| Title |
Kavos rūgšties adsorbcija chitozano milteliais ir gautų kompleksų savybės / |
| Translation of Title |
Caffeic acid adsorption onto chitosan powder and properties of obtained complexes. |
| Authors |
Zambžickaitė, Greta |
| Full Text |
|
| Pages |
55 |
| Keywords [eng] |
caffeic acid ; chitosan ; complexes ; adsorption |
| Abstract [eng] |
Chitosan (CH) and caffeic acid (KVR) complexes (KVR-CH) of different composition were obtained by adsorbing KVR from aqueous solutions on CH powder. The pseudo-second kinetic model was fitted to the data of adsorption. The mechanism of KVR equilibrium adsorption on the surface of CH powder was elaborated. The KVR-CH with KVR to CH optimal molar ratio of 0.47–0.49 were obtained. FT-IR spectra confirmed the composition of KVR-CH complexes. The molecular weight of CH no influence composition of the complex were obtained. Analysis of the Langmuir, Freundlich and DubininRadushkevich adsorption models parameters demonstrated that KVR is adsorbed on the ionized amino groups of CH due to electrostatic interactions between the latter groups and the carboxylic group of KVR. Analysis of thermodynamic parameters of adsorption showed that KVR adsorption on CH was spontaneous. However, the negative values of changes in Gibbs free energy decreased with an increase of adsorption temperature. The negative values of the changes of enthalpy and entropy implied that adsorption was exothermic process, and the order of systems during the course of adsorption increased. The thermal destruction of KVR-CH complexes occurred in three steps: release of physically retained water (first step), release ~ 25 % KVR from KVR-CH complex (second step) and decomposition of complex (third step). KVR can be released from KVR-CH complexes into solution of phosphate buffer (pH=6.8). The antioxidant activity estimated by ABTS assay showed that KVR-CH complexes containing higher amount of adsorbed KVR demonstrated prolonged antioxidant activity. |
| Dissertation Institution |
Kauno technologijos universitetas. |
| Type |
Master thesis |
| Language |
Lithuanian |
| Publication date |
2018 |
