THE SOLUBILITY OF (BA,SR)SO4 PRECIPITATES - THERMODYNAMIC-EQUILIBRIUM AND REACTION-PATH ANALYSIS

被引:33
作者
FELMY, AR
RAI, D
MOORE, DA
机构
[1] Battelle, Pacific Northwest Laboratories, Richland
关键词
D O I
10.1016/0016-7037(93)90487-H
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
The solubility of (Ba,Sr)SO4 precipitates, varying in SrSO4 mole fraction from 0.05-0.90, was investigated at room temperature with an equilibration period extending to almost three years. The data show that on or before 315 days of equilibration the precipitates reach a reversible equilibrium with the aqueous solution. The reversibility of this equilibrium was verified both by the attainment of steady-state concentrations with time and by heating the samples to perturb the equilibrium and then observing the slow return to the initial equilibrium state. The dissolution of the (Ba,Sr)SO4 precipitates does not, in general, follow limiting reaction paths as defined by the Lippmann solutus or stoichiometric dissolution curves. In addition, activity coefficient calculations for the BaSO4 and SrSO4 components of the solid phase, using either total bulk analysis or near-surface analysis of the component mole fractions, do not satisfy the Gibbs-Duhem equation, demonstrating that a single solid-solution phase does not control both the aqueous Ba and Sr concentrations. Instead, our long-term equilibration data can be explained by the unavoidable formation of small amounts of barite and substitution of Sr into a solid-solution phase with the BaSO4 component of the solid-solution phase never reaching thermodynamic equilibrium with the aqueous phase.
引用
收藏
页码:4345 / 4363
页数:19
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