CRYSTAL-CHEMICAL CONTROLS ON THE DISSOLUTION KINETICS OF THE ISOSTRUCTURAL SULFATES - CELESTITE, ANGLESITE, AND BARITE

被引:116
作者
DOVE, PM [1 ]
CZANK, CA [1 ]
机构
[1] ENVIRON CORP, PRINCETON, NJ 08540 USA
关键词
D O I
10.1016/0016-7037(95)00116-6
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 isostructural sulfates, barite (BaSO4), celestite (SrSO4), and anglesite (PbSO4), share the crystallographic space group Pnma. With their crystal structure and bulk stoichiometry invariant, we investigate controls on the kinetics of sulfate mineral dissolution. Dissolution rates were measured in hydrothermal mixed flow reactors with solutions of pH 2 to 10 and at 25-140 degrees C. Data were analyzed using a first order rate law. In general, dissolution rates follow the order celestite > anglesite > barite. Although the chemistry of lead differs from strontium and barium, anglesite has intermediate reactivity. All minerals exhibit a similar pH dependence of dissolution where rates decline with increasing pH for the range 2 to 5 and are approximately independent of pH over the range of 5 to 9. Above pH 9, anglesite dissolution rate increases sharply with increasing pH. An analysis of the temperature dependence of dissolution at near-neutral pH shows that the reactivity trend is controlled by differences in the preexponential component of the rate constant. Thus, reaction frequency, not energetics, primarily determines relative reactivity and suggests steric and/or solvation controls on reaction rate. Dissolution rates at near-neutral pH correlate inversely with both ionic radius and average bond length of the structural divalent atom. This leads us to consider the nature of the aqueous metal complexes that are released to solution upon hydrolysis. We find a positive correlation between solvation number and dissolution rate. This correlation extends to describe reported rates of anhydrite (CaSO4) dissolution. Combining evidence, we suggest that rates of isostructural sulfate mineral dissolution are limited by the relative solvation affinity of the divalent metal atoms for near-surface water. Hydrolysis of the sulfate group is probably not rate-limiting since anionic hydration is extremely fast and approximates rates of aqueous diffusion. Dissolution rates are limited by the mineral component having the lowest solvation affinity. This model predicts dissolution rates of sulfate minerals within a solid-solution compositional series and may describe other minerals with strong anisodesmic character. Our study reiterates the role of near-surface solvent properties in controlling mineral reactivity in aqueous solutions.
引用
收藏
页码:1907 / 1915
页数:9
相关论文
共 42 条
[1]   THEORETICAL STUDIES ON SOLVATION .2. NEW THEORY FOR EVALUATION OF IONIC SOLVATION NUMBER FOR DIVALENT IONS AT 25-DEGREES-C [J].
AZZAM, AM .
CANADIAN JOURNAL OF CHEMISTRY-REVUE CANADIENNE DE CHIMIE, 1960, 38 (06) :993-1002
[2]   DISSOLUTION RATES OF POLYCRYSTALLINE SAMPLES OF GYPSUM AND ORTHORHOMBIC FORMS OF CALCIUM SULPHATE BY A ROTATING DISC METHOD [J].
BARTON, AFM ;
WILDE, NM .
TRANSACTIONS OF THE FARADAY SOCIETY, 1971, 67 (588) :3590-&
[3]  
BERNER RA, 1980, EARLY DIAGENESIS
[4]  
BLOUNT CW, 1977, AM MINERAL, V62, P942
[5]   TRACER STUDY OF KINETICS OF DISSOLUTION OF BARIUM SULPHATE [J].
BOVINGTON, CH ;
JONES, AL .
TRANSACTIONS OF THE FARADAY SOCIETY, 1970, 66 (567) :764-+
[6]  
Bowers T.S., 1984, EQUILIBRIUM ACTIVITY
[7]  
BURGESS J, 1988, IONS SOLUTION
[8]   CRYSTALLIZATION AND DISSOLUTION OF STRONTIUM SULFATE IN AQUEOUS SOLUTION [J].
CAMPBELL, JR ;
NANCOLLA.GH .
JOURNAL OF PHYSICAL CHEMISTRY, 1969, 73 (06) :1735-&
[9]   CONTROL OF DISSOLUTION RATES OF ORTHOSILICATE MINERALS BY DIVALENT METAL OXYGEN BONDS [J].
CASEY, WH ;
WESTRICH, HR .
NATURE, 1992, 355 (6356) :157-159
[10]   KINETICS OF DISSOLUTION OF CALCIUM-SULFATE DIHYDRATE IN WATER [J].
CHRISTOFFERSEN, J ;
CHRISTOFFERSEN, MR .
JOURNAL OF CRYSTAL GROWTH, 1976, 35 (01) :79-88