2204 Korean J. Chem. Eng., 32(11), 2204-2211 (2015) DOI: 10.1007/s11814-015-0027-9 INVITED REVIEW PAPER pISSN: 0256-1115 eISSN: 1975-7220 INVITED REVIEW PAPER † To whom correspondence should be addressed. E-mail: aa_ghoreyshi@nit.ac.ir Copyright by The Korean Institute of Chemical Engineers. Performance evaluation and mass transfer study of CO 2 absorption in flat sheet membrane contactor using novel porous polysulfone membrane Nima Nabian * , Ali Asghar Ghoreyshi * ,† , Ahmad Rahimpour * , and Mohsen Shakeri ** *Chemical Engineering Department, Babol University of Technology, Babol, Iran **Mechanical Engineering Department, Babol University of Technology, Babol, Iran (Received 5 August 2014 • accepted 29 January 2015) Abstract-The performance of gas-liquid membrane contactor for CO 2 capture was investigated using a novel poly- sulfone (PSF) flat membrane prepared via non-solvent phase inversion method. Polyvinyl pyrrolidone (PVP) was used as an additive in the dope solution of PSF membranes. Morphological studies by scanning electron microscopy (SEM) analysis revealed that PSF membrane with PVP has a finger-like structure, but the PSF membrane without PVP has a sponge-like structure. Also, characterization results through atomic force microscopy (AFM) and contact angle meas- urement demonstrated that the porosity, surface roughness and hydrophobicity of the PSF membrane increased with addition of PVP to the dope solution. Mass transfer resistance analysis, based on CO 2 absorption flux, displayed that addition of PVP to the dope solution of PSF membrane decreased membrane mass transfer resistance, and signifi- cantly improved CO 2 absorption flux up to 2.7 and 1.8 times of absorption fluxes of PSF membrane without PVP and commercial PVDF, respectively. Keywords: CO 2 Absorption, Polysulfone, PVP Additive, Membrane Contactor, Mass Transfer INTRODUCTION The largest source of greenhouse gas emissions from human activ- ities is usually from burning fossil fuels such as coal, fuel oil and natural gas for electricity production in thermal power plants as well as heat generation in industrial, commercial and residential sectors. Petroleum processing and use of petroleum based fossil fuels such as gasoline and diesel for transportation systems are the other fundamental sources of greenhouse gas generation [1-3]. Some consequences of global warming could be environmen- tal hazards such as more droughts and floods, less ice and snow, more extreme weather incidents and rising sea levels. Water vapor, carbon dioxide, methane, nitrous oxide, ozone and CFCs are known as greenhouse gases. Among them, CO 2 is regarded as the most serious due to its high concentration in greenhouse gases and its remarkable function in enhanced greenhouse effect [4,5]. There- fore, it is essential to develop efficient separation processes to remove CO 2 from industrial off gas mixtures. There are different kinds of CO 2 removal methods, including physical or chemical absorption, molecular sieve based adsorption, cryogenic distillation systems and membrane applications [6-8]. The conventional processes extensively used in this field are CO 2 capturing by absorption into aqueous solutions using gas/liquid contacting operations such as packed towers, bubble columns, ven- turi scrubbers and tray columns [9-11]. However, the most com- mercial one is the packed column using alkanolamines as absorbent solutions. These contacting devices suffer some drawbacks, such as large size, low specific gas-liquid interfacial area, high capital and operating cost, and also some operational problems such as flooding, channeling, entrainment, and foaming [12]. Application of membrane-based gas separation is another tech- nique for the recovery of CO 2 . Despite the development achieved by decreasing the thickness and increasing the selectivity of mem- branes used for this purpose, their low permeability and low mass transfer rate have limited their commercial utilization [13-15]. Thus, a novel technology known as membrane contactor has been im- proved, which takes advantage of both membranes and gas-liquid absorption processes and overcomes their aforementioned prob- lems. In this way, the role of the membrane has been just a station- ary interface between gas and liquid phases and does not have any function in offering the selectivity between the species of gas streams [16]. Hence, the membrane contactor furnishes a modular system with high interfacial area per unit volume, easy scale-up with inde- pendent control of gas and liquid streams and high selectivity with high mass transfer flux provided by liquid absorbent [17,18]. On the other hand, in addition to the gas phase and liquid phase mass transfer resistances, the membrane contactor module has the draw- back of extra membrane mass transfer resistance, which reduces its performance. However, use of hydrophobic membranes with optimized pore size, which ensures completely gas-filled pores, can assist to minimize the membrane resistance due to the higher dif- fusivity of gas phase compared to liquid phase [19-21]. CO 2 removal using this technology has been extensively investi- gated by different membrane configurations, but most of them were devoted to hollow fiber membrane contactors [22-24] with few excep- tions of flat sheet ones [25-27]. Khaisri et al. [28] compared the