Browsing by Author "Koyuncu, Hulya"

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Adsorption of Dark Compounds With Bentonites in Apple Juice
(Elsevier Science Bv, 2007) Koyuncu, Hulya; Kul, Ali Riza; Calimli, Ayla; Yildiz, Nuray; Ceylan, Hasan
The adsorption equilibrium of dark-coloured Compounds from apple juice has been investigated as a function of several variables including activation conditions of bentonite (heat and acid treatments), clay concentrations (2 x 10(-3)-8 x 10(-3) kg clay/dm(3) apple juice) and temperature (range of 296-336 K). The adsorption efficiency with acid-activated bentonite was greater than that with heat-activated and native bentonite, depending on surface properties; specific surface areas were 95.31, 71.95 and 71.76 m(2)/g, respectively. Absorbance data at 420 nm were fitted reasonably well with the Langmuir and Freundlich isotherms. The parameters K, Q(0), K-fr and n were determined for different temperatures. Thermodynamic parameters such as Gibbs free energy (Delta G), enthalpy (Delta H) and entropy (Delta S) change of adsorption were determined as about -3.125, 9.43 and 0.039 kJ mol(-1) K-1, respectively, for acid-activated bentonite. These parameters were also determined for native and heat-activated bentonites. It was shown that the adsorption process was endothermic, spontaneous and controlled by physical mechanism. The adsorption and desorption rate constants (k(a), and k(d)) were obtained separately by applying a geometric approach to the first-order Langmuir model. k(a) varied from 5.717 x 10(-4) to 20.667 x 10(-3) s(-1) and k(d) from 1.425 x 10(-4) to 7.473 x 10(-3) s(-1). The results showed that acid-activated bentonite is more suitable for the adsorption of dark compounds from apple juice. (c) 2006 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.
Biosorption Study for Removal of Methylene Blue Dye From Aqueous Solution Using a Novel Activated Carbon Obtained From Nonliving Lichen (Pseudevernia Furfuracea (L.) Zopf.)
(Elsevier, 2020) Koyuncu, Hulya; Kul, Ali Riza
To the best of our knowledge, there is no study on the utilization of lichens in the production of activated carbon while lichens are natural, renewable and cheap sources. In this study, a novel activated carbon (ACLPF) from non-living lichen Pseudevernia furfuracea (L.) Zopf. (LPF) was produced, and physicochemical and morphological characterization of the ACLPF were examined with the help of Brauner-Emmett-Teller surface area (BET), X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) techniques. The obtained ACLPF had a high surface area (851.24 m(2)g(-1)) and a large pore volume (0.225 cm(3)g(-1)) with micropore size distribution (1.06 nm). To investigate the usability of the ACLPF in wastewater treatment, batch mode biosorption experiments were carried out, and the effect of various parameters on methylene blue (MB) dye removal from aqueous solution were studied. The experimental data were fitted with 4 different kinetic models (pseudo first-order (PFO), pseudo second-order (PSO), Elovich model (EM) and intra-particle diffusion (IDM)) and 3 different isotherm models (Langmuir, Freundlich and Dubinin-Radushkevich (D-R)). It was found that the maximum biosorption capacity and the removal efficiency (%) were as 243.9024 mgg(-1) and 91.38%, respectively. The biosorption of MB onto the ACLPF was chemical biosorption due to the activation energy (E-a) to be 42.63 kJmol(-1), and the process was endothermic (Delta H-0=61.4163 kJmol(-1)), feasible and spontaneous (Delta G(0)= -7.0278 kJmol(-1) at 318 K and Delta S-0 =0.1707 kJmol(-1)K(-1)) thermodynamically. The novelty of this study is that besides obtained and characterized the activated carbon (ACLPF) from the non-living LPF at the first time, the discussions on the biosorption capability of the ACLPF for the removal of MB dye from aqueous media are included in this paper.
Equilibrium and Kinetic Studies for the Sorption of 3-Methoxybenzaldehyde on Activated Kaolinites
(Elsevier Science Bv, 2007) Koyuncu, Hulya; Kul, Ali Riza; Yildiz, Nuray; Calimli, Ayla; Ceylan, Hasan
The sorption of 3-methoxybenzaldehyde on activated kaolinites has been investigated at different temperatures. Two types of activation tests were performed. The sorption equilibrium was studied by sorption isotherms in the temperature range 303-333 K for natural (untreated), thermally and acid activated kaolinites. It was shown that the isotherm shapes were not affected by temperature and activation types of kaolinite. The absorbance data at 312 nm were fitted reasonably well with the Langmuir and Freundlich isotherm models and the model parameters were determined for different temperatures. Thermodynamic quantities such as Gibbs free energy (Delta G), the enthalpy (Delta H) and the entropy change of sorption (Delta S) were determined for natural, thermally and acid activated kaolinites. It was shown that the sorption processes were an endothermic reactions, controlled by physical mechanisms and spontaneously. Adsorption capacity of acid activated kaolinite for 3-methoxybenzaldehyde was higher compared to that of natural and thermally activated kaolinites at various temperatures. The adsorption and desorption rate constants (k(a) and k(d)) were obtained separately by applying a geometric approach to the first order Langmuir model. This method provided good conformity between the K from Langmuir parameters and K-geo (k(a)/k(d)) from geometric approach. (c) 2006 Elsevier B.V. All rights reserved.
An Investigation of Cu(Ii) Adsorption by Native and Activated Bentonite: Kinetic, Equilibrium and Thermodynamic Study
(Elsevier Sci Ltd, 2014) Koyuncu, Hulya; Kul, Ali Riza
In this study, the adsorption kinetics, equilibriumand thermodynamics of Cu(II) ions on native (NB) and acid activated (AAB) bentonites were examined. The specific surface areas, pore size and pore size distributions of the samples were fully characterized. The adsorption efficiency of Cu(II) onto the NB and AAB was observed to increase with increasing temperature. The kinetics of adsorption of Cu(II) ions was discussed using three kinetic models, namely: the pseudo-first-order, the pseudo-second-order and the intra-particle diffusion model. The experimental data fitted the pseudo-second-order kinetic model very well. The initial sorption rate and the activation energy were also calculated. Experimental results were also analyzed by the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm equations at different temperatures. RL separation factor for Langmuir and the n value for Freundlich isotherm show that Cu(II) ions adsorbed favorably onto NB and AAB. Calculated thermodynamic quantities such as Gibbs free energy (DG), the enthalpy change (DH) and the entropy change of adsorption (DS) suggest that the adsorption processes were spontaneous, endothermic and controlled by physical mechanisms. (C) 2014 Elsevier Ltd. All rights reserved.
An Investigation of Natural and Modified Diatomite Performance for Adsorption of Basic Blue 41: Isotherm, Kinetic, and Thermodynamic Studies
(desalination Publ, 2021) Kul, Ali Riza; Aldemir, Adnan; Koyuncu, Hulya
In the present study, natural diatomite (ND) and Mn-modified diatomite (MD) were utilized for adsorption of Basic Blue 41 (BB 41) from aqueous solution at temperatures of 298, 308, and 318 K. Based on the results of isotherm studies, the Freundlich isotherm model is better than the Langmuir and Temkin models. Isotherm constants increase as the temperature increases, indicating that the removal process is favorable at higher temperatures. Adsorption kinetics for BB 41 on diatomite best fit the pseudo-second-order model which had kinetic constants that were higher than pseudo-first- order and intra-particle diffusion models. When the initial dye concentration rises from 10 to 80 mg L-1, adsorption capacity on ND and MD increase from 6.15 to 62.43 mg g(-1) and 9.06 to 75.95 mg g(-1) at 318 K, respectively. Gibbs free energy (Delta G degrees) values for BB 41 adsorption on ND and MD were determined as -11.224 and -15.586 kJ mol(-1) at 318 K, respectively. Enthalpy (Delta H degrees) values for this removal process were calculated as 31.746 and 48.706 kJ mol(-1), with entropy (Delta S degrees) values determined as 133.319 and 170.728 J mol(-1) K-1 for ND and MD, respectively. Activation energy (E A) values were determined as 42.7 and 58.83 kJ mol(-1) for BB 41 removal onto ND and MD adsorbents, respectively. Economic analysis of the preparation of Mn-modified diatomite was carried out. The results indicate that diatomite could be a good material compared to more costly adsorbents used for dye removal.
Investigation of the Adsorption Behaviors of Thymol Blue, Crystal Violet and Rhodamine B on Lichen-Derived Activated Carbon
(Serbian Chemical Soc, 2024) Koyuncu, Hulya; Kul, Ali Riza
Since thymol blue (TB), crystal violet (CV) and rhodamine B (RB) are frequently used in various industries, they cause environmental pollution owing to the wastewater treatment process. The current study focused on the removal of TB, CV and RB from aqueous media with lichen-derived activated carbon (LDAC) and comparing their adsorption behavior. The maximum Langmuir adsorption capacity for TB, CV and RB was found to be 400, 213 and 345 mg g(-1), respectively. The removal (%) of TB, CV and RB was found to be 86.38, 79.02 and 82.73 % at the same conditions, respectively. Experimental data were interpreted with some commonly used kinetic and isotherm models. Calculated activation energies, D-R model energies, enthalpy changes and evaluation of FT-IR, XRD and SEM/EDX images taken before and after dye loading showed that the adsorption of TB, CV and RB on the LDAC are physical processes. The pseudo-second-order kinetic model better described the adsorption behavior of TB, CV and RB on the LDAC. The boundary layer thickness value for all the dyes studied increased with increasing initial dye concentration and temperature, and CV also had a larger boundary layer thickness value than that of TB and RB.
Removal of Aniline From Aqueous Solution by Activated Kaolinite: Kinetic, Equilibrium and Thermodynamic Studies
(Elsevier, 2019) Koyuncu, Hulya; Kul, Ali Riza
In this study, the adsorption kinetics, equilibrium and thermodynamics of aniline on native (NK) and acid activated (AK) kaolinites were examined. It was shown that modification of kaolinite with acid not only increases the adsorption capacity of the adsorbent from 109.89 to 256.41 mgg(-1) for aniline but also its initial sorption rate for aniline, suggesting the activated kaolinite with higher adsorption capacity have great potential application in removal of aniline from water and wastewater. Adsorption efficiency for AK reached at about 91% while it was at about 75% for NK. The kinetics of adsorption of aniline was discussed using three kinetic models, the pseudofirst-order, the pseudo-second-order and the infra-particle diffusion model. The experimental data fitted very well the pseudo-second-order kinetic model due to the higher correlation coefficient and lower sum of squared errors (SSE,%) values, and a good agreement between the experimental and the calculated qe values. Experimental results were also analysed by the Langmuir, Freundlich and Dubinin-Redushkevich (D-R) isotherm models. R-L separation factor for Langmuir and the n value for Freundlich isotherm show that aniline are favourably adsorbed by NK and AK. The negative value of Delta G and positive value of Delta S showed that the adsorption of aniline onto NK and AK was feasible and spontaneous. The positive value of Delta H confirmed the endothermic nature of adsorption.
Removal of Methylene Blue Dye From Aqueous Solution by Nonliving Lichen (Pseudevernia Furfuracea (L.) Zopf.), as a Novel Biosorbent
(Springer Heidelberg, 2020) Koyuncu, Hulya; Kul, Ali Riza
The use of lichens is insufficient in industry. To the best of our knowledge, there is no study on the use of lichens in the removal of dyes from aqueous media. The aim of this study is to draw attention to the biosorption capabilities of lichens which are natural, renewable and inexpensive sources, and to investigate the usability of nonliving lichen Pseudevernia furfuracea (L.) Zopf. (LPF) in methylene blue (MB) dye removal from aqueous solution. With the green chemistry approach, no chemical treatment was applied to the LPF and it was used as a natural biosorbent for the biosorption. The LPF samples were prepared and characterized and performed batch mode biosorption experiments studying the effect of various parameters on MB biosorption. The experimental data were fitted with four different kinetic models (pseudo-first order, pseudo-second order, Elovich model and intra-particle diffusion) which were evaluated for their validity. Identification of the biosorption mechanism of MB onto the LPF was performed by isotherm studies via three isotherm models [Langmuir, Freundlich and Dubinin-Radushkevich (D-R)], and the parameters of each model were determined. It was concluded that the biosorption rate and yield were high, the type of biosorption of MB onto the LPF was defined as chemical biosorption, and the surface of the LPF was decided energetically heterogeneous. The results indicate that the LPF biomass can be attractive options for MB dye removal from aqueous media.