Browsing by Author "Yonten, Vahap"

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Adsorption of the 2,2-Dichlorovinylphosphate on Raw and Modified Bentonites
(Asian Journal of Chemistry, 2013) Yonten, Vahap; Kubilay, Senol
This study aims to investigate the adsorption of the 2,2-dichlorovinylphosphate (DDVP) on raw and modified bentonite via high pressure liquid chromatography and infrared spectroscopy. The modified bentonites were prepared by adding HNO3 and Na2CO3. The Freundlich adsorption isotherm defines 2,2-dichlorovinylphosphate adsorption in aqueous and aqueous ethanol solutions through raw and modified bentonite. Variables such as temperature, time and pH were observed on 2,2-dichlorovinylphosphate adsorption. Then the capacity for maximum 2,2-dichlorovinylphosphate adsorption was measured on modified bentonite with HNO3 under the conditions of pH 3 and 40 degrees C. The modified bentonite with Na2CO3 clay used in experimental work played a major role on the adsorption of 2,2-dichlorovinylphosphate; thus modified bentonite with Na2CO3 is considered to possess better characteristics than modified bentonite with HNO3 and raw bentonite. The Freundlich isotherms of modified bentonite with Na2CO3 in aqueous-ethanol solution were found to be better than isotherms of aqueous solution for a much better 2,2-dichlorovinylphosphate adsorption.
Adsorption of the 2,4-Dichlorophenoxyacetic Acid Dimethylamine by Raw and Modified Bentonite
(Asian Journal of Chemistry, 2012) Yonten, Vahap; Kubilay, Senol; Battal, Peyami
The adsorption of the 2,4-dichlorophenoxyacetic acid dimethyl amine on raw bentonite (Tokat, Turkey), modified bentonite with base and modified bentonite with acid has been studied using high pressure liquid chromatography (HPLC) and FT- infrared spectrophotometer. Sorption of 2,4-dichlorophenoxyacetic acid dimethyl amine on raw bentonite, modified bentonite with base and modified bentonite with acid was compared solving in different solutions such as aqueous and aqueous-ethanol solutions based on adsorption isotherms. The effect of temperature, time and pH were observed on adsorption of 2,4-dichlorophenoxyacetic acid dimethyl amine. Sorption mechanisms in soils, the effect of surface functional groups as well as parameters influencing adsorption were discussed. Then maximum adsorption of 2,4-dichlorophenoxyacetic acid dimethyl amine capacity was measured on modified bentonite with base in pH 5 at 40 degrees C for 24 h. The modified bentonite with base used in experimental work played a major role than on the adsorption of 2,4-dichlorophenoxyacetic acid dimethyl amine so, the modified bentonite with base has better characteristics than raw bentonite and modified bentonite with acid adsorbents. The Freundlich isotherms of aqueous-ethanol solution was better than isotherms of aqueous solution for much better to adsorb of 2,4-dichlorophenoxyacetic acid dimethyl amine.
Application of Experimental Design Methodology for Adsorption of Brilliant Blue Onto Amberlite Xad-4/Agaricus Campestris as a New Biocomposite Adsorbent
(Koya Univ, 2022) Ahmed, Ahmed A.; Yonten, Vahap
This research presents a new biocomposite adsorbents using response surface methodology (RSM) to find the best conditions for highest adsorption of Brilliant Blue G250 (BBG) from aqueous solution by Amberlite XAD-4/Agaricus campestris. The most effective parameters are determined by Plackett-Burman design (PBD) with specific ranges initial dye concentration (5-150 mg.L-1), temperature (20-50 degrees C), contact time (5-100 min), pH (3-11), shaking speed (150-300 rpm), sample volume (5-75 mL), and adsorbent dosage (0.05-0.6 g). Then, in the second step, the optimum condition of effective factors is predicted using steepest ascent design. Finally, optimal medium conditions of effective parameters with central composite design are located. According to RSM, the best adsorbent amount, contact time, initial dye concentration, and sample volume for maximum removal% of BBG (96.72%) are 0.38 g, 60.78 min, 107.13 mg.L-1, and 28.6 mL, respectively. The adsorption of brilliant blue is approved by scanning electron microscopy. Under optimum conditions, it is concluded that XAD-4/A. campestris biocomposite is a suitable adsorbent for removing BBG from aqueous solution.
Exploring the Optimum Conditions for Maximizing the Microbial Growth of Candida Intermedia by Response Surface Methodology
(Taylor & Francis inc, 2014) Yonten, Vahap; Aktas, Nahit
Exploring optimum and cost-efficient medium composition for microbial growth of Candida intermedia Y-1981 yeast culture growing on whey was studied by applying a multistep response surface methodology. In the first step, Plackett-Burman (PB) design was utilized to determine the most significant fermentation medium factors on microbial growth. The medium temperature, sodium chloride and lactose concentrations were determined as the most important factors. Subsequently, the optimum combinations of the selected factors were explored by steepest ascent (SA) and central composite design (CCD). The optimum values for lactose and sodium chloride concentrations and medium temperature were found to be 18.4g/L, 0.161g/L, and 32.4 degrees C, respectively. Experiments carried out at the optimum conditions revealed a maximum specific growth rate of 0.090 1/hr; 42% of total lactose removal was achieved in 24h of fermentation time. The obtained results were finally verified with batch reactor experiments carried out under the optimum conditions evaluated.
Exploring Thermodynamics and Kinetic Parameters of Immobilized Catalase Enzyme Via Adsorption on Krill Clay
(desalination Publ, 2017) Nas, Mehmet Salih; Gur, Aycan; Gur, Tugba; Yonten, Vahap
The thermodynamic parameters and immobilization kinetics of catalase enzyme via adsorption onto krill clay were performed in aqueous solution in batch system. The adsorbent was characterized by X-ray fluorescence, scanning electron microscope and Brunauer-Emmett-Teller N-2 adsorption measurements. The effect of some parameters to the adsorption process such as contact time, stirring speed, initial enzyme concentration, initial ionic strength, temperature and pH were analyzed. Maximum adsorption capacity (q(m)) showed a great dependence on pH and initial enzyme concentration. It was found at pH 5.5, and initial enzyme concentration, 0.0075 g L-1 values. Pseudo-first-order, pseudo-second-order and intraparticle diffusion were used to fit the kinetics data on kinetic models. Furthermore, thermodynamic activation parameters such as enthalpy, entropy, Gibbs free energy and activation energy (Delta H degrees, Delta S degrees, Delta G degrees and E-a) which reveal that catalase enzyme adsorption occur spontaneously and in endothermic nature were determined. The obtained results confirmed that the applicability of krill clay is an efficient immobilizing supporter for catalase enzyme and krill clay material can be used as a very effective adsorbent in immobilization of this enzyme from aqueous solutions.
Green Synthesis, Characterization and Antimicrobial Activity of Silver Nanoparticles Using Ornithogalum Narbonense L
(Taylor & Francis inc, 2022) Ozturk, Dilara; Ozguven, Ayse; Yonten, Vahap; Ertas, Metin
Green synthesis of silver nanoparticles (AgNPs) was performed using extracts from Ornithogalum narbonense L. (ONL) as a cost-effective and eco-friendly approach. A surface plasmon resonance peak was observed at 440 nm after 12 h. The intense reddish-brown coloration was observed higher than 1.5 mM AgNO3 concentrations. Bioactive compounds were found responsible for the reduction, stabilization, and capping of Ag+ to AgNPs. X-ray powder diffraction analysis confirmed the face-centered cubic silver crystalline structure. The average spherical-shaped individual particle size was around 8.46 nm, while hydrodynamic size ranged between 7-13 nm and 36-131 nm. The AgNPs have good stability (zeta = -31.15 mV). Energy-dispersive X-ray spectroscopy analysis proved the presence of elemental Ag (6.76%). The antibacterial activity with the zone of inhibition is as follows: P. aeruginosa > E. coli > S.aureus > B. cereus (10.35 +/- 0.12 mm > 9.40 +/- 0.14 mm > 8.20 +/- 0.10 mm > 7.0 +/- 0.24 mm). The AgNPs did not show antifungal properties against C. albicans.
A Statistical Optimization of Methylene Blue Removal From Aqueous Solutions by Agaricus Campestris Using Multi-Step Experimental Design With Response Surface Methodology: Isotherm, Kinetic and Thermodynamic Studies
(Elsevier, 2020) Kivanc, Mehmet Riza; Yonten, Vahap
In this study, a multi-step experimental design of Response Surface Methodology (RSM) was applied to optimize the medium conditions for the maximum removal of Methylene Blue (MB) from aqueous solution by a novel fungi A. campestris as a biosorbent. In first step, the effect of factors (initial dye concentration, temperature, contact time, pH, agitation speed and adsorbent dosage) was obtained using Plackett Burman Design (PBD). Then Steepest Ascent (SAD) used to predict the optimum region of effective factors in the second step. Central Composite Design (CCD) was utilized to evaluate the optimum medium conditions of effective parameters for the removal of cationic dye on last step. RSM indicated that optimum conditions of initial dye concentration, agitation speed and medium temperature for maximum removal of MB (95%) were achieved as 130.90 mg L-1, 125 rpm and 41.87 degrees C, respectively. The activation energy (Ea) was determined as 149.1, -178.6, 154.5 and 382.3 kJ/mol for 20, 50, 100 and 200 mgL(-1) respectively. The characterization of adsorption process was confirmed by Scanning Electron Microscope (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). Adsorption isotherm was used to describe the adsorption equilibrium studies at different temperatures. Langmuir isotherm shows better fit than Freundlich and Temkin isotherms. Thermodynamic parameters like the enthalpy 15 kJ/mol (Delta H-o), entropy 66.59 J/molK (Delta S-o) and Gibbs free energy -4.47 kJ/mol (Delta G(o)) were evaluated and also,.Go shows a negative values indicating that the adsorption process was spontaneous and endothermic in nature. The results show that a multi-step statistical optimization designs is successful applied to experiments and novel and endemic biomass of Agaricus Campestris is an appropriate biosorbent and has a specific affinity for removal of Methylene Blue at under optimal conditions.
A Thermodynamic and Kinetic Approach To Adsorption of Methyl Orange From Aqueous Solution Using a Low Cost Activated Carbon Prepared From Vitis Vinifera L
(Elsevier, 2020) Yonten, Vahap; Sanyurek, Nesrin Karaca; Kivanc, Mehmet Riza
In this paper, thermodynamic and kinetic parameters of the Methyl Orange adsorption process on active carbon prepared from endemic Vitis vinifera L. grape seeds (AC-VVL) grown in the Tunceli-Elazig region and % removal of dye from aqueous solutions were evaluated by using a batch system. Experiments were performed as a function of pH (2, 5, 8 and 11), temperature (15 degrees C, 30 degrees C and 45 degrees C) and initial concentration (100, 150, 300 and 1000 mg L-1). The mechanism and characterization of adsorption of dye was analyzed pre-adsorption (AC-VVL) and post-adsorption (AC-VVL+dye) using FTIR (Fourier Transform Infrared Spectroscopy), SEM (Scanning Electron Microscope) and Brauner Emmet and Teller (BET) analyzer. The activation energy (Ea) was determined as 24.80, 39.15, -22.40 and 61.73 kJ/mol for 100, 150, 300 and 1000 mg L-1, respectively. The Langmuir, Freundlich, Temkin and Harkins Jura isotherms were used to describe the adsorption equilibrium studies at different temperatures. The Freundlich isotherm shows better fit than other isotherms in the temperature range studied. Maximum adsorption occurred at pH 2 and was approximately 79.7 mg/g. The % Recycling Yield was found to be 20% and 9 mg/g with acetone. Thermodynamic parameters like the change in enthalpy (Delta H-o), entropy (Delta S-o) and Gibbs free energy (Delta G(o)) were evaluated and the adsorption process was found to be endothermic and spontaneous. The results show that this AC-VVL biomass is an appropriate biosorbent and has specific affinity for removal of Methyl Orange from aqueous solutions.