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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.
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    Öğe
    Preparation and Characterisation of Biochar from Hazelnut Shell and Its Adsorption Properties for Methylene Blue Dye
    (2018) Kaya, Nihan; Yıldız, Zeynep; Ceylan, Selim
    One of the major pollutants in water resources are organic dyes that are widely used by different industries. Methylene blue (MB) is one of them which is quite harmful for aquatic life. This pollutant must be removed with proper methods. Adsorption is one of the most popular methods because of its high purification yield and known as a cost effective process if the sorbent is inexpensive. In this study, biochar which is used as an adsorbent has been produced from hazelnut shells used as the raw material. Chemical, thermal and surface characteristics of raw hazelnut shell were investigated by FT-IR, TG/DTG, SEM and elemental analysis. Biochar characteristics were determined by FT-IR, BET and SEM analysis. The effect of different adsorption parameters such as pH, initial dye concentration, contact time, adsorbent dosage and temperature on the adsorption of MB onto hazelnut shell char were examined in batch experiments. The equilibrium of adsorption was modeled using Langmuir and Freundlich isotherm models. The maximum adsorption yield of MB was found to be 83% at pH 4.0, adsorbent dosage of 4 g/L, contact time of 300 min., initial dye concentration of 15 mg/L and temperature of 45 oC. In addition, the Freundlich isotherm was found to be the best fitting isotherm model for the adsorption process. The pseudo-first-order and pseudo-second-order kinetic models were applied to the experimental data and thermodynamic parameters such as Gibbs free energy, enthalpy and entropy were determined.