Surface activity of humic substances depending on their origin
DOI:
https://doi.org/10.15626/Eco-Tech.2005.058Nyckelord:
Surface tension; Humic substances; KineticsAbstract
Humic substances are a general category of naturally occurring, biogenic, heterogeneous
organic substances that can be characterised as being yellow to black in colour, of high
molecular weight and refractory. Surface tension measurement defined humic substances as
surface active substances. Unless micellar structural model of humic substances has been
suggested, in the same time there are only a few studies about the factors that affect the
surface activity of humic solutions. The objective of this study was to study changes in
surface activity depending on the origin and properties of humic substances.
The surface tension-pH curves of humic substances featured a minimum for all solutions,
declining steeply from higher and lower pH values. The decrease in surface tension with
decreasing pH reflects the gradual neutralization of acidic sites, which created amphiphilic
species that migrated to the surface. Surface tension of solutions of humic substances
decreased with increasing concentration, as well as in presence of metal salts. Many
industrially produced humic materials demonstrated no or insignificant impact on surface
tension of their solutions, but humic substances isolated from natural environments (water,
soil, peat, sediments) demonstrated significant impact of surface tension of their solutions.
Thus there exist direct links between origin, structure of humic substances and their ability to
influence surface tension of aquatic solutions.
Statistik
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