2
of copper oxide mineral, when oleic acid is used as the col-
lector, it adsorbs onto gangue minerals such as calcite and
dolomite as well, showing a low selectivity. Comparatively,
the hydroxamic acid type of collector, which has long been
known as a chelating agent towards heavy metal ions, has
shown very good selectivity of malachite against gangue.
Lee, et al. (2009) reported that by applying octyl hydroxa-
mate together with traditional xanthate collectors, the
blend ore of both copper sulfide and oxide minerals were
simultaneously floated successfully, and quote, “The copper
recovery from the blended ore using a mixture of collectors
was shown to be superior to the recovery obtained using
only xanthate after controlled potential sulphidisation.”
Marion et al. (2017) studied the effect of various hydroxa-
mate collectors for malachite flotation, and claimed that,
quote, “Benzo- and the two C8 alkyl hydroxamate result in
the best flotation response with all other collectors resulting
in low malachite recoveries.”
Because of its unique selectivity, it is of great interest to
study the adsorption of hydroxamic acid collector on the
surface of minerals. (Fuerstenau and Pradip, 1984) AFM
imaging technique has been successfully applied for the in-
situ study of the adsorption of chemicals on various min-
eral surfaces. (Zhang and Zhang, 2010, 2012, 2014, 2015,
2019, 2021, 2022 An
and Zhang, 2020) The novel analysis method has
greatly expanded the understanding of the impact of solu-
tion chemistry such as the type and dosage of chemicals,
solution pH and adsorption time on the collectors’ adsorp-
tion on mineral surface and the flotation mechanism as
well. In present investigation, an AFM has been applied
to get the surface morphology of malachite in hydroxamic
acid solutions. By comparing the AFM images obtained
under different conditions, such as the collector’s type, dos-
age, and contacting time, one can study the impact of water
chemistry on the adsorption of collectors on malachite. In
the present study, we also use an ATR-FTIR (Attenuated
Total Reflection-Fourier Transform Infrared) to chemi-
cally analyze the adsorption product of the collector on
malachite surface. Because the adsorption of collectors on a
mineral surface is vital to a successful flotation, the results
will help clarify the reaction and adsorption mechanisms of
hydroxamic acid on malachite changing with aqueous solu-
tions, and therefore the optimization of malachite flotation
using hydroxamic acid as the collector.
EXPERIMENTAL
Materials
Research grade malachite was obtained from Wards
Natural Science Establishment Inc. The samples were finely
polished, further cleaned by rinsing thoroughly with etha-
nol and water and a 1.2 cm ×1.2 cm sample was used for
the surface characterization. The DI water used in present
work has a conductivity of 18.2 MΩ-cm at 23°C and a
surface tension of 72.5 mN/m at 23°C. Sodium octano-
hydroxamate hydrate (98%) were obtained from Tokyo
Chemical Industry America (Portland, OR), and used
without further purification.
AFM Surface Image Measurements
Surface image measurements were carried out by using a
Digital Instrument Nanoscope IIID AFM at room tem-
perature (23+1°C). Triangular DNP cantilevers (Bruker,
CA) with nominal spring constant of 0.12~0.35 N/m
was used. For the study of mineral surface in water, sur-
face image measurements were carried out right after water
was injected into an AFM fluid cell. After surface images
were collected, a 10 ml solution was flushed through the
liquid cell and AFM measurement was commenced after
the exposure of the mineral plate to the chemical’s solu-
tion for a specific time. The AFM images reported in this
communication were processed by no image modification
other than being flattened include both height and deflec-
tion images obtained in the contact mode.
ATR-FTIR analysis
A Nicolet 6700 FTIR spectrometer equipped with the
Smart iTR accessory was used to collect mid-infrared spec-
tra. The system was equipped with a DTGS KBr detector
and a diamond ATR crystal with an angle of incidence of
45°. Fresh mineral surface was pressed and fastened against
the ATR crystal to collect background spectra. Sample spec-
tra was collected after the mineral surface contacted the col-
lector solution of a specific concentration for specific time.
The intensities in the FTIR spectra were shown in a relative
absorbance under the same scale for the sake of complexity
of reflection spectroscopy. No further treatment was made
towards spectra except baseline correction.
RESULTS AND DISCUSSION
AFM Surface Images
Figure 1 shows the surface images of a bare malachite sur-
face obtained in air. Figure 1A is the 2 µm × 2 µm height
image, from which one can see that the solid surface is quite
smooth in spite of some scratch lines on the sample sur-
face due to surface polishing. Figure 1B is the 3-D image.
Figure 1C is the section analysis of Figure 1A, which con-
firms that the polished malachite surface is smooth and it
is appropriate for an AFM imaging study. Figure 1D is the
deflection image with a 5 nm data scale.
of copper oxide mineral, when oleic acid is used as the col-
lector, it adsorbs onto gangue minerals such as calcite and
dolomite as well, showing a low selectivity. Comparatively,
the hydroxamic acid type of collector, which has long been
known as a chelating agent towards heavy metal ions, has
shown very good selectivity of malachite against gangue.
Lee, et al. (2009) reported that by applying octyl hydroxa-
mate together with traditional xanthate collectors, the
blend ore of both copper sulfide and oxide minerals were
simultaneously floated successfully, and quote, “The copper
recovery from the blended ore using a mixture of collectors
was shown to be superior to the recovery obtained using
only xanthate after controlled potential sulphidisation.”
Marion et al. (2017) studied the effect of various hydroxa-
mate collectors for malachite flotation, and claimed that,
quote, “Benzo- and the two C8 alkyl hydroxamate result in
the best flotation response with all other collectors resulting
in low malachite recoveries.”
Because of its unique selectivity, it is of great interest to
study the adsorption of hydroxamic acid collector on the
surface of minerals. (Fuerstenau and Pradip, 1984) AFM
imaging technique has been successfully applied for the in-
situ study of the adsorption of chemicals on various min-
eral surfaces. (Zhang and Zhang, 2010, 2012, 2014, 2015,
2019, 2021, 2022 An
and Zhang, 2020) The novel analysis method has
greatly expanded the understanding of the impact of solu-
tion chemistry such as the type and dosage of chemicals,
solution pH and adsorption time on the collectors’ adsorp-
tion on mineral surface and the flotation mechanism as
well. In present investigation, an AFM has been applied
to get the surface morphology of malachite in hydroxamic
acid solutions. By comparing the AFM images obtained
under different conditions, such as the collector’s type, dos-
age, and contacting time, one can study the impact of water
chemistry on the adsorption of collectors on malachite. In
the present study, we also use an ATR-FTIR (Attenuated
Total Reflection-Fourier Transform Infrared) to chemi-
cally analyze the adsorption product of the collector on
malachite surface. Because the adsorption of collectors on a
mineral surface is vital to a successful flotation, the results
will help clarify the reaction and adsorption mechanisms of
hydroxamic acid on malachite changing with aqueous solu-
tions, and therefore the optimization of malachite flotation
using hydroxamic acid as the collector.
EXPERIMENTAL
Materials
Research grade malachite was obtained from Wards
Natural Science Establishment Inc. The samples were finely
polished, further cleaned by rinsing thoroughly with etha-
nol and water and a 1.2 cm ×1.2 cm sample was used for
the surface characterization. The DI water used in present
work has a conductivity of 18.2 MΩ-cm at 23°C and a
surface tension of 72.5 mN/m at 23°C. Sodium octano-
hydroxamate hydrate (98%) were obtained from Tokyo
Chemical Industry America (Portland, OR), and used
without further purification.
AFM Surface Image Measurements
Surface image measurements were carried out by using a
Digital Instrument Nanoscope IIID AFM at room tem-
perature (23+1°C). Triangular DNP cantilevers (Bruker,
CA) with nominal spring constant of 0.12~0.35 N/m
was used. For the study of mineral surface in water, sur-
face image measurements were carried out right after water
was injected into an AFM fluid cell. After surface images
were collected, a 10 ml solution was flushed through the
liquid cell and AFM measurement was commenced after
the exposure of the mineral plate to the chemical’s solu-
tion for a specific time. The AFM images reported in this
communication were processed by no image modification
other than being flattened include both height and deflec-
tion images obtained in the contact mode.
ATR-FTIR analysis
A Nicolet 6700 FTIR spectrometer equipped with the
Smart iTR accessory was used to collect mid-infrared spec-
tra. The system was equipped with a DTGS KBr detector
and a diamond ATR crystal with an angle of incidence of
45°. Fresh mineral surface was pressed and fastened against
the ATR crystal to collect background spectra. Sample spec-
tra was collected after the mineral surface contacted the col-
lector solution of a specific concentration for specific time.
The intensities in the FTIR spectra were shown in a relative
absorbance under the same scale for the sake of complexity
of reflection spectroscopy. No further treatment was made
towards spectra except baseline correction.
RESULTS AND DISCUSSION
AFM Surface Images
Figure 1 shows the surface images of a bare malachite sur-
face obtained in air. Figure 1A is the 2 µm × 2 µm height
image, from which one can see that the solid surface is quite
smooth in spite of some scratch lines on the sample sur-
face due to surface polishing. Figure 1B is the 3-D image.
Figure 1C is the section analysis of Figure 1A, which con-
firms that the polished malachite surface is smooth and it
is appropriate for an AFM imaging study. Figure 1D is the
deflection image with a 5 nm data scale.