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Doktora Tezleri

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Browsing Doktora Tezleri by Subject "Adsorption"

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    Doctoral Thesis
    DNA adsorption on silica, alumina and hydroxyapatite and imaging of dna by atomic force microscopy
    (Izmir Institute of Technology, 2013) Yetgin, Senem; Balköse, Devrim
    The scope of the study is to investigate calf thymus DNA adsorption process on solid powders such as silica, alumina and hydroxyapatite (HAP) to improve DNA solid phase extraction efficiency and to visiulize DNA adsorption by atomic force microscopy (AFM). The equilibrium and kinetics of the DNA adsorption were investigated in batch adsorption on a commercial silica gel and a synthesized silica aerogel, commercial alumina and HAP powders from aqueous DNA solution. Commercial DNA extraction kit adsorbents were also characterized and used for adsorption. Adsorbed DNA was imaged in ambient air on flat surfaces of mica, silica and alumina wafers and HAP particles coated glass surfaces and a HAP pellet surface by AFM. Effects of ambient air, nitrogen flow and freeze drying methods on DNA morphology on the releted surfaces were also investigated. Adsorption of DNA on silica, alumina and HAP increased with the decrease of pH from 9.0 to 2.0. Enhancements of the adsorption capacities of adsorbents were obtained with the addition of MgCl2. It was found that the Van der Waals and the hydrogen bonds rather than the surface charge were the cause of the adsorption. The adsorption isotherms of DNA on silica, alumina and HAP were fitted to Langmuir model in pH range 2-9. The adsorption kinetics obeyed pseudo second order model. The sharpest image of DNA by AFM was obtained by freeze drying method on alumina surface. Dispersed DNA in water was adsorbed on the surfaces not as single molecules but as supercoils consisting of many molecules.
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    Doctoral Thesis
    An experimental and theoretical study on the improvement of adsorption heat pump performance
    (Izmir Institute of Technology, 2008) Demir, Hasan; Ülkü, Semra
    Adsorption heat pumps, which have considerably sparked attentions in recent years, have the advantage of being environmentally friendly and operating with heat sources such as waste heat, solar and geothermal energies as well as storing the energy.The present investigation covers working principle of adsorption heat pumps, a detailed literature survey on the performed studies, information about adsorption phenomena, experimental results of two differently designed and constructed systems, numerical simulation of heat and mass transfer in an annular adsorbent bed, and microcalorimetric study for obtaining isosteric heat of adsorption for water vapor-silica gel pair. The two intermittent adsorption heat pumps can operate without any leakage. The silica gelwater was employed as the adsorbent-adsorbate pair in both of the systems. The temperature and pressure in the evaporator, condenser and adsorbent bed were measured and the coefficients of performance, total entropy generation, the second law efficiency, specific heating and cooling power values were calculated based on these measured values for all of the representative cycles. The heat transfer area of the second designed adsorption heat pump is 550% greater than the first designed adsorption heat pump and this increase resulted in 170% and 200% of improvements in specific heating power (SHP) and specific cooling power (SCP) values respectively. The silica gel granules were mixed with small size metal pieces in order to accelerate heat transfer in the bed. Experiments were performed to measure the thermal diffusivity through the adsorbent bed in which adsorbent is mixed with metal pieces. It was observed that the mixing of silica gel grains with 10wt% of small size aluminum pieces increases the SHP and SCP values of the second heat pump by 250%.