Composition and stability of Cd(II)-chloro and -hydroxo complexes at the goethite ([alpha]-FeOOH)/water interface

Journal Article · Tue Mar 15 04:00:00 EST 1994 · Journal of Colloid and Interface Science; (United States)

DOI:https://doi.org/10.1006/jcis.1994.1127· OSTI ID:7282875

Gunneriusson, L ^[1]

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1. Univ. of Umeaa (Sweden). Dept. of Inorganic Chemistry

The surface complexation of Cd(II) to goethite ([alpha]-FeOOH) in the absence and presence of chloride has been investigated. Equilibrium measurements have been performed as potentiometric titrations at 298.2 K, within the range 2.7 < -log[H[sup +]] < 9.0, in 0.1 mol dm[sup [minus]3] NaNO[sub 3], NaCl, and a mixture (1:1) of both these media. The data were evaluated according to the electrostatic constant capacitance model, including a previously determined model for the acid-base reactions of the goethite surface. In the presence of excess Cd(II) ions to surface hydroxyl groups, it was found that the results could be explained by including bulk precipitation of Cd(OH)[sub 2]. The calculated formation constant for Cd(OH)[sub 2] (s) was within an order of magnitude from the literature value for the stable phase in solution, [beta]-Cd(OH)[sub 2]. Modeling of natural water conditions showed that relatively high concentrations of goethite have to be present to influence the concentrations of Cd(II). Furthermore, the reactions were found to be nearly fully reversible, which means that adsorbed Cd(II) can be released to the environment by a relatively moderate lowering of pH.

• OSTI ID: 7282875
• Journal Information: Journal of Colloid and Interface Science; (United States), Journal Name: Journal of Colloid and Interface Science; (United States) Vol. 163:2; ISSN 0021-9797; ISSN JCISA5
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540210* -- Environment
Terrestrial-- Basic Studies-- (1990-)
ADSORPTION
CADMIUM CHLORIDES
CADMIUM COMPOUNDS
CADMIUM HALIDES
CADMIUM HYDROXIDES
CHLORIDES
CHLORINE COMPOUNDS
DESORPTION
ENVIRONMENTAL TRANSPORT
GOETHITE
HALIDES
HALOGEN COMPOUNDS
HYDROGEN COMPOUNDS
HYDROXIDES
MASS TRANSFER
MINERALS
OXIDE MINERALS
OXYGEN COMPOUNDS
PH VALUE
SORPTION
SORPTIVE PROPERTIES
SURFACE PROPERTIES