XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2179
flotation of the mineral was completed, both the obtained
concentrate and the tail were filtered under vacuum and
dried at 100 °C for 5 hours to, finally, weigh each of these
products and calculate the recovery of chalcopyrite accord-
ing to the Equation 1.
R m mt
m
100
c
c #=+(1)
where R is the recovery of chalcopyrite (%),mc is the mass
of concentrate and mt is the mass of tail.
It is important to note that, to ensure the reproduc-
ibility of the results, all microflotation tests were performed
in duplicate.
Induction Time Measurements
Induction time measurements were carried out to analyze
the effect of the presence of flocculant under different phys-
icochemical conditions on the adhesion process between
chalcopyrite particles and air bubbles. This parameter is
defined as the average time in which the water film between
a particle and a bubble breaks after their collision, generat-
ing adhesion between both (Yoon and Yordan, 1991). In
this way, the induction time can be described as the prob-
ability that a particle is effectively collected by a bubble and
is inversely proportional to the recovery of a given min-
eral. The procedure to experimentally obtain the induction
time consists of generating a fresh bubble in the capillary
tube, which is then pushed against a bed of particles inside
the cell, and they remain in contact for a certain time.
Subsequently, the bubble is separated from the particle bed
and the existence of adhered particles is observed, recording
the number of effective adhesions. This same procedure is
repeated 10 times in different positions of the particle bed
and for different contact times, allowing a relationship to be
established between the effective adhesions and the contact
time, which allows defining the induction time as the con-
tact time in the which occurs in 50% of successful contacts.
The bed of mineral particles used for these experimental
tests was previously conditioned following the same pro-
cedure and dosages described for the microflotation tests.
Adsorption Isotherms
Adsorption isotherms of reagents were performed through
UV-Vis spectroscopy and total organic carbon measure-
ments. The first technique was used to estimate the remain-
ing concentration of PAX in solution at the different
experimental conditions evaluated, while with the second
it was possible to obtain the amount of total organic car-
bon and in this way, subtracting the carbon contributed by
PAX, it was estimated the adsorption of PAM on chalco-
pyrite particles. The adsorbed amount of the reagents on
the chalcopyrite particles was calculated inversely, that is,
by subtracting the amount of reagent remaining in solu-
tion from the initial dose prepared. The conditioning was
carried out in the same way as for the microflotation tests,
with the difference that, once this procedure was com-
pleted, the suspension was vacuum filtered, discarding the
solid fraction and analyzing only the filtered liquid. Prior
to executing these tests, calibration curves were established
by evaluating the absorbance for different concentrations at
a fixed wavelength and graphing these variables, so that a
linear trend could be verified.
RESULTS AND DISCUSSION
Microflotation Tests
Figures 1, 2 and 3 present the effect of the presence of PAM
with different levels of mechanical degradation in the recir-
culated process water on the recovery of chalcopyrite at pH
values 7, 9 and 11, respectively. In general, it is possible to
observe that, for all cases, there is a directly proportional
relationship between the residual PAM dosage in the pro-
cess water used in flotation and the chalcopyrite depression.
Particularly, Figure 1 shows that at pH 7 the NS-PAM gen-
erates the greatest impact on the recovery of chalcopyrite,
followed by the MS-PAM. In the case of SS-PAM, its mol-
ecules have molecules have the least depressant effect on
chalcopyrite flotation for all doses evaluated. In Figure 2,
the same trend described above can be noted, however, the
impact of MS-PAM is slightly greater than at pH 7 and
is equal to the effect of NS-PAM. Furthermore, although
SS-PAM has the least depressant effect on chalcopyrite,
the recovery decreases compared to that achieved at pH
7. A completely different effect is revealed in Figure 3. In
this case, the SS-PAM is the one that generates the great-
est impact on the recovery of chalcopyrite, which decreases
drastically to approximately 35% even at the lowest con-
centrations of the flocculant. On the other hand, it is also
possible to note that the depressant effect of NS-PAM and
MS-PAM is less than at lower pH values. These results
reveal that pH has an important effect on the interactions
between chalcopyrite particles and the different reagents
added to the process, especially with PAM. Although the
explanation for this impact is not clear at this stage of the
experimental program, it is reasonable to expect that at pH
11 the physicochemical conditions of the system allow the
surface of the SS-PAM molecules to be strongly activated
and because of that there is a great electrostatic interaction
between them, and the metal cations present on the sur-
face of the chalcopyrite particles. Regarding the NS and
MS-PAM molecules, due to their larger size and presence of
different active sites throughout their structure, it is likely
flotation of the mineral was completed, both the obtained
concentrate and the tail were filtered under vacuum and
dried at 100 °C for 5 hours to, finally, weigh each of these
products and calculate the recovery of chalcopyrite accord-
ing to the Equation 1.
R m mt
m
100
c
c #=+(1)
where R is the recovery of chalcopyrite (%),mc is the mass
of concentrate and mt is the mass of tail.
It is important to note that, to ensure the reproduc-
ibility of the results, all microflotation tests were performed
in duplicate.
Induction Time Measurements
Induction time measurements were carried out to analyze
the effect of the presence of flocculant under different phys-
icochemical conditions on the adhesion process between
chalcopyrite particles and air bubbles. This parameter is
defined as the average time in which the water film between
a particle and a bubble breaks after their collision, generat-
ing adhesion between both (Yoon and Yordan, 1991). In
this way, the induction time can be described as the prob-
ability that a particle is effectively collected by a bubble and
is inversely proportional to the recovery of a given min-
eral. The procedure to experimentally obtain the induction
time consists of generating a fresh bubble in the capillary
tube, which is then pushed against a bed of particles inside
the cell, and they remain in contact for a certain time.
Subsequently, the bubble is separated from the particle bed
and the existence of adhered particles is observed, recording
the number of effective adhesions. This same procedure is
repeated 10 times in different positions of the particle bed
and for different contact times, allowing a relationship to be
established between the effective adhesions and the contact
time, which allows defining the induction time as the con-
tact time in the which occurs in 50% of successful contacts.
The bed of mineral particles used for these experimental
tests was previously conditioned following the same pro-
cedure and dosages described for the microflotation tests.
Adsorption Isotherms
Adsorption isotherms of reagents were performed through
UV-Vis spectroscopy and total organic carbon measure-
ments. The first technique was used to estimate the remain-
ing concentration of PAX in solution at the different
experimental conditions evaluated, while with the second
it was possible to obtain the amount of total organic car-
bon and in this way, subtracting the carbon contributed by
PAX, it was estimated the adsorption of PAM on chalco-
pyrite particles. The adsorbed amount of the reagents on
the chalcopyrite particles was calculated inversely, that is,
by subtracting the amount of reagent remaining in solu-
tion from the initial dose prepared. The conditioning was
carried out in the same way as for the microflotation tests,
with the difference that, once this procedure was com-
pleted, the suspension was vacuum filtered, discarding the
solid fraction and analyzing only the filtered liquid. Prior
to executing these tests, calibration curves were established
by evaluating the absorbance for different concentrations at
a fixed wavelength and graphing these variables, so that a
linear trend could be verified.
RESULTS AND DISCUSSION
Microflotation Tests
Figures 1, 2 and 3 present the effect of the presence of PAM
with different levels of mechanical degradation in the recir-
culated process water on the recovery of chalcopyrite at pH
values 7, 9 and 11, respectively. In general, it is possible to
observe that, for all cases, there is a directly proportional
relationship between the residual PAM dosage in the pro-
cess water used in flotation and the chalcopyrite depression.
Particularly, Figure 1 shows that at pH 7 the NS-PAM gen-
erates the greatest impact on the recovery of chalcopyrite,
followed by the MS-PAM. In the case of SS-PAM, its mol-
ecules have molecules have the least depressant effect on
chalcopyrite flotation for all doses evaluated. In Figure 2,
the same trend described above can be noted, however, the
impact of MS-PAM is slightly greater than at pH 7 and
is equal to the effect of NS-PAM. Furthermore, although
SS-PAM has the least depressant effect on chalcopyrite,
the recovery decreases compared to that achieved at pH
7. A completely different effect is revealed in Figure 3. In
this case, the SS-PAM is the one that generates the great-
est impact on the recovery of chalcopyrite, which decreases
drastically to approximately 35% even at the lowest con-
centrations of the flocculant. On the other hand, it is also
possible to note that the depressant effect of NS-PAM and
MS-PAM is less than at lower pH values. These results
reveal that pH has an important effect on the interactions
between chalcopyrite particles and the different reagents
added to the process, especially with PAM. Although the
explanation for this impact is not clear at this stage of the
experimental program, it is reasonable to expect that at pH
11 the physicochemical conditions of the system allow the
surface of the SS-PAM molecules to be strongly activated
and because of that there is a great electrostatic interaction
between them, and the metal cations present on the sur-
face of the chalcopyrite particles. Regarding the NS and
MS-PAM molecules, due to their larger size and presence of
different active sites throughout their structure, it is likely