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Magnetic biocomposite materials for removal of significant xenobiotics from water systems
BALDÍKOVÁ, Eva
The theoretical part of this doctoral thesis provides a comprehensive overview on the topic of preparation and subsequent utilization of magnetic derivatives of biological materials for xenobiotic separation from water. Main attention is paid to magnetic modification of waste materials and by-products originating from agricultural and food industry, which represent widely available and low-cost materials, and also to magnetic modification of microbial cells. In addition to the description of magnetic particle preparation and individual developed techniques of magnetic modification, a brief characterization of selected pollutants and a detailed table overview on utilization of magnetically responsive biomaterials for biosorption of organic dyes, heavy metals, pharmaceutical and personal care products together with ubiquitous industrial endocrine disruptors and also of crude oil derivatives is presented. Experimental part of this thesis is focused on the preparation and optimization of new types of magnetic materials. Emphasis is placed on the employment of simple, fast and simultaneously low-cost magnetic modification techniques (e.g., postmagnetization using microwave-synthesized magnetic iron oxides or one-step modification by magnetic fluids). Selected plant materials (barley and rye straw) were chemically modified to significantly (up to five-times) increase the maximum adsorption capacities for tested dyes. All prepared biomaterials exhibited a great magnetic response and simultaneously relatively high adsorption capacity for selected xenobiotics under experimental conditions used. Factors substantially affecting adsorption process, such as pH, initial concentration, incubation time or temperature were also studied. Adsorption equilibrium data were assessed using Langmuir, Freundlich or Sips isotherm models. Experimental data from time dependence study were analyzed by chosen kinetic models, namely the pseudo-first-order and pseudo-second-order ones and by intraparticle diffusion model. Thermodynamic parameters (Gibbs free energy, enthalpy and entropy) describing the nature of adsorption were also included in study.
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Magnetic modification of microbial cells
BALDÍKOVÁ, Eva
Baker´s yeast (Saccharomyces cerevisiae) were magnetically modified by three different methods, namely, surface modification by magnetic fluid, entrapment of cells into alginate and covalent immobilization on particles of magnetic chitosan. The ability of H2O2 decomposition was tested for all types of modification. It is apparent that the most amount of hydrogen peroxid was degraded by magnetic fluid - modified cells (84-95%), while the efficiency of cell which were modified by other methods was much lower (40-60%). Thanks to immobilization on particles of magnetic chitosan, we made completely new type of magnetic material, which was tested for adsorption of Crystal violet and Safranin O. It was founded that magnetic chitosan adsorbs no dyes, so all adsorption belongs to immobilized yeast. The maximum adsorption capacities were determined using Langmuire isotherm at 69,4 mg/g for Crystal violet and 99,0 mg/g for Safranin O.
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Food-borne pathogens in milk and milk products
BALDÍKOVÁ, Eva
Thanks to its nutrition and pH values, milk is an excellent nutrient medium for the growth of food-borne pathogens. It therefore becomes a dangerous source of food-borne illness, especially in combination with infringement of hygiene guidelines during the production process and the 10 golden rules as published by the World Health Organization (WHO). The thesis describes the individual species of food-borne pathogens that occur in milk and dairy products, the factors that influence their growth and reproduction and, last but not least, it also describes the health risks that are linked to its consumption.
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