Zeynep Yıldız Uzun

Bio: Zeynep Yıldız Uzun is an academic researcher from Sinop University. The author has contributed to research in topics: Adsorption & Freundlich equation. The author has an hindex of 1, co-authored 3 publications receiving 6 citations.

Investigation of effectiveness of pine cone biochar activated with KOH for methyl orange adsorption and CO2 capture

Abstract: 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 ¼. 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 m2/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 °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 °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.

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

Abstract: 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 m2/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 (R2) were estimated as 0.770, 0.310, 0.037, and 0.999, respectively. Consequently, the prediction results showed well agreement with experimental results.

Kinetic and thermodynamic studies on the adsorption of Cu2+ ions from aqueous solution by using agricultural waste-derived biochars

Abstract: 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, Co1⁄4 15 ppm, adsorbent dosage1⁄4 3 g/L and mixing speed1⁄4 600 rpm. Experimental results showed that the adsorption efficiency for copper ions increased with the increase of temperature (T1⁄4 45 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.

Recent advances in developing engineered biochar for CO2 capture: An insight into the biochar modification approaches

Abstract: Carbon dioxide (CO2) is the primary anthropogenic greenhouse gas with a significant contribution to global warming; this excessive emission needs to be controlled through an effective carbon capture and storage (CCS) approach. Biochar has been considered a cost-effective adsorbent for CO2 capture; however, pristine biochar suffe from poor textural properties and surface chemistry. Here, developing engineered biochar requires careful tuning of the physicochemical properties of the biochar to obtain a high CO2 capture capacity. This work presents a review of recent studies on the synthesis of engineered biochar through various modifications for CO2 adsorption. In this context, the impact of different modification approaches, including physical, chemical, and physicochemical treatments, on the CO2 uptake properties of the engineered biochar are reviewed. Emphasis is given to the mechanisms through which the CO2 adsorption capacity of biochar is enhanced after each modification. This survey of literature stresses the importance of maintaining a balance between the textural (specific surface area and micropore volume) and surface chemical attributes (basicity, mineral content, various functional groups, non-polarity and hydrophobicity) to produce engineered biochar with high CO2 uptake capacity, strong selectivity towards CO2 over other gases and stable performance upon multiple cycles of CO2 adsorption-desorption.