Division of Information Technology, Engineering and the Environment
Applied Centre for Structural and Synchrotron Studies
Applied Centre for Structural and Synchrotron Studies
Project duration: 2002-2006
Funding: NSERC (Canada) Discovery Grant
Chief Investigators: Roger Smart, Brian Hart, Mark Biesinger
(Surface Science Western, Uni Western Ontario)
Description:
Surface chemistry is the principal determinant of the average contact angle for a specific mineral phase in a flotation pulp. The average contact angle is, in turn, the principal determinant of the bubble-particle attachment efficiency in the overall collection efficiency from which the flotation rate constant can be determined.
The recovery and selectivity in sulfide flotation is ultimately
dependent on the relative rate constants of the different mineral
phases. But the average contact angle is not only mineral-specific,
based on a statistical average of the mineral particles in that phase,
but also the contact angle for each particle is some sort of average of
hydrophobic and hydrophilic areas across the particle surface. There is
even evidence that these areas can be face-specific. Determination of
this hydrophobic/hydrophilic balance by particle therefore requires
selection of the particular mineral phase and statistical analysis of
the particles with an estimation of the spread of values. This is a tall
order in a flotation pulp containing many different mineral phases,
different particle sizes of individual phases, adsorbed and precipitated
species (often colloidal), and oxidised products.
Diagnosis of the surface chemical factors playing a part in flotation
separation of a value sulfide phase then requires measurement of the
species that are statistically different between the concentrate and
tail streams together with an estimate (if possible) of the magnitude of
the differences. The statistical methods described here, based on time
of flight secondary ion mass spectrometry (ToF-SIMS), have gone some way
towards this ultimate aim.
Objectives:
The overall objective is to develop a quantitative ToF-SIMS measure of
the difference between flotation characteristics of particles of the
same mineral phase in concentrate vs. tail streams incorporating all
statistically significant hydrophobicity and hydrophilicity factors.
The basic science to achieve this has 3 parts.
We will use the ToF_SIMS to develop a spread sheet recording of these factors from the statistical analysis.
More advanced principal component statistical analysis will be used to combine the data from the two sets of particles.
Single mineral phases (e.g. pyrite, chalcopyrite, pentlandite, sphalerite) will be studied with different collector reagents and dosages correlated to recovery to validate these combined indices.
The full methodology will then be tested for prediction of both recovery
and selectivity on specific separations, e.g. pentlandite/pyrrhotite;
sphalerite/pyrite; chalcopyrite/galena/pyrite.
Anticipated Significance:
The outcomes targeted would be to use this information to: optimise
separation due to chemical surface conditioning (eg addition rates,
conditioning times, stage addition, alternative reagents, depressant
suppression etc) and; to find where surface chemical discrimination is
no longer statistically significant down a flotation bank.
We have some preliminary results in the latter category indicating that
the surface chemistry of a fourth concentrate in a galena flotation was
not statistically different from that in the tail. This implies that
grade losses would be incurred.
Overall, there is potential to use this information to design flotation
testing for improved selectivity based on statistically significant
factors discriminating positive and negative flotation for different
mineral phases.
