water as bore fluid (membrane #M1) there is skin layer on the inner surface of mem- brane and some drop-shaped voids in the structure of membrane but in the case of pure NMP as bore fluid (membrane #M2), the inner surface of membrane is skinless with big pores and there are fingerlike macrovoids, originating from the inner surface and extending to the vicinity of outer surface which is related to the penetration of bore fluid and dissolving the polymer. Furthermore, membrane #M2 has higher mean pore size and effective surface porosity. The absorption flux of both fabricated membranes was investigated in the case of liquid in lumen side (case #1) and liquid in shell side (case #2) where in case #1, membrane #M1 has higher absorption flux but in case #2, membrane #M2 has higher absorption flux. The different trend in absorption flux confirms that the surface of membrane in contact with the gas phase in a membrane contactor should be skinless with big pores to facilitates the diffusion of solute gas through membrane but the pore size on the surface of membrane in contact with the liquid phase should be adjusted to obtain high absorption flux and low wettability. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction Separation processes are the key components in the chemical and petrochemical plants and their contribution on the total oper- ating costs of the plant is high. Therefore, development of new and efficient separation processes is essential to make the process more profitable. Membrane contactor is a new and versatile technology that can be used as an alternative to traditional separation equip- ment such as absorption towers and provides a variety of advanta- ges such as modularity, much higher flux, independency of liquid and gas flow rates. In membrane contactor, the membrane does not have any role to control the selectivity of separation process but the flux depends on the membrane structure since the properties of the membrane such as pore size, membrane porosity and tortuosity determine the membrane mass transfer resistance. Therefore, the structure and characteristics of membrane should be adjusted during membrane fabrication process to achieve higher performance. In hollow fiber membrane spinning, there are various parame- ters that affect the structure and properties of the membrane such as temperature and composition of spinning dope [1,2], composi- tion, temperature and flow rate of internal coagulant [3–7], com- position and temperature of external coagulant [8], humidity and length of the air gap [3,4]. It was reported that addition of solvent or weak nonsolvent to bore fluid can reduce the phase inversion rate. It can even remove the inner skin layer of membrane [9–11] completely. Chung et al. [4,12] reported that the chemistry of bore fluid is one of the key parameters to fabricate polyethersulfone hollow fi- ber membrane with ultrathin skin layer for the separation of air and other gaseous mixtures. As the water content in bore fluid in- creases, the selectivity of the fabricated membranes increases but the permeance decreases. Zhang et al. [13] investigated the effect of phase inversion promoters and bore fluid composition on the structure of polyvinyl butyral ultrafiltration hollow fiber 1383-5866/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.seppur.2012.07.024 ⇑ Corresponding author. Tel.: +60 7 5535592; fax: +60 7 5581463. E-mail addresses: afauzi@utm.my, fauzi.ismail@gmail.com (A.F. Ismail). Separation and Purification Technology 98 (2012) 262–269 Contents lists available at SciVerse ScienceDirect Separation and Purification Technology journal homepage: www.elsevier.com/locate/seppur