Sorption kinetics of hydrophobic organic compounds onto organic modified surfaces

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1988

OSTI ID:7196659

Szecsoedy, J E

The sorption of five chlorinated benzenes and sixteen other organic solutes was investigated by determining the extent and rate of sorption in a series of 40 batch and 139 column experiments using surface-modified silica of known chemical composition. These surfaces represented important functional groups in soil and consisted of porous silica with patchy surface coatings of aliphatic chains (C{sub 1}, C{sub 8}, and C{sub 18}) and other substituent groups (phenyl, amine, alcoholic, and carboxylic). Three possible rate-limiting steps were examined: diffusion through immobile pore fluid, diffusion through bound organic matter, and chemical binding and release. The free energies for sorption onto the phenyl-polymer surface ranged from {minus}4.0 kcal mol{sup {minus}1} for chlorobenzene to {minus}6.9 kcal mol{sup {minus}1} for pentachlorobenzene, both within the range expected for van der Waals interactions. The sorption energies observed are slightly stronger than those predicted for hydrophobic surfaces, possibly reflecting multiple pi-pi electron interactions between the solute and the surface. Hydrophobic solute partitioning onto natural soils observed by others is less than that observed on aliphatic and phenyl hydrophobic surfaces in this study, but greater than that on amine- or alcoholic-modified surfaces. The sorption of di-, tri-, and tetra-chlorobenzenes onto the phenyl-polymer surface is driven mainly by the overall sorption enthalpy and less by the entropy. The reactors observed in this study reached equilibrium within hours, indicating that they are important at field scales where residence times are hundreds of hours or less.

• Research Organization: Arizona Univ., Tucson, AZ (USA)
• OSTI ID: 7196659
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
54 ENVIRONMENTAL SCIENCES
540220 -- Environment
Terrestrial-- Chemicals Monitoring & Transport-- (1990-)
AROMATICS
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISORPTION
CHLORINATED AROMATIC HYDROCARBONS
DATA
DIFFUSION
EXPERIMENTAL DATA
HALOGENATED AROMATIC HYDROCARBONS
INFORMATION
KINETICS
MATERIALS
MINERALS
NUMERICAL DATA
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
POROUS MATERIALS
REACTION KINETICS
SEPARATION PROCESSES
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SOILS
SOLUTES
SORPTION