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Dissociation behaviour of humic acids
Karbanová, Kateřina ; Kratochvílová, Romana (referee) ; Klučáková, Martina (advisor)
Humic acids are substances of natural origin and form the finest part of humic substances. They are formed by biochemical transformations of organic residues (mainly plants). They act as a weakly acidic polyelectrolytes with not exactly described structure. Their solubility is affected by pH value. The higher the pH value is the higher the solubility is. They are almost insoluble in acids. Bachelor thesis deals with the study of the dissociation behaviour of humic acids. Dissociation constant of humic acids is determined by three different methods – conductometric, spectrophotometric and combination of measurment pH and the content of acidic functional groups in Na2SO4. On the basis of results the methods are compared.
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Behaviour of humic acids in aqueous solutions
Čechová, Eva ; Barančíková, Gabriela (referee) ; Klučáková, Martina (advisor)
Tato práce se zabývá chováním huminových kyselin ve vodných roztocích a to především jejich disociací a rozpustností. Disociace huminových kyselin byla studovaná jejich částečným rozpuštěním ve vodě a v roztocích solí o různých iontových silách. Analyzované huminové kyseliny pocházely jak z lignitických tak i půdních zdrojů a jedna z nich byla upravena plazmatem. Metodami použitými při experimentech byla potenciometrie, konduktomerie a UV/VIS spektroskopie. Podle Henderson-Hasselbalchovy závislosti byly vypočítány zdánlivé disociační konstanty. Dále byly určeny zdánlivé aktivitní koeficienty kyselých funkčních skupin. Poté byla studovaná rozpustnost huminových kyselin ve vodných roztocích solí. Byly sestrojeny závislosti pH hodnot, vodivostí a absorbancí jak na obsahu huminových kyselin ve vzorku tak na iontové síle roztoku. Studována byla také kinetika disociace huminových kyselin. Získaná data byla srovnána s navrženou hypotézou předpokládající několikakrokový mechanismus disociace huminových kyselin. Chovaní všech vzorků huminových kyselin odpovídalo navrženému mechanismu. Bylo potvrzeno, že stupeň disociace huminových kyselin ve vodných roztocích klesá s rostoucím obsahem huminové kyseliny stejně tak jako ve vodných roztocích solí s rostoucí iontovou silou.
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Metane hydrate extraction
Hanzlík, Martin ; Brázdil, Marian (referee) ; Šnajdárek, Ladislav (advisor)
Thesis describes the chemical and physical properties of methane hydrate, the presence and location of sites in various types of sediment. Goal of this work is to evaluate the proposed production methods of methane hydrate from the technological, logistical and economic aspects. With the technologies currently available, the best production method is depressurization. There is a high probability that in the next decade it will be used for the production of natural gas from methane hydrate. The conclusion is evaluating areas with high potential for industrial production.
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Determination of content of humic acids in solutions chronopotentiometrically
Viktorinová, Jana ; Kislinger, Jiří (referee) ; Klučáková, Martina (advisor)
Humic acids are part of humic substances, which are substances of natural origin occurring in soil, peats, sediments and young coal. These substances are mixture of compounds with different molecular weight and structures. Humic acids are only partially soluble in aqueous solutions and their solubility is growing up with icreasing pH value. Bachelor thesis uses method of chronopotentiometric titration, which has not been used yet for humic research. This bachelor thesis is trying to check possibility of exercise this method for assessment concentration of soluble humic acid. Especially trace amounts of analyt are measured by this method. Results obtained by chronopotentiometric titration are compared with results in common used method as UV/VIS spetctromerty and potentiometry.
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Solubility and dissociation of humic acids
Kratochvílová, Romana ; Jaroslav,, Záhora (referee) ; Klučáková, Martina (advisor)
The behaviour of humic acids in aqueous solutions is closely connected to the content of acid functional groups and their dissociation abilities. The titration methods are the most often used for the research of acid-basic characteristics of humic acids, their results should lead to the determination of the content of functional groups and their pKa. However the determined values depend on many factors including the titration speed. The aim of this bachelor’s thesis is to verify the possibility of UV/VIS spectrophotometry´s use as alternative method for the determination of pKa of humic acids and to compare the gained results with so far used method according to Henderson-Hasselbach. The principle of newly used spectrophotometry method is the preparation of humic acids solutions in three different media with different pH values. Acid groups of humic acids are practically completely dissociated in intensely basic environment and the measured absorbance is caused by anion of „humate“. On the contrary their dissociation in acid environment is suppressed so much that we measure the absorbance of non-dissociated molecules of humic acids. It was found out that after the modification it was possible to use the spectrophotometry method for the determination of pKa of these substances, while the use of method was verified within the three different samples of humic acids. The optimal ratio humic acids – water and the extent of wavelength for measuring UV/VIS spectra were determined. It was proved that the values of pKa determinated by these methods better describe the real dissociation behaviour of humic acids in water than traditional Henderson-Hasselbach method. The UV/VIS spectra gained in combination with the results of pH measuring and the conductivity next showed the differences in the behaviour of differently prepared samples of humic acids.
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dGO disociace pevných heterodimerů
Malijevská, I. ; Sedláková, Zuzana
Solid – liquid equilibria of two binary systems were measured. Both systems, propanoic acid – trifluoroacetic acid and acetic acid – trichloroacetic acid, form a compound in the solid phase. Activity coefficients in the liquid phase were calculated and thermochemical data of the given compounds dissociation determined.
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