Yazar "Ozekmekci, Mehtap" seçeneğine göre listele

Listeleniyor 1 - 6 / 6
  • Küçük Resim Yok
    Öğe
    Biodegradable Hydroxyethyl Cellulose (HEC)-Chitosan (CS)-Lemon Peel Composite Films: A Sustainable Alternative to Synthetic Food Packaging
    (Wiley, 2025) Kotancilar, Sena Karin; Gerigitmez, Yaren; Akin, Zeynep sude; Senturk, Kubra; Ozekmekci, Mehtap
    The presence of petroleum-based polymers in food packaging is detrimental to the environment, and biodegradable films from dried lemon peel powder (LMP) were developed as a sustainable alternative. The films were prepared by incorporating 1- to 4-wt% LMP into a solution of hydroxyethyl cellulose (HEC) and chitosan (CS) using a solvent casting method. Lemon peel powder was analysed for its components including phenol, lipid, lignin, flavonoid, pectin and ash content. The physicochemical, mechanical and functional properties of the films were investigated. According to Fourier transform infrared spectroscopy, the interaction between the lemon peel and the polymer matrix was confirmed. As the amount of lemon peel powder increased, the film became more hydrophilic and its water solubility, thickness and vapour permeability increased. The contact angle value for HEC-CS and HEC-CS-LMP4 films slightly decreased from 88.39 degrees to 54.39 degrees, respectively. The tensile strength decreased from 107.30 +/- 0.28 MPa (HEC-CS) to 58.13 +/- 0.19 MPa (HEC-CS-LMP4), and elongation at break also declined. Incorporation of lemon peel powder enhanced antioxidant activity from 27.33 +/- 3.47% in the lowest LMP film to 55.31 +/- 0.65% in the highest while also improving antimicrobial properties. The 12-day packaging test on the blueberries showed that unwrapped blueberries lost 64.39 +/- 1.20% of the weight, whereas HEC-CS-LMP4 film lost only 16.09 +/- 0.12%. These findings support the use of this biomaterial in sustainable and bioactive packaging.
  • Küçük Resim Yok
    Öğe
    CO2-Enhanced Synthesis of Trimethyl Borate from Ulexite: Innovations in Pervaporation Separation
    (Amer Chemical Soc, 2025) Ozekmekci, Mehtap; Copur, Mehmet; Unlu, Derya
    The primary objective of this research is to enhance a novel method for the eco-friendly production of trimethyl borate (TMB) from ulexite ore by utilizing carbon dioxide. Notably, CO2, a major greenhouse gas, is converted into thermodynamically stable CaCO3 following TMB synthesis. TMB, a significant organo-boron chemical, has a wide range of industrial applications. In this study, the trimethyl borate production process consists of three main steps: reaction, distillation, and pervaporation. Trimethyl borate was synthesized through the reaction of ulexite with methanol in a high-pressure reactor under a CO2 atmosphere. The obtained liquid product was subjected to distillation to produce the TMB-methanol azeotrope. Following the distillation process, the separation of TMB from the azeotrope mixture was achieved by utilizing pervaporation. The TMB-methanol azeotrope and pure TMB were characterized and confirmed by using Fourier transform infrared (FTIR) spectroscopy and gas chromatography (GC). In this research, hydroxyethyl cellulose (HEC) and polyvinylpyrrolidone (PVP) were used as the membrane materials. Blend membranes were prepared by the solution casting evaporation method. The morphologies of the membranes were characterized by FTIR spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and contact angle assessment. The pervaporation performance of all blend membranes was evaluated for the separation of the TMB-methanol azeotrope. The effects of the operating temperature, methanol feed concentration, and PVP ratios on separation performance were investigated. The results demonstrated that a TMB purity of 97.71 wt % was achieved when the PVP-HEC-2 membrane was utilized in pervaporation. In conclusion, this study introduces an innovative and environmentally friendly process for producing valuable chemicals, highlighting its potential for industrial applications.
  • Küçük Resim Yok
    Öğe
    Dissolution kinetics of ulexite with CO2 in methanol medium
    (Taylor & Francis Ltd, 2025) Ozekmekci, Mehtap; Copur, Mehmet
    In this study, the reaction kinetics of ulexite with CO2 in methanol were investigated in a pressurised reactor for the synthesis of trimethyl borate (TMB). The experimental parameters were varied as follows: temperature (T), 40-100 degrees C; solid-to-liquid ratio (SL), 0.05-0.2 g/mL; reaction time (t), 10-120 min; pressure (P), 10-30 bar; particle size (PS) 63-180 mu m; stirring speed (SS), 500-750 rpm. The results indicated that the dissolution rate increased with higher reaction temperatures and pressures, but decreased with larger particle sizes and higher solid to liquid ratio. However, stirring speed had no significant effect on the dissolution rate. It was observed that CaCO3 crystals that formed on the surface of the solid during the reaction, inhibiting the dissolution of the mineral. Calcium carbonate was produced in the aragonite phase without the use of additives. Thus, a method has been proposed to utilise CO2 and sequester it in a stable and permanent manner. In this study, a novel production process for trimethyl borate (TMB) was investigated, and the reaction mechanism was elucidated. A comprehensive analysis of the reaction mechanism related in the TMB synthesis process were obtained. For kinetic analysis, various empirical models were applied to fit the experimental data. Scanning Electron microscopy (SEM) and X-Ray diffraction (XRD) analyses were performed on the solid sample remaining after dissolution, and the results were supported by statistical analysis. The reaction rate was found to best described by the Avrami model. The activation energy of this process was calculated as 21 kJ/mol. Dans cette & eacute;tude, on a examin & eacute; la cin & eacute;tique de r & eacute;action de l'ulexite avec du CO2 dans le m & eacute;thanol, dans un r & eacute;acteur sous pression, pour la synth & egrave;se du borate de trim & eacute;thyle (TMB). Les param & egrave;tres exp & eacute;rimentaux variaient comme suit: temp & eacute;rature (T), 40 & agrave; 100 degrees C; rapport solide/liquide (SL), 0.05 & agrave; 0.2 g/ml; temps de r & eacute;action (t), 10 & agrave; 120 min; pression (P), 10 & agrave; 30 bar; taille des particules (PS), 63 & agrave; 180 mu m; vitesse d'agitation (SS), 500 & agrave; 750 tr/min. Les r & eacute;sultats ont indiqu & eacute; que le taux de dissolution augmentait avec des temp & eacute;ratures et des pressions de r & eacute;action plus & eacute;lev & eacute;es, mais diminuait avec des tailles de particules plus grandes et un rapport solide/liquide plus & eacute;lev & eacute;. Cependant, la vitesse d'agitation n'avait pas d'effet significatif sur le taux de dissolution. On a observ & eacute; que des cristaux de CaCO3, form & eacute;s & agrave; la surface du solide pendant la r & eacute;action, inhibaient la dissolution du min & eacute;ral. Du carbonate de calcium & eacute;tait produit dans la phase aragonite sans utilisation d'additifs. Ainsi, on a propos & eacute; une m & eacute;thode pour utiliser le CO2 et le s & eacute;questrer de mani & egrave;re stable et permanente. Dans cette & eacute;tude, on a examin & eacute; un nouveau proc & eacute;d & eacute; de production de borate de trim & eacute;thyle (TMB), et l'on a & eacute;lucid & eacute; le m & eacute;canisme de r & eacute;action. On a obtenu une analyse compl & egrave;te du m & eacute;canisme de r & eacute;action reli & eacute; au proc & eacute;d & eacute; de synth & egrave;se du TMB. Pour l'analyse cin & eacute;tique, on a appliqu & eacute; diff & eacute;rents mod & egrave;les empiriques pour ajuster les donn & eacute;es exp & eacute;rimentales. On a effectu & eacute; des analyses par microscopie & eacute;lectronique & agrave; balayage (MEB) et par diffraction des rayons X (XRD) sur l'& eacute;chantillon solide restant apr & egrave;s la dissolution, et les r & eacute;sultats ont & eacute;t & eacute; & eacute;tay & eacute;s par une analyse statistique. On a trouv & eacute; que le mod & egrave;le d'Avrami d & eacute;crivait le mieux le taux de r & eacute;action. On a calcul & eacute; l'& eacute;nergie d'activation de ce proc & eacute;d & eacute; & agrave; 21 kJ/mol.
  • Küçük Resim Yok
    Öğe
    Performance evaluation of cellulose acetate (CA)/polyvinylpyrrolidone (PVP) membranes in the pervaporation separation of trimethyl borate/methanol azeotrope
    (Turkish Energy, Nuclear and Mining Research Agency, 2025) Ozekmekci, Mehtap; Çopur, Mehmet
    In this study, the performance of cellulose acetate (SA)/polyvinylpyrrolidone (PVP) blend membranes for the separation of trimethyl borate (TMB)/methanol azeotrope was investigated. The membranes were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-Ray diffractometer (XRD), thermogravimetric analysis (TGA) and contact angle measurements. The characteristic XRD peak intensity and contact angle of SA decreased with increasing PVP ratio. The effect of PVP ratio, feed temperature and methanol concentration in the feed were investigated in the pervaporation process. It was observed that flux increased and selectivity decreased with increasing PVP ratio. Feed temperature was found to have a positive effect on flux. The increase in the amount of methanol in the feed concentration caused the polymer chains to become more flexible, facilitating the diffusion of both methanol and TMB. Additionally, the reusability of the membrane was tested, and its physical and chemical structure integrity was confirmed by FTIR and SEM analyses. The optimum operating conditions for the SA-PVP-3 membrane were found to be 35°C temperature and azeotrope containing 25 wt% methanol. Under these operating conditions, the flux and selectivity were determined as 302.08 g/(m2h) and 46.92, respectively. © 2025, Turkish Energy, Nuclear and Mining Research Agency. All rights reserved.
  • Küçük Resim Yok
    Öğe
    Polyvinyl pyrrolidone-chitosan blend membrane for pervaporation separation of trimethyl boratemethanol mixture
    (Springer, 2025) Ozekmekci, Mehtap; Copur, Mehmet; Unlu, Derya
    Trimethyl borate (TMB) is an essential chemical for applications ranging from organic synthesis to borohydride production and requires efficient separation from methanol for optimal utilization. This study investigates the pervaporation performance of blend membranes composed of different ratios of chitosan (CS) and polyvinyl pyrrolidone (PVP) to improve the separation of TMB/methanol mixtures through pervaporation. The structural morphology, thermal properties, and crystalline nature of these membranes were comprehensively characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, contact angle measurements, scanning electron microscopy, and X-ray diffraction analysis. Pervaporation experiments were conducted by varying feed compositions, operating temperatures, and PVP ratios. The results demonstrated that increasing PVP content has a significant effect on permeation flux. The best conditions were obtained at 45 degrees C of operation temperature and 75% (by wt) TMB-25% (by wt) methanol mixture by utilizing a PVP-CS-2 membrane, recording flux value of 335.44 g/m2 h. Additionally, PVP-CS-1 and PVP-CS-2 blend membranes were subjected to a crosslinking process to evaluate their separation performance. The crosslinked PVP-CS-1 membrane showed a good performance, with a selectivity value of 146.37. Additionally, the crosslinked PVP-CS-2 membrane exhibited remarkable stability 5 run experiments, indicating strong chemical and mechanical endurance.
  • Küçük Resim Yok
    Öğe
    Trimetil borat/metanol azeotropunun pervaporasyonla ayrılmasında selüloz asetat (SA)/ polivinilpirolidon (PVP) membranların performans değerlendirmesi
    (2025) Ozekmekci, Mehtap; Çopur, Mehmet
    Bu çalışmada trimetil borat (TMB)/metanol azeotropunu ayırmak için selüloz asetat (SA)/ polivinilpirolidon (PVP) blend membranların performansı incelenmiştir. Membranlar, Fourier dönüşümlü kızıl ötesi spektroskopisi (FTIR), taramalı elektron mikroskopisi (SEM), X-Ray difraktometresi (XRD), termogravimetrik analiz (TGA) ve temas açısı ölçümleri ile karakterize edilmiştir. PVP oranındaki artma ile SA’nın karakteristik XRD pik şiddeti ve temas açısı küçülmüştür. Pervaporasyon prosesinde PVP oranının, besleme sıcaklığının ve beslemedeki metanol konsantrasyonunun etkisi incelenmiştir. Artan PVP oranıyla akının arttığı, seçiciliğin azaldığı gözlemlenmiştir. Besleme sıcaklığının akı üzerinde olumlu bir etkiye sahip olduğu tespit edilmiştir. Besleme konsantrasyonundaki metanol miktarının artması, polimer zincirlerinin daha esnek hale gelmesine neden olarak hem metanolün hem de TMB’nin difüzyonunu kolaylaştırmıştır. Ayrıca membranın tekrar kullanılabilirliği test edilmiş olup fiziksel ve kimyasal bütünlüğünü koruduğu yapılan FTIR ve SEM analizleriyle doğrulanmıştır. SA-PVP-3 membranı için en uygun çalışma koşulları, 35°C sıcaklık ve ağırlıkça %25 metanol içeren azeotrop olarak tespit edilmiştir. Bu çalışma koşulları altında akı ve seçicilik sırasıyla 302,08 g/(m2sa) ve 46,92 olarak belirlenmiştir.