Effect of non-solvent additives on the structure and performance of PVDF hollow fiber membrane contactor for CO 2 stripping R. Naim a,b,c , A.F. Ismail a,b,n , A. Mansourizadeh d a Advanced Membrane Technology Research Centre (AMTEC), Universiti Teknologi Malaysia, 81310 Skudai, Johor, Malaysia b Department of Gas Engineering, Faculty of Petroleum and Renewable Energy Engineering, Universiti Teknologi Malaysia, 81310 Skudai, Johor, Malaysia c Faculty of Chemical Engineering and Natural Resources, Universiti Malaysia Pahang, Lebuhraya Tun Razak, 26300 Kuantan, Pahang, Malaysia d Department of Chemical Engineering, Gachsaran Branch, Islamic Azad University, Gachsaran, Iran article info Article history: Received 21 April 2012 Received in revised form 29 August 2012 Accepted 30 August 2012 Available online 8 September 2012 Keywords: PVDF hollow fiber membrane Non-solvent additive CO 2 stripping Membrane contactor abstract Microporous polyvinylidene fluoride (PVDF) hollow fiber membranes with various non-solvent additives, i.e. lithium chloride, glycerol, polyethylene glycol (PEG-400), methanol and phosphoric acid, were fabricated for CO 2 stripping via membrane contactors. The membranes were characterized in terms of liquid entry pressure, contact angle, gas permeation and morphology analysis. CO 2 stripping performance was investigated by using an in-house made stainless steel module with CO 2 -preloaded aqueous diethanolamine as the liquid absorbent. Hydrophobicity and gas permeability of the membranes reduced with the addition of a non-solvent additive in the polymer dope but increase in liquid entry pressure was observed as more sponge-like structures developed in the inner layer of the fibers. It was found that PVDF/PEG-400 membrane produced the highest stripping flux of 4.03  10 2 mol m 2 s 1 which can be correlated to its high gas permeation and high effective surface porosity. The result of long-term stripping operation indicated an approximatly 80% stripping flux reduction which can be related to the interaction of polymer membrane and amine solution at high temperature. & 2012 Elsevier B.V. All rights reserved. 1. Introduction Nowadays, membrane contactors have become a center of attention due to their beneficial features such as high surface area per unit volume, flooding-free or non-entrainment, independent of liquid and gas flow rates. Most importantly, its system modularity has efficiently reduced weight to fulfill the space constraint requirement. These applications not only cover CO 2 absorption and stripping in the field of oil and gas but further extend to the conventional process such as extraction [1], dega- sification and deoxygenation in boiler feed water [2,3], waste- water treatment [4] and air conditioning systems [5]. The successful applications of membrane contactor system in such diversified areas are probably due to the proper selection of membrane materials that are chemically stable with organic solvent and exhibit great hydrophobicity so that the resultant membranes are non-wetted in any condition applied. Polyvinylidene fluoride (PDVF) is a prominent polymer used in membrane preparation for wastewater treatment application [6], ultrafiltration [7], membrane distillation [8] and gas separation. Due to its favorable properties such as hydrophobicity and compatibility in organic solvent as well as resistance to heat and chemical reaction; a straightforward process in membrane preparation makes it a more preferable material over other commercial polymers such as polytetrafluorethylene (PTFE), poly- propylene (PP) and polyethylene (PE). The application of PVDF membrane in membrane contactor for CO 2 absorption or strip- ping has been reported by several researchers [9,10]. Mansour- izadeh et al. [11] applied PVDF hollow fiber membrane for CO 2 absorption by distilled water and it was proven that the mem- brane exhibited high performance of CO 2 absorption flux at ambient temperature. Similar membrane was tested for CO 2 stripping from water and moderate stripping flux was achieved due to the potential of water evaporation at elevated temperature [12]. However, it has been hypothesized that absorption/stripping via alkanolamine group would produce higher absorption/strip- ping flux due to chemical bonding of CO 2 to the amine solution [13]. Although there is no clear evidence to indicate that the addition of non-solvent additives would promote high stripping flux, increasing CO 2 absorption with addition of non-solvent additives [14] would be an indication that perhaps a similar trend might occur for the stripping process which can be related to the formation of combined finger-like and sponge-like structures. Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/memsci Journal of Membrane Science 0376-7388/$ - see front matter & 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.memsci.2012.08.052 n Corresponding author at: Advanced Membrane Technology Research Centre (AMTEC), Universiti Teknologi Malaysia, 81310 Skudai, Johor, Malaysia. Tel.: þ60 7 5535925; fax: þ60 7 5581463. E-mail addresses: afauzi@utm.my, fauzi.ismail@gmail.com (A.F. Ismail). Journal of Membrane Science 423–424 (2012) 503–513