wAbstract
@The dissolution rate-determining processes of carbonate rocks
include: (1) heterogeneous reactions on rock surfaces; (2) mass
transport of ions into solution from rock surfaces via diffusion;
and (3) the conversion reaction of CO2 into
H+ and HCO3-. Generally,
it is the slowest of these three processes that limits the dissolution
rate of carbonate rock. However, from experiment and theoretical
analysis under similar conditions not only were the initial dissolution
rates of dolomite lower by a factor of 3-60 than those of limestone,
but also there are different dissolution rate-determining mechanisms
between limestone and dolomite. For example, for limestone under
the condition of CO2 partial pressures (P
CO2)100 Pa dissolution
rates increased significantly by a factor of about ten after addition
of carbonic anhydrase (CA) into solution, which catalysed the
conversation reaction of CO2, whereas CA
had little influence on dolomite dissolution. For dolomite, the
increase of dissolution rate after addition of CA into solution
appeared at P CO210,000
Pa. Moreover, the enhancement factor of CA on dolomite dissolution
rate was much lower (by a factor of about 3). In addition, when
dissolution of both limestone and dolomite was determined by hydrodynamics
(rotation speed or flow speed), especially under P CO21,000 Pa, the dissolution
of limestone was more sensitive to hydrodynamic change than that
of dolomite. These findings are of significance in understanding
the differences in karstification and relevant problems of resource
and environment in dolomite and limestone areas.
Keywords: Rate-determining mechanisms; Heterogeneous surface reaction;
Mass transport; CO2 conversion reaction; Carbonic anhydrase; Hydrodynamics;
Limestone dissolution; Dolomite dissolutionx
Introduction
Study methods
@Materials
@Experimental set up
Experimental results
Interpretation of the experimental results
Conclusions and discussions
Acknowledgements
References