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    Adsorption of Congo red from aqueous solution onto KOH-activated biochar produced via pyrolysis of pine cone and modeling of the process using artificial neural network
    (Springer Heidelberg, 2022) Kaya, Nihan; Uzun, Zeynep Yildiz; Altuncan, Ceren; Uzun, Harun
    Most of dyes cause various environmental and health problems due to their toxic, mutagenic, and even carcinogenic properties. Therefore, several treatment methods are used to remove dyes from wastewater. Adsorption is one of the most preferred methods due to its easy application and high efficiency. The aim of this study is to prepare and characterize KOH-activated pine cone (APC) biochar and use it as adsorbent for removal of anionic diazo dye, Congo red (CR) from aqueous solution. The various operating parameters such as pH, contact time, temperature, initial dye concentration, and adsorbent dosage are optimized in batch adsorption system. Experimental results showed that the prepared APC biochar has a surface area of 1714.5 m(2)/g and was achieved 94.62% CR removal efficiency at an adsorbent dosage of 2 g/L. The Freundlich, Langmuir, and Temkin adsorption models were used for the mathematical description of the adsorption equilibrium. Experimental data showed the best compatibility with the Freundlich isotherm. Batch adsorption models, based on the assumption of the pseudo first-order, pseudo second-order, and intra particle diffusion mechanisms, were applied to examine the kinetics of the adsorption. Kinetic data fitted the pseudo second-order kinetic model. Calculated thermodynamic parameters indicated the spontaneous, endothermic, and the increased randomness nature of CR adsorption. Structural and morphological changes of APC biochar after adsorption process were determined by using Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM) analysis. The prediction of the CR adsorption capacity of the APC biochar using artificial neural network (ANN) algorithm was modeled. For this purpose, many different ANN models have been developed. Among them, ANN10 gave the best results. According to ANN10 results, root-mean-squared error (RMSE), mean bias error (MBE), mean absolute error (MAE), and correlation coefficient (R-2) were estimated as 0.770, 0.310, 0.037, and 0.999, respectively. Consequently, the prediction results showed well agreement with experimental results.
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    Experimental and modeling studies on the removal of bromocresol green from aqueous solutions by using pine cone-derived activated biochar
    (Springer Heidelberg, 2024) Kaya, Nihan; Uzun, Zeynep Yildiz
    This study was carried out to evaluate the potential application of pine cone (PC)-derived activated biochar which has a surface area of 1714.5 m(2)/g for bromocresol green (BCG) dye removal from aqueous solution. Batch adsorption experiments involved varying pH, temperature, contact time, adsorbent dosage, and initial dye concentrations and the maximum BCG removal (96.27%) occurred at pH: 2.0, T: 45 degrees C, m: 2 g/L, t: 15 min., and C-o: 25 mg/L. To study the characteristics of adsorption, the adsorption kinetic isotherm and thermodynamic parameters were employed. The experimental data was evaluated to fit well with the Temkin isotherm (R-2=0.99) and the adsorption process followed pseudo-first-order kinetics (R-2=0.96). Thermodynamic parameters obtained from the adsorptive uptake showed that the interaction was endothermic and spontaneous in nature. The regenerated activated PC biochar showed good performance (95.0%), even, after 4th regeneration. To predict the BCG adsorption capacity of activated PC biochar, many different artificial neural network (ANN) models have been developed. The optimal ANN model gave mean absolute error (MAE), mean bias error (MBE), root mean square error (RMSE), and R-2 values of 0.036, 0.578, 0.947, and 0.999, respectively. The results obtained showed that ANN can be used to effectively model the BCG adsorption process.
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    Hydrothermal carbonization of sugar beet pulp: optimization and characterization
    (Springer Heidelberg, 2024) Uzun, Zeynep Yildiz
    In this study, the optimum hydrothermal conditions of sugar beet pulp were investigated by Response Surface Methodology (RSM) based on Central Composite Design (CCD). The hydrochar obtained from sugar beet pulp (SBP) was optimized for maximum yield and carbon content. Process conditions were chosen with reaction temperatures of 200-240 degrees C, residence time 60-150 min, and biomass to water ratio of 1:3-1:10. The yield and carbon content of the hydrochar varied with the process parameters. In order to obtain hydrochar with the highest yield and carbon content in optimization, the reaction temperature should be 220.74 degrees C, the biomass to water ratio should be 1:3, and the residence time should be 95.58 min. High heating value, energy and mass yield, and energy densification ratio of sugar beet pulp and hydrochar were also investigated. The products were characterized using FT-IR, SEM, and ultimate analysis techniques. The Coats-Redfern method was used to estimate the kinetic parameters of the combustion processes. The activation energy values of SBP and SBP-HC products were calculated as 13.88 and 11.46 kJ/mol, respectively. The kinetic data were used to determine the thermodynamic parameters (Delta H, Delta G, and Delta S). As a result, the properties of hydrochar produced from sugar beet pulp under optimum conditions have been extensively investigated and the results have shown that hydrochar has potential for use in different areas.
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    Investigating the effectiveness of rice husk-derived low-cost activated carbon in removing environmental pollutants: a study of its characterization
    (Taylor & Francis Inc, 2024) Kaya, Nihan; Ozkeser, Esma Carus; Uzun, Zeynep Yildiz
    The chemically activated biochar was produced through the pyrolysis of rice husk. Thermal gravimetric and elemental analysis were conducted to characterize the raw rice husk. The activated biochar product underwent evaluation through SEM, BET and, FT-IR analysis. This cost-effective activated carbon was utilized as an adsorbent for the elimination of environmental pollutants. At a temperature of 25 & DEG;C, the activated biochar product exhibited an impressive maximum CO2 adsorption capacity of 152 mg/g. This exceptional performance can be attributed to its notable surface area and porosity, measuring at 2,298 m(2)/g and 0.812 cm(3)/g, respectively. This product was also utilized to remove methyl red (MR) dye from an aqueous solution. The optimal parameters for the removal of MR were determined as follows: a pH of 6.0, a temperature of 25 & DEG;C, an initial MR concentration of 50 mg/L, and an adsorbent dosage of 0.4 g/L. At a duration of 140 min, the system attained its maximum equilibrium adsorption capacity, reaching a value of 62.06 mg/g. Furthermore, the calculated maximum MR removal efficiency stood at an impressive 99.31%. The thermodynamic studies demonstrated that the MR removal process was spontaneous, exothermic, and increased randomness. Kinetic studies suggested that the pseudo-second-order model can fit well. Novelty statementRice is the staple food for a significant portion of the world's population. Rice husk, which is released during the production and processing of rice, is one of the most important agricultural wastes worldwide. In this study, low cost activated carbon was produced by converting renewable resource such as rice husk biomass into a product with high added value. The resulting product, with its high surface area, can offer a more sustainable, cost-effective, and versatile alternative for a range of industrial, environmental, and medical applications.
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    Investigation of effectiveness of pine cone biochar activated with KOH for methyl orange adsorption and CO2 capture
    (Springer Heidelberg, 2021) Kaya, Nihan; Uzun, Zeynep Yildiz
    In this study, pyrolysis of pine cone, a lignocellulosic biomass, was carried out in a fixed bed reactor. The biochar product obtained was activated by using chemical activation method. KOH was used as the activating agent with the impregnation ratio was 1/4. Activated pine cone biochars were characterized by using analysis techniques such as SEM, BET, and FT-IR. The usage potential of the activated biochar product with a surface area of 1714.5 m(2)/g has been investigated in two different application areas. As the first application area, the CO2 holding capacity of activated biochar was measured by using the thermogravimetric analysis method. The CO2 adsorption capacity of the activated biochar was determined as 160 mg/g (3.64 mmol/g) at 25 degrees C. As a second application area, the effectiveness of activated biochar product in the removal of dyestuff (methyl orange) from aqueous solutions was investigated. The methyl orange adsorption capacity of the activated biochar in optimum conditions (pH 2, temperature of 25 degrees C, initial concentration of 100 mg/L, adsorbent amount 0.8 g/L) was calculated as 109.5 mg/g. Isotherm modeling and kinetic investigations showed that Freundlich and pseudo-second-order models describe the adsorption equilibrium and kinetic behavior well. As a result, this type of biomass could be successfully evaluated in removing both methyl orange dye, which is a potential pollution risk for aquatic environment, and CO2 that is responsible for climate change and greenhouse effect in the atmosphere.
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    Investigation of fuel properties of hydrochars obtained from pomegranate peel: characterization and combustion kinetic
    (Springer Heidelberg, 2023) Uzun, Zeynep Yildiz
    In this study, hydrochars were obtained from pomegranate peel (PP), which is a waste biomass, by hydrothermal carbonization method at different temperatures (200-240 degrees C) and through 1 h of residence time. Analysis techniques such as proximate, elemental, FTIR, and SEM were used for the characterization of the samples. According to elemental analysis results, with the increase in temperature, the carbon content of hydrochars and higher heating value increased. FTIR analysis results showed that there are aromatic and oxygen-containing structures (C = C, C = O, C-O) on the surface of hydrochars. According to the SEM analysis results, there are fibrous and slightly porous structures on the surface of the hydrochars. The combustion behavior of the products was investigated by thermogravimetric analysis. Thermogravimetric analysis results showed that the fuel properties of hydrochars improved with the increase in temperature. The Coats-Redfern method was used to estimate the kinetic parameters of the combustion processes. The activation energy values of the hydrochars ranged between 5.95 and 18.66 kJ/mol.
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    Kinetic and thermodynamic studies on the adsorption of Cu2+ ions from aqueous solution by using agricultural waste-derived biochars
    (Iwa Publishing, 2020) Kaya, Nihan; Arslan, Ferhat; Uzun, Zeynep Yildiz; Ceylan, Selim
    In this study, it was aimed to investigate the adsorption properties of the biochars obtained by pyrolysis of hazelnut and walnut shells for removal of copper ions from aqueous solutions. The characterization of raw biomasses and also biochars were performed using TGA-DTG, FT-IR, BET, SEM, partial and elemental analysis techniques. The optimum conditions were determined by investigating the effect of adsorption parameters (initial concentration, temperature, adsorbent amount, pH, contact time and mixing speed) for efficient removal of copper ions from aqueous solution by batch adsorption experiments carried out under different conditions. The highest adsorption efficiencies were recorded as 82 and 86% respectively for hazelnut and walnut shell biochars at pH 4, C-o = 15 ppm, adsorbent dosage = 3 g/L and mixing speed = 600 rpm. Experimental results showed that the adsorption efficiency for copper ions increased with the increase of temperature (T = 45 degrees C) in studies only using biochar obtained from hazelnut shell. While the time of equilibrium in the aqueous solution containing copper ions was determined to be 75 min for walnut shell char, this duration was 30 min for hazelnut shell char. The experimental results were investigated in terms of Langmuir, Freundlich and Temkin isotherm models. Together with the calculated thermodynamic parameters, the adsorption mechanism was explained. In order to determine the kinetic model of the adsorption process, the experimental data were applied to pseudo first-order, pseudo second-order and intra-particle diffusion models, and the model constants were investigated.