Dissolution kinetics of anorthite (CaAl/sub 2/Si/sub 2/O/sub 8/) and synthetic strontium feldspar (SrAl/sub 2/Si/sub 2/O/sub 8/) in aqueous solutions at temperatures below 100/sup 0/C: with applications to the geological disposal of radioactive nuclear wastes

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1982

OSTI ID:5903833

Fleer, V N

The dissolution kinetics of anorthite and synthetic strontium feldspar were investigated in aqueous solutions of varying pH (2-10.5), ionic strength (0.01-0.001 m NaCl and SrCl/sub 2/) and temperature (25/sup 0/-70/sup 0/C) for a time period of up to 475 days. An initial region of rapid dissolution is followed by a region which obeys a zeroth order kinetic rate law. At a time of 4 to 21 days there is a sharp break in the slope of the solution curve due to the saturation of the solution with respect to a secondary solid. Rate constraints for the dissolution (forward) reaction were determined. They range from 3.7 x 10/sup -15/ at pH 5.6 and 25/sup 0/C to 1.6 x 10/sup -10/ at pH 2 and 70/sup 0/C. Rates increase with temperature, chloride concentration of the solutions, as the pH departs from neutrality, and as a function of the surface area of the solid to the solution volume ratio. The surface characteristics of the solids were examined by scanning electron microscopy and Auger spectroscopy. Well developed, rectangular etch pits form on all of the solids. Auger studies indicate that there is no depletion of the alkaline earth cation at depths up to 100 A from the crystal surface. Hence the alkaline earth feldspars undergo dissolution via a surface reaction-controlled mechanism. Due to the fairly rapid weathering observed for anorthite in nature and the similar dissolution kinetics behavior of the two alkaline earth feldspars studied, strontium fledspar is not a good choice as a host phase for the containment of radioactive strontium.

• Research Organization: Pennsylvania State Univ., University Park (USA)
• OSTI ID: 5903833
• Country of Publication: United States
• Language: English

Related Subjects

052002* -- Nuclear Fuels-- Waste Disposal & Storage
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
ANORTHITE
DISSOLUTION
FELDSPARS
MANAGEMENT
MEDIUM TEMPERATURE
MINERALS
PH VALUE
RADIOACTIVE WASTE DISPOSAL
SILICATE MINERALS
SURFACE PROPERTIES
UNDERGROUND DISPOSAL
WASTE DISPOSAL
WASTE MANAGEMENT