Chemical Engineering / Kimya Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/14
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Article Citation - WoS: 4Citation - Scopus: 5Antifouling Polydopamine-Modified Poly (ether Sulfone) Membrane Immobilized With Alumina-Calcium Oxide Catalyst for Continuous Biodiesel Production(Elsevier, 2023) Güngörmüş, Elif; Şeker, Erol; Alsoy Altınkaya, SacideBiodiesel is an alternative biofuel that can be blended with conventional petroleum-derived diesel fuel to partly reduce the dependence on the imported oil. Catalytic membrane reactors are promising candidates for sustainable biodiesel production. Herein, we report a novel catalytically active polydopamine-modified poly (ether sulfone) (PES) membrane immobilized with an alumina-calcium oxide catalyst. The reaction temperature, butanol to canola oil ratio, and transmembrane pressure applied through the membrane were optimized with response surface methodology and Box-Behnken design. In contrast to all previous catalytic membrane studies for biodiesel production, we used butanol as a co-reactant to improve the winter problems of biodiesel made with methanol. FTIR and SEM-EDX analysis confirmed the successful immobilization of the catalyst. At the end of 30 days of storage in the reactant mixture, 95% of the catalyst loaded to the membrane was still on the surface, and biodiesel yield values and butanol flux of the membrane did not change. We compared the batch and flowthrough operation modes by measuring the catalytic activity of membranes under static and dynamic conditions within 24 h (8-cycle). The biodiesel yield under dynamic condition decreased in the first three cycles from 54.54 +/- 0.65% to 47.31 +/- 0.70% and then stayed constant, whereas a continuous decrease from 25.42 +/- 0.57% to 17.19 +/- 0.58% was observed under static condition. In each cycle, the equilibrium limitation for the yield was overcome only when the membrane was operated under pressure. The main reason for the decrease in catalytic activities was the fouling on the catalyst surface which was quickly removed by backwashing with butanol. It is concluded that catalytic membranes with antifouling properties and alcohol stability can make biodiesel production more cost-effective and environmentally friendly.Research Project Kontrollü salım özelliklerine sahip antimikrobiyel, nanokompozit gıda ambalaj filmlerinin geliştirilmesi(TÜBİTAK - Türkiye Bilimsel ve Teknolojik Araştırma Kurumu, 2013) Alsoy Altınkaya, Sacide; Pekşen Özer, Bahar Başak; Oymacı, Pelin; Uz, Metin; Büyüköz, MeldaAntimikrobiyal gıda ambalaj malzemelerinde aktif maddenin kontrollü salımı kritiktir. Bu çalışmada kontrollü salım antimikrobiyal ajanı nanotanecik içine yükleyerek sağlanmıştır. Doğal bir antimikrobiyal ajan olan lisozim serbest halde ya da poliakrilik asit (PAA) ile tanecik oluşturarak peynir altı suyu izolatı (WPI) filmlerine ilave edilmiştir. Serbest lisozim içeren filmlerden salımın çok hızlı olduğu, 45 dakika gibi kısa bir sürede lisozimin tamamının ortama geçtiği, PAA içine yüklenmesi durumunda ise salım hızının oldukça yavaşladığı gözlenmiştir. PAA’nın molekül ağırlığı ile PAA/LIS oranının lisozimin salım hızı üzerinde oldukça etkili olduğu belirlenmiştir. Her iki parametrenin artması ile daha büyük boyutta tanecikler elde edilmiş ve bu tanecikleri içeren filmlerden lisozimin salım hızı düşmüştür. Film hazırlama esnasında lisozimin aktivitesinde kayıp yaşanmış, ancak salınan aktivite zamanla değişim göstermemiştir. Lisozim hem serbest, hem de PAA/LIS kompleksi içinde filme ilave edildiğinde ortama kontrollü bir şekilde salınarak antimikrobiyal etkisini daha uzun süre koruyabilmiştir. Çalışmada PAA/LIS komplekslerinin yanısıra kitosan nanotanecikler de hazırlanmış, bu taneciklerin WPI filmlerinin mekanik ve bariyer özellikleri üzerine olan etkileri incelenmiştir. %2 oranına kadar kitosan nanotanecik içeren filmlerin mekanik ve bariyer özelliklerinde önemli bir değişiklik olmazken, % 4 nanotanecik ilavesiyle çekme mukavemetinde ani bir artış, % uzama değerinde ve su buharı geçirgenliğinde de azalma gözlenmiştir. Ayrıca, kitosan nanotanecikler WPI filmlere antibakteriyel özellik de kazandırmıştır. Filme ilave edilen nanotanecik miktarının % 6’ya artırılması sonucunda homojen dağılımın sağlanamamasından dolayı mekanik ve bariyer özelliklerindeki iyileşme azalmaya başlamıştır. Bu çalışmada elde edilen sonuçlara dayanarak kitosan nanotaneciklerin WPI filminin mekanik ve bariyer özelliklerinin iyileştirilmesinde, PAA/LIS komplekslerinin de kontrollü salım yapabilen, antimikrobiyal özelliğe sahip WPI filmlerinin hazırlanmasında kullanılabileceği düşünülmektedir.Research Project Enzim immobilize edilmiş membranların hazırlanması ve karakterizasyonu: membran performanslarının belirlenmesi(2008) Alsoy Altınkaya, Sacide; Yemenicioğlu, Ahmet; Yürekli, YılmazBu çalışmada üreaz enzimi polietilenimin (PEI) ve kitosan (CHI) ile modifiye edilmiş poliakrilonitril (PAN) membranları üzerine immobilize edilmiştir. PEI ve CHI ile modifikasyon PAN membranı üzerine adsorbe olan üreaz miktarını etkilemezken, aktiviteler sırayla 2 ve 1.5 kat artış göstermiştir. Membranların üreye karşı gösterdikleri kinetik performans aşağıdaki şekilde bulunmuştur: PAN+PEI+CHI>PAN+PEI>PAN+CHI>PAN. pH 7 ile 9 aralığında modifiye edilmiş membranlar üzerine immobilize edilen üreaz PAN üzerine immobilize edilene göre daha iyi bir aktivite profili sergilemiştir. PAN+CHI ve PAN membranları üzerine immobilize edilen üreaz 30 ve 37 o C’de optimum aktivite gösterirken, PAN+PEI ve PAN+PEI+CHI üzerine immobilizasyon optimum aktivitenin gözlendiği sıcaklığın 50 ve 60 o C’ye yükselmesine neden olmuştur.Research Project Pentablok kopolimer bazlı yeni bir ince film kompozit nanofiltrasyon membranı geliştirilmesi(2018) Mallapragada, Surya K.; Alsoy Altınkaya, SacideDıs uyarıcılara tepki veren membranlar, farklı uygulamalarda kirlenmenin önlenmesi ve seçiciligin düzenlenmesi için kullanılmaktadır. Ince film kompozit membranlar genellikle bir uyarıcıya tepki veren monomerin yüzeyde polimerizasyonu veya uyarıcıya tepki veren bir polimerin yüzeye kaplanması ile üretilmektedir. Dıs etkilere duyarlılık, polimerin pH, sıcaklık ve iyonik kuvvet gibi dıs ortamdaki degisiklikler sonucunda kütle transferi ve ara yüzey özelliklerindeki degisikliklerden kaynaklanmaktadır. Bu çalısmada orta blok olarak sıcaklıga duyarlı Pluronik F127 (PEO-b-PPO-b-PEO) ve uç bloklar olarak pH'a cevap veren poli(N, N- (dietilamino) etil metakrilat) (PDEAEM) içeren bir pentablok kopolimer (PBC) yeni bir ince film kompozit (TFC) nanofiltrasyon membranının gelistirilmesi için kullanılmıstır. Kompozit membranın destek katmanı, polisülfon/sülfonlanmıs polietersülfon karısımı ile çözücü olmayan faz ayrımı yöntemi ile hazırlanmıs, PBC elektrostatik etkilesim yoluyla destege tutturulmustur. Yüzeye tutunan PBC zincirlerinin konformasyonu, adsorpsiyon çalısmaları ve X ray photoelektron spektroskopisi (XPS) karakterizasyonu ile tespit edilmistir. PDEAEM blok uzunlugu, kopolimer konsantrasyonu ve adsorpsiyon süresinin adsorbe olan PBC miktarı üzerine olan etkileri arastırılmıstır. Incelenen üç kopolimer numunesi (15, 20 ve 25 kDa) arasında pH ve sıcaklıga karsı en fazla cevabı 25 kDa?lık polimer örnegi verdiginden daha sonraki çalısmalarda bu örnekle hazırlanmıs membranların seçicilik ve kirlenme potansiyelleri belirlenmistir. pH ve sıcaklıgın membranın yapısı ve seçiciligi üzerindeki etkileri, saf su akısı ölçümleri ile nötr bilesiklerin membranlar tarafından itilme düzeylerinden gözenek boyutundaki degisimin belirlenmesi ile incelenmistir. Diger taraftan membranların pH ve sıcaklık duyarlılıgının kirlenme potansiyeli üzerindeki etkileri model kirletici olarak seçilen sıgır serum albumini, aljinat ve E coli ?nin filtrasyonu sonucu akılardaki azalma düzeylerine göre degerlendirilmistir. Membranlar SEM, AFM, temas açısı, XPS ve zeta potansiyeli ölçümleri ile karakterize edilmistir. Bu çalısmada pH ve sıcaklıga duyarlı, yüksek akıya sahip, yeni bir ince film kompozit nanofiltrasyon membranı üretilebilecegi gösterilmistir.Article Citation - WoS: 1Citation - Scopus: 2A New-Generation Poly (ether Imide Sulfone) Based Solvent Resistant Ultrafiltration Membrane for a Sustainable Production of Silica Nanopowder(Elsevier, 2023) Güngörmüş, Elif; Alsoy Altınkaya, SacideThe work presented here demonstrated the feasibility of using a membrane to improve the sustainability of silica nanopowder production. Due to superior chemical resistance, high thermal-oxidative stability, and good processability, poly (ether imide sulfone) has been used for membrane production and modified with amine-functionalized TiO2 nanoparticles. The membrane demonstrated good long-term leaching stability in 40% ethanol and silica synthesis solution and maintained its permeability and rejection characteristics under static and dynamic conditions. Additionally, the high antifouling property of the membrane allowed recovering 99.5% of the nanoparticles. Backwashing with water resulted in a high flux recovery ratio (>93%), and gravity-settling without energy can easily separate silica nanoparticles and water in the backwashing solution. Compared to classical freeze-drying and oven-drying methods, integrating membrane into silica nanopowder production can reduce energy consumption by a factor of 81 and 53. At the same time, the utility cost can be saved by 80% and 69%. Additionally, the solvent and catalyst recovered in the permeate stream can be reused in the synthesis, reducing disposal and purchasing costs. In conclusion, membrane-assisted nanopowder production can minimize the adverse effects caused by commonly used conventional drying methods and make the process more sustainable and environmentally friendly.Article Citation - WoS: 12Citation - Scopus: 12Biofouling-Resistant Ultrafiltration Membranes Via Codeposition of Dopamine and Cetyltrimethylammonium Bromide With Retained Size Selectivity and Water Flux(American Chemical Society, 2022) Cihanoğlu, Aydın; Schiffman, Jessica D.; Alsoy Altınkaya, SacideBiofouling is a serious problem in ultrafiltration (UF) membrane applications. Modifying the surface of membranes with low molecular weight, commercially available antibacterial chemistries is an excellent strategy to mitigate biofouling. Herein, we report a new strategy to impart antibacterial and anti-biofouling behavior without changing the support membrane’s size selectivity and pure water permeance (PWP). To this end, a strong antibacterial agent, cetyltrimethylammonium bromide (CTAB), was codeposited with dopamine onto commercial polyethersulfone (PES) UF membranes in the presence of nitrogen (N2) gas backflow. The PWP and pore size of the support membrane did not change with codeposition, confirming the benefit of N2 backflow in mitigating the solution intrusion phenomenon. X-ray photoelectron spectroscopy (XPS), surface ζ potentials, and contact angle measurements confirmed the successful codeposition of polydopamine (PDA) and CTAB onto the membrane. Among three different CTAB concentrations systematically investigated, the membrane functionalized with CTAB at the critical micelle concentration (CMC) provided the best anti-biofouling activity against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria and retained its surface ζ potential after being stored in 1 M NaCl (pH = 6.8) for 3 months. Our results demonstrate the potential of using a facile, one-step approach to modify commercial UF membranes without compromising their pore size or flux, while simultaneously endowing antibacterial activity.Article Citation - WoS: 16Citation - Scopus: 15Ultrasound-Assisted Dopamine Polymerization: Rapid and Oxidizing Agent-Free Polydopamine Coatings on Membrane Surfaces(Royal Society of Chemistry, 2021) Cihanoğlu, Aydın; Schiffman, Jessica D.; Alsoy Altınkaya, SacideHerein, we report a controllable pathway to accelerate the polymerization kinetics of dopamine using ultrasound as a trigger. The use of ultrasound was demonstrated to dramatically accelerate the slow liquid phase reaction kinetics and increase the deposition rate of the polydopamine coating on the surface of polymeric membranes.Article Citation - WoS: 54Citation - Scopus: 62A Positively Charged Loose Nanofiltration Membrane Fabricated Through Complexing of Alginate and Polyethyleneimine With Metal Ions on the Polyamideimide Support for Dye Desalination(Elsevier, 2021) Metecan, Ayşe; Cihanoğlu, Aydın; Alsoy Altınkaya, SacideNowadays, loose nanofiltration (NF) membranes are preferred for dye desalination to achieve high dye/salt selectivity and enable filtration at low operating pressure. However, current fabrication techniques require rigorous reaction conditions and long preparation times. Herein, we used the chelating ability of the polyethyleneimine (PEI) and alginate with the metal ions to fabricate loose NF membranes via a facile approach. The positively charged polyamide imide (PAI)/PEI support was used to build the assembly. Direct attachment of Zn or Fe ions to the PEI chains did not result in a stable complex in the presence of a high salt concentration (1000 ppm NaCl). On the other hand, alginate coated on the support allowed building permanent assemblies after crosslinked with Fe3+ and Zn2+ transition metal ions. The PAI/PEI-Alg-Fe3+ membrane exhibited the highest permeability, excellent antifouling behaviour upon exposure to synthetic textile wastewater, and maintained long-term stability under static and dynamic conditions. Also, the same membrane rejected dyes and coloured substances in real wastewater sample during 72 h continuous filtration. With alginate metal complex formation on a suitable support, a scalable loose NF membrane was manufactured, demonstrating improved throughput value compared to current NF membranes.Article Citation - WoS: 14Citation - Scopus: 16Facile Fabrication of Anti-Biofouling Polyaniline Ultrafiltration Membrane by Green Citric Acid Doping Process(Elsevier, 2021) Güngörmüş, Elif; Alsoy Altınkaya, SacideThis study aimed to enhance the anti-biofouling property of the polyaniline (PANI) based ultrafiltration (UF) membrane by utilizing its self-acid doping ability. A naturally derived biodegradable agent, citric acid, was doped to the membrane by filtering at 1 bar. Acid doping increased the hydrophilicity, made the surface nearly electroneutral, and imparted biocidal characteristics to the membrane. Biofouling was simulated by filtering a suspension of E.coli and S.aureus through the membranes. Most fouling on the doped membrane was reversible and easily removed by simple washing, leading to a high flux recovery ratio. The SEM images taken after filtration and washing steps showed that the modified membrane surface was free of bacteria while many bacteria accumulated on the pristine membrane surface. The doped membrane was stored in 1 M NaCl solution for up to five months. A tiny amount of citric acid was lost from the membrane, and at the end of storage, the flux, rejection, and antibacterial activity values did not change, demonstrating the antibacterial agent's stability. The protocol proposed in this study is fast, simple, facile, and easily scalable for large-scale production. Using a green antibacterial agent and its loading with a one-step process without consuming chemicals or functionalizing the support makes the proposed method environmentally friendly.Article Citation - WoS: 50Citation - Scopus: 51A Facile Route To the Preparation of Antibacterial Polysulfone-Sulfonated Polyethersulfone Ultrafiltration Membranes Using a Cationic Surfactant Cetyltrimethylammonium Bromide(Elsevier, 2020) Cihanoğlu, Aydın; Alsoy Altınkaya, SacideCetyltrimethylammonium bromide (CTAB), a cationic surfactant, is known to have strong bactericidal potential. In this study, we report a facile approach for preparing CTAB-containing polysulfone-sulfonated polyethersulfone (PSF-SPES) based ultrafiltration membranes with antibacterial properties. The CTAB was added in gelation medium at three different concentrations and made an electrostatic interaction with SPES at the polymer/bath interface during phase inversion. The successful incorporation of the CTAB in the membrane structure was confirmed by attenuated total reflectance Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The CTAB-containing membranes had higher contact angle, lower pure water permeability (PWP) and molecular weight cut-off than the pristine membrane. The membranes prepared at critical and above critical micelle concentration (CMC) of the CTAB showed excellent antibacterial activity on both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria. On the other hand, the PWP of the membrane decreased from 93 +/- 1.6 to 39.3 +/- 3.2 L/m(2) h bar upon increasing the CTAB concentration from 10(-3) M (=CMC) to 10(-2) M, consequently, CMC was chosen as the optimal concentration. The membrane prepared at the CMC displayed almost 100% flux recoveries after dynamic bacteria filtration followed by simple rinsing with PBS solution. Leaching experiments continued up to 30 days demonstrated that 96% of the CTAB remained in this membrane. Furthermore, at the end of 1 month of storage in 1 M NaCl solution, no change was observed in the antibacterial activity of this membrane compared to fresh membrane. These findings emphasize the potential of the facile approach proposed in this study to develop antibacterial ultrafiltration membranes in a single step.