This thesis was dedicated to the possibility of replacing glassy carbon electrode using cheaper composite carbon rod with carbon coating applied onto its surface and to the consequences of adding a modifier to the electrode material. To understand the effects of having pasting liquid contained in carbon paste electrode on substance accumulation, partitioning coefficient of mineral oil/water compound was experimentally determined for 2NP, 4NP, 24DNP and 24TNP. Adsorption coefficient was experimentally determined to find out sorption possibilities of 2NP and 4NP on MMT. Surface of the carbon coating was imaged using scanning electron microscope to find out distribution of MMT and polystyrene in said carbon coating. A method for accumulating 2-nitrophenol and 4-nitrophenol on montmorillonite-modified carbon coating was successfully developed

The voltammetric behavior of selected nitrophenols (2-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol and 2,4,6-trinitrophenol) was investigated by differential pulse voltammetry (DPV) and by adsorptive stripping voltammetry (AdSV) at an unmodified electrode (CPE) and a clay-modified carbon paste electrodes modified by montmorillonite (MMT-CPE) and sepiolite (SEP-CPE) using electrochemical reduction and oxidation in Britton-Robinson buffer. For reduction, optimum conditions have been found at pH 2 for 2-NP and 4-NP, at pH 3 for 2,4-DNP and at pH 4 for 2,4,6-TNP. For oxidation, optimum conditions have been found at pH 2 for 2-NP and 4-NP and at pH 5 for 2,4-DNP. Voltammetric determination using electrochemical oxidation is not a suitable method for 2,4,6-TNP. The lowest detection limits were obtained for 2-NP using cathodic AdSV on SEP-CPE with 2,9·10-7 mol.dm-3 , for 4-NP using cathodic DPV on MMT-CPE with 2·10-6 mol.dm-3 , for 2,4-DNP using cathodic AdSV on SEP-CPE with 2,7·10-7 mol.dm-3 and for 2,4,6-TNP using cathodic DPV on unmodified electrode with 4,8·10-7 mol.dm-3 . Determination of mixture 2-NP and 4-NP and the possibility of the selective determination using open circuit sorption with DPV detection was further studied.

This thesis investigate the structure of cadmium sulfide (CdS) nanoparticles and its stabilization by a surfactant - cetyltrimethylamonnium cation CTA+ and further describe interactions among stabilized CdS nanoparticles and the surface of the layered clay mineral - montmorillonite with using the molecular simulation methods. Initial models of the CdS nanoparticles were build for both crystal structures (Greenockit (G) and Hawleyit (H)). The preferred orientations of the molecules of CTA+ for both crystal types of CdS nanoparticles were found with respect to minimum energy. Prefered orientation is monolayer for Greenockite and bilayer for Hawleyite. Models with the preferred orientation of the molecules of CTA+ were placed on the surface of montmorillonite and after optimization, adsorption energy of CdS nanoparticles with its envelope and montmorillonite surface was calculated. All results and used procedures were compiled in the form of practice for the subject Computational experiments in the theory of molecules I - NBCM100 taught at MFF UK in Prague.

Amino derivatives of polycyclic aromatic hydrocarbons are well-known chemical carcinogens which should be carefully monitored in our environment. They are amenable to anodic oxida- tion on suitable solid or paste electrodes. This fact was exploited for voltammetric determina- tion of 4-aminobiphenyl on unmodified carbon paste electrode and carbon paste electrodes modified by montmorillonite and sepiolite. The optimum pH of BR buffer for measurement on unmodified carbon paste electrode is pH 2, pH 10 for CPE-SEP and pH 11 for CPE-MMT. It was possible to increase sensitivity of the determination using adsorptive stripping voltam- metry on modified electrodes. The optimum time for accumulation of 4-aminobiphenyl is 5 minutes. The limits of quantification of the order of 10−6 mol dm−3 were obtained for each electrode. After accumulation, the limits of quantification decreased to the 10−7 mol dm−3 . The newly developed method was tested for the determination of 4-aminobiphenyl in model sam- ples of drinking and river water, reaching limits of quantification of the order of 10−7 mol dm−3 .

Bentonite clay is intended to form one of the barriers in most repositories of spent nuclear fuel located in granite. One important function of the bentonite barrier is to retard transport of radionuclides in the event of waste canister failure. Bentonite has a high sorption capacity of cations and its main constituent is montmorillonite. In contact with groundwater of low ionic strength, montmorillonite colloids can be released from bentonite and thereby control transport of radionuclides sorbed onto the colloids. In colloid transport in bedrock fractures, size separation of clay colloids may occur due to physical and chemical interactions with the bedrock fracture surface. This may enhance or retard the overall transport of radionuclides, depending on the sorption capacities and stability of the differently sized clay colloids. The bentonite barrier will be exposed to γ-radiation from the spent nuclear fuel. Irradiation affects surface-related properties of bentonite. If an average sorption capacity value cannot be used for all colloid sizes or if sorption is affected by exposure to γ-irradiation, corrected sorption capacity values would give higher resolution in current reactive transport models. In order to study the size separation process, a protocol was developed and successfully applied to fractionate montmorillonite into different-sized colloid suspensions by means of sequential or direct centrifugation. The stability and sorption capacity were studied using these fractions. Both stability and sorption capacity were found to be similar for all colloid sizes. Bentonite exposed to γ-radiation sorbed less divalent cations with increasing radiation dose. The effect was not large enough to have any impact on diffusion. The presence of bentonite enhanced irradiation-induced corrosion of copper under anaerobic atmosphere. An average sorption capacity value for montmorillonite can be used for all colloid sizes in reactive transport models. The effect of γ-irradiation on sorption capacity is sufficiently large to require consideration in transport modelling. / Bentonite är planerad som en av barriärerna i de flesta slutförvar av använt kärnbränsle. Bentonite har en hög sorptionskapacitet för katjoner. Den huvudsakliga beståndsdelen av bentonit är montmorillonit. Montmorillonitkolloider kommer att frigöras från bentonitbufferten i kontakt med grundvatten av låg jonstyrka och på så vis styra transporten av sorberade radionuklider. Under den kolloidala transporten i bergsprickorna kan en separation med avseende på storlek uppstå genom interaktioner mellan kolloiderna och bergytan. Detta kan få till följd att den genomsnittliga transporten av radionuklider bromsas eller tilltar beroende på sorptionskapaciteten och stabiliteten av de olika kolloidstorlekarna. Bentonitbarriären kommer även att utsättas för γ-bestrålning från det använda kärnbränslet, vilket påverkar dess ytrelaterade egenskaper. Om inte ett medeltal för sorptionskapaciteten är giltigt för alla kolloidstorlekar eller om sorptionen påverkas av γ-bestrålning, behövs nya sorptionskapaciteter bestämmas och impliceras för noggrannare transportmodeller. En metod för att separera montmorillonitkolloider med avseende på storlek via direkt och stegvis centrifugering har utvecklats. Stabiliteten och sorptionskapaciteten för dessa fraktioner har studerats. Både stabilitet och sorptionskapacitet visade sig vara lika för alla kolloidstorlekar. Bestrålad bentonit sorberar mindre andel divalenta katjoner med ökad dos bestrålning. Effekten är dock inte stor nog för att slå igenom i diffusionsexperimenten. Förekomst av bentonit ökar även den strålningsinducerade korrosionen av koppar under anaeroba förhållanden. Ett medelvärde för sorptionskapaciteten kan användas för alla kolloidstorlekar i transportmodeller. Effekten av γ-bestrålning är dock stor nog för att implementeras i modellerna. / <p>QC 20150213</p>

Polypropylene (PP) has excellent mechanical and chemical properties. Thus, it is used in a wide range of applications. However, like for most polymers, the high flammability of PP limits its application in various fields requiring specific flame-retardant standards. Some of halogenated flame retardants are restricted by European Community directives ROHs, WEEE and REACH. Now metallic hydroxides flame retardants are widely used in industry, but the high loading (about 60 wt %) seriously destroys the mechanical properties of polymeric materials. To improve the performance of flame retardant polymers, an environment-friendly electron beam (EB) technology has been successfully used in modifying flame retardant and polymer matrix. In this work, high efficient functional intumescent flame retardants and functional surfactant are designed and prepared for EB technology. In-depth studies the thermal stability, fire behavior and mechanical properties of these flame retardant PP composites have been studied. The possible graft-linking and cross-linking mechanisms of such EB modified composites can be well established. Specially, it is shown that the novel surfactant has better thermal stability in comparison to traditionally used modifiers. Another part of this work deals with the exploration of novel allylamine polyphosphate (AAPP) as flame retardant crosslinker for PP by electron beam (EB) treatment. Multifunctional AAPP showed unique efficient intumescent flame retardant properties. The limiting oxygen index (LOI) value and the effective melt drop resistance in UL-94 test of multifunctional flame retardant PP composites is greatly enhanced. In the cone calorimeter test, a reduction of peak heat release rate, total heat release and smoke production is achieved. Moreover, EB treatment increased the thermal stability of these designed flame retardant PP composites. Furthermore, AAPP provided an excellent quality of char residue in the combustion stage due to P−N−C and P−O−C structure. In addition, synergistic mechanism of AAPP with montmorillonite (MMT) was explored. Finally, different EB parameters have been used to modify fire retardant polymer nanocomposites. The effects of EB treatment on thermal stability, fire behavior and mechanical properties of fire retardant PP nanocomposites have been discussed. The heat release, the production of toxic gases and the mass loss of EB modified fire retardant PP nanocomposites are delayed in accordance to the result of cone calorimeter test. Based on these results high performance fire retardant polymer nanocomposites can be developed for industrial applications such as insulated material of wire, cable, etc.

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Title: Application of Molecular Simulations in Complex Structural Analysis of Layered Materials Author: RNDr. Marek Veteška Department: Department of Chemical Physics and Optics Supervisor: RNDr. Miroslav Pospíšil, Ph.D., Dept. of Chemical Physics and Optics Abstract: Techniques of molecular simulations were used together with experimental measurements (X-ray diffraction, thermogravimetry, infrared spectroscopy, elemental analysis and others) to clarify the structure properties of various types of layered materials. The structure of Zn-Al-layered double hydroxide intercalated by pyrenetetra- sulfonate acid was solved. Depending on the relative humidity, the samples showed different arrangements with three planes of water molecules and with either one or two planes of pyrenetetrasulfonate anions. At the same time considerable variability of anions arrangement was demonstrated. The adsorption behavior of natural montmorillonite and montmorillonite modified by tetramethylammonium cations in relation to aniline and phe- nol was explored. Adsorption features differed according to both the type of adsorbed molecules and the type of adsorbents. An important role was played by the plane of water molecules right above the surface which medi- ated adsorption of anilines. The water plane area was reduced by...

Polypropylene (PP) has excellent mechanical and chemical properties. Thus, it is used in a wide range of applications. However, like for most polymers, the high flammability of PP limits its application in various fields requiring specific flame-retardant standards. Some of halogenated flame retardants are restricted by European Community directives ROHs, WEEE and REACH. Now metallic hydroxides flame retardants are widely used in industry, but the high loading (about 60 wt %) seriously destroys the mechanical properties of polymeric materials. To improve the performance of flame retardant polymers, an environment-friendly electron beam (EB) technology has been successfully used in modifying flame retardant and polymer matrix. In this work, high efficient functional intumescent flame retardants and functional surfactant are designed and prepared for EB technology. In-depth studies the thermal stability, fire behavior and mechanical properties of these flame retardant PP composites have been studied. The possible graft-linking and cross-linking mechanisms of such EB modified composites can be well established. Specially, it is shown that the novel surfactant has better thermal stability in comparison to traditionally used modifiers. Another part of this work deals with the exploration of novel allylamine polyphosphate (AAPP) as flame retardant crosslinker for PP by electron beam (EB) treatment. Multifunctional AAPP showed unique efficient intumescent flame retardant properties. The limiting oxygen index (LOI) value and the effective melt drop resistance in UL-94 test of multifunctional flame retardant PP composites is greatly enhanced. In the cone calorimeter test, a reduction of peak heat release rate, total heat release and smoke production is achieved. Moreover, EB treatment increased the thermal stability of these designed flame retardant PP composites. Furthermore, AAPP provided an excellent quality of char residue in the combustion stage due to P−N−C and P−O−C structure. In addition, synergistic mechanism of AAPP with montmorillonite (MMT) was explored. Finally, different EB parameters have been used to modify fire retardant polymer nanocomposites. The effects of EB treatment on thermal stability, fire behavior and mechanical properties of fire retardant PP nanocomposites have been discussed. The heat release, the production of toxic gases and the mass loss of EB modified fire retardant PP nanocomposites are delayed in accordance to the result of cone calorimeter test. Based on these results high performance fire retardant polymer nanocomposites can be developed for industrial applications such as insulated material of wire, cable, etc.