Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 14Citation - Scopus: 15Effect of Carbonic Anhydrase on Caco3 Crystallization in Alkaline Solution(American Chemical Society, 2016) Molva, Murat; Kılıç, Sevgi; Özdemir, Ekrem; Kılıç Özdemir, Sevgi; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe effect of bovine carbonic anhydrase (CA) on calcium carbonate (CaCO3) crystallization was investigated. A new method was developed to estimate the biocatalytic activity of CA in alkaline solution. The CA was immobilized within polyurethane (PU) foam, and compared its biocatalytic activity with the free-CA and bare-PU foam. A minireactor was created in a calcium hydroxide (Ca(OH)2) solution in order to control the CO2 transfer rate, and reproducible results were obtained. It was found that the free-CA lost its activity in less than 6 min at pH 12.5 in alkaline Ca(OH)2 solution. The CaCO3 crystallization rates for the immobilized-CA were found to be a U-shape, relatively lower at lower immobilized-CA amounts compared to those for the free-CA and bare-PU foam and higher when the amount of immobilized-CA increased. It was concluded that a higher immobilized-CA amount is required to accelerate the CaCO3 crystallization rates in Ca(OH)2 solution.Article Citation - WoS: 123Citation - Scopus: 134Effect of Moisture on Adsorption Isotherms and Adsorption Capacities of Co2 on Coals(American Chemical Society, 2009) Özdemir, Ekrem; Özdemir, Ekrem; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe effect of moisture on the adsorption isotherms and adsorption capacities of CO 2 on Argonne Premium coals has been investigated. In some experiments a small hysteresis was observed between the adsorption and desorption isotherms. The hysteresis was absent or negligible for high-rank and as-received coals but was discernible for lower rank and dried coals. An equation that accounted for the volumetric changes when an adsorbate alters the structure of an adsorbent was employed to interpret the data. The best-fit solutions indicate that the coal volume decreases upon drying. The microscopic shrinkage estimated using helium expansion was greater than the shrinkage reported using the bed-height technique. The microscopic shrinkage was 5-10% for low-moisture medium and high-rank coals and up to 40% for low-rank coals having higher moisture contents. The CO 2 swelling of coals during adsorption isotherm measurements was estimated to be about the same as the shrinkage that occurred during the moisture loss. The adsorption capacity, isosteric heat of adsorption, average pore size, and surface area of the as-received (moist) and dried Argonne coals were estimated after accounting for the volume changes. The isosteric heat of adsorption of CO 2 was found to be between 23 and 25 kJ/mol for as-received coals and between 25 and 27 kJ/mol for dried coals, regardless of the rank. The degree of drying was shown to affect the adsorption capacity and the calculated surface area. For dried coals, the adsorption capacity showed the typical 'U-shape' dependence on rank whereas the as-received coals displayed a more linear dependence. A relationship is proposed to quantify the effect of moisture on the adsorption capacity. The mechanism of CO 2 adsorption on moist coals and the implications of the lower adsorption capacity of wet coals to coal seam sequestration of CO 2 are presented.Article Citation - WoS: 88Citation - Scopus: 108Biomimetic Co2 Sequestration: 1. Immobilization of Carbonic Anhydrase Within Polyurethane Foam(American Chemical Society, 2009) Özdemir, Ekrem; Özdemir, Ekrem; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyBovine carbonic anhydrase (CA) was immobilized within polyurethane (PU) foam for biomimetic CO2 sequestration. The catalytic activities for the free and immobilized CA were estimated using paranitrophenyl acetate (p-NPA) as the substrate. Because the p-NPA has limited solubility in the aqueous phase, the activities were estimated in Tris buffer containing 10% acetonitrile. A Lineweaver-Burk relationship was employed to estimate the Michaelis-Menten kinetic parameters for the free and immobilized CA. The kcat, K m, and kcat/Km values for the free CA were found to be 2.02 s-1, 12.2 mM, and 166.4M-1 s-1, respectively. The Km value for the immobilized CA was estimated to be 9.6mMat the same conditions. The immobilized CA was stable and did not lose any activity over seven consecutive washings and activity tests. While the free CA lost its activity in 45 days stored at 4 °C in refrigerator, the immobilized CA maintained 100% of its activity over a 45 day period stored in Tris buffer at ambient conditions. It was concluded that the immobilized CA as a very stable biocatalyst could be employed in biomimetic CO2 sequestration.