Sürdürülebilir Kalkınma Amaçları
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- ArticleAçık Erişim2012Preparation of PEO/Clay Nanocomposites Using Organoclay Produced via Micellar Adsorption of CTAB
Gürses, Ahmet; Ejder-Korucu, Mehtap; Doǧar, Çetin
The aim of this study was the preparation of polyethylene oxide (PEO)/clay nanocomposites using organoclay produced via micellar adsorption of cethyltrimethyl ammonium bromide (CTAB) and their characterisation by X-ray diffraction (XRD), and Fourier transform infrared (FT-IR) spectra, and the investigation of certain mechanical properties of the composites. The results show that the basal distance between the layers increased with the increasing CTAB/clay ratio as parallel with the zeta potential values of particles. By considering the aggregation number of CTAB micelles and interlayer distances of organo-clay, it could be suggested that the predominant micelle geometry at lower CTAB/clay ratios is an ellipsoidal oblate, whereas, at higher CTAB/clay ratios, sphere-ellipsoid transition occurs. The increasing tendency of the exfoliation degree with an increase in clay content may be attributed to easier diffusion of PEO chains to interlayer regions. FT-IR spectra show that the intensity of Si-O stretching vibrations of the organoclays (1050 cm -1) increased, especially in the ratios of 1.0 g/g clay and 1.5 g/g clay with the increasing CTAB content. It was observed that the mechanical properties of the composites are dependent on both the CTAB/clay ratios and clay content of the composites.
RDL Kalıcı Kaydıİncele - Conference ObjectYalnız künye2012Biosorption of CR (VI) onto pseudevernia furfuracea /aqueous solution interface
Gürses, Ahmet; Özkan, Esra; Doǧar, Çetin
This study addresses the removal of a heavy metal, Cr (VI), from aqueous solutions by using dried Psedeuvernia furforcea biomass as biosorbent. The effects of factors, such as the initial chromium concentration, contact time, temperature, biosorbent dosage and mixing rate on biosorption of the heavy metal was investigated. Furthermore, the fitting of adsorption data on Langmuir, Freundlich, BET, Temkin, Redlich-Peterson, Henderson, Smith, Halsey and Harkins-Jura adsorption isotherm models was investigated. In order to explain the metal-functional group binding mechanisms, FTIR analysis was carried out. The sorption equilibrium time was determined to be 8 hours. The amount of Cr (VI) adsorbed onto Psedeuvernia furforcea increased with increasing sorbent dosage and increasing temperature indicating endothermic nature of biosorption process. The results suggest that the physical interactions between sorbent particles and sórbate ions play an important role for the adsorption of Cr (VI) onto the biosorbent. It was found that the biosorption data of Cr (VI) by Psedeuvernia furforcea biomass were fit on the Freundlich adsorption isotherms at 293, 313, and 333K. From the experimental results, it can be concluded that Psedeuvernia furforcea can be used as an economical sorbent in the removal of these heavy metal ions.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2010Thermodynamics and kinetic studies of biosorption of a basic dye from aqueous solution using green algae Ulothrix sp.
Doǧar, Çetin; Gürses, Ahmet; Açikyildiz, Metin; Özkan, Esra
This study addresses removal of a basic dye, methylene blue, from aqueous solutions by using dried Ulothrix sp. biomass as biosorbent. The effects of the initial dye concentration, contact time, temperature, solution equilibrium pH, biosorbent dosage, and mixing rate on biosorption of the dye have been investigated. It was found that 30 min is sufficient in order to reach adsorption equilibrium. The amount of methylene blue adsorbed onto Ulothrix sp. increased with increasing equilibrium pH and mixing rate, in contrary, it decreased with increasing temperature and sorbent dosage. The process followed the pseudo-second-order kinetic model. The isosteric enthalpy and entropy values were calculated as -11.8 kJ/mol and 37.5 J/(mol K), respectively. In addition, the results suggest that the physical interactions between sorbent particles and sorbate ions play an important role for the adsorption of methylene blue onto the biosorbent.
RDL Kalıcı Kaydıİncele - Conference ObjectAçık Erişim2010Measurement of secondary school student's test-anxiety levels and investigation of their causes
Gürses, Ahmet; Kaya, Özgür; Doǧar, Çetin; Günes, Kübra; Yolcu, H. Hasan; Keser, H; Ozcinar, Z; Kanbul, S
Test anxiety is concerned about a large portion of our society (students, family environment). The portion affected from the test anxiety is increasing year by year. Test anxiety is not related with studying or studying much. The idea that studying much and getting new knowledge cause anxiety and stress is common. A student being tired by studying much can rest after a brief relaxation and exercise. What creates the anxiety is the fear of being unsuccessful and the thought that is the end of some values because of the failure. Determination of students' test anxiety is very important for the success in applied teaching activities. In this study intending to determine secondary school students' test anxiety, test anxiety scale and data collected from interviews were evaluated from the view of gender, class grades and enrolled educational institutions. After the analyses gained by descriptive statistical techniques and One-Way ANOVA, it was found that the students had mid-level test anxiety, and girls had higher test anxiety level than boys.
RDL Kalıcı Kaydıİncele - Conference ObjectAçık Erişim2010An investigation on teachers to whom positive attitudes were developed by students
Gürses, Ahmet; Çamuroǧlu, Tuba; Açikyildiz, Metin; Doǧar, Çetin; Keser, H; Ozcinar, Z; Kanbul, S
In this study, it is aimed to analyze the effects of out of school activities of teachers to whom positive attitudes were developed by the students in instructional process and heir some personal features on developed attitude. For this aim, semi-structured interviews were applied to 80 students and 10 teachers working in three different high schools under the authority of Erzurum Directorate of National Education in the first semester of the academic year 2009-2010. After the analyses of gained data, it was found that teachers' personal features are much more effective than their professional knowledge in the process of developing positive attitudes.
RDL Kalıcı Kaydıİncele - Conference ObjectAçık Erişim2010Science and social science teacher's attitudes towards project studies
Gürses, Ahmet; Tutar, Zafer A.; Doǧar, Çetin; Mindivan, Ferda; Açikyildiz, Metin; Gözöm, Seda; Keser, H; Ozcinar, Z; Kanbul, S
This study aims to determine the ideas about project and project studies of teachers working at social and science branches of high schools. To accomplish this, a survey including twenty-five items about project attitudes scale and personal information was administrated to 10 social branch teachers and 15 science branch teachers working in Erzurum, Turkey. Studies of frequency, arithmetic mean, percentage, t-test and ANOVA techniques were used to analyze the obtained data. The results show that teachers are more optimistic in social branches towards project and project studies than those working in science branches. In addition, there is no statistically meaningful relationship among science and social science teachers' approaches to project studies, teachers' experiences, academic careers and project attendance. Finally, with results, suggestions on the effective usage of project studies are given.
RDL Kalıcı Kaydıİncele - Conference ObjectAçık Erişim2010The investigation of harmony between teacher's thoughts on nature of learning and their applied teaching activities in teaching and learning process
Gürses, Ahmet; Çaǧlayan, Dilek; Doǧar, Çetin; Yolcu, H. Hasan; Korucu, Mehtap Ejder; Köktepe, Sevda
This study is carried out in order to determine what a relation between different branch teachers' thoughts on nature of learning and these teachers' applied teaching activities in school exists. For this aim, observation rapports as data gathering instrument were created in order to assign teachers' teaching methods. Therefore, an interview was prepared to find out the thoughts about nature of learning. The observations and interviews were applied to 15 teachers working at different branches of different high schools like Ziya Gökalp High School, Nevzat Karabaǧ Anatolian Teacher Training High School, Erzurum High School, Nenehatun Girls High School, Cumhuriyet High School, Kazim Karabekir Industrial Vocational High School, 3 Temmuz High School, İMKB High School, Atatürk High School, Rifki Salim Burçak Girls Vocational High School and Atatürk Industrial Vocational High School which are under the authority of Erzurum Directorate of National Education. After the analyses of data, it was found that there is no harmony between teachers' thoughts on nature of learning and their teaching methods chosen in teaching and learning processes.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2007Adsorption studies on the treatment of textile dyeing effluent by activated carbon prepared from olive stone by ZnCl2 activation
Uǧurlu, Mehmet; Gürses, Ahmet; Doǧar, Çetin
This study aimed to investigate the removal of a reactive dye from aqueous solution by adsorption. Activated carbon prepared from olive stone, an agricultural solid by-product, was used as adsorbent. Different amounts of activating agent (ZnCl2) and adsorbent particle size were studied to optimise adsorbent surface area. The adsorption experiments were conducted at different process parameters such as adsorbent dose, temperature, equilibrium time and pH. The experimental results showed that at equilibrium time 120 min, optimum pH ranged between 3 and 4, and adsorbent dosage was 2.0 g 200 ml-1. While the kinetic data support pseudo-second order, a pseudo-first order model shows very poor fit. Adsorption isotherms were obtained at three different temperatures (288, 298 and 308 K). The fitness of adsorption data to the Langmuir and Freundlich isotherms was investigated. In addition, the thermodynamic parameters such as isosteric enthalpy of adsorption (ΔHads)y, isosteric entropy of adsorption (ΔSads)y and free energy of adsorption ΔG0 ads were calculated. BET surface area measurements were made to reveal the adsorptive characteristics of the produced active carbon. The surface area of the activated carbon produced with 20% w/w ZnCl2 solution was 790.25 m2 g-1.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2006An investigation on effects of various parameters on viscosities of coal-water mixture prepared with Erzurum-Aşkale lignite coal
Gürses, Ahmet; Açikyildiz, Metin; Doǧar, Çetin; Karaca, Semra; Bayrak, Ramis
In this study the effects of parameters such as coal loading (wt.%), the initial pH of mixture, the addition of various electrolytes, surfactants and temperature on the viscosity and rheologic parameters of coal-water mixture (CWM) have been investigated. The apparent viscosity was measured with a RV8-Brookfield rotating type viscosimeter. The additives used were AlCl3 and K2HPO4 as the electrolytes and Cetyltrimethyl Ammonium Bromide (CTAB), Sodium Dodecyl Sulphate (SDS) and Borrosperse NA-3A as the surfactants. It was found that the most effective additives, in terms of the viscosity reduction, were CTAB and K2HPO4, and that the CWM which had coal concentrations up to 50% (based on the weight of dry coal) could be prepared by using each additives. In addition, the viscosities of CWM with increasing temperature were found to increase at low speed, and decrease at high speed.
RDL Kalıcı Kaydıİncele - Conference ObjectYalnız künye2005Effect of temperature for the adsorption of methylene blue onto activated carbon produced from waste dogrose seeds
Gürses, Ahmet; Doǧar, Çetin; Açikyildiz, Metin; Özkan, Esra; Bayrak, Ramis
Activated carbon, produced from dogrose (Rosa section Caninae) seeds, was used for the removal of methylene blue (basic dye). Adsorption studies were carried out at 20°C and 40°C at various initial dye concentrations (20, 40, 60, 80, and 100 mg/L) and at different lengths of time (15, 30, 60, and 120 min). Adsorption isotherms of the basic dye on the prepared adsorbent were determined and correlated with common isotherm equations. Fitting of the isotherm data to the BET adsorption isotherm model was better in high concentration ranges than in the other models. Thermodynamic parameters such as change in isosteric adsorption enthalpy (ΔH)y and isosteric adsorption entropy (ΔS)y were also determined to 40.8 kJ and 0.141 kJ, respectively. It was concluded that the adsorption of methylene blue increases with increasing temperature. BET model fitting indicates that the hydrophobic interactions between the dye and the produced active carbon at the first layer and the dipole-dipole interactions between methylene blue molecules and the adsorbed molecules at the secondary layer predominate. To investigate the adsorptive characteristics of the produced active carbon, porosity and BET surface area measurements were made.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2003Investigation on settling velocities of aluminium hydroxide-dye flocs
Gürses, Ahmet; Yalçm, Mehmet; Doǧar, Çetin
The settling velocity of flocculated materials is one of the most important factors for the appropriate design and the effective operation of wastewater treatment plants. In this study, the effect of some variables, such as settling temperature and Ph, concentrations of a cationic surfactant and an electrolyte on the settling velocity of aluminium hydroxide-dye flocs have been investigated. The aluminium hydroxide was produced by dissolving metallic aluminium under high temperature in alkaline medium. The dyestuff chosen for this study is a reactive textile dye, Remazol Red RB. Cationic surfactant (CTAB) and electrolyte (NaCl) were used as settling aids. The experimental results showed that the settling velocity generally increased with the increasing settling temperature, Ph and dye concentration. By using the experimental data related to the temperature an empirical equation was developed and the Ea values for the settling process of the flocs with dye and without dye were determined as 20.40 kJ and 14.17 Kj, respectively.
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