Sürdürülebilir Yeşil Kampüs Koleksiyonu / Sustainable Green Campus Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7755
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Article Citation - WoS: 262Citation - Scopus: 286Dye Adsorption Behavior of Luffa Cylindrica Fibers(Elsevier Ltd., 2008) Demir, Hasan; Top, Ayben; Balköse, Devrim; Ülkü, SemraUsing natural Luffa cylindrica fibers as adsorbent removal of methylene blue dye from aqueous solutions at different temperatures and dye concentrations was investigated in this study. Thermodynamics and kinetics of adsorption were also investigated. The adsorption isotherms could be well defined with Langmuir model instead of Freundlich model. The thermodynamic parameters of methylene blue (MB) adsorption indicated that the adsorption is exothermic and spontaneous. The average MB adsorption capacity was found out as 49 mg/g and average BET surface area of fibers was calculated as 123 m2/g.Article Citation - WoS: 22Citation - Scopus: 26Thermodynamic Assessment of Gas Removal Systems for Single-Flash Geothermal Power Plants(Elsevier Ltd., 2009) Yıldırım Özcan, Nurdan; Gökçen Akkurt, GüldenGeothermal fluids contain non-condensable gases (NCGs) at various amounts. NCGs flow to a conventional geothermal power plant (GPP) with steam phase and should be withdrawn from the condenser by a gas removal system to prevent increase in condenser pressure and consequently decrease in power generation. Therefore, to remove NCGs from the system is critical especially at high NCG fractions. In this study, the net power output and specific steam consumption of a single-flash GPP is evaluated depending on the separator pressure, NCG fraction and wet bulb temperature of the environment, and three different conventional gas removal options which are two-stage steam jet ejector system, two-stage hybrid system and two-stage compressor system. A simulation code is written in EES to model the plant for each option. The model uses the data of Kizildere Geothermal Power Plant (KGPP) - Turkey, which is a single-flash plant with extremely high NCG fraction, to allow a comparison between the results of the modelling and the operational data of an actual single-flash GPP. Under given conditions, thermodynamic analysis resulted that NCG fraction is the most significant factor on GPP performance and the compressor system is the most efficient and robust option where the influence of the NCG fraction is limited.Article Citation - WoS: 44Citation - Scopus: 54Protection of Marble Surfaces by Using Biodegradable Polymers as Coating Agent(Elsevier, 2009) Ocak, Yılmaz; Sofuoğlu, Aysun; Tıhmınlıoğlu, Funda; Böke, HasanBiodegradable polymers have been replaced over the synthetic polymers in many applications due to their good properties such as reversibility and biodegradability. Therefore they allow new treatment on the surface of the material to be protected and they fulfil the principles generally accepted by the International Conservation Community of Historic Monuments and Buildings. In this study, the efficiency of four different biodegradable polymers as protective coatings on marble-SO2 reaction was investigated. The polymers used were zein, chitosan, polyhydroxybutyrate (PHB), and poly-l-lactide (PLA). The mineralogical composition, bulk density and porosity of uncoated marble were determined. The water vapor permeability, water absorption by capillary forces, surface wettability, and color alteration of uncoated and coated marbles were measured. For sulphation reaction, marble slabs were coated with these polymers and then they were exposed at nearly 8 ppm SO2 concentration at 100% relative humidity conditions together with uncoated ones in a reaction chamber for several days for testing their protection efficiency. The extent of reaction was determined by leaching of gypsum formed on the marble surfaces in deionized water and then determining the sulphate content by ion chromatography. The protection efficiency of polymer treatments was expressed as comparing the gypsum crust thickness of the coated and uncoated marble plates. The comparison among the polymers showed that the surface hydrophobicity, water capillary absorption and structure of polymer would be important factors affecting the protection efficiency. The use of high molecular weight PLA (HMWPLA) polymer on marble surfaces provided significant protection up to 60% which was indicated that HMWPLA polymer seems to be promising polymer as protective coating agent in reducing gypsum formation on marble surfaces in the polluted environment.Article Citation - WoS: 14Citation - Scopus: 15Neutralization of an Extremely Acidic Sludge and Stabilization of Heavy Metals in Flyash Aggregates(Elsevier Ltd., 2007) Polat, Mehmet; Güler, Erkan; Lederman, Eli; Cohen, HaimAn extremely acidic, heavy metal-rich sludge (pH = -1.2) was scrubbed with a Class-F fly ash in order to simultaneously neutralize the acidity and stabilize the heavy metals contained in both wastes. This paper outlines the leaching behavior of the aggregate material generated by scrubbing. For proper fly ash/sludge ratios, the fly ash acted as an outstanding neutralizer for the acidic waste. Leaching of heavy metals from the aggregate samples was below the environmental limits within a pH range between 3 and 9. Subsequent washing of the leached aggregate with acidic CALWET solutions did not result in an additional release of heavy metals. It is proposed that coordinative bonding of the metal cations onto neutral surface sites and electrostatic adsorption led to stabilization of the heavy metals within the aggregate structure below hydrolysis pHs.Article Citation - WoS: 33Citation - Scopus: 35Henry's Law Constant, Octanol-Air Partition Coefficient and Supercooled Liquid Vapor Pressure of Carbazole as a Function of Temperature: Application To Gas/Particle Partitioning in the Atmosphere(Elsevier Ltd., 2006) Odabaşı, Mustafa; Çetin, Banu; Sofuoğlu, AysunThe Henry's law constant for carbazole was experimentally determined between 5 and 35°C using a gas-stripping technique. The following equation was obtained for dimensionless Henry's law constant (H′) versus temperature (T, K):lnH′=-3982(T,K)-1+1.01 Temperature-dependent octanol-air partition coefficients (KOA) and supercooled liquid vapor pressures (PL, Pa) of carbazole were also determined using the GC retention time method. The temperature dependence of KOA and PL were explained by the following:logKOA=4076/(T,K)-5. 65logPL(Pa)=-3948(T,K)-1+11.84 The gas and particle-phase carbazole concentrations measured previously in Chicago, IL in 1995 was used for gas/particle partitioning modeling. Octanol based absorptive partitioning model consistently underpredicted the gas/particle partition coefficients (K p) for all sampling periods. However, overall there was a good agreement between the measured Kp and soot-based model predictions.Article Citation - WoS: 16Citation - Scopus: 18Kinematic Wave Model of Bed Profiles in Alluvial Channels(John Wiley and Sons Inc., 2006) Tayfur, Gökmen; Singh, Vijay P.A mathematical model, based on the kinematic wave (KW) theory, is developed for describing the evolution and movement of bed profiles in alluvial channels. The model employs a functional relation between sediment transport rate and concentration, a relation between flow velocity and depth and Velikanov's formula relating suspended sediment concentration to flow variables. Laboratory flume and field data are used to test the model. Transient bed profiles in alluvial channels are also simulated for several hypothetical cases involving different water flow and sediment concentration characteristics. The model-simulated bed profiles are found to be in good agreement with what is observed in the laboratory, and they seem theoretically reasonable for hypothetical cases. The model results reveal that the mean particle velocity and maximum concentration (maximum bed form elevation) strongly affect transient bed profiles.Article Citation - WoS: 50Citation - Scopus: 55Determination of Henry's Law Constants of Organochlorine Pesticides in Deionized and Saline Water as a Function of Temperature(Elsevier Ltd., 2006) Çetin, Banu; Özer, Serdar; Sofuoğlu, Aysun; Odabaşı, MustafaThe Henry's law constant (H) is an important parameter that is required to estimate the air-water exchange of semi-volatile organic compounds. Henry's law constants for 17 banned/restricted/currently used organochlorine pesticides (OCPs) were experimentally determined using a gas-stripping technique in deionized and saline water (3%) over a temperature range of 5-35 °C. H values (at 25 °C) ranged between 0.066±0.037 Pa m3 mol-1 (endosulfan II) and 62.0±24.2 Pa m3 mol-1 (heptachlor) in deionized water while the range in saline water was 0.28±0.03 Pa m3 mol-1 (γ-HCH) and 135.2±31.3 Pa m3 mol-1 (heptachlor). The increase in dimensionless Henry's law constants (H′) for OCPs over the studied temperature range was between 3 (γ-HCH)-19 times (chlorpyrifos) and 3 (endosulfan II)-80 times (trans-nonachlor) in deionized and saline water, respectively. The calculated enthalpies of phase change (ΔHH) were within the ranges previously reported for OCPs and other organic compounds (23.8-100.2 kJ mol-1). The salting-out constant, ks, ranged between 0.04 (γ-HCH) and 1.80 L mol-1 (endosulfan II) indicating the importance of assessing the H values of OCPs in saline water to accurately determine their partitioning and fate in seawater.Article Citation - WoS: 220Citation - Scopus: 234Determination of Octanol-Air Partition Coefficients and Supercooled Liquid Vapor Pressures of Pahs as a Function of Temperature: Application To Gas-Particle Partitioning in an Urban Atmosphere(Elsevier Ltd., 2006) Odabaşı, Mustafa; Çetin, Eylem; Sofuoğlu, AysunOctanol-air partition coefficients (KOA) for 14 polycyclic aromatic hydrocarbons (PAHs) were determined as a function of temperature using the gas chromatographic retention time method. log KOA values at 25° ranged over six orders of magnitude, between 6.34 (acenaphthylene) and 12.59 (dibenz[a,h]anthracene). The determined KOA values were within factor of 0.7 (dibenz[a,h]anthracene) to 15.1 (benz[a]anthracene) of values calculated as the ratio of octanol-water partition coefficient to dimensionless Henry's law constant. Supercooled liquid vapor pressures (PL) of 13 PAHs were also determined using the gas chromatographic retention time technique. Activity coefficients in octanol calculated using KOA and PL ranged between 3.2 and 6.2 indicating near-ideal solution behavior. Atmospheric concentrations measured in this study in Izmir, Turkey were used to investigate the partitioning of PAHs between particle and gas-phases. Experimental gas-particle partition coefficients (Kp) were compared to the predictions of KOA absorption and KSA (soot-air partition coefficient) models. Octanol-based absorptive partitioning model predicted lower partition coefficients especially for relatively volatile PAHs. Ratios of measured/modeled partition coefficients ranged between 1.1 and 15.5 (4.5±6.0, average±SD) for KOA model. KSA model predictions were relatively better and measured to modeled ratios ranged between 0.6 and 5.6 (2.3±2.7, average±SD).Article Determination of Henry's Law Constants of Organochlorine Pesticides in Deionized and Saline Water as a Function of Temperature(Elsevier Ltd., 2006) Çetin, Banu; Özer, Serdar; Sofuoğlu, Aysun; Odabaşı, MustafaThe publisher regrets that the second paragraph on p. 4545 was printed incorrectly. It now appears correctly, below. The presence of salts in aqueous solution affects the solubility of organic molecules, through the salting-out effect (Demou and Donaldson, 2002). The salting-out is defined as the decrease in aqueous solubility and increase in the activity coefficient observed for neutral non-polar compounds by dissolved inorganic salts. Ions in solution tightly bind several water molecules into hydration shells. This process (electrostriction), results in a reduction of the volume of the aqueous solution. A smaller aqueous volume results in less available water for cavity formation, and therefore less organic molecules are accommodated; their solubility decreases as a consequence (Schwarzenbach et al., 2002; Demou and Donaldson, 2002). The empirical relation for the effect of ionic strength on Henry’s law constant is described by Setschenow equation (Demou and Donaldson, 2002):Article Citation - WoS: 95Citation - Scopus: 114The Accelerating Effects of the Microorganisms on Biodeterioration of Stone Monuments Under Air Pollution and Continental-Cold Climatic Conditions in Erzurum, Turkey(Elsevier Ltd., 2006) Nuhoğlu, Yaşar; Ensar, Oğuz; Uslu, Hakan; Özbek, Ahmet; İpekoğlu, Başak; Ocak, İjlal; Hasenekoğlu, İsmetThe aim of this research was to determine the accelerating effects of microorganisms on the biodeterioration of stone under air pollution and continental-cold climatic region in Erzurum, Turkey. Studies have been carried out on specimens of the Rustempasa Bazaar, the Lalapasa Mosque, the Erzurum Castle Mosque, the Double Minarets-Madrasah, the Great Mosque and the Haji Mehmet Fountain aged from 441 to 823 years old. The results showed that vegetative and reproductive (generative) forms of the microorganisms could develop during the winter months when the night time average temperature was even - 25 °C. Also the reproductive forms had developed and the whole stone surface was covered with a biofilm caused by the microorganisms. Silicon, aluminum, calcium, potassium, titanium, magnesium, zinc, sulfur, iron, sodium, and niobium were found in the stones of the historical buildings with varying amounts through the SEM-EDS analysis. Some of these elements could be used as an energy resource for the microorganisms together with the air pollutants such as sulfur dioxide, nitrogen oxides and particles on the stone surfaces. Of 21 isolates, 15 species from 6 bacterium genera and 5 species from 5 fungi genera plus 1 fungi genera were identified on the deteriorated stone surfaces even during the coldest months by microbial identification system (MIS) and these findings were tested by SEM investigations.
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