İç ortamdaki inorganik ve organik kirleticilerin yeni teknolojiler ile giderilmesi
Removal of inorganic and organic pollutants in the indoor air by new technologies
Yazar: BİLGE BETÜL ÖZÇELİK
Danışman: PROF. DR. MELEK MÜMİNE EROL TAYGUN
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Kimya Mühendisliği Ana Bilim Dalı / Kimya Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2020
Konu: Kimya Mühendisliği = Chemical Engineering

Özet:
İç ortamda en yaygın olarak bulunan uçucu organik bileşikler (UOB), partiküler madde (PM), karbon monoksit (CO), ozon (O3), azot oksitleri (NOx), kükürt oksitleri (SOx), polisiklik aromatik hidrokarbonlar (PAH) ve klorlu dioksinlerdir. Bu kirleticilere uzun süre boyunca ve yüksek konsantrasyonda maruz kalındığında, özellikle kalp ve solunum yolu rahatsızlıklarına yakalanma ihtimalleri artmaktadır. Kirleticiler farklı kimyasal ve fiziksel özelliklere sahip olduğundan dolayı, tek bir teknoloji kullanılarak tamamının bertaraf edilmesi mümkün değildir. Bu çalışmada, yapılan araştırmalar sonucunda inorganik kirleticiler için adsorpsiyon teknolojisi seçilirken organik kirleticiler için fotokatalitik oksidasyon teknolojisi tercih edilmiştir. 
Çalışmanın ilk kısmında; iç ortam havasında bulunan inorganik kirleticilerden CO2'nin giderimi için kullanılan teknolojilerden, adsorpsiyon ve amin ile fonksiyonelleştirilmiş adsorbanların ev tipi uygulamalar için en uygun seçenek olduğuna karar verilmiştir. 3 farklı hava temizleyici prototip tasarımı yapılmış ve en iyi performansı gösteren tasarım için 50 çevrimlik adsorban ömür testi gerçekleştirilmiştir. Bu testler sırasında her 10 çevrimde bir numuneler alınmış ve bu numunelere TGA'da hızlandırılmış ömür testi uygulanmıştır. Adsorban yapısındaki kimyasal değişimleri gözlemlemek adına FTIR analizleri yapılmıştır.
Çalışmanın ikinci kısmında; iç ortam havasında bulunan uçucu organik bileşiklerden benzenin giderimi için en ideal yöntemin, TiO2'nin katalizör olarak kullanıldığı fotokatalitik oksidasyon yöntemi olduğuna karar verilmiştir. 
TiO2 bazlı fotokatalizör, titanyum tetraizopropoksit, hidroklorik asit, etanol ve su kullanılarak sol-jel yöntemi ile toz formda sentezlenmiştir. Aynı zamanda, UV ışığının yanısıra görünür bölge ışığı ile de aktifleşebilen metal katkılı TiO2 elde edebilmek için demir sülfat heptahidrat (FeSO4.7H2O) metal tuzu eklenerek sol-jel yöntemi ile Fe-TiO2 elde edilmiştir. 
Elektrospinning çözeltisi olarak ağırlıkça %10 PAN (poliakrilonitril), DMF (dimetilformamid) içinde çözülmüştür. PAN içeren elektrospinning çözeltisine ağırlıkça farklı oranlarda TiO2 (PAN/TiO2 1/0, 1/0.05; 1/0.1; 1/0.3; 1/0.5; 1/0.7; 1/1 a/a) eklenerek 24 saat boyunca manyetik karıştırma ile 30 dakika ultrasonik karıştırma işlemi uygulanmış, ardından elektrospinning yöntemi ile membran üretimi gerçekleştirilmiştir. ImageJ yazılımı yardımıyla nanolif yapılı membranların ortalama lif çapları ölçülmüştür.
TiO2 bazlı katalizörler kalsinasyon uygulanmadan ve kalsinasyon uygulanarak sentezlenmiş ve her iki tipteki katalizör de yukarıda belirtilen konsantrasyonlarda membran yapısına katılmış, SEM analizi ile iki yapı arasındaki fark gözlemlenmiştir. EDX dedektörü ile yarıkantitatif elementel analiz yapılarak membran yapısındaki TiO2 miktarları belilenmiştir. SEM analizleri incelendiğinde, en düzgün lif yapısının oluştuğu 3 farklı konsantrasyon (PAN/TiO2: 1/0.3; 1/0.7; 1/1 a/a) belirlenmiştir. Bu 3 farklı konsantrasyon için, TiO2 ve Fe-TiO2 bazlı fotokatalizör katkılı kompozit yapılı toplam 6 adet nanolif filtre elektrospinning yöntemi ile sentezlenmiştir. Her bir filtrenin boyutu 5 cm x 5 cm x 1 mm (en x boy x kalınlık) olacak şekilde ayarlanmış ve plastik çerçevelerle sabitlenmiştir. Fotokatalitik performans testleri, 25 L sızdırmaz kabin içinde, UV ışık kaynağı kullanılarak, TiO2 ve Fe-TiO2 katkılı kompozit membran filtreler tarafından yaklaşık 80 ppm başlangıç benzen konsantrasyonuyla, 5 saat boyunca gerçekleştirilmiştir. Bu testlerin sonucunda, TiO2 ve Fe-TiO2 katkılı membranlar arasından en iyi performansı gösteren numune ağırlıkça PAN/TiO2 oranı 1/0.3 olan membrandır. 
Katkısız PAN membran, TiO2 (PAN/TiO2: 1/0.3 a/a) ve Fe-TiO2 (PAN/Fe-TiO2: 1/0.3 a/a) bazlı üç filtrenin karakterizasyonu için EDX, TGA, FTIR, XRD, BET, UV-Vis analizleri yapılmıştır.

Abstract:
Air pollution has become an important problem in recent years due to its negative effects on human health. Since people spend most of their time indoors, public awareness is rising about the risks of poor indoor air quality. Volatile organic compounds (VOC), particulate matter (PM), carbon monoxide (CO), ozone (O3), nitrogen oxides (NOx), sulfur oxides (SOx), polycyclic aromatic hydrocarbons (PAH), and chlorinated dioxins are the most common air pollutants in the indoor environment. When people are exposed to these pollutants for a long time and in high concentrations, they are more likely to get heart and respiratory diseases. Therefore, characterization of the pollutants in the indoor air and determination of the most effective removal method is of great importance. However, since these pollutants have very different chemical and physical properties, it is not possible to remove all the pollutants using a single technology. In this study, two different technologies were used for the removal of inorganic and organic pollutants in the indoor environment. While determining the technologies to be used to increase indoor air quality and indoor comfort, both high performance and low cost systems are prioritized. In this context, as a result of researches, adsorption technology was chosen for inorganic pollutants, while photocatalytic oxidation technology was preferred for organic pollutants.
In the first part of the study, inorganic pollutants commonly found in indoor air were determined and the technologies used to remove these pollutants were investigated. The primary goal in this part of the study is to design an innovative air purifier that will improve indoor air quality and make a difference. As a result of the market research and customer reviews, it was observed that the increased CO2 concentration due to the lack of ventilation especially in the winter season caused problems such as headache, low sleep quality, and decreased performance of the work. Since there is no air purifier among the existing household products that claim to remove CO2 in room conditions, the conducted studies are pioneering.
According to the results of the patent researches, it was determined that the most ideal method for removing CO2 from indoor air is adsorption. The adsorbents commonly used in the adsorption process were examined, and many of them were found to have problems such as moisture retention and regeneration at high temperatures. In order to overcome these problems, high-tech materials were synthesized by applying various physical and chemical processes to conventional materials used as adsorbents. In the light of this information, it was decided that amine functionalized adsorbents are the most suitable option for household applications.
Inspired by industrial CO2 removal systems, an amine based commercial adsorbent was used to design a household air purifier that removes CO2. In this context, 3 different prototypes were designed and CO2 removal performances were determined. Among the 3 prototypes, the design with the best performance was selected and 50-cycle adsorbent life test was performed. During these tests, samples were taken every 10 cycles and accelerated life tests were applied to these samples in TGA. FTIR analyzes were carried out to observe the chemical changes in the adsorbent structure.
In the second part of the study, the technologies used for the removal of volatile organic compounds in the indoor air were examined. As a result of the researches, it was decided that the photocatalytic oxidation method, which can break down volatile organic compounds up to CO2 and H2O, is the most suitable method for indoor air cleaning applications. The most common volatile organic compounds in the internal environment are benzene, toluene, ethylbenzene and xylene. Therefore, in this study, removal of benzene, which can be described as the most harmful volatile organic compound to human health, by photocatalytic oxidation was emphasized. TiO2 nanoparticles were used in these studies because it is a non-toxic photocatalyst that displays efficient photocatalytic performance under UV light.
TiO2 nanoparticles are mostly used by coating on glass surfaces in air purifiying applications. The coating method makes it difficult to design a hybrid air purifier because air cannot pass through the glass surface. Another method is to use powder TiO2 nanoparticles by pelletizing, but this application prevents air from passing over the entire surface homogeneously. Therefore, TiO2 nanoparticles are incorporated into the polymer membrane structure synthesized by the electrospinning method. Thanks to this method, synthesis of the membrane filters with high air permeability, whose filter structure can be controlled and commercially produced are possible.
TiO2 based catalyst was synthesized in powder form by sol-gel method using titanium tetraisopropoxide, hydrochloric acid, ethanol and water. At the same time, Fe-TiO2 was obtained by sol-gel method by adding iron sulfate heptahydrate (FeSO4.7H2O) metal salt to obtain metal-added TiO2 that can be activated with visible light as well as UV light.
The electrospinning solution was prepared at 10 wt.% PAN/DMF using polyacrylonitrile (PAN) and dimethylformamide (DMF). PAN is preferred because it is a polymer that is widely used in electrospinning processes and can be easily spinned.
Different ratios of TiO2 (PAN/TiO2 1/0; 1/0.05; 1/0.1; 1/0.3; 1/0.5; 1/0.7; 1/1) were added to the electrospinning solution containing PAN and stirring was performed for 24 hours, then membrane production was made with electrospinning.
In order to examine the calcination effect, TiO2 based catalysts were synthesized with and without calcination. Both types of catalysts were incorporated into the membrane structure at the concentrations mentioned above, and the difference between the two structures was observed by SEM analysis. It was observed that TiO2 nanoparticles became smaller after calcination. In addition, TiO2 amounts in the membrane structure were determined by using semi-quantitative elemental analysis with EDX dedector. Average fiber diameters of nanofiber membranes were measured with ImageJ software.
In the light of the SEM analysis, three different concentrations (PAN/TiO2: 1/0.3; 1/0.7; 1/1) were determined in which the most uniform fiber structure was formed. For these 3 different concentrations, a total of 6 electrospun nanocomposite filters with a photocatalyst-containing TiO2 and Fe-TiO2 were synthesized. The size of each filter was set to be 5 cm x 5 cm x 1 mm (width x length x thickness) and fixed with plastic frames. Photocatalytic performance tests of TiO2 and Fe-TiO2 composite membrane filters were carried out in a 25 L sealed cabinet, using a UV light source, for about 5 hours with an initial benzene concentration of about 80 ppm. As a result of these tests, among the TiO2 and Fe-TiO2 doped membranes, the best performing PAN/TiO2 ratio was determined as 1/0.3 (w/w).
Characterization tests of three filters PAN (PAN/TiO2: 1/0 w/w), TiO2 (PAN/TiO2: 1/0.3 w/w) and Fe-TiO2 (PAN/Fe-TiO2: 1/0.3 w/w) were performed with EDX, TGA, FTIR, XRD, BET, UV-Vis analysis.
The chemical structures of the membrane filters were examined by FTIR analysis in the wavelength range of 650-4000 cm-1. The purpose of the XRD virtualization is to determine the crystal structures of the membranes. For this reason, measurement was made with a scanning speed of 4 °/minute in the range of 2θ = 10-90 ° at 5 kV and at 40 mA. BET analysis was carried out and the properties of photocatalytic membranes such as pore size, mean pore diameter and surface area were determined. Finally, UV-Vis analysis was performed to examine the optical properties of photocatalysts that use UV light to show the best photocatalytic activity.