Gürkan Karakaş

Middle East Technical University

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Umit S. Ozkan

The Ohio State University

Ufuk Bakır

Middle East Technical University

B. Korkmaz Erdural

Middle East Technical University

Yusuf Uludağ

Middle East Technical University

Alp Yürüm

Sabancı Üniversitesi

Burcu Mirkelamoglu

The Ohio State University

Mahesh W. Kumthekar

The Ohio State University

Ufuk Bölükbaşı

Middle East Technical University

MÇ

Merve Çinar

ODTÜ Teknokent (Turkey)

Pelin Yetisemiyen

Middle East Technical University

Cooperative Institutions

Middle East Technical University

The Ohio State University

Gazi University

Gazi Hastanesi

Romanian Academy

ODTÜ Teknokent (Turkey)

Ankara University

Academy of Romanian Scientists

Universidade Nova de Lisboa

National Tsing Hua University

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Supercritical Fluid Extraction and Temperature-Programmed Desorption of Phenol and Its Oxidative Coupling Products from Activated Carbon

Industrial & Engineering Chemistry Research (1998)

Raashina Humayun Gürkan Karakaş Philip R. Dahlstrom Umit S. Ozkan David L. Tomasko

Activated carbon remains one of the most economical adsorbents for the removal of contaminants from water. In particular, activated carbon is known to have an extremely high affinity for phenol and its derivatives. This has been shown to be the result of a catalytic process wherein activated carbon catalyzes the oxidative coupling reactions of phenol in aqueous solution when molecular oxygen is present. These reactions are believed to be the source of the difficulty of regenerating activated carbon loaded with phenol. This paper reports on our efforts toward using supercritical fluids to regenerate activated carbon combined with a concurrent temperature-programmed desorption study to identify reaction products and their binding strength to the carbon surface. The results show unequivocally that part of the phenol is chemisorbed on the surface and part of it undergoes polymerization. Dihydroxybiphenyls and phenoxyphenols are the major reaction products present on the surface. Isotope studies showed that surface carbon atoms do not directly participate in these reactions. Supercritical extraction was found to perform as well as solvent extraction for the regeneration of activated carbon loaded with phenol. However, due to the chemisorbed nature of these oxidative coupling products, the reduced mass-transfer limitations afforded by supercritical extraction cannot improve the overall extent of extraction even though the rate is improved with the addition of cosolvents.

Supercritical fluid extraction

Carbon fibers

10.1021/ie970936p

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Citations (29)

Preparation of conducting thin film surfaces for amperometric biosensor applications

New Biotechnology (2009)

Zeynep Eker Gürkan Karakaş Merve Çinar Ufuk Bakır

Silicon dioxide

Amperometry

Particle (ecology)

Deposition

10.1016/j.nbt.2009.06.481

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Vanadium promoted ZnO films: effects on optical and photocatalytic properties

Surface Engineering (2023)

Cemre Avşar Gürkan Karakaş

ABSTRACTThe effect of electrodeposition temperature, vanadium doping, and oxidation state of vanadium on the photocatalytic activity of ZnO thin films over ITO substrates were investigated. NH4VO3 aqueous solution was used as precursor to dope ZnO thin film samples with V5+ by dip coating method and oxalic acid was used as reducing agent to synthesize V+4 doped samples. UV-Vis spectroscopy was used to determine the direct and indirect band gap values of thin film samples. Methylene blue (MB) degradation assays were used to evaluate the photocatalytic activity. XPS analysis was used to determine the analyse oxidation state of vanadium over the samples. Photocatalytic activity studies revealed that ZnO samples electrodeposited at 70°C have higher band gap and MB degradation activity under artificial solar irradiation. The presence of vanadium also enhances the photocatalytic activity of ZnO and samples doped with V+4 have higher photocatalytic activity than the samples doped with V+5 sites.KEYWORDS: ZnOfilmelectrodepositionvanadiumdopingoxidationphotocatalyticactivity Disclosure statementNo potential conflict of interest was reported by the author(s).

Methylene blue

Oxalic Acid

Degradation

10.1080/02670844.2023.2264530

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Room Temperature Photocatalytic Oxidation of Carbon Monoxide Over Pd/TiO2–SiO2 Catalysts

Topics in Catalysis (2013)

Gürkan Karakaş Pelin Yetisemiyen

BET theory

Specific surface area

10.1007/s11244-013-0124-0

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Citations (19)

Modelling and simulation of chemical reaction of porous MgCl2 pellets with NH3 by including impact of heat and mass transfer and structure change

TURKISH JOURNAL OF CHEMISTRY (2023)

ZEYNEP KARAKAŞ HELVACI Gürkan Karakaş Yusuf Uludağ

The MgCl2?NH3 reactive system is investigated in terms of heat and mass transfer coupled with chemical reaction through numerical simulation. The reversible nature of the chemical reaction is captured by including adsorption and desorption terms in the rate expression simultaneously. The kinetic coefficients of the adsorption are directly adopted from the literature, while those for the desorption reaction are calculated based on the thermodynamic relations. The impact of changing pressure and pellet porosity are also investigated in the simulations. The initial temperature of the pellet is 300 K in all simulations. Temperature, NH3 pressure, and conversion distributions in the pellets, along with pellet swelling are obtained and presented as a function of time. The results indicated strong effects of heat transfer resistances in the pellets.

Pellet

Reaction rate

10.55730/1300-0527.3561

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Electrical and catalytic properties of SnO2/TiO2 measured in operando conditions

Reaction Kinetics Mechanisms and Catalysis (2011)

Cornel Munteanu M. Căldăraru Veronica Brătan Pelin Yetisemiyen Gürkan Karakaş

Propene

10.1007/s11144-011-0365-5

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Citations (3)