Yazar "Akalin, Mehmet Kuddusi" seçeneğine göre listele
Listeleniyor 1 - 13 / 13
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Analytical pyrolysis of biomass using gas chromatography coupled to mass spectrometry(Elsevier Sci Ltd, 2014) Akalin, Mehmet Kuddusi; Karagoz, SelhanBiofuels represent an important category of green and alternative energy, and they have high potential to meet the energy demands of society. They are obtained from various renewable sources, which include energy crops, wood and wood wastes, agricultural by-products, and algae. Pyrolysis is an advanced technology to produce biofuels from biomass. In this review, we focus on analytical pyrolysis of biomass, in which a sample is decomposed with the help of heat treatment in an inert atmosphere. In a Py-GC-MS system, the pyrolyzer unit is connected to a gas chromatograph with a mass detector. We provide insight into the analytical pyrolysis of various biomasses and biomass components, decomposition pathways, formation of possible decomposition products and the effects of catalysts in the degradation of biomasses. Also, we discuss sample preparation and instrumentation for analytical pyrolysis. (C) 2014 Elsevier B.V. All rights reserved.Öğe Application of response surface methodology to extract yields from stinging nettle under supercritical ethanol conditions(Elsevier Science Bv, 2013) Akalin, Mehmet Kuddusi; Karagoz, Selhan; Akyuz, MehmetResponse surface methodology was employed using a central composite design of experiments to optimize experimental conditions for stinging nettle extract yields under supercritical ethanol conditions. The following independent variables were investigated: extraction temperature, extraction time and plant concentration. The most significant factor was found to be the extraction temperature. A correlation coefficient was estimated to be 0.94, which demonstrates the effectiveness of the model. The values of the parameters in optimized conditions for the stinging nettle extract yield included an extraction temperature of 335 degrees C, an extraction time of 87 min, and a plant concentration of 9. A subsequent validation experiment was carried out at the optimal conditions. The validation experiment showed that the actual and predicted values for the stinging nettle extract yields were 45.3 and 42.7 wt%, respectively. The stinging nettle extracts consisted of a collection of compounds including fatty acid esters (FAE), phenols, indoles, and nitrogen containing compounds. (C) 2013 Elsevier B.V. All rights reserved.Öğe Comparison of effective removal of cationic malachite green dye from waste water with three different adsorbents: date palm, date palm biochar and phosphated biochar(Taylor & Francis Ltd, 2023) Sismanoglu, Sedef; Shakir, Safa Abdulmahdi; Kol, Hamiyet Sahin; Hani, Yahia Bani; Aghlara, Elham; Akalin, Mehmet KuddusiAdsorbents obtained from agricultural wastes attract attention because they are both effective, inexpensive and environmentally friendly. In this study, it was studied on the removal of malachite green (MG) from aqueous solutions by using date palm fronds (DPF), which are agricultural wastes, date biochar (DPC) obtained by pyrolysis and phosphated date biochar with the help of microwave pyrolysis (DPMW) as three different adsorbents. Characterisation of adsorbents was made by FTIR/ATR, SEM, TGA. According to the results of TGA, it was observed that thermal strengths decreased after adsorption. Adsorption studies were carried out at 25 degrees C in isothermal environment at the pH of the natural dye solution. Adsorption data of date palm, biochar and phosphated biochar were evaluated according to Freundlich, Langmuir, Temkin, Dubinin-Radushkevich (D-R), Flory-Huggings (F-H) and Fowler-Frumkin-Guggenheim (FFG) isotherm models. Maximum adsorption capacities (qmax) according to Langmuir isotherm were found as 334 mg/g, 125 mg/g and 32 mg/g for date palm, biochar and phosphated biochar, respectively. The heat of adsorption calculated using the Temkin and Fowler - Frumkin-Guggenheim (FFG) isotherms is exothermic for date palm and biochar, while it is endothermic for phosphated biochar. It was observed that the adsorption mechanism energy E calculated in D-R and the B values calculated in Temkin were compatible and the adsorption was physical. According to these results, the most effective adsorbent for the removal of malachite green from aqueous solutions is biochar, which is the pyrolysis product, while phosphated biochar is not very suitable.Öğe Effective Removal of Cationic Dyes from Aqueous Solutions by Using Black Cumin (Nigella sativa) Seed Pulp and Biochar(North Carolina State Univ Dept Wood & Paper Sci, 2023) Sismanoglu, Sedef; Akalin, Mehmet Kuddusi; Akalin, Gulen Oytun; Topak, FatimaBlack cumin seed pulp (C), as well as biochar (CC) produced via pyrolysis of black cumin seed pulp were used to remove methylene violet 2B (MV) and basic yellow 28 (BY28) from aqueous solution. Adsorption isotherms and kinetics were applied at 10, 25, and 35 degrees C. The adsorption of methylene violet 2B and basic yellow 28 on the black cumin seed pulp and biochar surface was exothermic; the heat of adsorption values were lower CC were 212.8, 625, 164, and 909 mg g-1 at 25 degrees C, respectively. The adsorption of black cumin seed pulp and biochar data were examined with Flory-Huggins (F-H) isotherm models. The kinetics of the adsorption were fitted to the pseudo first-order and pseudo second order equations. The pseudo second order equation gave a better fit than the pseudo first-order equation.Öğe The facile production of Fe2O3-biochar electrocatalyst for methanol oxidation reaction(Pergamon-Elsevier Science Ltd, 2024) Mert, Mehmet Erman; Hani, Yahia Bani; Akalin, Mehmet Kuddusi; Sismanoglu, Sedef; Aksaray, Goncaguel; Mert, Basak Dogru; Kol, Hamiyet SahinIn this study, the facile-green method was applied for the production of electroactive composite anode material. For this purpose, biochar was produced via pyrolysis of Pinus nigra (PN) sawdust in a stainless-steel reactor at 300, 400 and 500 degrees C with 10 degrees C/min heating rate. The Fe2O3 particles were fabricated via the green synthesis method. The Fe2O3-biochar electrocatalyst was operated on Ni foam electrode and the potential application as an anode for methanol fuel cell was investigated in an alkaline medium. Field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), Brunauer-Emmett-Teller analysis (BET), and attenuated total reflectance Fourier transform infrared spectroscopy (FTIR/ATR) were used to characterize the morphology of the electrocatalyst samples. The electrochemical measurements of electrocatalyst samples were achieved via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV) and chronoamperometry (CA). The enlarged surface area of biochar enabled the formation of more electroactive sites for methanol electrooxidation and favorable structures of biochar could support to increased electrocatalytic activity of catalysts for methanol oxidation and produce favorable matrices for Fe2O3 loading. The obtained results demonstrate that the electrooxidation of methanol occurred at 0.36 V. The favorable structures of biochar acted as a support, enhancing the electrocatalytic activity of Fe2O3 for methanol oxidation. The electrocatalyst demonstrated remarkable activity with almost 4 A g-1 current density at 0.55 V. The Rct values were 0.73 omega and 0.45 omega at 0.55 V, for Ni foam and Ni foam/Fe2O3-biochar, respectively. Long-term measurements demonstrated that the Ni foam/Fe2O3-biochar catalysts was remarkably stable, with a 4 % difference in current before and after the CA analysis.Öğe Hydrothermal liquefaction of microalgae with metal halides for bio-crude production(Gazi Univ, Fac Engineering Architecture, 2019) Akalin, Mehmet KuddusiIn this study, the microalgae Spirulina was converted into bio-crudes under hydrothermal conditions. In the first part (non-additive experiments), the effects of different hydrothermal processing temperatures (ranged from 250 to 375 degrees C), different initial pressures (ranged from 1 to 4 MPa) and residence times (ranged from 30 to 120 min) on the bio-crude and solid residue yields were investigated. The highest bio-crude yield was about 36wt% and obtained at 350 degrees C with a residence time of 30 min and an initial pressure of 1 MPa. In second part (experiments with metal halide additives), the effect of metal halides (CsCl, CsCl-KCl, CsCl-NaCl, CsCl-ZnCl2, and CsCl-SnCl2) on the bio-crude yields and compositions were investigated. The metal halides used in the experiments were ineffective on bio-crude yields. The highest diesel fuel content of the bio-crude was 78wt% and obtained from the run with CsCl-NaCl. The use of catalysts slightly increased the carbon content and slightly decreased the oxygen content in bio-crudes in comparison with the run without a catalyst. The key compounds in bio-crudes were nitrogen containing compounds including amines, amides, pyrrolidines, indoles, and pyrazines. The highest heating value of the bio-crude was about 33 MJ/kg and obtained in the runs with CsCl and CsCl-SnCl2.Öğe OPTIMIZATION OF ETHANOL SUPERCRITICAL FLUID EXTRACTION OF MEDICINAL COMPOUNDS FROM ST. JOHN'S WORT BY CENTRAL COMPOSITE DESIGN(Taylor & Francis Inc, 2014) Akalin, Mehmet Kuddusi; Karagoz, SelhanExtraction of medicinal compounds from St John's Wort was performed using supercritical ethanol. The supercritical fluid extraction parameters were optimized via response surface methodology which included a central composite design. The independent variables were extraction temperature (ranging from 300 degrees C to 340 degrees C), extraction times (ranging from 60 to 120 min), and plant concentration (ranging from 8% to 12%). The response was the St John's Wort extract yield. The extraction temperature was the most significant factor which affects St John's Wort yields according to statistical results. The coefficient of determination was estimated to be 0.98 which indicates the effectiveness of the model and its adaptability to the experimental data. The extract of St John's Wort was comprised of a wide array of compounds including phenols, acids, acid esters, and alkanes. The most prominent components of the extract of St. John's Wort in terms of their relative concentrations were linoleic acid ethyl ester, oleic acid ethyl ester, hexadecanoic acid ethyl ester, and nonacosane.Öğe Preparation and Characterization of Activated Carbons from Waste Melamine Coated Chipboard by NaOH Activation(Foundation Environmental Protection & Research-Fepr, 2012) Zengin, Ayse; Akalin, Mehmet Kuddusi; Tekin, Kubilay; Erdem, Murat; Tay, Turgay; Karagoz, SelhanActivated carbons were prepared from the pyrolysis of waste melamine coated chipboard at 600 and 800 degrees C by chemical activation with NaOH. The effects of the carbonization temperature and concentration of chemical reagent on their chemical-surface properties were investigated. The highest surface area was obtained at 600 degrees C with the 50 wt. % concentration of sodium hydroxide. The external surfaces of the activated carbons showed amorphous and heterogeneous structures.Öğe Production of Bio-oil via Catalytic Pyrolysis of Medlar Seeds(North Carolina State Univ Dept Wood & Paper Sci, 2023) Topak, Fatima; Akalin, Mehmet KuddusiThe pyrolysis of medlar seeds was performed at 350, 450, 550, and 650 degrees C with and without K2CO3, MgO, and expanded perlite (10 wt%). The maximum dichloromethane extract yield (6.70 wt%) was obtained at 450 degrees C in the pyrolysis experiments without catalyst, while the maximum biooil yield (50.3 wt%) was obtained at 650 degrees C in the presence of perlite. The dichloromethane extract and bio-oil yields decreased noticeably with the use of MgO and K2CO3. The bio-oils obtained from the non-catalytic runs mainly consisted of phenolic compounds. The use of catalysts had a noticeable effect on the composition and higher heating values of the biooils. The use of K2CO3 increased the relative content of 2-methoxyphenol at all tested temperatures and the relative content of 2,6-dimethoxyphenol and 2,6-dimethoxy-4-methylphenol increased with the use of expanded perlite at above 550 degrees C, while the use of MgO led to an increase in the relative content of 2,6-dimethoxy-4-methylphenol at above 550 degrees C. The bio-oil with the maximum higher heating value (30.4 MJ/kg) was obtained at 450 degrees C with the use of perlite. This study showed that medlar seeds are a good alternative source of waste biomass in the production of bio-oil that can be used as a biofuel.Öğe Production of crude bio-oil and biochar from hydrothermal conversion of jujube stones with metal carbonates(Taylor & Francis Ltd, 2018) Aykac, Gamze Nur; Tekin, Kubilay; Akalin, Mehmet Kuddusi; Karagoz, Selhan; Srinivasan, Madapusi PalaveduIn this study, hydrothermal processing was employed to produce crude bio-oil and biochar from waste jujube stones by deploying metal carbonates as catalysts. The effects of metal carbonate catalysts (K2CO3, Na2CO3 and SrCO3) in different concentrations on the product yields and properties were tested for the conversion studies. The use of metal carbonates (K2CO3, Na2CO3 and SrCO3) increased the yield of bio-oil almost twofold, with the highest yield (18.66 wt%) obtained using K2CO3 at a concentration of 10 wt%. (E)-9-octadecenoic acid (elaidic acid), 2,6-dimethoxyphenol (syringol) and 2-methoxyphenol (guaiacol) were some of the prominent compounds found in the crude bio-oils. The process also resulted in an efficient conversion of jujube stones to biochar with high content of oxygenated functional groups which makes it an effective precursor for various applications. The heating values of the bio-oils and biochars were significantly improved compared to those of the feedstock.Öğe Supercritical ethanol extraction of bio-oils from German beech wood: Design of experiments(Elsevier Science Bv, 2013) Akalin, Mehmet Kuddusi; Karagoz, Selhan; Akyuz, MehmetA central composite experimental design was used to investigate experimental process conditions (extraction temperature, extraction time and biomass loading) for the supercritical ethanol extraction of bio-oils from German beech wood. The effects of three independent variables and their interactions on the yields of ethanol extracts and biomass conversion were analyzed using response surface methodology (RSM). The most significant variable was found to be the temperature on the yields of ethanol extract and biomass conversion. High correlation coefficients (R-2) were obtained and they were 0.93 and 0.95 for ethanol extract and biomass conversion yields, respectively. The consistent matching of predicted values with the experimental values is an indication of validity of the model used in this study. Optimized conditions were in the range of the experimental design which shows the validity of the design. Optimal conditions for the ethanol extract yield were 315.81 degrees C extraction temperature, 123.67 min extraction time, and 15.95 wt% biomass loading. The bio-oil contained mainly phenolic compounds. The analyses of results show that the linear coefficient of x(1) and the quadratic coefficient of x(1)(2) are the most statistically significant factors on the ethanol extract and biomass conversion yield. The ethanol extracts (bio-oils) contained greater amounts of carbon and lesser amounts of oxygen than that of the raw material. (C) 2013 Elsevier B.V. All rights reserved.Öğe Supercritical Fluid Extraction of Bio-oils from Hawthorn Stones: A Box-Behnken Design for the Extraction Parameters(Wiley-V C H Verlag Gmbh, 2015) Akalin, Mehmet Kuddusi; Akyuz, Mehmet; Karagoz, SelhanHawthorn stones, a waste biomass, were subjected to supercritical ethanol extraction to obtain bio-oils. Optimization of the extraction parameters was performed according to the Box-Behnken design to estimate the effects of extraction temperature, extraction time, and biomass concentration on the yields of the bio-oil and the conversion of the biomass. High correlation coefficients (R-2) were obtained. The values of R-2 were 0.90 and 0.98% for bio-oil and biomass conversion, respectively. The validity of the model used in this procedure was indicated by the consistent matching of predicted values with the experimental values. The experimental results demonstrated that the optimized conditions fell within the range of the experimental design.Öğe Ultrasound bath-assisted extraction of essential oils from clove using central composite design(Elsevier Science Bv, 2015) Tekin, Kubilay; Akalin, Mehmet Kuddusi; Seker, Mine GulUltrasound-assisted extraction of essential oils from clove was carried out using central composite design (CCD). The extraction parameters were optimized with response surface methodology (RSM). Three independent variables were extraction temperatures (ranging from 32 to 52 degrees C), extraction times (ranging from 30 to 60 min), and plant concentrations (ranging from 3 to 7%). The dependent (response) variable was clove extract. In this study, all the experiments were carried out in an ultrasound bath with a frequency of 53 kHZ. A high coefficient of correlation (0.94) was obtained between the predicted and actual clove extract yields. This result demonstrates the validity of the model used in the experiment. The statistical results showed that the extraction temperature had the most significant influence on the clove extract yield. The clove extract contained the following compounds: eugenol, a-caryophyllene, and 2-methoxy-4-(2-propenyl) phenol acetate. The major compound in the clove extract was eugenol. Antibacterial studies showed that essential oils derived from the ultrasound extraction of clove may be used as alternative bactericidal and bacteriostatic agents in the pharmaceutical industry. (C) 2015 Elsevier B.V. All rights reserved.
