Preparation and modification of nano-porous polyimide (PI) membranes by UV photo-grafting process: Ultrafiltration and nanofiltration performance

Ahmad Rahimpour 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.1

Polyimide (PI) membranes were prepared via non-solvent induced phase separation. The prepared PI membranes were modified by ultraviolet light (UV) and graft polymerization of hydrophilic acrylic and amino monomers in the absence and presence of benzophenone (BP) onto the membrane surface to introduce more hydrophilic and lower fouling membranes. Acrylic acid (AA) and 2-hydroxyethylmethacrylate (HEMA) as acrylic monomers, 1,3-phenylenediamine (mPDA) as amino monomer and BP as photo-initiator were used. The unmodified and modified PI membranes were characterized by degree of grafting (DG) and contact angle measurements. They were also characterized by their ultrafiltration performance with pure water and non-skim milk and nanofiltration performance with 500 ppm NaCl and MgSO_4 single solutions. The DG was increased with increasing monomer concentration, especially at presence of BP. The contact angle measurements indicated that hydrophilicity of PI membrane was improved after UV photografting of hydrophilic monomers onto the membrane surface in all cases. The ultrafiltration results showed that the pure water fluxes and milk water permeation of PI membrane declined after monomer photo-grafting while the protein rejection was extremely increased. The decrease in permeability was remarkable in the presence of BP. The mean pore size of base and modified PI membranes ranged from 8.3 to 0.55 nm when calculated from the solute transport data. Moreover, the irreversible flux loss and flux recovery of PI membrane were modified by UV photo-grafting of hydrophilic monomers. All modified membranes showed considerable NaCl and MgSO_4 rejections. In addition, the membrane modified with mPDA at presence of BP showed highest NaCl and MgSO_4 rejections.

Engineering the Cellular Protein Secretory Pathway for Enhancement of Recombinant Tissue Plasminogen Activator Expression in Chinese Hamster Ovary Cells: Effects of CERT and XBP1s Genes

( Azam Rahimpour ),( Behrouz Vaziri ),( Reza Moazzami ),( Leila Nematollahi ),( Farzaneh Barkhordari ),( Leila Kokabee ),( Ahmad Adeli ),( Fereidoun Mahboudi ) 한국미생물 · 생명공학회 2013 Journal of microbiology and biotechnology Vol.23 No.8

Cell line development is the most critical and also the most time-consuming step in the production of recombinant therapeutic proteins. In this regard, a variety of vector and cell engineering strategies have been developed for generating high-producing mammalian cells; however, the cell line engineering approach seems to show various results on different recombinant protein producer cells. In order to improve the secretory capacity of a recombinant tissue plasminogen activator (t-PA)-producing Chinese hamster ovary (CHO) cell line, we developed cell line engineering approaches based on the ceramide transfer protein (CERT) and X-box binding protein 1 (XBP1) genes. For this purpose, CERT S132A, a mutant form of CERT that is resistant to phosphorylation, and XBP1s were overexpressed in a recombinant t-PA-producing CHO cell line. Overexpression of CERT S132A increased the specific productivity of t-PA-producing CHO cells up to 35%. In contrast, the heterologous expression of XBP1s did not affect the t-PA expression rate. Our results suggest that CERTS132A- based secretion engineering could be an effective strategy for enhancing recombinant t- PA production in CHO cells.

Synthesis and characterization of PVA/PES thin film composite nanofiltration membrane modified with TiO2 nanoparticles for better performance and surface properties

Sarah Pourjafar,Ahmad Rahimpour,Mohsen Jahanshahi 한국공업화학회 2012 Journal of Industrial and Engineering Chemistry Vol.18 No.4

Novel polyethersulfone (PES)/poly (vinyl alcohol) (PVA)/titanium dioxide (TiO2) composite nanofiltration membranes were prepared by dip-coating of PES membrane in PVA and TiO2 nanoparticles aqueous solution. Glutaraldehyde (GA) was used as a cross-linker for the composite polymer membrane in order to enhance the chemical, thermal as well as mechanical stabilities. TiO2nanoparticles with different concentrations (0, 0.05, 0.1, 0.5 wt.%) were coated on the surface of PVA/PES composite membrane. The morphological study was investigated by atomic force microscopy (AFM), scanning surface microscopy (SEM) and along with X-ray diffraction (XRD). In addition, the membranes performances, in terms of permeate flux, ion rejection and swelling factor were also investigated. It was found that the increase in TiO2 solution concentration can highly affect the surface morphology and filtration performance of coated membranes. The contact angle measurement and XRD studies indicated that the TiO2 nanoparticles successfully were coated on the surface of PVA/PES composite membranes. However, rougher surface was obtained for membranes by TiO2 coating. The filtration performance data showed that the 0.1 wt.% TiO2-modified membrane presents higher performance in terms of flux and NaCl salt rejection. Finally, TiO2 modified membranes demonstrated the lower degree of swelling.

Interfacially polymerized thin film nanofiltration membranes on TiO2 coated polysulfone substrate

Arash Mollahosseini,Ahmad Rahimpour 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.4

In this study, a new approach was developed to prepare the novel thin film composite nanofiltration membranes. In this new approach, nanoparticles were coated completely under the polymeric thin film layer. Thin film composite (TFC) membranes were fabricated by interfacial polymerization on polysulfone (PSf) sublayer using m-phenylenediamine (MPD) and trimesoyl chloride (TMC) respectively as amine monomer and acid chloride monomer. Scanning electron microscopy and atomic force microscopy were used to study surface morphology and roughness properties of NF membranes. Energy dispersive X-ray microanalysis (EDX) was used to analyze the elemental change before and after filtration experiment. Chemical structure and thickness of polyamide formed on TFC membranes were observed by Fourier transmission infrared attenuated total reflectance (FTIR-ATR) spectroscopy. Permeability, salt rejection and pepsin macromolecule rejection of prepared membranes were tested using dead end filtration cell. Antifouling behavior of the membranes was studied by filtering pure water before and after pepsin solution filtration. A smoother and thicker surface without any defect appeared as the concentration of nanoparticle was increased. NaCl rejection was increased from 70% for neat nanofiltration membrane to 84% for 0.5 wt% TiO2 modified nanofiltration membrane. Antifouling and permeability behavior of the prepared membranes were improved in the new approach. Antibacterial property of prepared membranes was improved as a result of photocatalytic characteristic of TiO2 nanoparticles.

Exploiting the effects of zirconium-based metal organic framework decorated carbon nanofibers to improve CO2/CH4 separation performance of thin film nanocomposite membranes

Mohammad Mozafari,Ahmad Rahimpour,Reza Abedini 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.85 No.-

The challenges of interfacial defects andfiller uniform dispersion are still preventing the design of mixedmatrix membranes (MMMs) for the purpose of high gas selectivity. In this study, in-situ growth of UiO-66-NH2 on the external surface of carbon nanofibers (CNFs) resulted in the synthesis of a novel CNF/metalorganic framework (MOF) composite which embedded into the pebax selective layer of thin-filmnanocomposite (TFN) membrane. The uniform structure and defect-free interface was observed by FESEManalysis that reveals superior compatibility between polymer chains and CNF/UiO composite. Gassorption analysis was investigated for pristine thinfilm composite (TFC) and TFN membranes and thenthe obtained experimental data were analyzed by Henry–Langmuir and Henry–Freundlich model. Theresults illustrated that gas permeation for the membranes followed the Henry–Freundlich model. Accordingly, synthesized TFN membranes demonstrated a higher CO2 permeability as well as properCO2/CH4 selectivity compared to pristine TFC membrane. For instance, the pure and mixed gaspermeation results of TFN membrane including 3 wt% of CNF/UiO composite represented a high CO2permeability of around 328 (pure gas permeability) and 230 (mixed gas permeability) Barrer andCO2/CH4 selectivity of around 27 (ideal selectivity) and 21 (real selectivity) at feed pressure of 6 bar. Consequently, the TFN membranes exhibit exceptional separation performance in terms of overcomingthe Robeson upper bound. The approach of decoration of MOFs on the surface of CNFs can be effectivetechnique to enhance TFN membranes performance.

Novel carbon nano-fibers (CNF)/polysulfone (PSf) mixed matrix membranes for gas separation

Mohsen Jahanshahi,Ahmad Rahimpour,Mohsen Jahanshahi,Ali Asghar Ghoreyshi 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.22 No.-

Mixedmatrixmembranes (MMM) included of carbon nanofibers (CNFs) fabricated and characterized forgas separation performance. For preparation of MMM, carbon nanofibers content was varied from 0.01 to1 wt% in polysulfone (PSf) casting solution. The fabricated CNFs/PSF MMMs characterized by scanningelectron microscopy (SEM), atomic force microscopy (AFM), ATR–FTIR spectra and pure gas permeationand sorption test. The gas transport properties ofMMMmeasured using single gas permeation set up (N2,O2, CO2, and CH4) at ambient temperature and different feed pressures. Additionally, sorption isothermsformixed matrixmembranesmade for CH4 and CO2. The sorption data were analyzed by the dual-modesorption model. Themorphological studies show that the incorporation of CNFs appreciably changed thesurface properties of membranes. The permeation test showed that the mixed matrix membraneexhibited high permeability. With increasing CNF concentration, CNFs/PSF membrane permeabilityraised from 2.134 to 12.04 Barrer for CO2. The results found that this unique membrane had increasedpermeability and enhanced selectivity. Also it has a great potential to be used practically in gasseparation technology.

Surface modification of novel polyether sulfone amide (PESA) ultrafiltration membranes by grafting hydrophilic monomers

Alisa Mehrparvar,Ahmad Rahimpour 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.28 No.-

In this study, new polymeric material namely polyether sulfone amide (PESA) containing hydrophilegroup was synthesized via polycondensation reaction of diamine with dicarboxylic acid. SynthesizedPESA was used as main polymer to fabrication of novel PESA UF membranes to improve the membraneproperties especially in view of fouling reduction. The PESA membrane was modified by grafting twohydrophilic monomers i.e. 3,5-diaminobenzoic acid (DBA) and gallic acid (GA) via interfacialpolymerization. The prepared membranes were characterized by contact angle measurement,equilibrium water content (EWC), scanning electron microscopy (SEM), atomic force microscopy(AFM), FTIR-ATR analyses. Membrane performance was evaluated by measuring the pure water flux andhumic acid (HA) solute separation with dead-end filtration system. As a result, the contact anglemeasurement showed that the PESA membrane had high hydrophilic surface. Also, super hydrophilicsurfaces were introduced by grafting DBA and GA on the surface of PESA membrane. The SEM imagesproved the formation of large finger-likes in the sublayer for PESA membrane. Filtration tests showedthat pure water flux and HA solution flux of the PESA membranes were higher in comparison to the PESmembrane. Although fluxes were obviously decreased after grafting monomers onto the PESAmembrane surface, higher HA separation efficiency was achieved. Meanwhile fouling tendency wasdecreased. All these results indicated that the new PESA modified membranes showed superiorperformance compared to the PES membrane. Furthermore, GA was found to be the most effectivehydrophilic monomer to improve the membrane hydrophilicity and fouling resistibility.

A preferential CO2 separation using binary phases membrane consisting of Pebax®1657 and [Omim][PF6] ionic liquid

Kamran Shahrezaei,Reza Abedini,Mostafa Lashkarbolooki,Ahmad Rahimpour 한국화학공학회 2019 Korean Journal of Chemical Engineering Vol.36 No.12

Pebax ® 1657 and [Omim][PF6] ionic liquid (IL) were used to fabricate a blend membrane and applied for CO2 separation. The changes upon adding ionic liquid into the polymer matrix as well as the membrane characteristics were studied through SEM, FTIR, DSC and TGA analysis. The obtained gas permeation results indicated that the CO2 permeability in all membranes was much higher than the other studied gases. CO2 permeability of Pebax containing 8wt% IL increased from 82.3 Barrer up to 125.6 Barrer at a pressure of 2bar, which showed a 53% increment compared to the neat Pebax membrane. Furthermore, as the [Omim][PF6] loading within the polymer matrix was increased, the CO2/CH4 and CO2/N2 selectivities improved. In addition, the permeability and selectivity of gases was enhanced as the feed pressure increased. Upon increasing feed pressure to 10bar, the CO2 permeability of Pebax containing 8wt% IL reached 185.3 Barrer, which was approximately 48% higher than the permeability at a pressure of 2bar. Moreover, the selectivity of CO2/CH4 and CO2/N2 for the Pebax/8wt% IL membrane at pressure of 2bar was 15.3 and 46.5, respectively, which improved to 19.7 and 59.8 as the pressure increased to 10bar.

Performance evaluation and mass transfer study of CO2 absorption in flat sheet membrane contactor using novel porous polysulfone membrane

Nima Nabian,Ali Asghar Ghoreyshi,Ahmad Rahimpour,Mohsen Shakeri 한국화학공학회 2015 Korean Journal of Chemical Engineering Vol.32 No.11

The performance of gas-liquid membrane contactor for CO2 capture was investigated using a novel polysulfone (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 measurement 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 CO2 absorption flux, displayed that addition of PVP to the dope solution of PSF membrane decreased membrane mass transfer resistance, and significantly improved CO2 absorption flux up to 2.7 and 1.8 times of absorption fluxes of PSF membrane without PVP and commercial PVDF, respectively.

Feasibility of membrane processes for the recovery and purification of bio-based volatile fatty acids: A comprehensive review

Sadegh Aghapour Aktij,Alireza Zirehpour,Arash Mollahosseini,Mohammad J. Taherzadeh,Alberto Tiraferri,Ahmad Rahimpour 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.81 No.-

Volatile fatty acids (VFAs) can be produced from fermentation/anaerobic digestion of wastes and are avaluable substrate for numerous applications, such as those related to the food, tanning, petrochemicals,pharmaceuticals, cosmetics, and chemicals industry. They are also inexpensive raw materials fordeveloping alternative sources of energy. However, the separation and purification of VFAs producedfrom fermented wastewaters are not straightforward goals, due to the low concentration of thesecompounds in the fermentation broths and owing to the complexity of these mixtures. Cost-effective andsustainable technologies must be developed to recover VFAs efficiently and allow their beneficial use. Inthis paper, a comprehensive review of VFAs recovery/purification methods is provided, with focus onmembrane-based processes. First, the VFAs production methods, application, and conventional processes(distillation, precipitation, adsorption, and extraction) for their recovery are briefly reviewed. Then, theability of various membrane-based techniques to separate and purify VFAs are evaluated and discussed indetail. This discussion includes the processes of microfiltration/ultrafiltration, nanofiltration, reverseosmosis, forward osmosis, membrane distillation, electrodialysis, membrane contractor, and pervapo-ration. Extensive background and examples of applications are also provided to show the effectiveness ofmembrane processes. Finally, challenges and future research directions are highlighted.