Synthesis, characterization and Cr(VI) adsorption properties of modified magnetite nanoparticles

In this study, magnetite (Fe 3 O ) nanoparticles were synthesized by chemical co-precipitation method, coated with silica, and then the surface of silica coated magnetite (Fe 4 3 O 4 @SiO ) nanoparticles was modified with (3aminopropyl)triethoxysilane (APTES) at first. Secondly, attained nanoparticles were characterized by the Fourier transform infrared, X-ray diffraction, transmission electron microscopy, the Brunauer–Emmett–Teller, vibrating sample magnetometer, and zeta-sizer devices/methods. Finally, detailed adsorption experiments were performed to remove hexavalent chromium (Cr(VI)) from aqueous media by synthesized nanoparticles. Mean size and specific surface area of synthesized nanoparticles were about 15 nm and 89.5 m 2 2 /g, respectively. The highest adsorption capacity among used adsorbents (Fe 3 O 4 , Fe 3 O 4 @SiO 2 , Fe 3 O 4 @SiO 2 @L) was attained by Fe nanoparticles and it was determined that adsorption capacity of the other two adsorbents was too low when compared to the Fe nanoparticles. Optimum conditions for Cr(VI) adsorption by Fe 3 O nanoparticles were: pH, 3; temperature, 55 4 C; contact time, 90 min; adsorbent concentration, 0.5 g/l and initial Cr(VI) concentration 10 mg/l. Under these conditions, adsorption capacity and removal percentage of Cr(VI) were found to be 33.45 mg/g and 88%, respectively. 3 O 4 3 O 4AKÜ-BAPK / 14.FEN.BIL.3

Production of barite and boroncarbide doped radiation shielding polymer composite panels

Developments in nuclear technology in the last century have lead to the use of radiation in different areas of human activity. These are not just the energetics but also food, agriculture, medicine, industry and science. Thus, radiation has become an inevitable phenomenon in our lives. Since we cannot isolate radiation from our life, the radiation protection methods should be available. As alternatives to conventional radiation prevention methods, such as lead and heavy concrete shielding, more functional materials need to become the focus of research. The development of the least harmful to the environment, easily applicable, flexible radiation shields has become very important. In this study, silicon matrix composite panels, doped with different ratios of barite and boron carbide, were produced and characterized by optical and scanning electron microscopy (SEM). Gamma and neutron radiation shielding properties of these materials were investigated. The results have been compared with the lead as the standard shielding material

Investigation of equilibrium, kinetic, thermodynamic and mechanism of basic blue 16 adsorption by montmorillonitic clay

The adsorption of a cationic dye, Basic Blue 16 (BB16), by montmorillonitic clay was studied in detail. Changes in the molecular structure during adsorption were analyzed by FTIR spectroscopy. BB16 adsorption onto the clay mainly results from hydrogen bonding between OH and NH groups of dye molecules and OH groups of clay and electrostatic interaction between the negatively charged clay surface and cationic dye. The montmorillonitic clay dose had an inverse effect on the adsorption performance, while the highest dye removal was 305 mg/g at pH 3.6. An increase in temperature and dye concentration positively enhanced the adsorption capacity of the montmorillonitic clay. Temperature had no effect on the adsorption at a dye concentration less than 500 mg/L, while dye adsorption was positively enhanced at elevated dye concentrations. Three-parameter equations provided higher better fitting than two-parameter equations while the Freundlich model had the highest correlation coefficient and the lowest error values with experimental data. The BB16 adsorption was well followed by pseudo-second order model and the rate of adsorption process was controlled by surface and intraparticle diffusion. Thermodynamic evaluations revealed that the adsorption process was spontaneous and endothermic, while the randomness increased during adsorption. Experimental results indicate that montmorillonitic clay from Eskisehir is a promising adsorbent for the removal of cationic dye molecules from aqueous solutions.TUBITAK /109Y16

Investigation of wear strength of blast furnace slag blended polymer materials

Having symmetrical and balanced material properties, polymer matrix composites are increasingly becoming popular due to easiness of construction and are use in the production of aerospace and automotive structures. In the study, we developed polymer composites based on epoxy resins, containing up to 40 wt.% of blast furnace slag and determined their pin-on-disc dynamic friction, wear, Shore hardness and surface roughness values. Wear tests were performed using a pin-on-disc under dry friction conditions, at the loads of 5, 10, 15 and 30 N, using slip velocity of 0.3 m/s and along distance of 500 m. The hardness and wear resistance values increased with the increase in the content of blast furnace slag. Showing the relationship between wear rate and hardness, an equation with parameters dependent on load was provided. There was an increase in the dynamic friction with an increase in the surface roughness. In addition, dynamic friction was an increasing function of the wear rate. The wear surfaces of the polymer composites were analyzed using scanning electron microscopy. It was observed that the wear rate of the epoxy composites and pure epoxy samples ranged from 19.85 to 171.42 mm /N m. 3TÜBİTAK / 114M15

Production of glass fiber reinforced hydroxyapatite

Hidroksiapatit (HA), biyomedikal alanda bilinen en yaygın biyoseramiktir. Hidroksiapatit formülü Ca10 (PO4)6(OH)₂ şeklindedir. Bu çalışmada, cam elyafın (CF) HA'e etkisi çalışıldı. HA, sol-jel prosesi ile sentezlendi. Ağırlıkça % 10 oranında CF içeren karışım, hidrolik presle şekillendirildi. Homojen tozlar 4 saat 1100C'de sinterlendi. Tozların mineralojik yapısı ve tane boyutu, X-ışını difraktometresi (XRD) ve tane boyut analiz cihazı ile yapılmıştır. XRD analizinden HA tozu, JCPDS No.09-0432 kart ile uyumlu olarak elde edildi. Daha sonra şekillendirilmiş örnekler taramalı elektron mikroskobu (SEM), ve üniversal test cihazı ile karakterize edildi. CF ilavesi ile 3 nokta eğilme mukavemeti ve basınç dayanımı iyileştirildi. Cam fiber katkılı HA’nın eğme ve basma mukavemetinde artmanın katkısız HA’ya nazaran sırasıyla % 20,3 ve % 23,3 olduğu görülmüştür.Hydroxyapatite is the most common known bioceramics in biomedical area. The formula of Hydroxyapatite (HA) is Ca₁₀(PO₄)₆(OH)₂. In this study, the effect of glass fiber (GF) to HA was performed. HA was synthesized by sol-gel process. Mixture containing 10 wt% of GF was shaped by hydraulic press. Homogenous powders were sintered at 1100C for 4 hours. Mineralogical properties and particle size and distribution of powders were performed by X-ray diffractometer (XRD) and particle size analyzer. From XRD analysis, the HA powder was obtained as confirmed by the JCPDS file No.09-0432. Then shaped samples were performed by universal testing machine and scanning electron microscope (SEM). 3 point bending strength and compressive strength were improved by GF addition. Increase in the bending and compressive strength of the glass fiber doped HA is observed to be 20.3% and 23.3% compared to the undoped HA, respectively

Farklı mineral katkıların epoksi zemin kaplama malzemesinin ıslanmazlığına ve yüzey enerjisine etkisi

Bu çalışmada epoksi esaslı zemin kaplama malzemesinin ıslanmazlık ve yüzey enerjisi üzerine mineral katkı türü ve miktarının etkisi incelenmiştir. Mineral katkı olarak üç farklı atık ürün (uçucu kül, silis dumanı ve yüksek fırın cürufu) ile kireçtaşı kullanılmıştır. Üretilen her bir katkılı ve katkısız epoksi malzemesinin ıslanmazlık özelliğinin belirlenmesinde, damla yayınım (sessile drop) yöntemi kullanılarak su ile temas açıları ölçülmüştür. Epoksi malzemelerin yüzey enerjisi hesaplamaları için ise 3 polar sıvı su, etilen glikol ve formamid ile 1 apolar sıvı diiodometan kullanılarak temas açıları ölçülmüş ve sonra bu temas açısı verilerine göre Fowkes yaklaşımı kullanılarak yüzey enerjileri hesaplanmıştır. Elde edilen sonuçlara göre, mineral katkılar az ya da çok epoksinin ıslanmazlık özelliğini düşürmekte ve buna uygun olarak yüzey enerjisini artırmaktadır. Katkı türleri içerisinde epoksinin ıslanmazlık ve yüzey enerjisi özelliklerine en az etki edenin uçucu kül ve en çok etki edenin ise kireçtaşı olduğu belirlenmiştir.In this study, the effect of type and amount of mineral additives on non-wettability and surface free energy of epoxy based floor coating material have been examined. Three different types of waste products (fly ash, fume silica and blast furnace slag) and limestone were used as mineral additive. Contact angle with water of each produced epoxy material with and without additive were measured by using sessile drop method to determine the hydrophobicity of the materials. For surface energy calculations of epoxy materials, their contact angles first were measured by using three polar (water, ethylene glycol and formamide) and one apolar (diiodomethane) liquid and their surface energies were then calculated according to these contact angles data by using Fowkes approach. Test results show that mineral additives have more or less decreased the hydrophobicity and increased surface energy. It was also determined that in additives fly ash has minimum and limestone has maximum effect on hydrophobicity and surface energy properties of epoxy.TÜBİTAK / 114M15

Effect of mineral admixture type on rheological properties of polymeric self-consolidating mortar

Polimer matrisli kompozitler, simetrik ve dengeli malzeme özelliklerine sahip olmaları, üretim ve kullanım kolaylıklarından dolayı inşaat, hava-uzay yapıları ve otomobil yapıları için popülerlik kazanmaktadır. Günümüzde yeni kullanım alanı oluşturan polimerik malzemelerden birisi de epoksi esaslı kendiliğinden yerleşen harçlardır. Bu harçlar, inşaat sektöründe başta yüzey kaplamaları olmak üzere bina güçlendirmelerinde yaygın bir şekilde kullanılmaktadır. Bu malzemelerin yüzeye uygulanmasında hem yüksek olan maliyetlerinin azaltılması hem de dayanımlarının arttırılması amacıyla atık halde bulunan ve büyük ölçüde çevre kirliliği oluşturan malzemelerin filler olarak kullanımı araştırılmaktadır. Bu çalışmada yüksek fırın cürufu, uçucu kül, silis dumanı, kireçtaşı tozu ve doğal kum kullanılarak üretilen epoksi esaslı kendiliğinden yerleşen harçların viskozite, yayılma çapı ve katılaşma gibi reolojik özellikleri belirlenerek karakterize edilmiştir. Elde edilen deney sonuçlarına göre yüzey alanı yüksek olan mineral katkıların kullanım oranının artmasıyla polimer esaslı harçların işlenebilirliklerini azaltmıştır.Polymer matrix composites are gaining popularity for construction, air-space structures and automobile constructions due to their symmetrical and balanced material properties and their ease of production and use. One of the polymeric materials that make up the new application area is epoxy based self-consolidating mortar. These mortars are widely used in the construction industry, especially in surface coatings in building constructions. Both to reduce the high costs and to increase the strengths of these materials applied to the surface, i t i s bei ng i nvesti gated t he use of t he waste materi al s as a filler which cause environmental pollution. In this study, the rheological properties such as viscosity, spreading diameter and setting of epoxy based selfcompacting mortars produced by using blast furnace slag, fly ash, silica fume, limestone dust and natural sand have been characterized. According to the results of the experiment, the use of mineral admixtures wit h high surface area has been decreased the workability of polymer-based mortars.TÜBİTAK / 114M11

Adsorption of basic blue-16 dye onto clay

Katyonik bir boya olan bazik mavi-16 (BB16)’nın kesikli bir sistemde montmorillonitik kil üzerine adsorpsiyonu çalışıldı ve adsorpsiyon dengesi, adsorpsiyon termodinamiği ve adsorpsiyon mekanizmaları incelendi. Bu kapsamda farklı sıcaklıklarda, farklı boya başlangıç konsantrasyonlarında ve farklı pH’larda adsorpsiyon testleri uygulandı. Ayrıca farklı sıcaklıklarda zeta potan siyel (ZP) ölçümleri yapıldı ve adsorpsiyondan önce ve sonra kilin FTIR spektrumları alındı. Deneysel olarak elde edilen adsorpsiyon verilerine, iki parametreli (Freundlich, Langmuir, Tempkin, Dubinin-Radushkevich (D-R)) ve üç parametreli (Redlich-Peterson(R-D), Sips, Toth and Khan) adsorpsiyon izoterm modelleri uygulanarak modellendi ve izoterm sabitleri hesaplandı. İki parametreli izoterm modelleri içerisinde Freundlich ve üç parametreli izoterm modelleri içerisinde ise Sips ve Khan modelleri deney verilerine en uygun mod eller oldu. Giriş konsantrasyonu 1400 mg/l BB16 için montmorillonitik kilin maksimum adsorplama kapasitesi 15, 25 ve 35 ºC sıcaklıklar için sırasıyla 509,7, 525,0 ve 570,7 mg/g’dır. Farklı sıcaklıklarda elde edilen adsorpsiyon izotermleri kullanılarak adsorpsiyon gibbs serbest enerjisi (G o ), entalpisi(H o ) ve entropisi (S o ) hesaplandı. Elde edilen negatif G değerleri, adsorpsiyonun kendiliğinden meydana geldiğini göstermektedir. BB16’nın montmorillonitik kil üzerine adsorpsiyonunu sağlayan olası mekanizmalar hidrojen b ağı oluşumu, elektrostatik etkileşim ve boya-boya etkileşimi şeklinde sıralanabilir.Cationic dye, basic blue 16 (BB16), adsorption onto montmorillonitic clay was studied in a batch system, and adsorption equilibrium, thermodynamics and mechanism were investigated. In this scope, adsorption tests were carried out at various temperatures, initial dye concentrations and pHs. Also, zeta potential measurements at different temperatures were performed and FTIR spectrums of clay samples were obtained before and after dye adsorption tests. Three-parameter (Redlich–Peterson, Sips, Toth and Khan) and two-parameter (Freundlich, Langmuir, Temkin and Dubinin–Radushkevich) adsorption isotherm models were applied on the obtained experimental results and the model constants were calculated. Three-parameter isotherms showed relatively higher regression coefficients and lower relative errors (<5%) than two-parameter isotherms. Of the two-parameter isotherms, the Freundlich isotherm best described the experimental data while the best fitting isotherms were Sips and Khan for three-parameter isotherms. Maximum experimental adsorption capacity was found to be 509.7, 525.0 and 570.7 mg/g for 15, 25 and 35 ºC, respectively, for the initial BB16 concentration of 1400 mg/l. Gibbs adsorption free energy(Go), enthalpy (Ho) and entropy(So) were calculated using the adsorption isotherms obtained at various temperatures. Negative Gibbs free energy shows the BB16 dye adsorption onto clay is spontaneous. The possible interaction mechanisms causing to dye adsorption between the dye molecule and clay can be listed as hydrogen bonding, electrostatic interaction and dye-dye interaction.TÜBİTAK / 109Y16

Zeta potential-viscosity relationship in kaolinite slurry in the presence of dispersants

AKÜ-BAPK / 042.MUH.03Kaolinite is a widely used additive for industrial applications. Hence, the properties of kaolinite affect the quality of the final materials. The fact that kaolinite is a heterogeneous mineral with dual charges has to be taken into account. In this study, the zeta potentials and the apparent viscosities of kaolinite suspensions in water in the presence of three dispersants; sodium silicate, sodium tripolyphosphate and sodium-polyacrylate at pH values of 4, 7 and 10 were determined. Diagrams of zeta potentials (ZPs) and viscosity as a function of dispersant concentration all show minima. The concentrations at which minima of these two properties appear do not coincide, except for those mineral dispersants at high pH values. The results are explained in terms of the spatial distribution of charges on basal and edge surfaces of kaolinite plates in acidic, neutral, and basic media.AKÜ-BAPK / 042.MUH.0

The effect of BaCO3 addition on the sintering behavior of lignite coal fly ash

The effect of BaCO 3 (witherite) addition on the sintering behavior of lignite coal fly ash taken from the Seyitömer power plant of Kütahya/Turkey was examined at temperatures of 1100, 1150 and 1200 C in air atmosphere. Bloating of the fly ash samples sintered at 1150 C was prevented, that is, the decomposition temperature of CaSO in the fly ash is shifted to a higher temperature, and their physicomechanical properties (porosity, water absorption, bulk density and bending strength) were improved with BaCO 3 4 addition. Positive effects of BaCO , however, were not seen on the fly ash samples sintered at 1100 C. All the fly ash samples sintered at 1200 C were bloated due to the gas evolving and also they melted. During the thermal treatment at 1150 C a phase transformation from CaSO (Barite) occurred in the fly ash with BaCO 3 3 4 addition as seen from the X-ray diffraction (XRD) patterns and the bar shaped fly ash samples with BaCO 3 (anhydrite) to BaSO saved their structural integrity up to 1150 C.