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Öğe Adsorption of Pb(II) and Cd(II) Ions Onto Dye-Attached Sawdust(Wiley, 2016) Tekin, Kubilay; Akalin, Mehmet K.; Uzun, Lokman; Karagoz, Selhan; Bektas, Sema; Denizli, AdilSawdust from Pinus sylvestris was modified with Cibacron Blue F3GA. The dye was attached to the sawdust through a chemical reaction under alkaline conditions. The modified sawdust was then used to evaluate the adsorption of Pb(II) and Cd(II) ions by investigating the effects adsorption time, pH and metal ion concentration. Adsorption rates were rapid and reached equilibrium after 15min. The Langmuir isotherm was better fitted than the Freundlich isotherm for both metal ions. The maximum capacities of the monolayer adsorption were 56 mu mol/g for Pb(II) and 72 mu mol/g for Cd(II). Adsorption-desorption studies showed that Cibacron Blue F3GA-attached sawdust from P. sylvestris can be used repeatedly to adsorb heavy metal ions without significant loss of adsorptive capacity.Öğe Cellulose-derived carbon spheres produced under supercritical ethanol conditions(Springer, 2016) Tekin, Kubilay; Pileidis, Filoklis D.; Akalin, Mehmet K.; Karagoz, SelhanThis study investigates the production of spherical carbons from cellulose under sub- and supercritical ethanol conditions with and without the addition of a potassium hydroxide (KOH) catalyst. Different temperatures (200 and 280 A degrees C), residence times (0.5, 1, 2, and 4 h), and KOH concentrations (5, 10, and 20 wt% of cellulose) were used for the carbonization process. Carbon spheres could only be obtained under supercritical ethanol conditions (at 280 A degrees C and 9.5 MPa). Supercritical ethanol decreases the oxygen content by a significant amount, thereby increasing the heating value. Morphological studies show that the carbons are essentially spherical of different sizes depending on the operating conditions (such as the presence of a catalyst and time). For the first time, we showed that spherical carbons can be obtained under supercritical ethanol conditions. This is a useful result as, for instance, ethanol can be produced from cellulose, and this opens the possibility for the development of a green and simple procedure to synthesize carbon spheres that may have many different applications including gas separation, catalysis, and energy storage.Öğe Deconstruction of lignocellulosic biomass with hydrated cerium (III) chloride in water and ethanol(Elsevier Science Bv, 2017) Akalin, Mehmet K.; Das, Parthapratim; Alper, Koray; Tekin, Kubilay; Ragauskas, Arthur J.; Karagoz, SelhanLignocellulosic biomass was decomposed to produce crude bio-oil in water and ethanol using hydrated cerium (III) chloride as a catalyst. Use of the catalyst affected not only the yield of crude bio-oil but also the composition of bio-crude for both water and ethanol. The catalyst had a detrimental effect on the crude bio-oil yields obtained from water processing for all runs. However, in ethanol, use of the catalyst improved the crude bio-oil yields in all tested runs. The solid residue yields decreased with the catalyst use in the runs with water but increased in all studies with ethanol, except those with the shortest tested residence time of 10 min. The highest crude bio-oil yield of 48.2 wt% was obtained at 300 degrees C using 5 mmol of hydrated cerium (III) chloride at a residence time of 90 min in ethanol. The heating values of the crude bio-oils increased with the catalyst use for both water and ethanol processing. The highest heating value of 33.3 MJ kg(-1) was obtained with hydrated cerium (III) chloride at 300 degrees C and a residence time of 120 min.Öğe Experimental design for extraction of bio-oils from flax seeds under supercritical ethanol conditions(Springer, 2016) Tekin, Kubilay; Akalin, Mehmet K.; Karagoz, SelhanA central composite design was applied to the extraction of bio-oils from flax seeds under supercritical ethanol (Sc-EtOH) conditions. The effects of three factors (temperature, time, and biomass concentration) on bio-oil and biomass conversion yields were examined. Extraction temperature was statistically found to be the most significant factor which affected both bio-oil yield and biomass conversion. The predicted results matched the experimental results with the following coefficient of determination: (R (2)) 0.95 for bio-oil yield and 0.92 for biomass conversion yield. The composition of bio-oils consisted mainly of fatty acid ester derivatives, and other oxygenated hydrocarbons. Based on the relative concentrations of the compounds, the major compound was ethyl oleate.Öğe Hydrothermal liquefaction of cornelian cherry stones for bio-oil production(Elsevier Sci Ltd, 2012) Akalin, Mehmet K.; Tekin, Kubilay; Karagoz, SelhanHydrothermal liquefaction of cornelian cherry stones, fruit processing wastes, was performed at 200, 250 and 300 degrees C with residence times of 0, 15, and 30 min. The highest total bio-oil yield was obtained at both 250 and 300 degrees C for the shortest residence time (0 min) and found to be 28 wt.%. ca. The solid residue yields were reduced as both the hydrothermal liquefaction temperature and the holding time was increased. The highest heating values of LBO and HBO were estimated to be 23.86 and 28.35 Mj kg(-1), respectively. The major compounds identified in the LBOs were furfurals, phenols, acetic acid and vanillin. The major components of the HBOs contained furfurals, phenols and fatty acids. Among major identified compounds in the HBOs, the relative concentration of Linoleic acid was the highest both at 250 and 300 degrees C. (C) 2012 Elsevier Ltd. All rights reserved.Öğe Hydrothermal wood processing using borax decahydrate and sodium borohydride(Elsevier Science Bv, 2013) Tekin, Kubilay; Akalin, Mehmet K.; Bektas, Sema; Karagoz, SelhanHydrothermal liquefaction experiments were carried out at 250,300 and 350 degrees C with the use of an additive (either borax decahydrate (Na2B4O7 center dot 10H(2)O) or sodium borohydride (NaBH4)). The effects of both temperature and types of additives on the product distributions and bio-crude compositions were viewed. The use of additives (either Na2B4O7 center dot 10H(2)O or NaBH4) increased bio-crude yields at all liquefaction temperatures. The highest bio-crude yield was achieved with Na2B4O7 center dot 10H(2)O at 300 degrees C. The use of additives (either Na2B4O7 center dot 10H(2)O or NaBH4) decreased the char yield at 300 and 350 degrees C. The heating values of ether extracts from all experimental runs including the run without additives were close to each other. However, the heating values of the acetone extract from chemical runs were higher than the heating values of the non-chemical run. The highest heating value of the acetone extract was 28.05 MJ kg(-1) and it was obtained from the run with Na2B4O7 center dot 10H(2)O at 300 degrees C. The identified compounds in ether extracts and acetone extracts were mainly oxygenated compounds. The compositions of ether extract and acetone extract were affected when using additives. (C) 2013 Elsevier B.V. All rights reserved.Öğe PYROLYSIS OF TOBACCO RESIDUE. PART 2: CATALYTIC(North Carolina State Univ Dept Wood & Paper Sci, 2011) Akalin, Mehmet K.; Karagoz, SelhanThe pyrolysis of tobacco residue in the presence of metal oxides and metal chlorides was investigated at 300, 400, and 500 degrees C. Catalysts used were Al(2)O(3), Fe(2)O(3), AlCl(3), and SnCl(4) in concentrations from 1 up to 5 wt% of the tobacco residue feedstock. The amount of catalysts and the pyrolysis temperature had significant effect on both product distributions and bio-oil composition. The catalytic effect was dominant at the lowest temperature (300 degrees C). The pyrolysis temperature was decreased by 200 degrees C compared to the thermal run. Bio-oil contained a large variety of compounds. Nicotine, which is very stable until temperatures in excess of 600 degrees C, could be degraded at the lowest temperature by using 1 wt% of AlCl(3) and 1 wt% of Fe(2)O(3).Öğe PYROLYSIS OF TOBACCO RESIDUE: PART 1. THERMAL(North Carolina State Univ Dept Wood & Paper Sci, 2011) Akalin, Mehmet K.; Karagoz, SelhanThe pyrolysis of two types of tobacco residue was carried out at different pyrolysis temperatures between 300 and 600 degrees C and a residence time of 1 h in a nitrogen atmosphere. The effect of pyrolysis temperature on the product distributions was investigated and the composition of the bio-oils identified. The variation in product distribution depended on both the temperature and the type of tobacco residues. The maximum liquid yields were obtained at 400 degrees C for one sample and at 500 degrees C for the other. The compositions of bio-oils from the pyrolysis of the two samples were found to be very similar. N-containing compounds were found to be the major compounds identified in ether extracts for both samples.Öğe Sage oil extraction and optimization by response surface methodology(Elsevier Science Bv, 2015) Akalin, Mehmet K.; Tekin, Kubilay; Akyuz, Mehmet; Karagoz, SelhanSage oil extraction is important as most of the components in sage play an important role in the treatment of various diseases. The aim of the present study was to optimize supercritical extraction parameters for sage (Salvia officinalis L.) oil yield by response surface methodology. A 3-factor Box-Behnken design was used to generate factor combinations. The optimal conditions for the sage oil extraction yield were 2800 degrees C extraction temperature, 110 min extraction time and 11% (wt/v) plant concentration in ethanol. The validation experiment showed that the actual and predicted values were 49.21 and 47.04 wt%, respectively. The composition of sage essential oil consisted mainly of acid esters together with phenols, limonene, indoles, and pyrroles. These compounds can be used in various industrial applications. (C) 2015 Elsevier B.V. All rights reserved.Öğe Supercritical fluid extraction of biofuels from biomass(Springer Heidelberg, 2017) Akalin, Mehmet K.; Tekin, Kubilay; Karagoz, SelhanA sustainable source of energy production can be provided using renewable resources. For instance, biomass is transformed into biofuels using several techniques such as supercritical fluid extraction, an effective thermochemical process. Here we review results on biofuels obtained from lignocellulosic and algal biomass using supercritical fluids. Biofuel yield and composition are controlled by operating conditions such as extraction temperature, pressure, biomass and solvent type, and the presence of catalysts. The extraction temperature is the major factor controlling biofuel yield. Biofuel yields can also be improved with the use of catalysts. Major compounds in biofuels from lignocellulosic biomass are phenols, catechols, guaiacols, syringols, syringaldehydes, syringyl acetone, acids, and esters. Most of these compounds are produced by lignin decomposition in lignocellulose. Furfural and derivatives are produced by the decomposition of cellulose and hemicellulose. Fatty acid alkyl esters are formed from lignin fragmentation by condensation of compounds bearing C-O or C=O. Prominent compounds in biofuels from algal biomass are saturated or unsaturated fatty acid alkyl esters.
