Precipitation and dissolution kinetics of kaolinite under hydrothermal conditions

Conference · Wed Jan 01 04:00:00 EST 1992 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5821467

Soong, Chie; Barnes, H L ^[1]

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1. Pennsylvania State Univ., University Park, PA (United States)

The dependence of precipitation and dissolution kinetics (Dry Branch, Ga) on the solution saturation state was measured in dilute aqueous solutions at 130 C to 230 C and pH 4.5 and 7.2 using a dual-fluid source, flow-through system. For precipitation experiments, Al and Si concentrations of input solutions were carefully controlled to be supersaturated with respect to kaolinite only but not other possible aluminous and silicate phases to limit the precipitation reactions. Equilibrium solubilities of the kaolinite at run temperatures were also obtained from the rates of change of Al and Si concentrations versus their input concentrations where interpolated to zero rates, providing a self-consistent reference for the saturation state at run conditions. From measured solubilities and available temperature-dependent thermodynamic data of kaolinite and the aqueous species, [Delta]G[degree][sub f], of the kaolinite is [minus]906.23 kcal/mol at 298.15 K. Within [Delta]G[sub r]= [+-] 4.2 kcal/mol from equilibrium in the above reactions, where [Delta]G[sub r] = O defines equilibrium, the reaction rates can be fit to the expression for the deviation from equilibrium: rate = [minus]k(1-exp([Delta]G[sub r]/RT))[sup n], where k (mol/m[sup 2]/sec) is the rate constant. The activation energies of the reactions, E[sub act] (kcal/mol), were calculated from Arrhenius equation. Calculations from the measurements are given. The linear dependence of the reaction rates on saturation state occurred within [+-]0.4 [le] [Delta]G[sub r] [le] 0 indicating that detailed reversibility along a single dominant reaction path may only exist for both dissolution and precipitation near equilibrium.

• OSTI ID: 5821467
• Report Number(s): CONF-921058--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 24:7
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
152002* -- Geothermal Data & Theory-- Properties of Minerals & Rocks
58 GEOSCIENCES
580000 -- Geosciences
ACTIVATION ENERGY
ALUMINIUM COMPOUNDS
ALUMINIUM SILICATES
CHEMICAL REACTION KINETICS
DISSOLUTION
ENERGY
ENERGY SYSTEMS
GEOTHERMAL SYSTEMS
HYDROTHERMAL SYSTEMS
KAOLINITE
KINETICS
MINERALS
OXYGEN COMPOUNDS
PHASE STUDIES
PHYSICAL PROPERTIES
PRECIPITATION
REACTION KINETICS
SEPARATION PROCESSES
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
SOLUBILITY
THERMODYNAMIC PROPERTIES