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Öğe A novel Microcystis aeruginosa supported manganese catalyst for hydrogen generation through methanolysis of sodium borohydride(Pergamon-Elsevier Science Ltd, 2020) Duman, Fatih; Atelge, M. R.; Kaya, Mustafa; Atabani, A. E.; Kumar, Gopalakrishnan; Sahin, U.; Unalan, S.In this study, Microcystis Aeruginosa (MA)- microalgae species was used for the first time as a support material with metal ions loading to fabricate a highly efficient catalyst for the hydrogen generation through methanolysis of sodium borohydride (NaBH4). Microalgae was pre-treated with hydrochloric acid (3 M HCl) for 24 h at 80 degrees C. Subsequently, different metal ions (Mn, Co, and Mo) were loaded to the pre-treated samples. Finally, metal-loaded samples were subjected to burning in oven to fabricate the catalyst. Primarily, manganese metal was selected based on the best metal performance. Afterwards, different metal loading ratios, burning temperatures and burning times were evaluated to synthesize the optimal MA-HCl-Mn catalyst. Results showed the optimal conditions as Mn ratio, burning temperature and time as 50%, 500 degrees C and 45 min, respectively. To characterize the catalyst, FTIR, SEM-EDX, XRD, XPS and TEM analyses were performed. Hydrogen generation via methanolysis was performed at various NaBH4 ratio of 1-7.5% while changing concentrations from 0.05 to 0.25 g catalysts with diverge temperatures of (30, 40, 50 and 60 degrees C). The maximum hydrogen generation rate (HGR) by this novel catalyst was found as 4335.3, 5949.9, 7649.4 and 8758.9 mLmin(-1)gcat(-1), respectively. Furthermore, the activation energy was determined to be 8.46 kJ mol(-1). (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Öğe DNA Cleavage Properties, Antimicrobial and Cytotoxic Activity and 4D-QSAR Analysis of Some Pyrazole Derivatives(Bentham Science Publ Ltd, 2019) Kopru, Semiha; Kup, Fatma Ozturk; Sabanci, Nazmiye; Cadir, Mehmet; Bulut, Duygu Cemre; Duman, Fatih; Ilhan, Ilhan OzerBackground: An extensive study of 19 pyrazole derivatives were carried out based on the evaluation of DNA cleavage properties, antimicrobial and cytotoxic activities and 4D-QSAR analysis including pharmacophore modelling and bioactivity prediction by the Electron Conformational-Genetic Algorithm (EC-GA) method. Methods: The pyrazole derivatives were tested for their antimicrobial activity against certain human pathogenic organisms using the agar diffusion procedure. Binding of compounds with DNA was studied by gel electrophoresis using plasmid pBR322 DNA. The compounds were investigated for their properties as cytotoxic agents by brine shrimp lethality bioassay. To identify the pharmacophoric elements and find out the most important molecular properties which govern cytotoxic activity, multiple conformations of the compounds were used. Results: The urea derivatives of pyrazole had higher antibacterial activities against Gram-negative bacteria than against Gram-positive bacteria. Many of the compounds were found to cleave plasmid pBR322 DNA from the supercoiled form to the nicked circular. The cytotoxicity values of the compounds ranged from 13.87 to 84.1 mu g/mL. The generated QSAR model was evaluated through the use of the Leave-One-Out Cross Validation (LOO-CV) method. A statistically significant and considerably predictive QSAR model was obtained with 4- descriptors resulting in R2 training = 0.8223, R2 test = 0.9346, q2=0.6201, q2 ext1 0.8672, q2 ext2= 0.8662 and q2 ext3=0.9511. Discussion: The generated model demonstrates that geometrical parameters are more correlated with cytotoxic activity. The resulting EC-GA model would provide benefits to design novel bioactive pyrazole derivatives which are more potent and have less side effects. Conclusion: It is believed that the generated QSAR model gives insight into developing new more potent pyrazole derivative drugs.Öğe Dual-function macroalgae biochar: Catalyst for hydrogen production and electrocatalyst(Elsevier Sci Ltd, 2024) Bekirogullari, Mesut; Abut, Serdar; Duman, Fatih; Hansu, Tulin AvciIn the current study, Enteromorpha intestinalis, a green macroalgae, has been utilized as a substrate to synthesise a new environmentally friendly and cheap dual -functional (catalyst and electrocatalyst) material. The catalyst was used for efficient hydrogen production from alcoholises sodium borohydride and as an anode catalyst for direct methanol fuel cell applications. At the catalyst synthesis stage, orthogonal arrays of Taguchi is used to find the optimum levels of independent variables for the superior catalyst performance that bears the modest kinetics. The experiments performed in accordance with the L16(45) type orthogonal array. The samples treated at relatively moderate acid, impregnation temperature, impregnation time, burning temperature and burning time showed higher catalytic activities with Exp(5) presenting the optimal catalytic activity followed by Exp(1), Exp (15), Exp(8) and Exp(12), respectively. The experimental levels of coded variables (acid molarity, impregnation temperature and time, burning temperature and time) for Exp(5) were 3 M, 50 C-degrees, 24 h, 500 C-degrees and 2 h., respectively. These finding suggest that providing maximum levels of each of independent variable will not provide high catalytic activity. Taking into account the binary and ternary interactions is an efficient way to determine optimal level of each parameter with regards to maximum hydrogen production rate. The morphological and structural characterization of the optimal catalyst was finally carried out with SEM- EDS, XRD and FT-IR. CV and EIS measurements were taken to determine the electrocatalytic activity of final biochar. Experimental studies revealed that the utilization of E. intestinalis-based electrocatalyst as an anode catalyst for direct fuel cell applications is promising. By employing advanced Taguchi -based experimentation, this research establishes the optimum levels of independent variables, enhancing the catalyst's performance, and highlighting a novel approach to modest kinetics improvement.Öğe Lake sediment based catalyst for hydrogen generation via methanolysis of sodium borohydride: an optimization study with artificial neural network modelling(Springer, 2021) Bekirogullari, Mesut; Abut, Serdar; Duman, Fatih; Hansu, Tulin AvciIn the current study, lake sediment, a heterogeneous and complex organic matter, utilized as a catalyst upon acid treatment for efficient hydrogen generation from sodium borohydride. In order to synthesise the catalyst that bears the best catalytic activity, ANOVA, cubic stepwise linear regression and artificial neural network optimization techniques were applied to determine the optimal level of treatment parameters. The results suggest that only Taguchi orthogonal arrays method was able to accurately reflect the overall surface of objective variable. Among the 16 catalyst samples Exp(15) showed the superior catalytic activity followed by Exp(13), Exp(12), Exp(14) and Exp(7). The minimum reaction completion time for Exp(15) corresponding to maximum hydrogen production rate of 3247.15 mL/min/gcat was 2.25 min. A detailed characterization of the final product was carried out by using a Fourier transform infrared spectra (FTIR-Perkin Elmer), an X-ray diffractometer (Bruker D8 Advance XRD), a scanning electron microscopy and energy dispersive X-ray spectroscopy. [GRAPHICS] .
