4
calculated by dividing the effective volume of the slurry in
the conditioning tank by the volumetric flow rate.
During investigation of the column flotation responses
of all feedstocks, the wash water rate, flotation feed solids
content, and feed particle size (P80) were adjusted based
on the experiment design shown in Table 1 and Table 2.
Once steady-state conditions were obtained, timed samples
of the feed, overflow and underflow were collected. The
slurry samples were then filtered, dried, weighed, and split
for assay by ARL ™ PERFORM’X sequential X-Ray fluo-
rescence spectrometer. Measured mass yields and sample
assays were used to perform a mass balance on each set of
samples taken under a given set of test conditions. The mass
balances were reconciled using a sum of squares minimiza-
tion algorithm on the error residuals.
RESULTS AND DISCUSSIONS
Ultrafine Particles and Bubble Attachment
One major problem for ultrafine phosphate flotation is the
low flotation probability. This is because of
• the low probability of bubble-particle collision due
to the limited inertia of ultrafine particles to pen-
etrate streamlines and collide with bubbles
• the low probability of bubble-particle adhesion
because of the short of particles’ sliding time on bub-
ble surface upon bubble-particle collision.
Figure 3 displays the microscopic observations of
ultrafine phosphate particles successfully attached to fine
and ultrafine bubbles generated by Eriez’ CavTube sparger.
It can be seen from this microscopic photo that coagulation
and flocculation occurred in this ultrafine ore slurry after
being treated by Eriez’ CavTube sparger, which significantly
improved the ultrafine phosphate flotation probability. This
flotation probability can be further increased by using gum
or starch. A previous study [88] found that fine guar gum/
starch particles readily attached to fine bubbles as a result
of generally negatively charged bubbles [5–6, 89–90] and
positively charged cationic guar gum particles.
Ultrafine Gangue Minerals Entrainment
Figure 4 shows the ultrafine black and red iron oxides
entrained during benchtop mechanical cell ultrafine phos-
phate direct flotation. Figure 5 presents the microscopic
observations of ultrafine iron oxide particles entrained to
froth phosphate product during benchtop mechanical cell
flotation.
Hydraulic entrained gangue minerals are generally pro-
portional to feed water recovered in froth product, which
can be reduced using deep froth or wash water. Figure 6
shows that the froth zone becomes whiter and the inter-
face between the collection zone and froth zone becomes
clearer as the flotation column wash water rate increases
from 0 liter/minute to 400 liter/minute and 800 liter/min-
ute. The wash water used in flotation column provides the
bias water and the water necessary to overflow the collected
solids into the concentrate launder. The bias water replaces
the water naturally draining from the froth, which tends
to promote froth stability and can increase froth height.
Therefore, the wash water can reduce entrained gangue
minerals by decreasing feed water to froth product and
increasing froth depth.
50 µm
Ultrafine particles attached to ultrafine/fine bubbles
Figure 3. Ultrafine phosphate particle flotation
Black iron oxides entrained Red iron oxides entrained
Figure 4. Ultrafine black and red iron oxides entrained
during benchtop mechanical cell flotation
calculated by dividing the effective volume of the slurry in
the conditioning tank by the volumetric flow rate.
During investigation of the column flotation responses
of all feedstocks, the wash water rate, flotation feed solids
content, and feed particle size (P80) were adjusted based
on the experiment design shown in Table 1 and Table 2.
Once steady-state conditions were obtained, timed samples
of the feed, overflow and underflow were collected. The
slurry samples were then filtered, dried, weighed, and split
for assay by ARL ™ PERFORM’X sequential X-Ray fluo-
rescence spectrometer. Measured mass yields and sample
assays were used to perform a mass balance on each set of
samples taken under a given set of test conditions. The mass
balances were reconciled using a sum of squares minimiza-
tion algorithm on the error residuals.
RESULTS AND DISCUSSIONS
Ultrafine Particles and Bubble Attachment
One major problem for ultrafine phosphate flotation is the
low flotation probability. This is because of
• the low probability of bubble-particle collision due
to the limited inertia of ultrafine particles to pen-
etrate streamlines and collide with bubbles
• the low probability of bubble-particle adhesion
because of the short of particles’ sliding time on bub-
ble surface upon bubble-particle collision.
Figure 3 displays the microscopic observations of
ultrafine phosphate particles successfully attached to fine
and ultrafine bubbles generated by Eriez’ CavTube sparger.
It can be seen from this microscopic photo that coagulation
and flocculation occurred in this ultrafine ore slurry after
being treated by Eriez’ CavTube sparger, which significantly
improved the ultrafine phosphate flotation probability. This
flotation probability can be further increased by using gum
or starch. A previous study [88] found that fine guar gum/
starch particles readily attached to fine bubbles as a result
of generally negatively charged bubbles [5–6, 89–90] and
positively charged cationic guar gum particles.
Ultrafine Gangue Minerals Entrainment
Figure 4 shows the ultrafine black and red iron oxides
entrained during benchtop mechanical cell ultrafine phos-
phate direct flotation. Figure 5 presents the microscopic
observations of ultrafine iron oxide particles entrained to
froth phosphate product during benchtop mechanical cell
flotation.
Hydraulic entrained gangue minerals are generally pro-
portional to feed water recovered in froth product, which
can be reduced using deep froth or wash water. Figure 6
shows that the froth zone becomes whiter and the inter-
face between the collection zone and froth zone becomes
clearer as the flotation column wash water rate increases
from 0 liter/minute to 400 liter/minute and 800 liter/min-
ute. The wash water used in flotation column provides the
bias water and the water necessary to overflow the collected
solids into the concentrate launder. The bias water replaces
the water naturally draining from the froth, which tends
to promote froth stability and can increase froth height.
Therefore, the wash water can reduce entrained gangue
minerals by decreasing feed water to froth product and
increasing froth depth.
50 µm
Ultrafine particles attached to ultrafine/fine bubbles
Figure 3. Ultrafine phosphate particle flotation
Black iron oxides entrained Red iron oxides entrained
Figure 4. Ultrafine black and red iron oxides entrained
during benchtop mechanical cell flotation