Effect of SMM concentration on morphology and performance of surface modified PVDF hollow fiber membrane contactor for CO 2 absorption M. Rahbari-Sisakht a,b,c , A.F. Ismail a,b,⇑ , D. Rana d , T. Matsuura d , D. Emadzadeh a,c a Advanced Membrane Technology Research Center (AMTEC), Universiti Teknologi Malaysia, 81310 Skudai, Johor, Malaysia b Gas Engineering Department, Faculty of Petroleum and Renewable Energy Engineering, Universiti Teknologi Malaysia, 81310 Skudai, Johor, Malaysia c Department of Chemical Engineering, Gachsaran Branch, Islamic Azad University, Gachsaran, Iran d Department of Chemical and Biological Engineering, University of Ottawa, 161 Louis Pasteur St., Ontario, Canada K1N 6N5 article info Article history: Received 21 January 2013 Received in revised form 3 May 2013 Accepted 3 May 2013 Available online 24 May 2013 Keywords: PVDF hollow fiber membrane Surface modifying macromolecule (SMM) Membrane contactor CO 2 absorption abstract Surface modified polyvinylidene fluoride (PVDF) hollow fiber membranes were fabricated via a dry–wet phased inversion process. Surface modifying macromolecules (SMMs) (0, 2, 4 and 6 wt.%) were used as additives in the spinning dope. During phase inversion SMM migrates to the membrane surface, resulting in different surface morphology and surface chemistry. The surface modified PVDF membranes showed the larger pore size, higher gas permeance, effective surface porosity, contact angle and overall porosity but lower critical water entry pressure compared to the PVDF hollow fiber membrane without SMM. The performance of the surface modified membrane in contactor application for physical CO 2 absorption was investigated by the fabricated gas–liquid membrane contactor module, where distilled water was used to dissolve CO 2 . It was found that the liquid phase resistance was dominant in the absorption experiment. The results show that the surface modified PVDF membrane has a higher performance compared to con- trol PVDF membrane. By increasing SMM concentration in the spinning dope, the CO 2 absorption flux increased significantly. With the membrane prepared from 6 wt.% of SMM in the spinning dope, a max- imum CO 2 absorption flux of 5.4  10 3 mol/m 2 s was achieved at 300 ml min 1 of absorbent flow rate, which was almost 650% more than the fabricated membrane without SMM. Ó 2013 Elsevier B.V. All rights reserved. 1. Introduction Recently, carbon dioxide (CO 2 ) removal and recovery has at- tracted considerable attention from researchers. CO 2 is one of the most important greenhouse gases which have significant effects on the climate change. Recently, several techniques have been developed for CO 2 capture. One of the most favored methods is CO 2 absorption/desorption using the hollow fiber membrane cont- actor system [1–8]. In this system, the porous membrane acts as a fixed interface between the gas and liquid phases without dispers- ing one phase into another. The membrane wetting is one of the most important factors in gas–liquid contacting process, because membrane wetting increases membrane mass transfer resistance and decreases CO 2 flux. Therefore, in order to prevent membrane wetting, the pores of the membrane in membrane contactor should be gas filled. Membrane pore wetting can be largely avoided by using mem- branes with a high hydrophobic surface. In order to enhance sur- face hydrophobicity, surface modifying macromolecules (SMMs) which are polymeric materials with an amphipathic structure can be used as an additive to the spinning dope. The main chain of SMMs comprise of a polyurea or polyurethane polymer (hydro- philic part), which is end-capped with two low polarity fluorine- based polymer (oligomer) chains (hydrophobic part). After spin- ning the polymer solution SMMs depart to the membrane surface due to their lower surface energy. Migration of SMMs to the mem- brane surface form nano-scale accumulates and changes the sur- face properties of the membrane [9]. It should, however, be noted that when and how the surface migration takes place still re- mains a questionable. The investigations on SMM application for the surface modifica- tion of hollow fiber membranes for CO 2 absorption are rare [3,10]. In our previous work [3], a novel surface modified PVDF hollow fi- ber membrane using SMM as an additive was fabricated and char- acterized. The fabricated PVDF membrane possessed larger pore sizes, higher effective surface porosity, larger contact angle and overall porosity compared to the plain PVDF membrane. The re- sults of CO 2 absorption experiments using distilled water as an absorbent showed that the surface modified PVDF membrane had better performance compared to the plain PVDF membranes. In a long-term stability study, CO 2 flux was decreased by only 1383-5866/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.seppur.2013.05.008 ⇑ Corresponding author at: Advanced Membrane Technology Research Center (AMTEC), Universiti Teknologi Malaysia, 81310 Skudai, Johor, Malaysia. 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 116 (2013) 67–72 Contents lists available at SciVerse ScienceDirect Separation and Purification Technology journal homepage: www.elsevier.com/locate/seppur