Chromium reactions in geologic materials: Interim report

Technical Report · Thu Mar 31 23:00:00 EST 1988

OSTI ID:5119079

Rai, D; Zachara, J M

This report contains new laboratory data and equilibrium constants for key reactions needed to predict the geochemical behavior of Cr in soils and groudwater. These new data include 1) the solubility of BaCrO/sub 4/(c) and Ba(S,Cr)O/sub 4/(c) solid solutions, 2) the Fe(II)-mediated reduction of Cr(VI) to Cr(III), and 3) Cr(VI) adsorption by kaolinite and Al-substituted goethite. The new mechanistic data along with the previously developed data have improved the understanding of reactions that limit Cr(III) and Cr(VI) mobility in soils and groundwater. Experiments show that both BaCrO/sub 4/(c) and Ba(S,Cr)O/sub 4/(c) solid solution form rapidly under the geochemical conditions expected in the environment. Solubility products were experimentally determined for BaCrO/sub 4/(c) and for Ba(S,Cr)O/sub 4/(c) at several mole fractions of Cr(VI). The Ba(S,Cr)O/sub 4/(c) solid solution is of special importance because it maintains lower aqueous Cr(VI) concentrations than BaCrO/sub 4/(c) and is likely to form and control Cr(VI) mobility in the utility environment, where Ba/sup 2/plus// levels are controlled by BaSO/sub 4/(c). The ferrous ion (Fe(II)) was found to be a rapid and effective reductant for Cr(VI) to Cr(III). This redox transformation is important in predicting migration of chromium species because the resulting Cr(III) concentrations in groundwater are kept low by the solubility of (Cr,Fe)(OH)/sub 3/. Chromium(VI) adsorption was measured on kaolinite and Al-substituted goethite. Both solids adsorb Cr(VI) only under acidic and near-neutral conditions. The observed Cr(VI) adsorption by both solids was described with a multiple-site surface complexation model and binding constants for single-phase oxides. 132 refs., 68 figs., 27 tabs.

• Research Organization: Pacific Northwest Lab., Richland, WA (USA)
• OSTI ID: 5119079
• Report Number(s): EPRI-EA-5741; ON: TI88007528
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
510200* -- Environment
Terrestrial-- Chemicals Monitoring & Transport-- (-1989)
520200 -- Environment
Aquatic-- Chemicals Monitoring & Transport-- (-1989)
54 ENVIRONMENTAL SCIENCES
58 GEOSCIENCES
580400 -- Geochemistry-- (-1989)
ADSORPTION
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM OXIDES
BIOTITE
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISTRY
CHROMIUM
CHROMIUM COMPOUNDS
CHROMIUM OXIDES
DATA BASE MANAGEMENT
DISPERSIONS
DOCUMENT TYPES
ELEMENTS
ENVIRONMENTAL EXPOSURE
ENVIRONMENTAL QUALITY
GEOCHEMISTRY
GROUND WATER
HEMATITE
HYDROGEN COMPOUNDS
IRON
IRON COMPOUNDS
IRON ORES
IRON OXIDES
KINETICS
LEACHATES
MANAGEMENT
METALS
MICA
MINERALS
MIXTURES
ORES
OXIDATION
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PH VALUE
PROGRESS REPORT
REACTION KINETICS
REDUCTION
SILICATE MINERALS
SOILS
SOLID WASTES
SOLUBILITY
SOLUTIONS
SORPTION
SORPTIVE PROPERTIES
SULFUR COMPOUNDS
SULFUR OXIDES
SURFACE PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
WASTE DISPOSAL
WASTE MANAGEMENT
WASTES
WATER
WATER QUALITY