Kinetics of silica deposition from simulated geothermal brines
Supersaturated brines were passed through columns packed with several forms of silica (crystalline ..cap alpha.. quartz, polycrystalline ..cap alpha.. quartz, and porous Vycor). Also, silica deposition on ThO/sub 2/ microspheres and titanium powder was studied under controlled conditions of supersaturation, pH, temperature, and salinity. The residence time was varied by adjustments of flow rate and column length. The silica contents of the input and effluent solutions were determined colorimetrically by a molybdate method which does not include polymers without special pretreatment. Essentially identical deposition behavior was observed once the substrate was thoroughly coated with amorphous silica and the BET surface area of the coated particles was taken into account. The reaction rate is not diffusion limited in the columns. The silica deposition is a function of the monomeric Si(OH)/sub 4/ concentration in the brine. The deposition on all surfaces examined was spontaneously nucleated. The dependence on the supersaturation concentration, hydroxide ion concentration, surface area, temperature and salinity were examined. Fluoride was shown to have no effect at pH 5.94 and low salinity. The empirical rate law which describes the data in 1 m NaCl in the pH range 5-7 and temperatures from 60 to 120/sup 0/C is given.
- Research Organization:
- Oak Ridge National Lab., TN (USA)
- DOE Contract Number:
- W-7405-ENG-26
- OSTI ID:
- 5477234
- Report Number(s):
- ORNL/TM-7117
- Country of Publication:
- United States
- Language:
- English
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ACTINIDE COMPOUNDS
ALKALI METAL COMPOUNDS
BRINES
CHALCOGENIDES
CHLORIDES
CHLORINE COMPOUNDS
CRYSTAL GROWTH
DEPOSITION
ELEMENTS
FLOW RATE
FLUIDS
FLUORIDES
FLUORINE COMPOUNDS
GEOTHERMAL FLUIDS
Geothermal Legacy
HALIDES
HALOGEN COMPOUNDS
HYDROGEN COMPOUNDS
HYDROXIDES
KINETICS
METALS
MINERALS
MOLYBDATES
MOLYBDENUM COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PH VALUE
QUARTZ
REACTION KINETICS
SALINITY
SATURATION
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SIMULATION
SODIUM CHLORIDES
SODIUM COMPOUNDS
SUPERSATURATION
THORIUM COMPOUNDS
THORIUM OXIDES
TITANIUM
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS