RSM optimizasyonu ile çörekotu (Nigella Sativa L.) atık biyokütlesi-esaslı üretilen aktif karbon kullanılarak uçucu organik bileşiklerin giderilmesi ve fotovoltaik uygulamalarının incelenmesi
[ X ]
Tarih
2021
Yazarlar
Dergi Başlığı
Dergi ISSN
Cilt Başlığı
Yayıncı
Siirt Üniversitesi
Erişim Hakkı
info:eu-repo/semantics/openAccess
Özet
Bu çalışmada, yanıt yüzey metodolojisi (RSM) kullanılarak çinko klorür (ZnCI2) ile kimyasal aktivasyon yoluyla yağı alınmış çörekotu (Nigella Sativa L.) atık biyokütlesi-esaslı üretilen aktif karbonun hem uçucu organik bileşik (UOB)'lerin giderimi hem de fotovoltaik uygulamalarındaki performansı değerlendirilmiştir. Bu amaçla ilk etapta, aktif karbon üretim prosesi, aktivasyon süresi (30-60 dakika), aktivasyon sıcaklığı (400-600 °C) ve impregnasyon oranı (çörekotu atığı/ZnCI2, %50-150 ağırlıkça) gibi faktörler ile hedeflenen yanıt olarak iyot sayısı esas alınarak RSM'nin bir yaklaşımı olan merkezi kompozit tasarım (CCD) ile optimize edilmiştir. Ayrıca, aktif karbon üretimini etkileyen bu önemli faktörler, bir varyans analizi (ANOVA) ile tanımlanmıştır. Aktif karbon üretiminde, 57 dakika aktivasyon süresi, 550 °C aktivasyon sıcaklığı ve %105 impregnasyon oranı optimum değerler olarak saptanmış ve bu koşullar altında 1055 mg/g yüksek iyot sayısı alımına ulaşılmıştır. Optimum koşullarda üretilen aktif karbonun yüzey özellikleri, taramalı elektron mikroskobu (SEM), Fourier dönüşümü kızılötesi spektroskopisi (FTIR) ve Brunauer–Emmett–Teller (BET) yüzey alanı gibi çeşitli analitik teknikler ile karakterize edilmiştir. Sonuçlar, optimal aktif karbonda önemli miktarda mikrogözeneklilik (%53,93) ve mezogözeneklilik (%46,07) oluştuğunu göstermiştir. Ayrıca optimal aktif karbon, 1213,32 m2/g spesifik yüzey alanı (SBET), 0,89 cm3/g toplam gözenek hacmi ve 787,65 m2/g mikrogözenek yüzey alanı ile oldukça gözenekli bir yapı sergilemiştir. Birçok endüstriyel proses, çok bileşenli sistem olarak ortaya çıkan UOB kirleticileri üretmektedir. Bu nedenle, UOB'lerin karşılaştırmalı ve rekabetçi adsorpsiyonunun araştırılması, pratik ve bilimsel öneme sahiptir. Bu anlamda, ikinci etapta, optimal aktif karbon kullanılarak UOB'ler olarak hedeflenen benzen, toluen ve ksilen (BTK) buharının tekli-bileşen, ikili-bileşen ve üçlü-bileşen sistemlerdeki karşılaştırmalı ve rekabetçi adsorpsiyon davranışları aydınlatılmıştır. Tekli-bileşen sistem ile karşılaştırıldığında, ikili-bileşen ve üçlü-bileşen sistemlerde, giriş konsantrasyonunun değişimine bağlı olarak BTK buharı oldukça farklı rekabetçi adsorpsiyon kapasitesi sergilemiştir. Çok bileşenli sistemlerdeki her bileşenin adsorpsiyon kapasitesi, tek-bileşen sistemdekinden çok daha azdır. Ayrıca, çok bileşenli sistemlerde K-buharının optimal aktif karbon üzerine dinamik adsorpsiyon kapasitesi, hem B-buharı hem de T-buharınkinden daha fazladır. Bu sonuçlar, optimal aktif karbonun K-buharı için adsorpsiyon seçiciliğinin T-buharı ve B-buharı için olandan daha yüksek olduğu gerçeğine atfedilebilir. Ayrıca, tekli-bileşen, ikili-bileşen ve üçlü-bileşen sistemlerinde, adsorpsiyon kapasitelerinde görülen K-buharı > T-buharı > B-buharı durumu, BTK buharının sahip olduğu rekabetçi hakimiyet, fiziksel adsorpsiyon bağlayıcı enerjiler, moleküler ağırlıklar ve metil grupları ile açıklanabilir. Bu uygulamadaki bulgular, belirli bir adsorbentle ilişkili olarak farklı UOB kirleticiler arasındaki karşılaştırmalı ve rekabetçi adsorpsiyon davranışının daha iyi anlaşılması için yardımcı olacaktır. BTK buharının optimal aktif karbon üzerine dinamik adsorpsiyon mekanizması, deneysel adsorpsiyon verilerine çeşitli kinetik ve izoterm modellerin uygulanmasıyla detaylı olarak açıklanmıştır. Reaksiyon temelli sözde-birinci-derece (SBD) kinetik modeli takip eden BTK buharının giderim prosesleri fiziksel adsorpsiyon mekanizmasını işaret etmektedir. Ayrıca, uygulanan difüzyon temelli partikül-içi difüzyon ve Boyd'nin film-difüzyonu kinetik modellerin değerlendirmelerine dayanarak, BTK buharı adsorpsiyon prosesi dengeye ulaşana kadar film-difüzyon direncinden (ilk aşama) ve ayrıca partikül-içi difüzyon direncinden (BTK molekülleri gaz filmi boyunca difüze olduktan sonra) etkilendiği sonucuna varılmıştır. Bunun yanı sıra, BTK buharı adsorpsiyonunda genel kütle transfer ve film kütle transfer faktörleri iç difüzyon faktöründen daha yüksek bulunmuştur ([kLa]g > [kLa]f > [kLa]d), bu da genel kütle transferi ve film kütle transferinin iç difüzyondan daha etkili olduğunu göstermektedir. Bir kadmiyum sülfür (CdS) tabanlı güneş pilinde, duyarlaştırıcı olarak CdS yarıiletken malzemesi çok önemli bir rol üstlenmektedir. Fotovoltaik uygulamalarda geniş bir şekilde kullanılan CdS tabanlı güneş pillerine ait fotovoltaik verimliliğin aktif karbon desteğiyle arttırılması büyük önem taşımaktadır. Ayrıca, aktif karbon, fotovoltaik cihazların elektrotlarına elektro-iletken katkılar, aktif malzemeler için destek olarak dahil edilmektedir. Bu nedenlerden dolayı, son etapta, literatürde sıklıkla kullanılan katkısız-katkılı CdS yarıiletken malzemeleri yerine optimal aktif karbon kullanılarak kimyasal çöktürme yöntemi ile aktif karbon destekli CdS (CdS/aktif karbon) ve üç farklı konsantrasyona (%0,33, %1 ve %3 ağırlıkça) sahip molibden (Mo)-katkılı CdS/aktif karbon, lantan (La)-katkılı CdS/aktif karbon ve mangan (Mn)-katkılı CdS/aktif karbon yarıiletken malzemeleri üretilmiştir. Tezin bu uygulamasındaki temel amaç; optimal aktif karbon destek malzemesi varlığında katkısız ve katkılı CdS yarıiletken malzemelerin güç dönüşüm verimliliklerinin nasıl değiştiğini belirlemek ve gözlemlenen bu etkiyi literatür ışığında yorumlamaktır. Üretilen saf CdS/aktif karbon, Mo-katkılı CdS/aktif karbon, La-katkılı CdS/aktif karbon ve Mn-katkılı CdS/aktif karbon yarıiletken malzemeler gelen fotonu akıma çevirme etkinliği (IPCE), SEM, X-ray ışınım kırınımı (XRD), enerji dağılımlı X-ışını spektroskopisi (EDX) ve X-ışını fotoelektron spektroskopisi (XPS) ölçümleri ile karakterize edilmiştir. Mo-katkılı CdS/aktif karbon, La-katkılı CdS/aktif karbon ve Mn-katkılı CdS/aktif karbon yarıiletken malzemelerin kristalit boyutları sırasıyla 11,09, 11,86 ve 10,52 nm olarak hesaplanmıştır. Bu sayısal veriler yarıiletken malzemelerin nano boyutta üretildiğinin bir göstergesi olarak kabul edilebilir. Bu uygulama kapsamında yapılan çalışmalar ile fotovoltaik uygulamalarda geniş bir şekilde kullanılan CdS tabanlı güneş pillerine ait fotovoltaik verimliliğin aktif karbon desteğiyle arttırılabilme kabiliyeti açıkça ortaya konulmuştur. Bu çalışma, RSM optimizasyonu ile biyoatık-esaslı üretilen aktif karbon kullanılarak UOB'ler olarak hedeflenen BTK buharının tekli, ikili ve üçlü-bileşen sistemlerdeki karşılaştırmalı ve rekabetçi dinamik adsorpsiyon mekanizmasını açıklığa kavuşturmak ve aktif karbon destekli CdS yarıiletken malzemeler kullanılarak elde edilen yarıiletken tabanlı güneş pil yapılarının güneş pil verimliliğini arttırmak için yeni bir strateji sunmaktadır.
In this study, the performance of activated carbon derived from de-oiled black cumin (Nigella Sativa L.) waste biomass through chemical activation with zinc chloride (ZnCI2) using response surface methodology (RSM), in both volatile organic compounds (VOCs) removal and photovoltaic applications was evaluated. To this end, in the first stage, activated carbon production process was optimized using central composite design (CCD), an approach of RSM, based on factors such as activation time (30-60 min), activation temperature (400-600 °C) and impregnation ratio (black cumin waste/ZnCI2, 50-150% by weight), and iodine number as the targeted response. Furthermore, these important factors that affect activated carbon production were defined by an analysis of variance (ANOVA). For production of activated carbon, an activation time of 57 min, activation temperature of 550 °C and impregnation ratio of 105% were found to be optimum values and a high iodine number of 1055 mg/g was achieved under these conditions. Surface properties of activated carbon produced under optimum conditions were characterized by various analytical techniques such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and Brunauer-Emmett-Teller (BET) surface area. The results showed that a significant amount of microporosity (53.93%) and mesoporosity (46.07%) occurred in the optimal activated carbon. Moreover, optimal activated carbon exhibited a highly porous structure with a specific surface area (SBET) of 1213.32 m2/g, total pore volume of 0.89 cm3/g and micropore surface area of 787.65 m2/g. Many industrial processes produce VOC pollutants that occur as multi-component systems. Therefore, investigation of comparative and competitive adsorption of VOCs is of practical and scientific importance. In this regard, in the second stage, comparative and competitive adsorption behaviours of benzene, toluene and xylene (BTX) vapor targeted as VOCs using optimal activated carbon in single-component, binary-component and ternary-component systems were elucidated. Compared to single-component system, in binary-component and ternary-component systems, depending on the initial concentration, BTX vapor exhibited highly different competitive adsorption capacity. Adsorption capacity of each component in multi-component systems is much less than that in single-component system. In addition, dynamic adsorption capacity of X-vapor onto optimal activated carbon in multi-component systems is higher than that of both B-vapor and T-vapor. These results may be attributed to the fact that adsorption selectivity of optimal activated carbon for X-vapor is higher than that for T-vapor and B-vapor. Also, the state of X-vapor > T-vapor > B-vapor observed in adsorption capacities in single-component, binary-component and ternary-component systems, can be explained by the competitive dominance of BTX vapor, binding energies of physisorption, molecular weights and methyl groups. The findings of this application will help to understand comparative and competitive adsorption behaviour between different VOC pollutants with respect to a specific adsorbent. Dynamic adsorption mechanism of BTX vapor onto optimal activated carbon was explained in detail by applying various kinetic and isothermal models to the experimental adsorption data. The BTX vapor removal processes that follow the reaction-based pseudo-first-order (PFO) kinetic model indicate the physical adsorption mechanism. In addition, based on evaluations of diffusion-based intra-particle diffusion and Boyd's film-diffusion kinetic models, it was concluded that the BTX vapor adsorption process was affected by the film-diffusion resistance (first stage) as well as the intra-particle diffusion resistance (after the BTX molecules diffuse through the gas film) until reaching equilibrium. Besides, overall mass transfer and film mass transfer factors were found to be higher than internal diffusion factor ([kLa]g > [kLa]f > [kLa]d) in BTX vapor adsorption, which showed that global mass transfer and film mass transfer were more effective than internal diffusion. In a cadmium sulfide (CdS) based solar cell, the CdS semiconductor plays a very important role as a sensitizer. It is of great importance to increase, with the support of activated carbon, photovoltaic efficiency of CdS based solar cells that are widely used in photovoltaic applications. Furthermore, activated carbon is included in the electrodes of photovoltaic devices as electro-conductive additives, and support for active materials. For these reasons, in the final stage, instead of undoped-doped CdS semiconductor materials that are frequently used in the literature, activated carbon supported CdS (CdS/activated carbon) and molybdenum (Mo)-doped CdS/activated carbon, lanthanum (La)-doped CdS/activated carbon and manganese (Mn)-doped CdS/activated carbon semiconductor materials of different concentrations (0.33%, 1% and 3% by weight) were produced through chemical precipitation using optimal activated carbon. The main objective of this application in the thesis was to determine how energy conversion efficiencies of undoped and doped CdS semiconductor materials varied in the presence of optimal activated carbon support material and interpret such observed effect in the light of literature. Produced pure CdS/activated carbon, Mo-doped CdS/activated carbon, La-doped CdS/activated carbon and Mn-doped CdS/activated carbon semiconductor materials were characterized by incident photon-to-current efficiency (IPCE), SEM, X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) measurements. The studies carried out under this application clearly revealed the ability to increase photovoltaic efficiency of CdS based solar cells that are widely used in photovoltaic applications with the support of activated carbon. This study presents a new strategy to clarify comparative and competitive dynamic adsorption mechanism in single, binary and ternary-component systems of BTX vapor targeted as VOCs using biowaste-based activated carbon through RSM optimization and to increase solar cell efficiency of semiconductor-based solar cell structures derived by using activated carbon supported CdS semiconductor materials.
In this study, the performance of activated carbon derived from de-oiled black cumin (Nigella Sativa L.) waste biomass through chemical activation with zinc chloride (ZnCI2) using response surface methodology (RSM), in both volatile organic compounds (VOCs) removal and photovoltaic applications was evaluated. To this end, in the first stage, activated carbon production process was optimized using central composite design (CCD), an approach of RSM, based on factors such as activation time (30-60 min), activation temperature (400-600 °C) and impregnation ratio (black cumin waste/ZnCI2, 50-150% by weight), and iodine number as the targeted response. Furthermore, these important factors that affect activated carbon production were defined by an analysis of variance (ANOVA). For production of activated carbon, an activation time of 57 min, activation temperature of 550 °C and impregnation ratio of 105% were found to be optimum values and a high iodine number of 1055 mg/g was achieved under these conditions. Surface properties of activated carbon produced under optimum conditions were characterized by various analytical techniques such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and Brunauer-Emmett-Teller (BET) surface area. The results showed that a significant amount of microporosity (53.93%) and mesoporosity (46.07%) occurred in the optimal activated carbon. Moreover, optimal activated carbon exhibited a highly porous structure with a specific surface area (SBET) of 1213.32 m2/g, total pore volume of 0.89 cm3/g and micropore surface area of 787.65 m2/g. Many industrial processes produce VOC pollutants that occur as multi-component systems. Therefore, investigation of comparative and competitive adsorption of VOCs is of practical and scientific importance. In this regard, in the second stage, comparative and competitive adsorption behaviours of benzene, toluene and xylene (BTX) vapor targeted as VOCs using optimal activated carbon in single-component, binary-component and ternary-component systems were elucidated. Compared to single-component system, in binary-component and ternary-component systems, depending on the initial concentration, BTX vapor exhibited highly different competitive adsorption capacity. Adsorption capacity of each component in multi-component systems is much less than that in single-component system. In addition, dynamic adsorption capacity of X-vapor onto optimal activated carbon in multi-component systems is higher than that of both B-vapor and T-vapor. These results may be attributed to the fact that adsorption selectivity of optimal activated carbon for X-vapor is higher than that for T-vapor and B-vapor. Also, the state of X-vapor > T-vapor > B-vapor observed in adsorption capacities in single-component, binary-component and ternary-component systems, can be explained by the competitive dominance of BTX vapor, binding energies of physisorption, molecular weights and methyl groups. The findings of this application will help to understand comparative and competitive adsorption behaviour between different VOC pollutants with respect to a specific adsorbent. Dynamic adsorption mechanism of BTX vapor onto optimal activated carbon was explained in detail by applying various kinetic and isothermal models to the experimental adsorption data. The BTX vapor removal processes that follow the reaction-based pseudo-first-order (PFO) kinetic model indicate the physical adsorption mechanism. In addition, based on evaluations of diffusion-based intra-particle diffusion and Boyd's film-diffusion kinetic models, it was concluded that the BTX vapor adsorption process was affected by the film-diffusion resistance (first stage) as well as the intra-particle diffusion resistance (after the BTX molecules diffuse through the gas film) until reaching equilibrium. Besides, overall mass transfer and film mass transfer factors were found to be higher than internal diffusion factor ([kLa]g > [kLa]f > [kLa]d) in BTX vapor adsorption, which showed that global mass transfer and film mass transfer were more effective than internal diffusion. In a cadmium sulfide (CdS) based solar cell, the CdS semiconductor plays a very important role as a sensitizer. It is of great importance to increase, with the support of activated carbon, photovoltaic efficiency of CdS based solar cells that are widely used in photovoltaic applications. Furthermore, activated carbon is included in the electrodes of photovoltaic devices as electro-conductive additives, and support for active materials. For these reasons, in the final stage, instead of undoped-doped CdS semiconductor materials that are frequently used in the literature, activated carbon supported CdS (CdS/activated carbon) and molybdenum (Mo)-doped CdS/activated carbon, lanthanum (La)-doped CdS/activated carbon and manganese (Mn)-doped CdS/activated carbon semiconductor materials of different concentrations (0.33%, 1% and 3% by weight) were produced through chemical precipitation using optimal activated carbon. The main objective of this application in the thesis was to determine how energy conversion efficiencies of undoped and doped CdS semiconductor materials varied in the presence of optimal activated carbon support material and interpret such observed effect in the light of literature. Produced pure CdS/activated carbon, Mo-doped CdS/activated carbon, La-doped CdS/activated carbon and Mn-doped CdS/activated carbon semiconductor materials were characterized by incident photon-to-current efficiency (IPCE), SEM, X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) measurements. The studies carried out under this application clearly revealed the ability to increase photovoltaic efficiency of CdS based solar cells that are widely used in photovoltaic applications with the support of activated carbon. This study presents a new strategy to clarify comparative and competitive dynamic adsorption mechanism in single, binary and ternary-component systems of BTX vapor targeted as VOCs using biowaste-based activated carbon through RSM optimization and to increase solar cell efficiency of semiconductor-based solar cell structures derived by using activated carbon supported CdS semiconductor materials.
Açıklama
Fen Bilimleri Enstitüsü, Kimya Mühendisliği Ana Bilim Dalı
Anahtar Kelimeler
Kimya Mühendisliği, Chemical Engineering
