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Öğe A comprehensive study on adsorption behavior of some azo dyes from aqueous solution onto different adsorbents(IWA Publishing, 2017) Kaya, NihanOne of the major environmental problems is the existence of dye materials in water sources. This pollutant must be removed from water by appropriate methods. Although most of these methods are efficient for the treatment of waters contaminated with dye pollutants, they are very costly and commercially unattractive. Adsorption is one of the most popular methods for the removal of dye pollutants from water especially if the sorbent is inexpensive. Sorbents are classified as natural sorbents, commercial sorbents, and the sorbents obtained from industrial and agricultural wastes. Although commercial activated carbon is widely used in wastewater treatment applications, it is very expensive. In this study, usability of inexpensive materials - sepiolite as a natural adsorbent, and walnut shell and hazelnut shell as agricultural wastes - was investigated instead of commercial activated carbon to remove some azo dyes (methyl red, methyl orange and methyl yellow) from aqueous solution. Batch experiments were carried out to determine the effect of different adsorption parameters such as pH, initial dye concentration, contact time, adsorbent dose and temperature. The equilibrium of adsorptions was modeled using Langmuir and Freundlich isotherm models. This comprehensive study showed that these alternative adsorbents had sufficient binding capacity to remove these azo dyes from water. © IWA Publishing 2017.Öğe Adsorption of Congo red from aqueous solution onto KOH-activated biochar produced via pyrolysis of pine cone and modeling of the process using artificial neural network(Springer Heidelberg, 2021) Kaya, Nihan; Yıldız Uzun, Zeynep; Altuncan, Ceren; Uzun, HarunMost of dyes cause various environmental and health problems due to their toxic, mutagenic, and even carcinogenic properties. Therefore, several treatment methods are used to remove dyes from wastewater. Adsorption is one of the most preferred methods due to its easy application and high efficiency. The aim of this study is to prepare and characterize KOH-activated pine cone (APC) biochar and use it as adsorbent for removal of anionic diazo dye, Congo red (CR) from aqueous solution. The various operating parameters such as pH, contact time, temperature, initial dye concentration, and adsorbent dosage are optimized in batch adsorption system. Experimental results showed that the prepared APC biochar has a surface area of 1714.5 m(2)/g and was achieved 94.62% CR removal efficiency at an adsorbent dosage of 2 g/L. The Freundlich, Langmuir, and Temkin adsorption models were used for the mathematical description of the adsorption equilibrium. Experimental data showed the best compatibility with the Freundlich isotherm. Batch adsorption models, based on the assumption of the pseudo first-order, pseudo second-order, and intra particle diffusion mechanisms, were applied to examine the kinetics of the adsorption. Kinetic data fitted the pseudo second-order kinetic model. Calculated thermodynamic parameters indicated the spontaneous, endothermic, and the increased randomness nature of CR adsorption. Structural and morphological changes of APC biochar after adsorption process were determined by using Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM) analysis. The prediction of the CR adsorption capacity of the APC biochar using artificial neural network (ANN) algorithm was modeled. For this purpose, many different ANN models have been developed. Among them, ANN10 gave the best results. According to ANN10 results, root-mean-squared error (RMSE), mean bias error (MBE), mean absolute error (MAE), and correlation coefficient (R-2) were estimated as 0.770, 0.310, 0.037, and 0.999, respectively. Consequently, the prediction results showed well agreement with experimental results.Öğe Alümina aerojellerin fiziksel özellikleri üzerine yaşlandırma ve kurutma süresinin etkisi(2018) Öz, Dilek Cantürk; Öz, Beytullah; Kaya, NihanDüşük yoğunluğa, yüksek gözenekliliğe ve çok iyi yalıtım kabiliyetine sahip olan aerojeller son yıllarda giderek önem kazanmış ve birçok alanda kullanım yeri bulmuştur. Dayanıklı ve çevre dostu malzemeler olmaları sebebiyle günümüzde yapılan çalışmalar aerojeller üzerine yoğunlaşmış olup, özellikle gözenek yapıları ve yüzey alanlarının geliştirilebilmesi için etkili yollar araştırılmaktadır. Bu çalışmada, oldukça viskoz alüminyum tri-sek-bütoksitin kontrollü hidrolizi ve sol-jel yöntemi ile hazırlanan alümina aerojellerin aseton banyosunda yaşlandırılma ve süper kritik şartlarda kurutma sürelerinin, jelin yapısal ve fiziksel özelliklerine etkisinin incelenmesi amaçlanmıştır. Hazırlanan aerojeller, metanol banyosunda en az 24 saat dinlendirildikten sonra 7 gün ve 30 gün olmak üzere iki farklı zaman periyodunda aseton banyosunda yaşlandırılmış ve bu süre içerisinde aseton banyosu en az dört kez değiştirilmiştir. Elde edilen alümina aerojeller süper kritik koşullarda 2 saat ve 4 saat boyunca farklı sürelerde kurutulmuştur. Bu işlem için süper kritik CO2 sıcaklığı 45oC ve basıncı 100 bar’dır. Aseton banyosundaki yaşlandırma süresi ve kurutma süresi değiştirilerek gerçekleştirilen sistematik çalışma ile farklı koşullarda hazırlanan aerojellerin karakterizasyonu, FT-IR, SEM ve çok noktalı BET analizleri ile gerçekleştirilmiştir. Deneysel sonuçlar göstermektedir ki, gerek yaşlandırma süresi gerekse kurutma süresi arttıkça, numunelerin yoğunluğu azalmıştır. Kurutma süresinden ziyade yaşlandırma süresinin yüzey alanının artmasında daha etkili olması sonucu en yüksek yüzey alanı değeri 30 gün yaşlandırma işlemi sonucu 825,614 m2/g olarak bulunmuştur. Yüzey alanının artmasıyla birlikte gözenek boyut ve dağılımında da iyileşmeler meydana gelmiştir. Farklı yaşlandırma ve kurutma şartlarında elde edilen ürünün kimyasal yapısında herhangi bir değişim olmamıştır.Öğe Artificial neural network approach for lead removal from aqueous solution by agricultural waste derived biochars(YILDIZ TECHNICAL UNIV, 2023) Kaya, Nihan; Erdem, FatmaLead (Pb2+) which is one of the most important heavy metals found in water sources, has a toxic effect on living things in aquatic environment. Therefore, the removal of Pb2+ ions from wastewater is very important if its concentration is above the determined discharge limits. Due to its advantage such as high efficiency, the adsorption process is a widely used successful technique for heavy metals removal from an aqueous solutions. On the other hand, determining the adsorption efficiencies of different adsorbents experimentally is both costly, and timeconsuming considering that there are large number of process variables. Therefore, ANN can be used to make theoretical predictions with high efficiency in this treatment process. In this study, modeling of Pb2+ removal from an aqueous solution by using biochars that produced by pyrolyzing of hazelnut, and walnut shell was studied at different adsorption conditions; pH (2.5-5), temperature (25-45oC), initial Pb2+ concentration (15-45 mg/L), adsorbent amount (1-3 g/L), and mixing speed (200-600 rpm). The purpose of modeling studies with ANN approach was to estimate lead ions removal (%) as an output. Inputs for ANN modeling approach were selected as pH, initial Pb2+ concentration, temperature, adsorbent dosage, and mixing speed. Experimental data were categorized 50:25:25 for two adsorption systems. Levenberg-Marquardt (LM) was preferred as a training function, and tansig was used as an activation function. The number of hidden neurons in the hidden layer was found by trial, and error. Values of correlation coefficient (R2 ), and Mean Square Error (MSE) were taken to be performance criteria of the ANN modeling. R2 values were found to be 97%, and 98% for biochars derived from walnut, and hazelnut shells, respectively. Results showed that ANN is an effective tool for modeling of adsorption system for the removal of lead ions from an aqueous solution. Additionally, different training algorithms such as Bayesian Regularization (BR), and Scaled Conjugate Gradient (SCG) were used to compare the prediction capability.Öğe Cam elyaf ile katkılandırılmış tarımsal atıklar kullanılarak üretilen lif levhaların (MDF) mekanik ve fiziksel özelliklerinin incelenmesi(Gazi Üniversitesi, 2018) Kaya, NihanOrman ve orman ürünleri, ülkelerin ekonomik kalkınmalarında önemli bir rol oynamaktadır. Özellikle mobilya sektörü malzeme ve ürün çeşitliliğinin yüksek olması sebebiyle ihracatını sürekli arttıran, yeniliklere açık bir sektördür. Ancak ormanlar gibi doğal kaynakların, tüketiminden sonra telafisi uzun zaman gerektirmektedir. Dolayısıyla bu kaynakların kullanımı ve ekonomiye kazandırılması en verimli şekilde olmalıdır. Bu kapsamda mobilya sektörünün ana hammaddesi olan masif ağaç malzemeler yerine ahşap esaslı kompozit malzemelerin kullanılması daha uygun olacaktır. Bu çalışmada, ülkemizde yıllık üretim miktarı oldukça yüksek olan ceviz kabuğu ve ayçiçeği sapı gibi tarımsal atıkların, orta yoğunlukta lif levhaların (MDF) üretiminde dolgu maddesi olarak kullanılabilirliği araştırılmıştır. Bağlayıcı olarak fenol formaldehit reçinesi kullanılan çalışmada, farklı oranlarda cam elyaf ile katkılandırılmış lif levhaların mekanik ve fiziksel özelliklerindeki değişimler incelenmiştir. Deneysel sonuçlar, lif levha üretiminde kullanılan selülozik yapıda odunsu hammadde türü ve miktarı ile reçine oranına bağlı olarak levhalarda fiziksel (% hacimsel genişleme ve % su tutma) ve mekanik (eğilme dayanımı, basma dayanımı, elastisite modülü, sertlik ve kesme kuvveti) özelliklerin değişkenlik gösterdiğini ancak üretilen çoğu levhada standartlarda istenilen değerlerin sağlandığını göstermiştir. Cam elyafın üretilen lif levhalarda mekanik dayanımı geliştirmesi ise cam elyaf ile katkılandırılmış tarımsal atıkların ekonomik açıdan üretimde değerlendirilmesinin mümkün olabileceğini ortaya koymuştur.Öğe Effect of carbon nanoparticles on the I V characteristics of dye doped nematic liquid crystal(Czech Society of Chemical Engineering, 2014) Akkurt, Fatih; Kaya, Nihan; Alıcılar, Ahmet[No abstract available]Öğe Fındık ve çeltik kabukları ve odun talaşı ile takviye edilmiş termoset kompozitlerde reçine türünün fiziksel özelliklere etkisi(Afyon Kocatepe Üniversitesi, 2017) Kaya, NihanEkonomik ve çevresel kaygılar sebebiyle son yıllarda mobilya sektörünün ana hammaddesi olan masif ağaç malzemeler yerine ahşap esaslı kompozit malzemelerin kullanılması tercih edilmektedir. Fındıkkabuğu ve çeltik kabuğu, ülkemizde henüz endüstriyel kullanıma girmemiş yenilenebilir doğal kaynaklardır. Çalışmanın amacı bu tarımsal atıkların ahşap kompozit panellerin üretimine uygunluğunu değerlendirmek ve kullanılan reçine türünün levhaların fiziksel ve mekanik özellikleri üzerine etkisini incelemektir. Bu çalışmada, iki tip reçine (fenol formaldehit (FF) ve melamin-üre formaldehit (MÜF)) kullanılarak levhalar üretilmiştir. Levhaların su tutma ve hacimsel genişleme gibi bazı fiziksel özellikleri ile eğilme dayanımı ve elastikiyet modülü gibi bazı mekanik özellikleri standart metotlara göre belirlenmiştir. Deneysel sonuçlar, levha üretiminde kullanılan selülozik yapıda odunsu hammadde türü ve miktarı ile reçine türüne bağlı olarak levhalarda fiziksel ve mekanik özelliklerin değişkenlik gösterdiğini ancak üretilen çoğu levhada standartlarda istenilen değerlerin sağlandığını göstermiştir. Gözlemlenen sonuçlar, melamin-üre formaldehit kullanılarak üretilen levhaların fenol formaldehit kullanılarak üretilen levhalara kıyasla nispeten düşük hacimsel genişleme ve su tutma değerleri verdiğini göstermiştir. Yani melamin-üre formaldehit reçinesi levhalarda suya dayanımı geliştirmiştir. Mekanik testler ise fenol formaldehit reçinesi ile üretilen levhaların daha yüksek eğilme ve iç bağ dayanım değerlerine sahip olduğunu göstermiştirÖğe Guest-host interaction of some chloroanthraquinone dyes doped in liquid crystalline matrix and effect of addition of carbon nanotube(2013) Şen, Eylem; Kaya, Nihan; Alıcılar, AhmetLiquid crystals (LCs) are commonly used in displays. For practical guest-host applications, it is important to choose dyes with a high ability of orientation in the liquid crystal matrix. In this work, two different nematic liquid crystals (E7 and ZLI-1132) were separately doped (1% m/m) with four different dyes (1-chloro, 2-chloro, 1,5-dichloro and 1,8-dichloro anthraquinone). Their solubilities, textures, phase transition temperatures and order parameters were determined. At the second stage, carbon nanotubes (CNTs) were added (0.05% m/m) to these solutions and the same parameters except solubilities were studied again. Although the solubilities of dyes in the liquid crystal ZLI-1132 were lower than those of E7, the order parameters were much higher. Addition of carbon nanotubes as dopant resulted in an increase in order parameter. Nematic/isotropic microphase separation in doped liquid crystal samples was detected by polarised microscopy. Determination of both phase transition temperatures and phase type was done by temperature dependent texture investigations between crossed polarisers. The dyes and CNTs did not significantly destabilise the mesomorphic phase of nematic hosts. When passing a phase transition, characteristic textures and structures changed with the temperature increasing and decreasing. The nematic-isotropic transition occurred in several pictures (textures). An appreciable change in textures was not observed with the addition of dopant(s) when compared with pure liquid crystal textures. © 2013 Elsevier B.V.Öğe Investigation of effectiveness of pine cone biochar activated with KOH for methyl orange adsorption and CO2 capture(Springer Heidelberg, 2021) Kaya, Nihan; Uzun, Zeynep YildizIn this study, pyrolysis of pine cone, a lignocellulosic biomass, was carried out in a fixed bed reactor. The biochar product obtained was activated by using chemical activation method. KOH was used as the activating agent with the impregnation ratio was 1/4. Activated pine cone biochars were characterized by using analysis techniques such as SEM, BET, and FT-IR. The usage potential of the activated biochar product with a surface area of 1714.5 m(2)/g has been investigated in two different application areas. As the first application area, the CO2 holding capacity of activated biochar was measured by using the thermogravimetric analysis method. The CO2 adsorption capacity of the activated biochar was determined as 160 mg/g (3.64 mmol/g) at 25 degrees C. As a second application area, the effectiveness of activated biochar product in the removal of dyestuff (methyl orange) from aqueous solutions was investigated. The methyl orange adsorption capacity of the activated biochar in optimum conditions (pH 2, temperature of 25 degrees C, initial concentration of 100 mg/L, adsorbent amount 0.8 g/L) was calculated as 109.5 mg/g. Isotherm modeling and kinetic investigations showed that Freundlich and pseudo-second-order models describe the adsorption equilibrium and kinetic behavior well. As a result, this type of biomass could be successfully evaluated in removing both methyl orange dye, which is a potential pollution risk for aquatic environment, and CO2 that is responsible for climate change and greenhouse effect in the atmosphere.Öğe Investigation of effectiveness of pyrolysis products on removal of alizarin yellow GG from aqueous solution: a comparative study with commercial activated carbon(Iwa Publishing, 2020) Kaya, Nihan; Yildiz Uzun, ZeynepThe increasing use of dyestuff in industrial applications brings with it environmental problems. These dyes, which are an eco-toxic hazard, are common water pollutants, even at very low concentrations in water resources. Therefore, they must be removed in an economical way. In this study, low-cost biosorbents such as pine cone char, walnut shell char, and hazelnut shell char were prepared by pyrolysis process at different carbonization temperatures in the range of 400-700 degrees C. Biochars with the highest surface area were used to remove alizarin yellow GG from aqueous solution and the adsorption capacities of these materials were compared to commercially available activated carbon. Biomasses and prepared biochars were characterized using Fourier transform infrared spectroscopy, thermogravimetric/differential thermogravimetry analysis, Brunauer-Emmett-Teller (BET), scanning electron microscopy/energy dispersive X-ray spectroscopy, partial and elemental analysis techniques. Operational parameters such as contact time, temperature, pH, adsorbent dosage, and initial dye concentration were considered as variables for the batch adsorption experiments. Among the biochars used, the highest adsorption efficiency (82%) was obtained in pine cone char (BET surface area 259.74 m(2)/g) at pH = 3, T = 45 degrees C, adsorbent dosage of 8 g/L, and initial dye concentration of 20 ppm. The adsorption mechanism has been investigated by applying different kinetic and isotherm models with the aid of time-dependent adsorption data. The adsorption process was best described by Langmuir isotherm and pseudo-second order kinetic model.Öğe Kinetic and thermodynamic studies on the adsorption of Cu2+ ions from aqueous solution by using agricultural waste-derived biochars(Iwa Publishing, 2020) Kaya, Nihan; Arslan, Ferhat; Uzun, Zeynep Yildiz; Ceylan, SelimIn this study, it was aimed to investigate the adsorption properties of the biochars obtained by pyrolysis of hazelnut and walnut shells for removal of copper ions from aqueous solutions. The characterization of raw biomasses and also biochars were performed using TGA-DTG, FT-IR, BET, SEM, partial and elemental analysis techniques. The optimum conditions were determined by investigating the effect of adsorption parameters (initial concentration, temperature, adsorbent amount, pH, contact time and mixing speed) for efficient removal of copper ions from aqueous solution by batch adsorption experiments carried out under different conditions. The highest adsorption efficiencies were recorded as 82 and 86% respectively for hazelnut and walnut shell biochars at pH 4, C-o = 15 ppm, adsorbent dosage = 3 g/L and mixing speed = 600 rpm. Experimental results showed that the adsorption efficiency for copper ions increased with the increase of temperature (T = 45 degrees C) in studies only using biochar obtained from hazelnut shell. While the time of equilibrium in the aqueous solution containing copper ions was determined to be 75 min for walnut shell char, this duration was 30 min for hazelnut shell char. The experimental results were investigated in terms of Langmuir, Freundlich and Temkin isotherm models. Together with the calculated thermodynamic parameters, the adsorption mechanism was explained. In order to determine the kinetic model of the adsorption process, the experimental data were applied to pseudo first-order, pseudo second-order and intra-particle diffusion models, and the model constants were investigated.Öğe Light-scattering determination of visco-elastic and electro-optic parameters of azo and anthraquinone dye-doped liquid crystal molecules and consistent neural network empirical physical formula construction for scattering intensities(2011) Yıldız, Nihat; Polat, Ömer; San, Sait Eren; Kaya, NihanIn this paper, we achieved two aims. Firstly, laser light-scattering intensities in methyl red (MR) azo and disperse red (DR) anthraquinone dye-doped nematic liquid crystal (NLC) molecules were measured versus scattering angle and applied bias voltage. The following three NLC molecular structure parameters were determined: the visco-elastic constant ratios K11/K 22 and K33/K22 by data-regression and Freedericksz voltages from the graphs drawn. All these NLC parameters were found to be dependent on the kind of the dye used. As the second aim, by nonlinear universal function approximator layered feedforward neural network (LFNN), we constructed explicit form of empirical physical formulas (EPFs) for theoretically unknown nonlinear azo and anthraquinone dye-doped NLC scattering intensity functions. Excellent LFNN test set (i.e. yet-to-be measured experimental data) predictions prove that the constructed LFNN-EPFs estimate unknown intensity functions consistently. The LFNN-EPFs, too, confirmed the dependency on the kind of dye used. In conclusion, physical laws embedded in the scattering data can be consistently extracted by LFNN. One significant potential application in molecular nonlinear optics domain is that these LFNN-EPFs, by various mathematical tools such as differentiation, integration, and minimization, can be used to obtain further NLC scattering intensity knowledge related molecular structural parameters. Such knowledge in turn may prove useful in developing new optical materials. © 2011 Elsevier B.V. All rights reserved.Öğe Phase transitions and molecular orientation in nematic liquid crystals doped with blue-red dye mixtures and carbon nanotubes(2013) Alıcılar, Ahmet; Kaya, Nihan; Akkurt, FatihPhase transitions and molecular orientation in nematic liquid crystals (E7, E8, E63 and ZLI-1132) doped with blue dye (disperse blue 1, 3, 14 or 134) and blue 14 + red dye (disperse red 1, 60 or methyl red) mixtures were studied. At the second stage, effects of single-walled carbon nanotubes (SWCNTs) added to them were determined. When blue-red dye mixtures were doped into the liquid crystals, an increase in order parameter was observed compared to those of single dyes and a value of 0.70 was attained. The addition of carbon nanotubes resulted in very higher values of order parameter (Smax = 0.79). To determine the threshold value of order parameter for saturation, the experiments were repeated in various DC voltages. The threshold voltage was significantly reduced with addition of CNTs. With addition of dopants, an appreciable change in textures was not observed. Shifts in phase transition temperatures were in limitations required. Copyright © Taylor & Francis Group, LLC.Öğe Preparation and Characterisation of Biochar from Hazelnut Shell and Its Adsorption Properties for Methylene Blue Dye(2018) Kaya, Nihan; Yıldız, Zeynep; Ceylan, SelimOne of the major pollutants in water resources are organic dyes that are widely used by different industries. Methylene blue (MB) is one of them which is quite harmful for aquatic life. This pollutant must be removed with proper methods. Adsorption is one of the most popular methods because of its high purification yield and known as a cost effective process if the sorbent is inexpensive. In this study, biochar which is used as an adsorbent has been produced from hazelnut shells used as the raw material. Chemical, thermal and surface characteristics of raw hazelnut shell were investigated by FT-IR, TG/DTG, SEM and elemental analysis. Biochar characteristics were determined by FT-IR, BET and SEM analysis. The effect of different adsorption parameters such as pH, initial dye concentration, contact time, adsorbent dosage and temperature on the adsorption of MB onto hazelnut shell char were examined in batch experiments. The equilibrium of adsorption was modeled using Langmuir and Freundlich isotherm models. The maximum adsorption yield of MB was found to be 83% at pH 4.0, adsorbent dosage of 4 g/L, contact time of 300 min., initial dye concentration of 15 mg/L and temperature of 45 oC. In addition, the Freundlich isotherm was found to be the best fitting isotherm model for the adsorption process. The pseudo-first-order and pseudo-second-order kinetic models were applied to the experimental data and thermodynamic parameters such as Gibbs free energy, enthalpy and entropy were determined.Öğe Production and characterization of carbon-based adsorbents from waste lignocellulosic biomass: their effectiveness in heavy metal removal(Taylor & Francis Inc, 2020) Kaya, Nihan; Arslan, Ferhat; Yildiz Uzun, ZeynepIn this study, hazelnut shell and walnut shell which are the agricultural wastes existent abundantly in many countries were pyrolyzed at different temperatures in the temperature range of 400-700 degrees C in order to optimize the physicochemical properties of biochars. The biochars with large surface area were used to removal of lead (Pb2+) ions, one of the most important heavy metal pollutant, from aqueous solutions. The characterization of raw biomass and also biochars produced by pyrolysis were performed using FT-IR, BET, SEM, partial and elemental analysis techniques. In order to determine the adsorption characteristics of both biochars, batch adsorption experiments were carried out under different experimental conditions. The optimum conditions were determined by investigating the effect of adsorption parameters (initial heavy metal concentration, temperature, adsorbent amount, pH, contact time and mixing speed) for efficient removal of Pb2+ ions from aqueous solution. The experimental results were investigated in terms of Langmuir, Freundlich and Temkin isotherm models. Together with the calculated thermodynamic parameters, the adsorption mechanism was tried to be explained. In order to determine the kinetic model of the adsorption process, the experimental data were applied to pseudo first-order, pseudo second-order and intra-particle diffusion model, and the model constants were investigated.Öğe Pyrolysis and optimization of chicken manure wastes in fluidized bed reactor: CO2 capture in activated bio-chars(Elsevier, 2019) Yildiz, Zeynep; Kaya, Nihan; Topcu, Yildiray; Uzun, HarunIn this study, the Response Surface Methodology (RSM) based on Central Composite Design (CCD) was used to determine the optimization of bio-char production from chicken manure wastes. The effects of temperature, heating rate and reaction time on pyrolysis of chicken manure waste were investigated in the fluidized bed reactor. Operation conditions were selected between the reaction temperatures was 200-500 degrees C, the heating rate was 5-20 degrees C/min and the reaction time was 30-120 min. The optimum condition was determined using the surface area results of the bio-chars. As a result of the optimization studies, it was determined that the temperature should be 400 degrees C, the heating rate should be 5 degrees C/min and the reaction time should be 110 min in order to obtain bio-char with highest surface area. Bio-char obtained in optimum condition in fluidized bed reactor was subjected to chemical activation with KOH and HCl, respectively. The CO2 adsorption capacity of raw and activated bio-char products was determined as 48.7, 76.8 and 85.7 mg/g at 25 degrees C using thermogravimetric analysis method, respectively. As a result, it has been found that the activated bio-chars are effective adsorbents for CO2 storage and it has been demonstrated that it is possible to evaluate chicken manure wastes for removing environmental pollutant in an economical way. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.Öğe Removal of Congo Red and Rhodamine B dyes from aqueous solution using unmodified and NH3/HCl-modified wood charcoal: a kinetic and thermodynamic study(Taylor & Francis Inc, 2021) Kaya, NihanIn recent years, color removal processes from industrial wastewater which contains dyestuffs have gained great importance. Especially, textile industry wastewater with high volume and variable composition comes first among these wastewaters. These waters bring along many ecological and esthetic problems. In this study, unmodified and acid/base-modified wood charcoal derived from oak wood has been utilized as an eco-friendly adsorbent for removal of anionic dye Congo Red (CR) and cationic dye Rhodamine B (RhB) from aqueous solution. The characterization of raw charcoal was performed using FT-IR, BET and SEM/EDS analysis. The optimum conditions were determined by investigating the effect of adsorption parameters (initial dye concentration, temperature, adsorbent amount, pH and contact time) for efficient removal of dye molecules from aqueous solution by batch adsorption experiments carried out under different conditions and the experimental results were investigated in terms of Langmuir and Freundlich isotherm models. Together with the calculated thermodynamic parameters, the experimental data were applied to pseudo first order, pseudo second order, intra-particle diffusion, Boyd kinetic models and the adsorption mechanism was tried to be explained. The highest removal efficienciency of CR and RhB was achieved as 98% and 92%, respectively. As a result of this study, in which the effectiveness of modified and unmodified adsorbents was compared, it was determined that CR dye was removed at higher efficiency with HCl-modified charcoal. On the other hand, the RhB dye was better removed with NH3-modified charcoal.Öğe Sol-jel yöntemiyle üretilen alümina alkojelin fizikokimyasal ve yapısal özellikleri üzerine kurutma türünün etkisi(Gazi Üniversitesi, 2020) Cantürk Öz, Dilek; Kaya, NihanÜstün termal ve mekanik özellikleri sebebiyle başta uzay teknolojisi olmak üzere pek çok alanda kullanılmakta olan alkojeller, düşük yoğunluğa ve yüksek gözenekliliğe sahip süper yalıtkan ve çevre dostu malzemeler olarak bilinmektedir. Genel olarak inorganik tuzlar ya da metal alkoksitlerin hidrolizi ve kondenzasyonu olarak bilinen sol-jel tekniği kullanılarak, üç aşamada üretilmektedirler. Son aşama hazırlanan ıslak jellerin kurutulması olup, ıslak jelin gözenekliliği ve jel ağının korunması için en uygun kurutma tekniğinin seçilmesi büyük önem arz etmektedir. Bu çalışmada, sol-jel yöntemiyle sentezlenen alümina alkojellerden süperkritik şartlarda, atmosfer basıncında ve dondurarak olmak üzere üç farklı kurutma koşullarında elde edilen gözenekli malzemelerin fizikokimyasal ve yapısal özellikleri XRD, TGA/DSC, FT-IR ve BET analizleri ile karakterize edilmiştir. Farklı kurutma koşullarında aerojel, kriyojel ve ambijel ismini alan amorf yapıya sahip bu jellerin fizikokimyasal özellikleri ve ısısal davranışlarındaki değişimler dikkate alındığında, ıslak jellerin kurutulmasında en uygun kurutma tekniğinin ön işlem yapılmadan dondurarak kurutma olduğu sonucuna ulaşılmıştır.Öğe Sol-Jel Yöntemiyle Üretilen Alüminanın Fizikokimyasal Ve Yapısal Özellikleri Üzerine Kalsinasyon Sıcaklığının Etkisi(2020) Kaya, Nihan; Öz, Dilek CantürkAlümina; sert, kimyasal olarak inert, yüksek erime noktasına sahip, oksidasyona, korozyona, termal ve mekanik şoklara ve aşınmaya karşı yüksek direnç gösteren bir malzeme olduğu için başta seramik endüstrisi olmak üzere elektronik, kozmetik ve sağlık gibi pek çok endüstride geniş uygulama alanı bulmaktadır. Günümüzde, teknolojinin gelişmesiyle ve üretimin artmasıyla birlikte alüminanın kullanım alanları da her geçen yıl artış göstermektedir. Üstün fiziksel ve teknik özellikleri sebebiyle endüstriyel açıdan önemli bir mineral olan alümina, genellikle boksit cevherinden Bayer prosesi ile üretilmekte ve cevherden üretim nedeniyle de safsızlıklar barındırabilmesi önemli bir sorun teşkil etmektedir. Bu çalışmada, sol-jel yöntemiyle sentezlenen alümina kriyojelin 600-1300 oC aralığında farklı sıcaklıklarda kalsine edilmesiyle, endüstriyel alanda geniş bir kullanım alanına sahip alümina formuna dönüştürülmesi amaçlanmıştır. Elde edilen ürünlerin karakterizasyonu FT-IR, BET, SEM, XRD, TGA/DTA ve DSC analizleri ile yapılmış ve alüminanın fizikokimyasal özellikleri ile faz geçişleri incelenerek, kalsinasyon sıcaklığının son ürünün yapısal özellikleri üzerine etkisi belirlenmiştir.Öğe The orientational behaviour of some aminoanthraquinone dyes in E8 and ZLI-1132 nematic solvents and effect of addition of carbon nanotubes(2011) Kaya, NihanGuest-host liquid crystal displays have been widely utilised because of their many advantages such as colour, wide viewing angle and high brightness. For practical guest-host applications, it is important to choose dyes with a high ability of orientation in the liquid crystal matrix. In this work, two different nematic liquid crystals (E8 and ZLI-1132) were separately doped with three different dyes (1,2-, 1,4- and 2,6-diaminoanthraquinone). Their solubilities, textures, phase transition temperatures and order parameters were determined. At the second stage, single-walled carbon nanotubes (CNTs) were added (0.05% m/m) to these solutions and the same parameters (except solubilities) were studied again. The highest solubility and order parameter values were attained with 1,4- diaminoanthraquinone dye in ZLI-1132 nematic host. When CNTs in a small amount were added to the dye mixtures as co-dopant, the further increases in order parameters (S) were observed in mixtures with low S values. These dyes and CNTs did not significantly destabilise the mesomorphic phase of nematic hosts. An appreciable change in textures was not observed with addition of dopant(s). © 2011 Taylor & Francis.
