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Title: Formation constants for aqueous ferrous acetate complexes from magnetite solubility measurements from 100/sup 0/ to 250/sup 0/C and 250 to 1250 bars

Abstract

The authors previous results on the kinetics of acetate decarboxylation demonstrated that acetate is sufficiently stable below 300/sup 0/ to be effective in transporting metals in hydrothermal solutions by enhancing the solubility of minerals through complexation. The overall reaction studied to evaluate metal-acetate formation constants is expressed by the general equations: Fe/sub 3/O/sub 4/ (magnetite) + 2CH/sub 3/COOH in equilibrium Fe(CH/sub 3/COO)/sub n//sup 2-n/ + (2-n)CH/sub 3/COO- + H/sub 2/O + Fe/sub 2/O/sub 3/ (hematite) (1). The experiments, which cover a compositional range from .03-.70 m acetate and .01-.20 m acetic acid, indicate that FeCH/sub 3/COO/sup +/ (n=1) predominates up to 150/sup 0/ but is subordinate to Fe(CH/sub 3/COO)/sub 2/ (n = 2) at higher temperatures. The data have a precision of +/- 10%. ..delta..V for reaction 1 is about -34 cc/mol when n = 1 (150/sup 0/) and ranges from -45 cc/mol (200/sup 0/) to -51 cc/mol (250/sup 0/) when n=2. Elimination of the redox and hydrolysis equilibria from reaction (1) allows the complex formation to be expressed simply: Fe/sup 2 +/ + nCH/sub 3/COO- in equilibrium Fe(CH/sub 3/OO)/sub n//sup 2-n/ (2). Inasmuch as these formation constants are 2-3 orders of magnitude greater than current estimates for the correspondingmore » ferrous-chloride complexes, it is quite likely that acetate complexing accounts for the majority of iron and perhaps other metals in many hydrothermal solutions below 300/sup 0/. This concept is particularly attractive in environments where other ligands are insufficient to account for the metals in solution and where there is a source for acetate. Oil and gas field waters, Mississippi-Valley and Carlin-Gold ore solutions are among the likely candidates.« less

Authors:
;
Publication Date:
Research Org.:
Oak Ridge National Laboratory, TN (USA)
OSTI Identifier:
6874288
Report Number(s):
CONF-8510489-
Journal ID: CODEN: GAAPB
Resource Type:
Conference
Journal Name:
Geol. Soc. Am., Abstr. Programs; (United States)
Additional Journal Information:
Journal Volume: 17; Conference: 98. annual meeting of the Geological Society of America, Orlando, FL, USA, 28 Oct 1985
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 15 GEOTHERMAL ENERGY; ACETATES; CHEMICAL REACTION KINETICS; GEOTHERMAL FLUIDS; GEOCHEMISTRY; IRON COMPOUNDS; PRESSURE EFFECTS; TEMPERATURE EFFECTS; MAGNETITE; SOLUBILITY; CHEMICAL REACTIONS; EXPERIMENTAL DATA; HEMATITE; CARBOXYLIC ACID SALTS; CHALCOGENIDES; CHEMISTRY; DATA; FLUIDS; INFORMATION; IRON ORES; IRON OXIDES; KINETICS; MINERALS; NUMERICAL DATA; ORES; OXIDE MINERALS; OXIDES; OXYGEN COMPOUNDS; REACTION KINETICS; TRANSITION ELEMENT COMPOUNDS; 580400* - Geochemistry- (-1989); 152002 - Geothermal Data & Theory- Properties of Minerals & Rocks

Citation Formats

Drummond, S E, and Palmer, D A. Formation constants for aqueous ferrous acetate complexes from magnetite solubility measurements from 100/sup 0/ to 250/sup 0/C and 250 to 1250 bars. United States: N. p., 1985. Web.
Drummond, S E, & Palmer, D A. Formation constants for aqueous ferrous acetate complexes from magnetite solubility measurements from 100/sup 0/ to 250/sup 0/C and 250 to 1250 bars. United States.
Drummond, S E, and Palmer, D A. Tue . "Formation constants for aqueous ferrous acetate complexes from magnetite solubility measurements from 100/sup 0/ to 250/sup 0/C and 250 to 1250 bars". United States.
@article{osti_6874288,
title = {Formation constants for aqueous ferrous acetate complexes from magnetite solubility measurements from 100/sup 0/ to 250/sup 0/C and 250 to 1250 bars},
author = {Drummond, S E and Palmer, D A},
abstractNote = {The authors previous results on the kinetics of acetate decarboxylation demonstrated that acetate is sufficiently stable below 300/sup 0/ to be effective in transporting metals in hydrothermal solutions by enhancing the solubility of minerals through complexation. The overall reaction studied to evaluate metal-acetate formation constants is expressed by the general equations: Fe/sub 3/O/sub 4/ (magnetite) + 2CH/sub 3/COOH in equilibrium Fe(CH/sub 3/COO)/sub n//sup 2-n/ + (2-n)CH/sub 3/COO- + H/sub 2/O + Fe/sub 2/O/sub 3/ (hematite) (1). The experiments, which cover a compositional range from .03-.70 m acetate and .01-.20 m acetic acid, indicate that FeCH/sub 3/COO/sup +/ (n=1) predominates up to 150/sup 0/ but is subordinate to Fe(CH/sub 3/COO)/sub 2/ (n = 2) at higher temperatures. The data have a precision of +/- 10%. ..delta..V for reaction 1 is about -34 cc/mol when n = 1 (150/sup 0/) and ranges from -45 cc/mol (200/sup 0/) to -51 cc/mol (250/sup 0/) when n=2. Elimination of the redox and hydrolysis equilibria from reaction (1) allows the complex formation to be expressed simply: Fe/sup 2 +/ + nCH/sub 3/COO- in equilibrium Fe(CH/sub 3/OO)/sub n//sup 2-n/ (2). Inasmuch as these formation constants are 2-3 orders of magnitude greater than current estimates for the corresponding ferrous-chloride complexes, it is quite likely that acetate complexing accounts for the majority of iron and perhaps other metals in many hydrothermal solutions below 300/sup 0/. This concept is particularly attractive in environments where other ligands are insufficient to account for the metals in solution and where there is a source for acetate. Oil and gas field waters, Mississippi-Valley and Carlin-Gold ore solutions are among the likely candidates.},
doi = {},
journal = {Geol. Soc. Am., Abstr. Programs; (United States)},
number = ,
volume = 17,
place = {United States},
year = {1985},
month = {1}
}

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