National Repository of Grey Literature 113 records found  beginprevious112 - 113  jump to record: Search took 0.00 seconds. 
Molecular organization of humic acids in solutions
Chytilová, Aneta ; Enev, Vojtěch (referee) ; Klučáková, Martina (advisor)
The diverse structure and content of the highly varied functional groups of humic acids determine these substances as a worthwhile study material for a number of scientific institutions. Above all, the structure causes a wide range of their interesting properties, especially spectral, colloidal, electrochemical, ion-exchange and adsorption properties. Humic acids have variety of utilization in the industry while they have been the subject of a range of further research and development. The character of these complex heterogeneous polydisperse substances is mainly cyclic and aromatic, which according to some studies results in their brown color. Generally, there are multiple theories assuming their potential secondary structure. The aim of this study is the analysis of structure and conformation of humic acids in aqueous solutions. For the purposes mentioned above a concentration series of humic acids have been prepared in four different mediums: 0,1 M NaOH, humic acids in water with pH modified to 12 (basic medium), 0,1 M NaOH + 0,1 M HCl, 0,1 M NaCl (neutral medium). In order to study conformations several analytic methods have been used: ultraviolet and visible spectroscopy, dynamic light scattering, electrophoretic light scattering, potentiometric determination of pH and direct conductimetry. Throughout the experimentation the emphasis was mainly on the purity of humic acids extracted from lignite.
Study of humic and fullvic acids by excitation emission matrix method
Enev, Vojtěch ; Vala, Martin (referee) ; Fasurová, Naděžda (advisor)
A bachelor thesis was focused on fluorescence measurement by emission-excitation matrix method (EEM) and finding of the main fluorophores of soil humic and fulvic acids samples. The results of the position of the main peak of fulvic acid isolated from soil type Cambisol were compared and were similar to the position of Elliot soil FA standard II. For determining of secondary peaks of fulvic acids the synchronous method (3D SFS) at lower wavelengths was used.

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