Influence of humic substances on Co[sup 2+] sorption by a subsurface mineral separate and its mineralogic components
- Pacific Northwest Laboratory, Richland, WA (United States)
The sorption of Co[sup 2+] (10[sup [minus]6] mol/L) was measured on subsurface mineral materials in the absence and presence of a sorbed leonardite humic acid (LHA) to (1) evaluate the sorptive role of mineral-bound humic substances, and (2) establish approaches to model metal ion binding in composite materials. The subsurface materials were a <2.0 [mu]m size fraction of an ultisol saprolite (CP) and this same material treated with dithonite-citrate-bicarbonate (DCB) to remove Fe-oxides (DCP). Comparable experiments (with and without LHA) were also performed with mineral sorbents representing dominant phases in the CP separate (gibbsite, Al-geothite, and kalonite) to evaluate their potential contributions to Co sorption. The mineral-bound LHA ranged in concentration between 0.1-0.4 mg-C/m[sup 2], representing approximately 0.7% of the subsurface isolate by mass. In solid-free suspensions, the affinity of LHA for Co increased with pH and decreasing I (K[sub d] ranging 20-450 L/g). Mineral-bound LHA increased Co sorption on all the sorbents by factors of 10-60%, with the greatest augmentation noted at pH values (4.5-6.5) where (1) maximum LHA sorption occurred, and (2) Co sorption to the mineral phase was weak and dominated by ion exchange. The LHA appeared simply to augment, rather than to change the intrinsic adsorption behavior of the mineral sorbents. Accordingly, predictions of the K[sub d] for Co on the LHA-coated subsurface materials (DCP, CP) based on a linear additivity model agreed well with the experimental data, suggesting that the complex humic-mineral association acted as a noninterative sorbent mixture at low aqueous Co concentrations.
- DOE Contract Number:
- AC06-76RL01830
- OSTI ID:
- 5217864
- Journal Information:
- Geochimica et Cosmochimica Acta; (United States), Journal Name: Geochimica et Cosmochimica Acta; (United States) Vol. 58:2; ISSN GCACAK; ISSN 0016-7037
- Country of Publication:
- United States
- Language:
- English
Similar Records
Microbial release of 2,4-dichlorophenyl bound to humic acid or incorporated during humification
Influence of mineral-bound humic substances on the sorption of hydrophobic organic compounds
Related Subjects
540220* -- Environment
Terrestrial-- Chemicals Monitoring & Transport-- (1990-)
ADSORPTION
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CHALCOGENIDES
COBALT
ELEMENTS
ENVIRONMENTAL TRANSPORT
HUMIC ACIDS
IRON COMPOUNDS
IRON OXIDES
MASS TRANSFER
METALS
MINERALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
SILICATE MINERALS
SOILS
SORPTION
SORPTIVE PROPERTIES
SURFACE PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS