The sorption of humic acids to mineral surfaces and their roles in contaminant binding
Humic substances dissolved in groundwater may adsorb to certain mineral surfaces, rendering hydrophilic surfaces hydrophobic and making them sorbents for hydrophobic organic compounds (HOC). The sorption of humic and fulvic acids (International Humic Substance Society, IHSS, reference samples) on hematite and kaolinite was investigated to determine how natural organic coatings influence HOC sorption. The sorption behavior of the humic substances was consistent with a ligand-exchange mechanism, and the amount of sorption depended on the concentration of hydroxylated surface sites on the mineral and the properties of the humic substance. The sorption of the humic substances to two solids was proportional to their aromatic carbon content and inversely proportional to the O/C ratio. Increasing quantities of sorbed humic substances (f{sub oc}0.01 to 0. 5%) increased the sorption of carbazole, dibenzothiophene, and anthracene. Peat humic acid, the most aromatic coating, showed the greatest sorption enhancement of HOC when sorbed to hematite. In addition, HOC sorption was greater on organic coating formed at low ionic strength (I = 0.005) as compared to higher ionic strength (I = 0.1). We suggest that both the mineral surface and the ionic strength of the electrolyte affect the interfacial configuration of the sorbed humic substance, altering the size or accessibly of hydrophobic domains on the humic molecule to HOC. 30 refs., 5 figs.
- Research Organization:
- Pacific Northwest Lab., Richland, WA (USA)
- Sponsoring Organization:
- DOE/ER
- DOE Contract Number:
- AC06-76RL01830
- OSTI ID:
- 6280294
- Report Number(s):
- PNL-SA-18877; CONF-9008177--1; ON: DE91005678
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360603 -- Materials-- Properties
54 ENVIRONMENTAL SCIENCES
540210* -- Environment
Terrestrial-- Basic Studies-- (1990-)
58 GEOSCIENCES
580000 -- Geosciences
ADSORPTION ISOTHERMS
ALUMINIUM COMPOUNDS
ALUMINIUM SILICATES
ANTHRACENE
AROMATICS
AZAARENES
AZOLES
CARBAZOLES
CHALCOGENIDES
CONDENSED AROMATICS
ENVIRONMENTAL TRANSPORT
FULVIC ACIDS
HEMATITE
HETEROCYCLIC COMPOUNDS
HUMIC ACIDS
HYDROCARBONS
ION EXCHANGE
IONIC COMPOSITION
IRON COMPOUNDS
IRON ORES
IRON OXIDES
ISOTHERMS
KAOLINITE
LIGANDS
MASS TRANSFER
MINERALS
ORES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PH VALUE
POLYCYCLIC SULFUR HETEROCYCLES
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
SORPTION
SORPTIVE PROPERTIES
SURFACE PROPERTIES
SURFACES
TRANSITION ELEMENT COMPOUNDS