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    Evaluation of optimum carbonization conditions of the blended domestic polymeric waste, biomass and lignite in the presence of catalyst by Taguchi and ANOVA optimization analysis
    (Elsevier, 2022) Basar, Canan Akmil; Korkmaz, Aydan Aksogan; Onal, Yunus; Utku, Tugba
    In this work, the effects of blending mass ratio, pyrolysis temperature, pyrolysis time, heating rate, and amount of catalyst on the pyrolysis of the blended lignite (EL), pistachio shell (PS) and domestic wastes (DW) were investigated. The influence of experimental parameters on the char, liquid and gas efficiency was statistically evaluated by the Taguchi method and ANOVA analysis. The optimum experimental conditions is a1b1c2d1e3, a3b1c1d1e2, a2b3c2d3e2 for liquid efficiency, char efficiency and gas efficiency respectively. The amount of catalyst was found to be the most effective parameter for solid efficiency and the mass ratio for both liquid and gas efficiency. The char, liquid and gas efficiencys estimated by the Taguchi method under optimum experimental conditions are 39.58%, 18.5% and 47.04%, respectively. The char efficiency of 42.54%, liquid efficiency of 19.78% and gas efficiency of 49.83% were determined under optimum experimental conditions obtained by the Taguchi method. Analysis of Variance (ANOVA) was also used to determine the mean response magnitudes of each controllable process parameter. ANOVA analysis results support the results found by the Taguchi method. In the carbonization process, FTIR, XRD and SEM analyzes were performed to determine the structural change of the solid product depending on the temperature.
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    Immobilization of α-Amylase onto Quantum Dots Prepared from Hypericum perforatum L. Flowers and Hypericum capitatum Seeds: Its Physicochemical and Biochemical Characterization
    (Springer/Plenum Publishers, 2023) Acari, Idil Karaca; Dik, Gamze; Bakar, Busra; Ulu, Ahmet; Onal, Yunus; Ates, Burhan
    Enzyme immobilization is an effective way to increase the catalytic activity and stability of the alpha-amylase (Amy) enzyme for industrial uses. For this purpose, carbon and graphene quantum dot (QDs) structures were prepared from Hypericum perforatum L. flowers (QD-1), and Hypericum capitatum seeds (QD-2) obtained from an herbalist in Hatay province of Turkey. Structural and morphological characterization of the prepared QDs and QDs/Amy were carried out by Fourier transform infrared spectrophotometer (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive X-ray (EDX). Meanwhile, biochemical characterizations such as optimum pH and temperature, kinetic parameters, effects of metal ions, organic solvents, and trypsin digestion on enzyme activity were performed and compared with free Amy. The Amy enzyme was immobilized with an activity efficiency of 71.15% for QD-1/Amy, and 81.51% for QD-2/Amy under optimal conditions. The difference in activity efficiency between QD-1/Amy and QD-2/Amy was likely due to a change in the surface porosity of QDs structures. While the optimal pH value of all three forms of Amy was recorded as 6.0, their optimal temperature was found to be 40 degrees C. The activation energy (E-a) of the free Amy was found to be 4.81 kJ/mol, while it was 9.61 kJ/mol, and 3.20 kJ/mol for QD-1/Amy, and QD-2/Amy, respectively. K-m values were calculated as 1.18, 1.57, and 1.35 mg/mL for free Amy, QD-1/Amy, and QD-2/Amy, respectively, and V-max values were calculated as 37.52, 37.60, and 39.93 mu mol/min, respectively. Kinetic data revealed that the immobilized enzymes had lower substrate affinity compared to the free Amy. Besides, the QD-1/Amy and QD-2/Amy exhibited more stability than free Amy against metal ions, organic solvents as well as trypsin digestion due to the increment in conformational rigidity caused by changes in the secondary structures of the immobilized enzyme. For instance, after incubation with trypsin for 120 min, free Amy, QD-1/Amy, and QD-2/Amy retained approximately 20%, 35%, and 26% of initial activities, respectively. Finally, it can be proposed that the prepared carriers in this work may a useful to produce stable and active immobilized Amy to be used in industrial applications.
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    Sustainable approach to dye adsorption: hemp-based activated carbon as an effective adsorbent
    (Taylor & Francis Ltd, 2025) Toptas, Yeliz; Yavuz, Bahar; Korkmaz, Aydan Aksogan; Onal, Yunus
    In industry, the use of dyes that threaten human health is increasing day by day. RB 19 (Reactive Blue 19, Remazol brilliant blue R), one of the most common dyes that adversely affect natural life, is the subject of this article. In this article, the waste parts of the hemp plant (root, stem and other) were evaluated for use in scientific studies. Hemp wastes were carbonised at 500 degrees C at a heating rate of 10 degrees C/min for 1 hour in the N2 atmosphere. Chemical activation was then carried out with 1:4 potassium hydroxide (KOH) at 800 degrees C under the same conditions. Activated carbon (AC) used as an adsorbent was characterised by elemental analysis (73.3% C, 0.3% H, 0.46% N, 0.02% S and 25.92% O), XRD, SEM, BET and FT-IR analysis. Activated carbon (AC) with 850 mu m size, 1858.70 m2/g surface area was obtained by chemical activation of carbonised hemp waste with KOH. SEM images showed that the activated carbon is structurally similar to a honeycomb. Kinetic parameters were analysed with six different equations (Intra Particle Diffusion, Pseudo First, Pseudo Second, Elovich, Avrami, Bangham) and adsorption mechanism with eight different equations (Henry, Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Koble-Corrigan, Flory-Huggins, Harkin-Jura). According to the calculated diffusion coefficient (19.299), it is concluded that diffusion is externally controlled. The Intra-Particle Diffusion constant (75.34) indicated that the outer adsorption layer of activated carbon was thick. When the correlation coefficients of the equations were examined according to the kinetic analysis results, the highest correlation coefficient was observed in the Pseudo-First kinetic model for all temperatures. However, it was determined that it also fits the Bangham and Avrami models. Since Bangham and Avrami models have high regression coefficients (0.96-0.99), it can be said that adsorption also fits these models. Also, the negative Gibbs Free Energy values indicate that adsorption can occur spontaneously and is thermodynamically favourable.