Browsing by Author "Demirbaş A."
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Item Effects of ground hazelnut shell, wood, and tea waste on the mechanical properties of cement(Elsevier Ltd, 1998) Demirbaş A.; Aslan A.In this study, the mechanical properties of Portland cement mixes with an admixture such as ground hazel nut shell, spruce and beech woods, and tea waste were studied. The compressive and bending strengths test results obtainned from these mixes were investigated with comparing to the control mix. From results, it was obtained that especially ground hazelnut shell and beech wood can be used as additives or partial replacement for Portland cement. © 1998 Elsevier Science Ltd.Item Analyses of boronic ores and sludges and solubilities of boron minerals in CO2-saturated water(Elsevier, 1998) Erdogan Y.; Aksu M.; Demirbaş A.; Abali Y.In this study, the potential of boron in Turkey, commercial most-used compounds of boron and their production trends according to years and analyses of boronic samples obtained different sources were investigated. Besides classic analysis technics, X-ray fluorescence spectrometric (XRF) and flame photometric methods were carried out for boronic samples. Chemical compositions of original and concentrated samples were studied with respect to the contents of B, Li, Ca, Al, Fe, Mg, S, As, Si, Sr and Na. The leaching of boric acid with CO2-saturated water from boron minerals was also investigated. Copyright (C) 1998 Elsevier Science B.V.Item Heavy metal bioaccumulation by cultivated Agaricus bisporus from artificially enriched substrates(Springer Verlag, 1998) Tüzen M.; Özdemir M.; Demirbaş A.Cultivated Agaricus bisporus possess the ability to bioaccumulate seven heavy metals (Pb, Cd, Hg, Fe, Cu, Mn, and Zn). The cultivated champignon mushroom A. bisporus was grown in soil composts of 16 different compositions. An edible mushroom, A. bisporus was also cultivated on humic compost artificially fortified with the seven heavy metals at five different concentrations (0.1 mg/ kg, 0.5 mg/kg, 1.0 mg/kg, 3.0 mg/kg, and 10.0 mg/kg) and on control substrate (0 mg/kg) on a dry weight basis. The method of measuring bioaccumulation was flame atomic absorption spectrophotometry. © Springer-Verlag 1998.Item Heavy metal bioaccumulation by cultivated Agaricus bisporus from artificially enriched substrates(1998) Tüzen M.; Özdemir M.; Demirbaş A.Cultivated Agaricus bisporus possess the ability to bioaccumulate seven heavy metals (Pb, Cd, Hg, Fe, Cu, Mn, and Zn). The cultivated champignon mushroom A. bisporus was grown in soil composts of 16 different compositions. An edible mushroom, A. bisporus was also cultivated on humic compost artificially fortified with the seven heavy metals at five different concentrations (0.1 mg/ kg, 0.5 mg/kg, 1.0 mg/kg, 3.0 mg/kg, and 10.0 mg/kg) and on control substrate (0 mg/kg) on a dry weight basis. The method of measuring bioaccumulation was flame atomic absorption spectrophotometry. © Springer-Verlag 1998.Item Recovery of phosphate from calcinated bone by dissolution in hydrochloric acid solutions(1999) Demirbaş A.; Abali Y.; Mert E.In this study, the optimum conditions of dissolution of calcinated bone in HCl solutions with different concentrations are investigated. Recovery of phosphate from calcinated bone by dissolution with hydrochloric acid solutions was investigated in a batch reactor, it was observed that a 32% hydrochloric acid solution can dissolve the calcinated bone effectively. Using the Taguchi fractional design method, it was found that the optimum process conditions, at which 67.2% P2O5 dissolution was reached, were as follows: Reaction temperature: 318 K, solid-to-liquid ratio: 1/5 (g ml-1), acid concentrations:32 (% w/v), stirring speed:400 min-1 and reaction time: 60 min. Copyright (C) 1999 Elsevier Science B.V.Item Evaluation of lignite combustion residues as cement additives(Elsevier Science Ltd, 1999) Demirbaş A.; Aslan A.In this study the physical and chemical properties of lignite fly ashes obtained from electrostatic precipitator and cyclone, lignite bottom ash, cement+lignite ash mixtures, and their effects on mechanical properties of concrete were investigated. The ashes were classified into two general types based on total silica, alumina, and iron-III oxide: class A and class B. When 25% of the cement was replaced by class A lignite bottom ash (the combined three oxide contents were 30.2%), the 28-day compressive strength increased by 18.9% compared to the control mix, and when 25% of the cement was replaced by class B lignite ash (the combined three oxide contents were 78.1%), the compressive strength decreased by 3.5% compared to the control mix. The results obtained were compared with the Turkish Standards and, in general, were found to be within the limits. As a result, the lignite fly ash and bottom ash samples may be used as cementitious materials.Item Dehydration kinetics of howlite, ulexite, and tunellite using thermogravimetric data(Elsevier, 1999) Erdogan Y.; Zeybek A.; Şahin A.; Demirbaş A.In this study, some boron mineral samples (howlite, ulexite and tunellite) have been analysed by DTA and TG methods. The thermochemical reactions of these boron compounds have been studied. The dehydration kinetic parameters for howlite, ulexite and tunellite were activation energies: 65.0, 39.5 and 50.4 kJ mol-1; the pre-exponential factors: 50.8×105, 6.60×105, 32.4×105 s-1 and rate constants: 70.1, 113.1 and 82.3 s-1, respectively, at a constant heating rate of 10 K min-1. The average particle size was 200 μm for all samples. The order of dehydration reactions (n) was accepted as first order.Item Removal of heavy metal ions from aqueous solutions via adsorption onto modified lignin from pulping wastes(2005) Celik A.; Demirbaş A.The aim for this research is to study inexpensive and effective metal ion adsorbents from biomass sources of modified lignin to offer these adsorbents as replacements for existing commercial materials. The initial concentrations were increased up to 12.7 ppm for Pb2+, Cd2+, and Zn 2+ in order to reach the plateau values which represent saturation of the active points which are available for interaction with metal ions on the lignin samples. The maximum adsorption capacities are 11.3, 17.5, and 7.7 mg per g of the lignin for Zn2+, Pb2+, and Cd2+, respectively. The maximum adsorption capacity is higher than 20 mg per g of the lignin for Cu2+ ion. The maximum adsorption percentage is 96.7 for Pb2+ for 4 h at 330 K and is 95.0 for Zn2+ for 10 h at 290 K. The adsorption of all heavy metal ions first increases with pH and almost reaches a plateau value around 4.0 for Cu2+, 4.5 for Zn2+, 5.0 for Pb2+. High adsorption at higher pH values implies that metal ions interact with lignin by ion exchange. Copyright © Taylor & Francis Inc.Item Degradation of poplar and spruce wood chips using alkaline glycerol(2005) Demirbaş A.; Celik A.Poplar and spruce wood chips were degraded by using glycerol as a solvent and alkaline glycerol with and without alkali media at different temperatures: 440, 450, 460, 470, 480, 490, and 500 K, then the results were compared with the other organic solvent systems. The degradation reactions were mainly occurred as delignification and partly decomposition of cellulose. The effects of solvent, temperature, catalyst, delignification time and wood species on the yield of delignification were discussed. Major byproducts from delignification rections of wood chips include lignin degradation products. Lignin and its degradation products can be utilized as fuels. Copyright © Taylor & Francis Inc.