Chemical Engineering / Kimya Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/14
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Article Citation - WoS: 56Citation - Scopus: 58Clinoptilolite Supported Rutile Tio2 Composites: Synthesis, Characterization, and Photocatalytic Activity on the Degradation of Terephthalic Acid(Elsevier Ltd., 2017) Yener, H. B.; Yılmaz, M.; Deliismail, Özgün; Özkan, Seher Fehime; Helvacı, Şerife ŞerefClinoptilolite supported rutile TiO2 composites were synthesized for the enhancement of its photocatalytic performance in the degradation of the aqueous terephthalic acid solution under UVC illumination by the increase in its surface area and to simplify its recovery from the treated solution after use. The XRD spectra of the composites revealed the formation of pure rutile TiO2 on the surface of the clinoptilolite. The SEM images showed the formation of the spherical TiO2 clusters were composed of nano fibers on the surface of the clinoptilolite. For all composites synthesized, the dispersion of the TiO2 particles on the clinoptilolite led to a surface area larger than that of the bare TiO2 and clinoptilolite. The materials synthesized in the present study exhibited higher catalytic activity compared with the commercial Degussa P25 and anatase. Among the catalysts synthesized the TiO2/clinoptilolite with a weight ratio of 0.5 was found to be the most photoactive catalyst even though it contains a lesser amount of active TiO2. The kinetic of the reactions for different catalyst was found to be consistent with the pseudo-first order kinetic model. The results of the Langmuir-Hinshelwood model showed the slight contribution of the adsorption on the degradation. The activity of the TiO2/clinoptilolite with a weight ratio of 0.5 decreased after repetitive use due to the accumulation of the TPA molecules on the surface of the catalyst.Article Citation - WoS: 35Citation - Scopus: 41Batch and Column Studies on Heavy Metal Removal Using a Local Zeolitic Tuff(Elsevier Ltd., 2010) Balköse, Devrim; Ülkü, Semra; Can, ÖzgeIon exchange is considered to be one of the most cost effective methods if low cost ion exchangers such as natural zeolites are used in waste water treatment. In this study, a zeolitic tuff rich in clinoptilolite from Gördes Manisa Turkey was examined to evaluate its ion exchange performance for the removal of copper, nickel and cobalt ions from metal (II) nitrate solutions at various concentrations by performing both batch and packed column experiments. A clinoptilolite tuff with purity around 60% was used in ion exchange experiments. Copper, nickel and cobalt exchange capacities of the tuff were determined as 8.3mg (0.26meq) Cu2+/g, 6.6mg (0.23meq) Ni2+/g and 4.5mg (0.15meq) Co2+/g, respectively. The equilibrium behavior of the system was best described by classical Langmuir model. The experimental breakthrough curves from the column experiments were fitted to solid diffusion control model. The study showed that efficient metal ion removal can be done by using the local clinoptilolite rich tuff. © 2010 Elsevier B.V.Article Citation - WoS: 10Citation - Scopus: 10Clinoptilolite-Rich Mineral as a Novel Carrier for the Active Constituents Present in Ginkgo Biloba Leaf Extract(Elsevier Ltd., 2008) Göktaş, Selda; Ülkü, Semra; Bayraktar, OğuzThe possible use of clinoptilolite-rich mineral as a novel carrier for the active constituents present in Ginkgo biloba leaf extract solutions was investigated. The flavonoid aglycone constituents were found to be selectively adsorbed on the clinoptilolite surface. The antioxidant activity determinations of the extract solutions were performed by the Trolox Equivalent Antioxidant Capacity (TEAC) assay. The antioxidant activity measurements performed for the Ginkgo leaf extract solutions showed decreasing antioxidant activities due to adsorption. The decrease in antioxidant activity was attributed to the adsorption of phenolic constituents on the clinoptilolite surface.Article Citation - WoS: 29Citation - Scopus: 31Cure Kinetics of Epoxy Resin-Natural Zeolite Composites(Springer Verlag, 2008) Cansever Erdoğan, Beyhan; Seyhan, Abdullah Tuğrul; Ocak, Yılmaz; Tanoğlu, Metin; Balköse, Devrim; Ülkü, SemraThe cure kinetics of epoxy resin and epoxy resin containing 10 mass% of natural zeolite were investigated using differential scanning calorimetry (DSC). The conformity of the cure kinetic data of epoxy and epoxy-zeolite system was checked with the auto-catalytic cure rate model. The results indicated that the hydroxyl group on the zeolite surface played a significant role in the autocatalytic reaction mechanism. This group was able to form a new transition state between anhydride hardener and epoxide group. The natural zeolite particles acted as catalyst for the epoxy system by promoting its curing rate.Article Citation - WoS: 12Citation - Scopus: 17Diffusion Mechanism of Water Vapour in a Zeolitic Tuff Rich in Clinoptilolite(Springer Verlag, 2008) Çakıcıoğlu Özkan, Seher Fehime; Ülkü, SemraThe adsorption kinetics of H2O in a clinoptilolite rich zeolitic tuff was experimentally investigated at 18°C. In the identification of the diffusion mechanism the isothermal adsorption model equation was used. It was found out that the intraparticle mass transfer becomes more dominant over the heat transfer with increase in particle size and the adsorptive dose pressure. Although initially intraparticle mass transfer was the controlling resistance later external heat transfer also contributes to the transfer mechanism.Article Citation - WoS: 112Citation - Scopus: 130The Effect of Hcl Treatment on Water Vapor Adsorption Characteristics of Clinoptilolite Rich Natural Zeolite(Elsevier Ltd., 2005) Çakıcıoğlu Özkan, Fehime; Ülkü, SemraIn this study, water vapor adsorption properties of the clinoptilolite rich zeolite tuff, from Bigadic (Turkey), and its modified forms were examined. The modified forms were obtained by treating the tuff with HCl solutions (0.032, 0.16, 0.32, 1.6 or 5 M) at 25,40,75 and 100°C for 3 h. Infrared spectroscppy and water vapor adsorption were used for the characterization of the zeolites. Langmuir, BET and Dubinin-Raduschevich methods were applied in the analysis of water vapor adsorption data. Applications of Dubinin Raduschevich equation to the water adsorption data displayed that the super-micropore volume was not very sensitive to acid treatment. It was found out that the Langmuir surface area and ultra-micropore volume depend on the degree of the removal of aluminum from the structure.Article Citation - WoS: 249Citation - Scopus: 268Silver, Zinc, and Copper Exchange in a Na-Clinoptilolite and Resulting Effect on Antibacterial Activity(Elsevier Ltd., 2004) Top, Ayben; Ülkü, SemraAg+-Na+, Zn2+-Na+, and Cu2+-Na+ equilibria for clinoptilolite-rich mineral from Gördes (Western Anatolia) were investigated at 25 °C and 0.1 N total solution normality. While silver exchange was favorable over the whole concentration range, zinc and copper were partially exchanged and preferred only at low concentrations. The standard free energies of exchanges for Ag+-Na+, Zn2+-Na+, and Cu2+-Na+ pairs were found as -6.0, 2.03, and 3.09 kJ/equiv., respectively. From these values, selectivity sequence was determined as Ag+>Na+ >Zn2+>Cu2+. Antibacterial activities of the exchanged samples were measured as a function of exchange level against Pseudomonas aeruginosa and Escherichia coli. Considering the selectivity sequence of the clinoptilolite and antibacterial activity results, Ag-clinoptilolite seemed to be promising antibacterial material.Article Citation - WoS: 47Citation - Scopus: 52Isomerization of ?-Pinene Over Ion-Exchanged Natural Zeolites(Elsevier Ltd., 2003) Özkan, Fehime; Gündüz, Gönül; Akpolat, Oğuz; Beşün, Nurgün; Murzin, Dmitry Yu.Catalysts prepared by ion exchange of clinoptilolite-based natural zeolite tuffs with NH4 +, Ba2+ and Pb2+ were investigated in the isomerization reaction of α-pinene at atmospheric pressure under nitrogen flow. Activity and selectivity to mono-, bi- and tricyclic products were correlated with acidity strength.