TY - JOUR
T1 - Metal-organic complexes in geochemical processes
T2 - Estimation of standard partial molal thermodynamic properties of aqueous complexes between metal cations and monovalent organic acid ligands at high pressures and temperatures
AU - Shock, Everetr L.
AU - Koretsky, Carla M.
N1 - Funding Information:
Acknowledgments-We are indebted to Dimitri Sverjensky and Dave Sassani for many helpful discussions about complex formation in aqueous solution. We have strived to employ their estimation methods in the spirit in which they were intended to be used, but take any responsibility for pushing these techniques to their extreme. Thanks are due Patty DuBois, Jennifer Thieme, Mitch Schulte, Tom Mc-Collom, Johnson Haas, Allison Shock, Julie Morris, Heidi Betz, Rebecca Lloyd, Stephan Schmidt, Dee Becker, and Harold Helgeson for assistance, encouragement, and support during the course of this study, inter-library loan at Washington University, Schulte’s Translation Services, and especially Patty DuBois and Jennifer Thieme for technical help with data management. Jeremy Fein and Don Palmer provided helpful reviews. Acknowledgment is made to the Donors of the Petroleum Research Fund, administered by the American Chemical Society, for support of this research through grant 23870- AC8, which included an undergraduate GEOPIG Contribution #74.
PY - 1995/4
Y1 - 1995/4
N2 - Regression of standard state equilibrium constants with the revised Helgeson-Kirkham-Flowers (HKF) equation of state allows evaluation of standard partial molal entropies (So) of aqueous metal-organic complexes involving monovalent organic acid ligands. These values of So provide the basis for correlations that can be used, together with correlation algorithms among standard partial molal properties of aqueous complexes and equation-of-state parameters, to estimate thermodynamic properties including equilibrium constants for complexes between aqueous metals and several monovalent organic acid ligands at the elevated pressures and temperatures of many geochemical processes which involve aqueous solutions. Data, parameters, and estimates are given for 270 formate, propanoate, n-butanoate, n-pentanoate, glycolate, lactate, glycinate, and alanate complexes, and a consistent algorithm is provided for making other estimates. Standard partial molal entropies of association (Δ - Sro) for metal-monovalent organic acid ligand complexes fall into at least two groups dependent upon the type of functional groups present in the ligand. It is shown that isothermal correlations among equilibrium constants for complex formation are consistent with one another and with similar correlations for inorganic metal-ligand complexes. Additional correlations allow estimates of standard partial molal Gibbs free energies of association at 25°C and 1 bar which can be used in cases where no experimentally derived values are available.
AB - Regression of standard state equilibrium constants with the revised Helgeson-Kirkham-Flowers (HKF) equation of state allows evaluation of standard partial molal entropies (So) of aqueous metal-organic complexes involving monovalent organic acid ligands. These values of So provide the basis for correlations that can be used, together with correlation algorithms among standard partial molal properties of aqueous complexes and equation-of-state parameters, to estimate thermodynamic properties including equilibrium constants for complexes between aqueous metals and several monovalent organic acid ligands at the elevated pressures and temperatures of many geochemical processes which involve aqueous solutions. Data, parameters, and estimates are given for 270 formate, propanoate, n-butanoate, n-pentanoate, glycolate, lactate, glycinate, and alanate complexes, and a consistent algorithm is provided for making other estimates. Standard partial molal entropies of association (Δ - Sro) for metal-monovalent organic acid ligand complexes fall into at least two groups dependent upon the type of functional groups present in the ligand. It is shown that isothermal correlations among equilibrium constants for complex formation are consistent with one another and with similar correlations for inorganic metal-ligand complexes. Additional correlations allow estimates of standard partial molal Gibbs free energies of association at 25°C and 1 bar which can be used in cases where no experimentally derived values are available.
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U2 - 10.1016/0016-7037(95)00058-8
DO - 10.1016/0016-7037(95)00058-8
M3 - Article
AN - SCOPUS:0028870761
SN - 0016-7037
VL - 59
SP - 1497
EP - 1532
JO - Geochimica et Cosmochimica Acta
JF - Geochimica et Cosmochimica Acta
IS - 8
ER -