Browsing by Author "Koyuncu, Huelya"

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Adsorption of Pb(Ii) Ions From Aqueous Solution by Native and Activated Bentonite: Kinetic, Equilibrium and Thermodynamic Study
(Elsevier, 2010) Kul, Ali Riza; Koyuncu, Huelya
In this study, the adsorption kinetics, equilibrium and thermodynamics of Pb(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 Pb(II) onto the NB and AAB was increased with increasing temperature. The kinetics of adsorption of Pb(II) ions was discussed using three kinetic models, the pseudo-first-order, the pseudo-second-order and the intra-particle diffusion model. The experimental data fitted very well the pseudo-second-order kinetic model. The initial sorption rate and the activation energy were also calculated. The activation energy of the sorption was calculated as 16.51 and 13.66 kJ mol(-1) for NB and AAB, respectively. Experimental results were also analysed by the Langmuir, Freundlich and Dubinin-Redushkevich (D-R) isotherm equations at different temperatures. R-L separation factor for Langmuir and the n value for Freundlich isotherm show that Pb(II) ions are favorably adsorbed by NB and AAB. Thermodynamic quantities such as Gibbs free energy (Delta G), the enthalpy (Delta H) and the entropy change of sorption (Delta S) were determined as about -5.06, 10.29 and 0.017 kJ mol(-1) K-1, respectively for AAB. It was shown that the sorption processes were an endothermic reactions, controlled by physical mechanisms and spontaneously. (c) 2010 Elsevier B.V. All rights reserved.
Comparative Research of Isotherm, Kinetic, and Thermodynamic Studies for Neutral Red Adsorption by Activated Carbon Prepared From Apple Peel
(Springer int Publ Ag, 2023) Kul, Ali Riza; Koyuncu, Huelya; Turan, Aysenur; Aldemir, Adnan
In this study, activated carbon (AC) obtained with apple peel was used for removal of Neutral Red (NR) from aqueous solutions. The characterization of AC was evaluated with the Brunauer-Emmett-Teller (BET), Fourier transform infrared spectra (FTIR), X-ray diffraction (XRD), and scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX) analyses. Isotherm, kinetic, and thermodynamic parameters were determined for NR removal with AC. Eighteen isotherm models and eight kinetic models were analyzed for three temperatures and six initial dye concentrations. The experimental data best agree with the Langmuir model among the isotherm models, and the maximum adsorption capacity (q(m)) was calculated 142.857 mg/g at 318 K. It was determined that the pseudo-second-order (PSO) model was the best choice among the kinetic models with the highest correlation coefficients. The removal percentage of NR dye with AC obtained 82.13%, 84.79%, and 87.20% for 120 mg/L initial dye concentration at 298 K, 308 K, and 318 K, respectively. The negative free energy, enthalpy, and entropy values of adsorption obtained - 6386 J/mol, 46280 J/mol, and 165.48 J/mol.K for 20 mg/L NR concentration at 318 K, respectively. The results of this separation process shown spontaneous essence, and workability coinciding with the negative free energy and activation energy was found 13.651 kJ/mol. The assessment of the isotherm, kinetic, and thermodynamic results were evaluated with error functions. The highest correlation coefficient (R-2) values and the lowest sum of squares (SS), sum of the square of error (SE), and mean square of error (MSE) values were determined with Langmuir isotherm and PSO kinetic models. This research showed that AC prepared from biomass can be used effectively for wastewater treatment using adsorption technique.
Synthesis and Characterization of a Novel Activated Carbon Using Nonliving Lichen Cetraria Islandica (L.) Ach. and Its Application in Water Remediation: Equilibrium, Kinetic and Thermodynamic Studies of Malachite Green Removal From Aqueous Media
(Elsevier, 2020) Koyuncu, Huelya; Kul, Ali Riza
Although lichens are natural and cheap sources, there is no study in the literature about the production of activated carbon from lichen species. In this study, a novel activated carbon (ACCI) from non-living lichen Cetraria islandica (L.) Ach. (LCI) was produced, and physicochemical and morphological characterizations of the LCI and ACCI 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 BET surface area, Barrett-JoynerHelenda (BJH) adsorption total volume of pores and BJH adsorption average pore diameter of the ACCI were determined as 394.417 m(2).g(-1), 0.1216 cm(3).g(-1) and 12.768 angstrom (1.28 nm), respectively, while these values for non-living LCI were 1.103 m(2).g(-1), 0.0044 cm(3). g(-1) and 140.18 angstrom (14.02 nm), respectively. To investigate and compare the biosorption properties of the LCI and ACCI in wastewater treatment, batch mode biosorption experiments were carried out, and the effect of various parameters on malachite green (MG) dye removal from aqueous media 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)). The biosorption of MG onto both the LCI and ACCI follows well the PSO kinetics. The rate constants k(2) for the LCI and ACCI were found as 0.0125-0.0157 g.mg(-1).min(-1) and 0.00612-0.00979 g.mg(-1).min(-1), respectively (298-318 K). The equilibrium time was 80 min for the ACCI, and the maximum biosorption capacity and the removal efficiency (%) for the ACCI were found as 666.22 mg.g(-1) and 93.46%, respectively. The biosorption mechanism of MG onto both the LCI and ACCI was physical biosorption. This result was confirmed by the activation energies (9.095 kJ.mol(-1) for LCI and 18.450 kJ.mol(-1) for ACCI), the D-R mean energies (6.8041-7.4536 kJ.mol(-1) for LCI and 7.3323-8.0582 kJ.mol(-1) for ACCI in the temperature range 298-318 K), and FTIR, XRD, TGA and SEM/EDX results. The enthalpy change (Delta H-0) values for the LCI and ACCI were found to be in the range of 8.7987-17.2582 kJ.mol(-1) and 20.4899-29.2728 kJ.mol(-1), respectively (20-70 mg.L-1 initial MG concentrations). This indicated the endothermic behaviour of the biosorption. The novelty of this study is that besides obtained and characterized the activated carbon (ACCI) from the nonliving LCI for the first time, the comparisons and discussions on the biosorption capability of the ACCI and LCI for the removal of MG dye from aqueous media are included in this paper. All results showed that the synthesized ACCI is an effective, cheap and promising biosorbent for the cleaning treatment of MG dye from wastewaters.