『Abstract
A macroscopic (mixed-flow reactor) and microscopic (hydrothermal
atomic force microscopy, HAFM) approach was used to quantify sphalerite
(ZnS) dissolution rates and to investigate the stoichiometry of
dissolution and leached layer formation. HAFM observations of
reacted (110) surfaces at room temperature revealed surface roughening
which was likely generated by pit formation, local surface swelling
of re-deposition of sulphur compounds, as also evidenced by a
decreased hardness of the roughened surface. At 125℃, appearance
of hillocks with three-sided facets was observed on the (110)
surface, most likely of the forms {111} or {111}（3つの1の頭に-）.
On the facets, terraces were separated by steps. At these steps,
preferential release of material tool place during dissolution
and caused the steps to retreat.
Macroscopic dissolution rates measured in mixed-flow reactors
at pH 2 and 125, 150 and 200℃ are in reasonable agreement with
literature data and yielded an apparent activation energy of Zn-release
of 96±4 kJ/mol. Elevated dissolution rates were observed during
the initial stage of the experiment. The time necessary to attain
stead-state ranged from 110 to 250 h. Measured Zn/S concentration
ratios in the reactor effluent were at average 1.1±0.1. These
ratios do not indicate extensive leached layer formation and agree
with HAFM observations that revealed a morphology transition from
{110} to {111} or {111}（3つの1の頭に-）. The addition
of FeCl3 to the solution yielded a strong
rate increase with an apparent reaction order with respect to
Fe3+(aq) ranging from 0.41 to 0.48.
Keywords: Sphalerite; Dissolution kinetics; Leaching; Atomic force
microscopy; Surface』
1. Introduction
2. Experimental
3. Results and discussion
3.1. Surface morphology
3.2. Dissolution rates - effect of temperature, time of reaction
and stoichiometry
3.3. Implications to Earth surface conditions and effect of Fe(III)
4. Conclusions
Acknowledgements
References