Inhaltszusammenfassung

Analytical and physical-chemical techniques, such as elemental analysis, FTIR, surface tension (ST) measurement, high performance size exclusion chromatography (HPSEC) and high resolution ultrasonic spectroscopy (HRUS) were combined in order to assess the surface activity of lignite sodium humic acids salts (humates). Humates were obtained from parental and modified South Moravian lignite pre-treated either by oxidation or by small organic acids. It was shown that unlike common surfactants, h...Analytical and physical-chemical techniques, such as elemental analysis, FTIR, surface tension (ST) measurement, high performance size exclusion chromatography (HPSEC) and high resolution ultrasonic spectroscopy (HRUS) were combined in order to assess the surface activity of lignite sodium humic acids salts (humates). Humates were obtained from parental and modified South Moravian lignite pre-treated either by oxidation or by small organic acids. It was shown that unlike common surfactants, humates dissolved in water do not exhibit the critical micelle concentration and form micelle-like aggregates also in diluted solutions. As revealed by HRUS, the aggregation and/or reconformation of humic aggregates in solution takes up to ten minutes; in contrast, the ST measurements showed long-term stabilization associated with a slow decrease in ST of the solution. Correlation with results of HPSEC indicated that the surface activity of lignite humates is caused predominantly by aggregates with apparent molecular weight between 50-75 kDa (detected by refractivity index detector). Therefore, the long-term processes of ST equilibration were attributed to the slow re-orientation of molecules in humate aggregates adsorbed in the air/water interface in which hydrophobic parts of humates were moved towards air and hydrophilic parts towards to the water bulk. The efficacy of prepared surfactants to decrease the surface tension of aqueous solution was compared with activity of common surface active molecules using Szysz-kowski equation and it was found out that humic products can compete with some commercially available surfactants used in remediation technologies. » weiterlesen» einklappen

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