Adsorption of aquatic humic substances on colloidal-size aluminum oxide particles: Influence of solution chemistry

Journal Article · Sat Oct 01 00:00:00 EDT 1994 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(94)90334-4· OSTI ID:6446744

Schlautman, M A; Morgan, J J ^[1]

---

1. California Institute of Technology, Pasadena, CA (United States)

The adsorption of Suwannee River humic substances (HS) on colloidal-size aluminum oxide particles was examined as a function of solution chemistry. The amount of humic acid (HA) or fulvic acid (FA) adsorbed decreased with increasing pH for all solutions of constant ionic strength. In NaCl solutions at fixed pH values, the adsorption of HA and FA increased with increasing ionic strength. The presence of Ca[sup 2+] enhanced the adsorption of HA but had little effect on FA. For identical solution conditions, the amount (by mass) of HA adsorbed to alumina was always greater than FA. Adsorption densities for both HA and FA showed good agreement with the Langmuir equation, and interpretations of adsorption processes were made from the model parameters. For FA, ligand exchange appears to be the dominant adsorption reaction for the conditions studied here. Ligand exchange is also a major adsorption reaction for HA; however, other reactions contribute to adsorption for some solution compositions. At high pH, cation and water bridging become increasingly important for HA adsorption with increasing amounts of Na[sup +] and Ca[sup 2+], respectively. At low to neutral pH values, increases in these same two cations make hydrophobic bonding more effective. Calculations of HS carboxyl group densities in the adsorbed layer support the proposed adsorption reactions. From the adsorption data it appears that fewer than 3.3 HS-COO[sup [minus]] groups per nm[sup 2] can be bound directly as inner-sphere complexes by the alumina surface. The authors propose that the influence of aqueous chemistry on HS adsorption reactions, and therefore on the types of HS surface complexes formed, affects the formation and nature of organic coatings on mineral surfaces.

• OSTI ID: 6446744
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Journal Name: Geochimica et Cosmochimica Acta; (United States) Vol. 58:20; ISSN GCACAK; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540320* -- Environment
Aquatic-- Chemicals Monitoring & Transport-- (1990-)
ADSORPTION
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CALCIUM IONS
CHALCOGENIDES
CHARGED PARTICLES
CHEMISTRY
FULVIC ACIDS
HUMIC ACIDS
IONS
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PH VALUE
RIVERS
SODIUM IONS
SORPTION
SORPTIVE PROPERTIES
STREAMS
SURFACE PROPERTIES
SURFACE WATERS
WATER CHEMISTRY