Chemical Engineering / Kimya Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/14
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Article Citation - Scopus: 2A Comparative Assessment for Efficient Oleuropein Extraction From Olive Leaf (olea Europaea L. Folium)(Murat Yakar, 2023) Recepoğlu, Yaşar Kemal; Gümüşbulut, Gülin; Yüksel Özşen, AslıSince oleuropein has long been known in the health sector and is abundant directly in our country as the fourth largest olive producer, oleuropein, the predominant phenolic ingredient in olive leaves, was recovered in this study using Soxhlet extraction. The effects of different solvent types (acetonitrile, ethanol, methanol, and water), extraction period (4 cycles, 4 h, and 8 h), particle size (250-500 µm and 900-2000 µm), and pretreatment of olive leaves on the yield of oleuropein were examined to determine the maximum yield. A greater oleuropein yield was obtained when the particle size of olive leaves utilized for extraction was lowered. Furthermore, aqueous solvents revealed a higher yield of oleuropein than pure solvents and prolonging the extraction duration resulted in a significant increase in the amount of oleuropein extracted. On the other hand, pretreatment of olive leaves resulted in a reduction in oleuropein output. As a result, with 36% extraction efficiency in terms of olive leaf conversion, the highest oleuropein extraction yield was obtained as 13.35 mg g-1 dry leaf for 8 h of extraction time using olive leaves with a particle size of 250-500 µm and an 80% methanol solution as solvent. © Author(s) 2023.Article Citation - WoS: 40Citation - Scopus: 47Boron in Geothermal Energy: Sources, Environmental Impacts, and Management in Geothermal Fluid(Elsevier, 2022) Mott, A.; Baba, Alper; Hadi Mosleh, Mojgan; Ökten, Hatice Eser; Babaei, Masoud; Gören, Ayşegül Yağmur; Feng, C.; Recepoğlu, Yaşar Kemal; Uzelli, Taygun; Uytun, Hüseyin; Morata, Diego; Yüksel Özşen, AslıThe problem of hazardous chemicals in geothermal fluid is a critical environmental concern in geothermal energy developments. Boron is among the hazardous contaminants reported to be present at high concentrations in geothermal fluids in various countries. Poor management and inadequate treatment of geothermal fluids can release excessive boron to the environment that has toxic effects on plants, humans, and animals. Despite the importance of boron management in geothermal fluid, limited and fragmented resources exist that provide a comprehensive understanding of its sources, transport and fate, and the treatment strategies in geothermal energy context. This paper presents the first critical review from a systematic and comprehensive review on different aspects of boron in geothermal fluid including its generation, sources, toxicity, ranges and the management approaches and treatment technologies. Our research highlights the origin of boron in geothermal water to be mainly from historical water-rock interactions and magmatic intrusion. Excessive concentrations of boron in geothermal fluids have been reported (over 500 mg/L in some case studies). Our review indicated that possible boron contamination in geothermal sites are mostly due to flawed construction of production/re-injection wells and uncontrolled discharge of geothermal water to surface water. The dominancy of non-ionic H3BO3 species makes the selection of the suitable treatment method for geothermal waters limited. Combining boron selective resins and membrane technologies, hybrid systems have provided effluents suitable for irrigation. However, their high energy consumption and course structure of boron selective resins encourage further research to develop cost-effective and environmentally friendly alternatives.Article Citation - WoS: 2Citation - Scopus: 2Electrolytic Oxidation of 1,8-Diazabicyclo[5.4.0]undec in Hot-Compressed Water on a Titanium Electrode(American Chemical Society, 2020) Orak, Ceren; Yüksel Özşen, AslıThe nitrogen-containing heterocyclic organic compound, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), was chosen to prepare a model solution to represent nitrogen-containing industrial waste streams. A hybrid reactor system was designed to combine electrolysis with wet oxidation in hot compressed water using a titanium electrode. The effects of current density, NaOH concentration, and reaction time on DBU and total organic carbon (TOC) removal were investigated via Minitab 18 software to clarify the main and interaction effects. Statistical analysis shows that the NaOH concentration and current density had significant effects on DBU removal. The highest DBU (91.2%) and TOC (45%) removal was observed at the lowest DBU concentration (3 mM) for 90 min of reaction time. Last, the effect of temperature on DBU and TOC removal was investigated. TOC removal was described with the first-order reaction kinetic model. Rate constants were determined as 0.0025, 0.041, and 0.050 min(-1) at 200, 240, and 280 degrees C, respectively. The activation energy was calculated as 79.86 kJ/mol.Article Citation - WoS: 1Citation - Scopus: 1Mineralization of Olive Mill Wastewater Under Hydrothermal Conditions(Desalination Publications, 2019) Ersanlı, Çağlar; Yüksel Özşen, AslıOlive mill wastewater (OMW) is highly dangerous for land and aquatic environments because of its high phenolic content, acidity, and salinity. Hence, hydrothermal degradation of OMW in subcritical water medium with and without using external oxidizer (H2O2) was studied to decrease its total organic carbon (TOC), total phenolic content (TPC), and color. Effects of reaction temperature (150 degrees C-250 degrees C), reaction time (30-120 min), and H2O2 content (0-100 mM) on TOC and TPC of OMW were investigated. Box-Behnken-type experimental design and statistical analysis (analysis of variance) were practiced by Design Expert 11. According to statistical analysis, effect of reaction temperature significantly affected TOC removal efficiency. The best TOC reduction (31.65%) was achieved without using H2O2 at 250 degrees C for 120 min.