Chemical Engineering / Kimya Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/14
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Article Citation - WoS: 15Citation - Scopus: 16A Machine Learning Ensemble Approach for Predicting Solar-Sensitive Hybrid Photocatalysts on Hydrogen Evolution(IOP Publishing, 2024) Bakır, Rezan; Orak, Ceren; Yuksel, AsliHydrogen, as the lightest and most abundant element in the universe, has emerged as a pivotal player in the quest for sustainable energy solutions. Its remarkable properties, such as high energy density and zero emissions upon combustion, make it a promising candidate for addressing the pressing challenges of climate change and transitioning towards a clean and renewable energy future. In an effort to improve efficiency and reduce experimental costs, we adopted machine learning techniques in this study. Our focus turned to predictive analyses of hydrogen evolution values using three photocatalysts, namely, graphene-supported LaFeO3 (GLFO), graphene-supported LaRuO3 (GLRO), and graphene-supported BiFeO3 (GBFO), examining their correlation with varying levels of pH, catalyst amount, and H2O2 concentration. To achieve this, a diverse range of machine learning models are used, including Random Forest (RF), Decision Tree (DT), Support Vector Machine (SVM), XGBoost, Gradient Boosting, and AdaBoost-each bringing its strengths to the predictive modeling arena. An important step involved combining the most effective models-Random Forests, Gradient Boosting, and XGBoost-into an ensemble model. This collaborative approach aimed to leverage their collective strengths and improve overall predictability. The ensemble model emerged as a powerful tool for understanding photocatalytic hydrogen evolution. Standard metrics were employed to assess the performance of our ensemble prediction model, encompassing R squared, Root Mean Squared Error (RMSE), Mean Squared Error (MSE), and Mean Absolute Error (MAE). The yielded results showcase exceptional accuracy, with R squared values of 96.9%, 99.3%, and 98% for GLFO, GBFO, and GLRO, respectively. Moreover, our model demonstrates minimal error rates across all metrics, underscoring its robust predictive capabilities and highlighting its efficacy in accurately forecasting the intricate relationships between GLFO, GBFO, and GLRO values and their influencing factors.Article Citation - WoS: 4Citation - Scopus: 5Numerical Study of Fluid Flow and Mixing in the Argon Oxygen Decarburization (aod) Process(Iron and Steel Institute of Japan, 2023) Cheng, Zhongfu; Wang, Yannan; Dutta, Abhishek; Blanpain, Bart; Guo, Muxing; Malfliet, AnneliesA three-dimensional (3D) model has been developed based on the Eulerian multiphase flow approach to investigate the fluid flow behavior and mixing efficiency in the multi-tuyere AOD process. The interphase forces, including drag force, lift force, virtual force, turbulent dispersion force, and wall lubrication force, were incorporated into this model. The model was used to simulate six-tuyere and seven-tuyere AOD processes. The phenomena of multi-jet penetration, bubble plume merging, 3D turbulent flow and mixing characteristics were considered. The results indicate that the bubble plume merging occurs in the upper part of the liquid bath, forming a typical plume cluster. The predicted penetration length for a single tuyere jet agrees well with the previous work. For the multi-jet system, the side jets penetrate deeper than the inside ones. The six-tuyere AOD has a good flow condition in the center of the liquid bath, while the seven-tuyere AOD has a better flow pattern in the sidewall region and the lower bath. Overall, the seven-tuyere AOD performs better in mixing efficiency than the six-tuyere AOD under the same gas flow rate. These findings increase the understanding of the AOD process, allowing further optimization of process parameters. This model can be further extended to incorporate the thermochemical reactions into the modeling of the AOD reactor.Article Citation - WoS: 47Citation - Scopus: 54Olive Leaf Extracts Protect Cardiomyocytes Against 4-Hydroxynonenal Toxicity in Vitro: Comparison With Oleuropein, Hydroxytyrosol, and Quercetin(Georg Thieme Verlag, 2014) Bali, Elif Burcu; Ergin, Volkan; Rackova, Lucia; Bayraktar, Oğuz; Küçükboyacı, Nurgün; Karasu, ÇimenOlive (Olea europaea) leaf, an important traditional herbal medicine, displays cardioprotection that may be related to the cellular redox modulating effects of its polyphenolic constituents. This study was undertaken to investigate the protective effect of the ethanolic and methanolic extracts of olive leaves compared to the effects of oleuropein, hydroxytyrosol, and quercetin as a positive standard in a carbonyl compound (4-hydroxynonenal)- induced model of oxidative damage to rat cardiomyocytes (H9c2). Cell viability was detected by the MTT assay; reactive oxygen species production was assessed by the 2′,7′-dichlorodihydrofluorescein diacetate method, and the mitochondrial membrane potential was determined using a JC-1 dye kit. Phospho-Hsp27 (Ser82), phospho-MAPKAPK-2 (Thr334), phospho-c-Jun (Ser73), cleaved-caspase-3 (cl-CASP3) (Asp175), and phospho-SAPK/JNK (Thr183/Tyr185) were measured by Western blotting. The ethanolic and methanolic extracts of olive leaves inhibited 4-hydroxynonenal-induced apoptosis, characterized by increased reactive oxygen species production, impaired viability (LD50: 25 μM), mitochondrial dysfunction, and activation of pro-apoptotic cl-CASP3. The ethanolic and methanolic extracts of olive leaves also inhibited 4-hydroxynonenal-induced phosphorylation of stress-activated transcription factors, and the effects of extracts on p-SAPK/JNK, p-Hsp27, and p-MAPKAPK-2 were found to be concentration-dependent and comparable with oleuropein, hydroxytyrosol, and quercetin. While the methanolic extract downregulated 4-hydroxynonenal-induced p-MAPKAPK-2 and p-c-Jun more than the ethanolic extract, it exerted a less inhibitory effect than the ethanolic extract on 4-hydroxynonenal-induced p-SAPK/JNK and p-Hsp27. cl-CASP3 and p-Hsp27 were attenuated, especially by quercetin. Experiments showed a predominant reactive oxygen species inhibitory and mitochondrial protecting ability at a concentration of 1-10 μg/mL of each extract, oleuropein, hydroxytyrosol, and quercetin. The ethanolic extract of olive leaves, which contains larger amounts of oleuropein, hydroxytyrosol, verbascoside, luteolin, and quercetin (by HPLC) than the methanolic one, has more protecting ability on cardiomyocyte viability than the methanolic extract or each phenolic compound against 4-hydroxynonenal-induced carbonyl stress and toxicity.Article Citation - WoS: 20Citation - Scopus: 23Rice-Like Hollow Nano-Caco3 Synthesis(Elsevier Ltd., 2016) Ülkeryıldız, Eda; Kılıç, Sevgi; Özdemir, EkremWe have shown that Ca(OH)2 solution is a natural stabilizer for CaCO3 particles. We designed a CO2 bubbling crystallization reactor to produce nano-CaCO3 particles in homogenous size distribution without aggregation. In the experimental set-up, the crystallization region was separated from the stabilization region. The produced nanoparticles were removed from the crystallization region into the stabilization region before aggregation or crystal growth. It was shown that rice-like hollow nano-CaCO3 particles in about 250 nm in size were produced with almost monodispersed size distribution. The particles started to dissolve through their edges as CO2 bubbles were injected, which opened-up the pores inside the particles. At the late stages of crystallization, the open pores were closed as a result of dissolution-recrystallization of the newly synthesized CaCO3 particles. These particles were stable in Ca(OH)2 solution and no aggregation was detected. The present methodology can be used in drug encapsulation into inorganic CaCO3 particles for cancer treatment with some modifications.Article Citation - WoS: 14Citation - Scopus: 15Chitosan-Immobilized Pumice for the Removal of As(v) From Waters(Springer Verlag, 2014) Turan, Dilek; Kocahakimoğlu, Cemre; Boyacı, Ezel; Sofuoğlu, Sait Cemil; Eroğlu, Ahmet EminA novel sorbent, chitosan-immobilized pumice, has been prepared for the sorption of As(V) from waters prior to its determination by hydride generation atomic absorption spectrometry. The success of the immobilization has been checked with such characterization techniques as scanning electron microscopy, thermal gravimetric analysis, and elemental analysis. Points of zero charge of the sorbents were determined with potentiometric mass titration. Batch-type equilibration studies have shown that the novel sorbent can be employed at a wide pH range resulting in quantitative sorption (>90 %) at pH 3.0-7.0 and greater than 70 % sorption at pH >8.0. These results demonstrate the advantage of immobilizing chitosan onto pumice, because, under the same conditions, pumice displays <20 % sorption toward As(V), whereas chitosan gives approximately 90%sorption only at pH 3.0. The validity of the method was verified through the analysis of ultrapure, bottled drinking, and tap water samples spiked with arsenate; the respective sorption percentages of 93.2 (±0.7), 89.0 (±1.0), and 80.9 (±1.3) were obtained by batch-type equilibration. Arsenic sorption was also examined in the presence of common interfering ions resulting in competing effects of PO3- 4 and NO- 3on As(V) adsorption.Article Citation - WoS: 21Citation - Scopus: 23Activated Carbon Adsorption of Fuel Oxygenates Mtbe and Etbe From Water(Springer Verlag, 2009) İnal, Fikret; Yetgin, Senem; Aksu, Gülsüm T.; Şimşek, Selvi; Sofuoğlu, Aysun; Sofuoğlu, Sait CemilThe aqueous phase adsorption of fuel oxygenates methyl tertiary butyl ether (MTBE) and ethyl tertiary butyl ether (ETBE) onto commercially available granular activated carbon (GAC; Norit GAC 1240) was investigated in a batch system at 27°C. The oxygenate concentrations were determined by headspace gas chromatography/mass spectrometry analyses. The experimental data were used with four two-parameter isotherm models (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich) and two kinetic models (pseudo first-order and pseudo second-order) to determine equilibrium and kinetic parameters. Considering the correlation coefficient and root mean square error, Dubinin-Radushkevich isotherm showed better fit with the equilibrium data for MTBE. However, the performances of Langmuir and Dubinin-Radushkevich models were comparable for ETBE. The adsorption capacities were calculated as 5.50 and 6.92 mg/g for MTBE and ETBE, respectively, at an equilibrium solution concentration of 1 mg/L using Dubinin-Radushkevich isotherm. The differences between the model predictions and experimental data were similar for the pseudo first-order and pseudo second-order kinetic models. Gibbs free-energy changes of adsorption were found to be -22.59 and -28.55 kJ/mol for MTBE-GAC and ETBE-GAC systems, respectively, under the experimental conditions studied.