Gümüş nanopartikülleri ile kompozit ince boşluklu fiber membran üretimi, karakterizasyonu ve uygulaması
Nanocomposite hollow fiber membrane fabrication with silver nanoparticle, characterization and application
Yazar: TÜRKER TÜRKEN
Danışman: PROF. DR. İSMAİL KOYUNCU
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Çevre Mühendisliği Ana Bilim Dalı / Çevre Bilimleri ve Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2013
Konu: Kimya Mühendisliği = Chemical Engineering ; Çevre Mühendisliği = Environmental Engineering
Dizin: Gümüş = Silver ; Membran teknolojileri = Membrane technologies ; Membranlar = Membranes ; Nanopartiküller = Nanoparticles ; Polimerik membranlar = Polymeric membranes ; Ultrafiltrasyon = Ultrafiltration

Özet:
Su günümüzde en değerli doğal kaynakların başında gelmektedir. Artan nüfus ile birlikte değişen iklim şartları ve dünya koşulları su bakımından en zengin ülkeleri bile ilerleyen yıllar da su stresi içerisine sokacaktır. Bu nedenle endüstride ve evsel kullanımda suyun geri kazanılması ihtiyaç haline gelmiştir. Su geri kazanımında en verimli yöntem olarak bahsedebileceğimiz membran teknolojileri günümüzde deniz suyundan içme suyu eldesi, proses suyu, içme suyu ve konsantre sıvılar elde etme de endüstri ve insani amaçlı olarak yaygın olarak kullanılmaktadır. Bu amaçla polimerik ve seramik malzemeden üretilmiş düz levha ve içi boşluklu (hollow fiber) membranlar kullanılmaktadır. Yaygın kullanımlarının yanı sıra membran teknolojileri, araştırma çalışmalarının yürütülmesi, proseslerin iyileştirilmesi ve membran performanslarının geliştirilmesi gibi birçok araştırma ve Ar-Ge konusunu bünyesinde barındırmaktadır. Membran üretiminde gümüş (Ag+) nanopartiküller ile polimerik metariyallerin kombinasyonunun kullanılması gümüşün yüksek iletkenliği, optik ve antibakteriyel özelliklerinden dolayı son zamanlarda dikkat çeken çalışma konularının başında gelmektedir. Ag nanopartiküller yüksek antibakteriyel özelliğe sahip olduklarındandolayı membranların yüzeylerinde birikip tıkanmaya neden olan bakteriler için bir çözüm olacağı düşünülerek kullanılmaktadır. Düşük yükleme oranı ile yüksek antibakteriyel verim elde etmek ve gümüş nanopartiküllerinin polimer matriksi içerisinde homojen dağılımı kompozit membranların üretimi esnasında hesaba katılması gereken unsurlardır. Nano kompozit membran üretiminde selüloz asetat (CA), chitosan, poliakrilonitril (PAN), and polisulfon (PSf) literatürde en çok kullanılan polimerik malzemelerdir. Ancak CA ve PAN solventte zayıf çözünme, maliyet gibi unsurlardan dolayı bazı dezavantajları vardır. Bu sebeple polietersülfon (PES) polimeri organik solventte kolayıkla çözünebilmesi, ucuz olması, iyi düzeyde kimyasal direnç ve yüksek stabilite özelliklerinden dolayı en çok kullanılan polimerik malzemedir. Bu çalışmanın amacı gümüş nanopartikülllerinin anti bakteriyel özelliğinden faydalanarak yeni ve yüksek verimli hollow fiber membran üretmektir. Gümüş nanopartiküller membran yüzeyinde biriken bakterileri parçalayarak membranın tıkanma süresini uzatacak veya engelleyecektir. Böylece membran performası artmış olacaktır. Bunun yanı sıra bu nanopartiküller membranların mekanik dayanımlılığını artırdığı da düşünülmektedir. Üretilen membranlar ultrafiltrasyon düzeyinde olup içme suyu arıtımında ve membran biyoreaktörlerde kullanılacaktır.

Abstract:
Water is one of the leading natural resource nowadays. With the increasing population; changing climate conditions and world circumstances in the forthcoming years even water-rich countries will become water scarce. Because of this reason, water recycling became a necessity in industrial and domestic usage. In the water recycling process the best efficient system is membrane technology which has uses on commonly desalination, process water, drinking water treatment processes, by this way one can obtain concentrate liquids and intended for human consumption. For this purpose flat-sheet and hollow fiber membranes have been produced from polymeric and composite materials. Besides common uses, reseach activites carrying out such as membrane technology studies, improving processes and performances, also on the subject of research and development (R&D) contains within itself. The goal of this study; take advantage of anti-bacterial characteristics of silver nanoparticles, produce novel and high efficient hollow fiber membrane. Silver nanoparticles kill bacteria accumulated on the surface of the membranes so that membrane clogging time is extended and bacteria formation restrained. Thereby membrane performance increases. In addition to this, nanoparticles which used in the membrane production increases of the mechanical strength. Produced membranes can be classified as Ultrafiltration and their utilization areas are drinking water treatment and membrane bioreactors. In the experimental studies, four different concentration of silver nanoparticles used in the hollow fiber membrane production as 0,2-0,4-0,8 and 1,2 %. As blank sample, hollow fiber membrane produced from pure polymer(without nanoparticles). In the membrane production step, four types of parameters have taken into consideration. While coagulation bath temperature was set to a constant value, air and winding speed have being increased. Besides the effect of the nanoparticle contents on membrane production; effects of operation parameters have been investigated. SEM (Scanning Electron Microscope) images were taken for produced hollow fiber membranes. With the toxicicity test, effects of silver nanoparticles on bacteria had been observed. Mechanical strength of fabricated membranes have been investigated with mechanical strength analysis. Porosity of membranes was identified with porosity experiments and observation have been made whether nanoparticles have effects on membrane porosity or not. With pure water flux and protein filtration experiments, clogging tendency and performances of membranes have been observed. Membranes were produced using 4 different parameters. In the first two testing set, air gap was kept at 0 cm. However, take ?up speed have increased x2. In the first testing set, take-up speed was chosed as 4,82 m/min , but this value have changed at 8,35 m/min at second testing set. When take-up speed was increased, tensile force was also increased on membranes. According to the first testing set because of tensile force membrane thickness was less than before. Membrane exterior diameter will decrease from 1,4 to 0,9 ?m. For the 3. and 4. testing set air gap increased to 15 cm. Take-up speeds were set as 8,35 m/min at the 3. testing set and 4,82 m/min at the 4. testing test. External coagulant that contains the same concentration with the bore liquid continously pumped during air xxiigap exterior surface of fibers. Solvent in the coagulant decrease the precipitation speed provides more porous membrane selective layer. According to results of experimental studies, membranes which are included silver nanoparticles prevented growth of bacteria on membrane surface. But, due to accumulation of nanoparticles on membrane pores, membrane performances decreased. In all testing sets when SEM pictures were analyzed, it can be seen that all pristine membranes have spongelike morphology. Increasing concentration of nanoparticles, macrovoids and finger like structure was formed. As it is explained in the literature, change on membrane morphology is due to solvent exchange. It is considered that nanoparticle based membrane matrix , precipitation rate increases and phase inversion is completed faster. Since silver nanoparticles conduct temperature better, precipitation rate increases. Also, in the 3rd and 4th testing setup air gap changed surface morphology and so interior and exterior surfaces had spongelike structure, middle part or membrane walls had finger like structures. Permeability tests of hollow fiber membranes were done with distilled water. Flux tests were done at 3 different pressure and membranes pressure- flux graphs drawn. The slope of drawn line gave membrane permeability value. The highest membrane permeability was 198 L/m2.h.bar due to the first operation parameter which was 0,2-1 membrane. Membranes that were produced according to the second operation parameter, the highest flux was 177 L/m2.h.bar at pristine membranes. While nanoparticle concentration increased, nanoparticles deposited into the membrane pores which results in flux decrease. Meanwhile, in the 2. testing setup since take-up speed increased membranes behave discordantly. Because of this reason due to 1. Testing setup tensile strength on membranes decreased. In the third and fourth setup, air gap was increased. The highest permeability value 211 L/m2.h.bar that belongs to 0,2-3 membrane and 212 L/m2.h.bar belongs to 0,4-4 membrane at 4th testing set. Membrane fouling tests were performed with 100 ppm BSA solution which was filtrated from the membranes. At the end of 1 hour filtration, total fouling rate, cake fouling rate and pore fouling rates were calculated. Also FRR values have been calculated and shown in the same graph. FRR value shows fouling resistance of membranes towards to membrane. Meanwhile, BSA removal efficiency have been investigated. BSA removal efficiency was found as over 70%. Toxicity tests performed on produced membranes to assert nanoparticles antibacterial property. For this experiments pure E.Coli culture was filtered from membranes. After 1 hour filtration membranes were inserted on agar plates and were kept in incbator for 48 hours. At the end of the experiments pristine membranes had colonies around but silver added membranes bacterial growth did not occured. Mechanical strength tests were done with Dynamic Mechanical Analyses device. Youngs modulus, tensile strength ve elongation rates of membranes were found. Young?s Modulus value represents materials stiffness. Higher Young?s modulus value means more rigorous membrane structure. According to the mechanical strength analysis, all membranes wtih nanoparticles had better mechanical strength than pristine membranes. Zeta potential analysis were done in order to see surface charge of silver nanoparticle added nanocomposite membranes. In this test electrokinetic analyzer device was used and ph rage used was between 3 to 10. According to the results at the beginning pristine membrane zeta potential was -15 mV, with the increasing of nanoparticle concentration surface load approached to neutral level then continue to raise up to +5 mV. Then porosity experimets were done to see the possible effects of silver nanoparticles. According to the experiment results silver addition increased porosity values. But , this increase was due to the change in kinetic and termodynamic conditions as increase in silver concentration. This situation was supported with SEM pictures. xxiiiAfter morphology and performance experiments membranes were exposed to activated sludge filtration process in order to find the most efficient membrane. According to tests operation parameter 4 was found as the most efficient. As a result addition of silver nanoparticles in membrane matrix provided antibacterialproperty on membranes and biofouling was decreased