Chemical Engineering / Kimya Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/14
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Article Citation - WoS: 34Citation - Scopus: 35Development of High Flux Nanofiltration Membranes Through Single Bilayer Polyethyleneimine/Alginate Deposition(Elsevier Ltd., 2019) Tekinalp, Önder; Alsoy Altınkaya, SacideThe aim of this study is to prepare high flux, stable, antifouling nanofiltration membranes through single bilayer polyelectrolyte deposition. To this end, a tight ultrafiltration support membrane was prepared from a polysulfone/sulfonated polyethersulfone blend. Deposition of a polyethyleneimine and alginate pair on this support has reduced the molecular weight cut off from 6 kDa to below 1 kDa. The pure water permeability and polyethylene glycol 1000 rejection of the coated membrane were found to be 15.5 ± 0.3 L/m2·h·bar and 90 ± 0.6%, respectively, by setting the deposition pH for each layer to 8 and the ionic strengths to 0.5 M and 0 M. This membrane has exhibited significantly higher permeability than commercial membranes with the same molecular weight cut off, retaining 98% of the initial flux during 15 h filtration of bovine serum albumine. In addition, the membrane has been able to completely remove anionic dyes from aqueous solution by showing 99.9% retentions to Reactive red 141, Brilliant blue G and Congo red with a 2 bar transmembrane pressure. High flux and membrane stability in acidic and salty environments have been achieved when deposition conditions favor high adsorption levels for the first layer and strong ionic cross-linking between the carboxyl group on the alginate and the amine groups on the polyethyleneimineArticle Citation - WoS: 43Citation - Scopus: 42Immobilization of Superoxide Dismutase/Catalase Onto Polysulfone Membranes To Suppress Hemodialysis-Induced Oxidative Stress: a Comparison of Two Immobilization Methods(Elsevier Ltd., 2015) Yaşar Mahlıçlı, Filiz; Şen, Yasin; Mutlu, Mehmet; Alsoy Altınkaya, SacideThe objective of this study is to improve the blood compatibility of polysulfone (PSF) based hemodialysis membranes through generating antioxidative surfaces with superoxide dismutase (SOD)/catalase (CAT) enzyme couple immobilization. Enzymes were attached both covalently and ionically on the plasma treated and polyethyleneimine (PEI) deposited membranes, respectively. The loss of enzymes from PEI modified surface at the end of 4 h was found to be relatively higher during storage in phosphate buffered saline (PBS) at pH 7.4 when compared to the enzymes on the plasma treated surface. The kinetic studies indicated that SOD catalyzed the reaction in the diffusion-limited regime at all substrate concentrations and its inactivation by hydrogen peroxide was prevented in the presence of CAT. SOD/CAT coated PSF membranes were capable of reducing the levels of reactive oxygen species in blood and can significantly prolong activated partial thromboplastin time. In addition, both the adsorption of human plasma proteins and platelet activation on all modified membranes decreased significantly compared to the unmodified PSF membranes. Proposed modification methods did not affect high permeability, high mechanical strength or the non-toxic properties of the PSF membranes.Article Citation - WoS: 30Citation - Scopus: 33Preparation and Characterization of Polyacrylonitrile Membranes Modified With Polyelectrolyte Deposition for Separating Similar Sized Proteins(Elsevier Ltd., 2012) Yaşar Mahlıçlı, Filiz; Alsoy Altınkaya, Sacide; Yürekli, YılmazOne of the challenges faced by ultrafiltration membranes is to separate proteins with a small difference in their molecular weights. Recently, some researchers tried to overcome this problem by using charged membranes. This study examined the use of layer by layer deposition of polyelectrolytes on the chemically-modified polyacyronitrile membrane to increase the selectivity of the ultrafiltration. The membranes were prepared by wet-phase inversion technique and polyethylenimine (PEI) and alginate (ALG) were chosen as cationic and anionic polyelectrolytes for the modification of the surfaces. Sieving coefficient data were obtained with myoglobin and lysozyme as model proteins. The influences of solution pH, ionic strengths of the protein and polyelectrolyte solution and the number of polyelectrolyte bilayers on both selectivity and throughput were investigated. The highest selectivity and throughput were achieved with the 1-bilayer PEI-ALG coated polyacrylonitrile (PAN) membrane. Increasing the number of coating bilayers or the ionic strength of the protein solution or adding salt into the polyelectrolyte coating solution decreased both the maximum selectivity and throughput of the modified membranes.Article Citation - WoS: 46Citation - Scopus: 52Effect of Enzyme Location on Activity and Stability of Trypsin and Urease Immobilized on Porous Membranes by Using Layer-By Self-Assembly of Polyelectrolyte(Elsevier Ltd., 2010) Guedidi, Sadika; Yürekli, Yılmaz; Deratani, André; Déjardin, Philippe; Innocent, Christophe; Alsoy Altınkaya, Sacide; Roudesli, Sadok; Yemenicioğlu, AhmetThe layer-by-layer (LbL) self-assembly of polyelectrolyte is one of the simplest ways to immobilize enzyme on membrane. In this paper, the immobilization of trypsin (TRY) and urease (URE) on polyacrylonitrile based membranes using the LbL assembly technique was presented. The studied systems consisted in bilayered assemblies with the enzyme layer as the outer layer and trilayered assemblies with the enzyme layer as the inner sandwiched layer. The membrane pore size was chosen so that the smaller enzyme TRY was mainly immobilized within the membrane and confined in the porous membrane structure while URE immobilization mainly took place at the membrane surface. No dramatic difference on reactivity was evidenced between these two enzyme locations. The catalytic activity of immobilized enzymes was found to be lower than the free ones in solution but their stability was dramatically enhanced. The higher activity was observed when the enzyme is deposited as the outer layer of the LbL assembly. On the other hand, the more stable catalytic membranes were obtained when the outer layer consists of a polyelectrolyte covering the enzyme layer. © 2010 Elsevier B.V.Article Citation - WoS: 21Citation - Scopus: 23Adsorption of Anionic Polyelectrolyte and Comb Polymers Onto Lead Magnesium Niobate(Elsevier Ltd., 2008) Şakar-Deliormanlı, Aylin; Çelik, Erdal; Polat, MehmetThis paper presents the results concerning the adsorption mechanism of polyacrylic acid (PAA) and polyacrylic acid/polyethylene oxide (PAA/PEO) comb polymer onto lead magnesium niobate (PMN) powders. In the study adsorption behavior of PAA and PAA/PEO onto PMN surface were determined in aqueous solutions and the influence of pH and ionic strength was investigated. Results showed that adsorption of PAA or PAA/PEO increased with decreasing pH of the suspensions. The increase in the ionic strength or the presence of divalent cations caused an increase in the adsorption of both polyelectrolytes. It was observed that the adsorption reaches a maximum when PAA is fully complexed in solution. On the other hand, the increase in the adsorption of PAA/PEO onto PMN in the presence of monovalent or divalent salt was attributed to the decrease in the electrostatic forces rather than complex formation with the divalent metal ions in solution. Turbidity measurements showed that there is no complex formation between the divalent metal ions and PAA/PEO comb polymers due to shielding effect of the PEO teeth.