Browsing by Author "Erdem, Ilker"

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Modification of surface charge characteristics for unsupported nanostructured titania-zirconia UF/NF membrane top layers with calcination temperature
(SPRINGER, ONE NEW YORK PLAZA, SUITE 4600, NEW YORK, NY, UNITED STATES, 2020) Erdem, Ilker; Ciftcioglu, Muhsin; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü
Ceramic membranes are more advantageous alternatives especially for harsh working conditions when compared with the polymeric membranes. The porous multilayer structure of the ceramic membranes (composed of support, intermediate, and top layers) can be prepared via different oxides. Titania and zirconia, having superior properties, are mainly preferred for the top layer formation. The separation properties of the membrane are both dependent on pore morphology and surface charge of the oxide(s) forming the top layer. The effect of surface charge in separation may be very significant in case of filtration of charged species with relatively lower mass as in the ultrafiltration (UF) and nanofiltration (NF). In this study, unsupported membrane top layers were prepared with varying titania/zirconia ratios by sol-gel technique. Their surface charges at different pH conditions after calcination at varying temperatures (400 degrees, 500 degrees, and 600 degrees C) were determined. The surface charge of the pure titania (full Ti) top layer was decreasing with the increasing calcination temperature. The highest magnitudes of zeta potential for both acidic and basic conditions were measured via Zr rich top layer (TiZr2575) at calcination temperatures >= 500 degrees C, which was composed of anatase, rutile (titania), and tetragonal (zirconia) phases after calcination. The tailor-made top layer can be prepared with modifications during membrane preparation.
Sol-gel Applications for Ceramic Membrane Preparation
(AMER INST PHYSICS, 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA, 2017) Erdem, Ilker; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; Erdem, Ilker
Ceramic membranes possessing superior properties compared to polymeric membranes are more durable under severe working conditions and therefore their service life is longer. The ceramic membranes are composed of some layers. The support is the layer composed of coarser ceramic structure and responsible for mechanical durability under filtration pressure and it is prepared by consolidation of ceramic powders. The top layer is composed of a finer ceramic micro-structure mainly responsible for the separation of components present in the fluid to be filtered and sol-gel method is a versatile tool to prepare such a tailor-made ceramic filtration structure with finer pores. Depending on the type of filtration (e.g. micro-filtration, ultra-filtration, nano-filtration) aiming separation of components with different sizes, sols with different particulate sizes should be prepared and consolidated with varying precursors and preparation conditions. The coating of sol on the support layer and heat treatment application to have a stable ceramic micro-structure are also important steps determining the final properties of the top layer. Sol-gel method with various controllable parameters (e.g. precursor type, sol formation kinetics, heat treatment conditions) is a practical tool for the preparation of top layers of ceramic composite membranes with desired physicochemical properties.
The surface charge of unsupported nano-structured titania ceramic membrane top layers with varying calcination temperatures
(University of Chemical Technology and Metallurgy, 2019) Erdem, Ilker; Çiftçioğlu, Muhsin; 0000-0001-5743-0835; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; Erdem, Ilker
Titania is one of the most preferable ceramic membrane materials of superior durability (as zirconia) when compared to that of other ceramics, e.g. alumina or silica. The surface charge of the membrane top layer is an important parameter of the separation performance of the multilayer ceramic membrane due to the Donnan exclusion mechanisms. In this study, the change of the surface charge of unsupported nano-structured titania top layer is investigated with calcination temperature variation. The effect observed indicates the possibility of preparation of tailor-made top layers for multilayer ceramic membranes.