|
|
Transport and sorption properties of modified humic acids studied in hydrogels matrixes
Polášková, Nikola ; Pekař, Miloslav (referee) ; Smilek, Jiří (advisor)
This diploma thesis is focused on transport and sorption properties of humic acids studied in hydrogel matrixes, which are similar to their natural environment (soil). These properties are studied by diffusion techniques. The humic acid standard isolated from Leonardite (from International Humic Substances Society, identification number 1S104H-5) was chosen as a representative of humic acids. Their transport and sorption properties were studied in agarose-based biopolymer hydrogel matrixes (agarose is a nonreactive, thermoreversible polysaccharide) with use of model pollutant Rhodamine 6G (positively charged organic dye), that simulates common pollutants. Humic acids were modified to block their specific functional groups in their structure. Then we are able to study the influence of each functional groups on the interactions with other compounds individually, that was the main goal and motivation of this work. Carboxyl functional groups were modified by methylation with a methylating agent trimethysilyldiazomethane (TMS-DM). For blocking carboxyl and phenolic functional groups together we repeated methylation of carboxyl groups with TMS-DM and then we acetylated phenolic functional groups with acetic anhydride. The successful modification was confirmed by thermogravimetry (TGA), Fourier transform infrared spectroscopy (FT-IR) and acid-base titrations (direct, indirect and carboxyl titration). The techniques of diffusion cell and non-stationary diffusion in cuvettes were chosen to study how organic dye interacts with unmodified and modified humic acids in inert hydrogel matrix. Humic acids were characterised by their structure-based reactivity, respectively by the acidic functional groups content. This thesis verifies the use of the diffusion techniques as a low-cost and universal techniques suitable for studying properties of humic acids mentioned above. Due to the finding that acidic functional groups have a minor influence on these properties, the possibilities of taking other factors into account (such as hydrophobic interactions, hydrogen bonds, van der Waals forces or specific surface area) are opened up.
|
guest ::
