Browsing by Author "Gigova A."

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    Natural Zeolite-Cellulose Phosphate Nanocomposites: Preparation and Advance Electrochemical Study
    (2023-07-01) Tsacheva I.; Dimitrova M.; Gigova A.; Dimitrov O.; Uzun D.
    The scope of this research study is to investigated the green method for preparing and applying cost-effective and environmentally friendly electrocatalytic materials from natural zeolite (clinoptilolite) and cellulose phosphate using microwave irradiation. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDX) and Brunauer-Emmett-Teller (BET), were used for the physicochemical characterization of nanocomposites. The newly obtained nanocomposites were studied electrochemically using cyclic voltammetry, linear sweep, galvanostatic measurements, and Tafel slopes. The results show that the obtained nanocomposites can find applications as promising electrocatalytic materials for seawater electrolysis for hydrogen production at oxygen evolution reactions (OER) and for electrochemical purification of organic pollutants.
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    STUDY ON THE PREPARATION OF CERAMIC MEMBRANES BASED ON NATURAL AND WASTE MATERIALS
    (2020-01-01) Yoleva А.; Djambazov S.; Sabrieva S.; Gigova A.
    The production of low cost ceramic membranes has been studied by many researchers using a variety of natural raw materials such as clays, kaolins, limestones, dolomites, zeolites, diatomites and various kinds of wastes such as fly ash, sawdust, sewage sludge, bagasse, waste glass, ceramic scrap, etc., modifying the membranes microstructure with the aim to improve their surface porosity, pore size, pore distribution and mechanical strength. Compositions of ceramic membranes containing halloysite clay, limestone and waste diatomite from the brewery industry are prepared. The change of the ceramic membranes properties varying the presence of halloysite clay and diatomite is followed. The ceramic membranes studied are prepared by dry pressing at 50 MPa and sintering at 1100°C within 2 h. The water absorption, the apparent density, the apparent porosity, the mechanical bending strength and the shrinkage of the ceramic membranes obtained are determined. The water absorption and the apparent porosity increase, while the apparent density and the mechanical bending strength decrease with an increase of the waste diatomite content and a decrease of halloysite clay presence in the ceramic membrane compositions. XRD and SEM are used to identify the phase composition and the microstructure. The average pore size of the ceramic membranes studied is determined by mercury porosimetry