Ústav chemie

Browse

Recent Submissions

Now showing 1 - 5 of 52
  • Thumbnail Image
    Item
    Relationship Between Centrifugation and Drying of Sludge and The Organic Halogenes
    (Mendel University in Brno, 2010-05-01) Hrich, Karel; Groda, Bořivoj
    This work is focused on determination of adsorbable organic halogens (AOX) concentration in the digested sludge from the sewage treatment plant and the losses of this component during dewatering and drying of sludge.
  • Thumbnail Image
    Item
    Suitability of denitrifying woodchip bioreactor outflows for use in irrigation
    (Mendel University in Brno, 2017-11-08) Schrimpelová, Kateřina; Malá, Jitka; Bílková, Zuzana; Hrich, Karel
    The contribution is focused on aplication of denitrifying woodchip bioreactor outflow for irrigation of drained area.
  • Thumbnail Image
    Item
    Content changes of adsorbable organically bound halogens during sludge centrifugation and drying
    (Czech Academy of Agricultural Sciences, 2011-03-31) Hrich, Karel; Groda, Bořivoj
    The aim of this work was to calculate the material balance in the treatment process (centrifugation and drying). Control places were chosen and then samples of water and sludge (at the inlet and outlet of the system) were collected. The adsorbable organically bound halogens concentration was detected in these samples by the coulometric method.
  • Thumbnail Image
    Item
    Physico-Mechanical Properties and Hydration Processes of Cement Pastes Modified with Pumice, Trass and Waste Chalcedonite Powder
    (MDPI, 2023-12-31) Spychal, Edyta; Vyšvařil, Martin
    In this article, the physico-mechanical properties and hydration processes of cement pastes containing three additives are introduced. Cement was replaced with pumice, trass, waste chalcedonite powder at 30% by mass and a combination of pumice or trass and waste chalcedonite powder in the amounts of 15% each. The main aim of this research was to assess the properties of two- or three-component binders to save cement in these binders. Rheological properties such as consistency, yield stress, viscosity and thixotropy were determined, in addition to porosity, 7-day and 28-day flexural and compressive strength and bulk density. Additionally, the heat evolution and degree of hydration of the tested pastes were compared. The use of all additives resulted in a reduction in the consistency of the tested pastes. The highest compressive strength measured after 28 days was observed for the cement paste with a 30% content of waste chalcedonite powder, which is related to it having the best pozzolanic activity of the materials used. The results of this research have confirmed that pumice, trass and waste chalcedonite powder can be used as components of blended Portland cements.
  • Thumbnail Image
    Item
    Impedance spectroscopy – comparison of dielectric model with experimental results
    (IOP Publishing, 2023-08-25) Kusák, Ivo; Luňák, Miroslav; Mizerová, Cecílie; Rovnaník, Pavel
    Impedance measurements of building materials have been gaining popularity especially in the last twenty years. No electrical component has only resistance, capacitance or inductance, as there is an interplay of these parameters. This is compounded in the case of building materials, which contain a significant number of different phases that vary in chemical composition, crystalline structure and properties. It is, therefore, necessary to choose a connection and measurement system that provides the most accurate information about the building material. This information is primarily meant to include the complex impedance, its components and the quantities derived from them. The derived quantities are electrical resistance or electrical capacitance. Using these quantities we can point out the composition of the material, its conductivity and identify the percolation threshold or describe its sensory properties in more detail. For measurements, an alternating electric field is crucial, and the range of frequencies depends on the instruments used. For materials characterization, the most used frequency range is 100 Hz to 100 kHz; however, we can measure down to 1 MHz.