8
adsorbate is physically not “oily soft” in nature and the
detachment of the AFM probe from the mineral surface
takes little effort.
AFT-FTIR Results
Figure 10 shows the ATR-FTIR spectra of malachite surface
before and after it contacts OHA solution. The assignment
of the peaks on the spectra is listed in Table 1. For the case
of bare malachite surface, on the spectra, the main peaks
shown at 3400 cm–1 and 3300 cm–1 are due to the stretch-
ing vibration of hydroxyl group (-OH) the peaks shown
at 1490 cm–1 and 1384 cm–1 are due to the asymmetric
stretching vibration of CO32– the peaks of 1096 cm–1 is due
to the symmetric stretching vibration of CO32– the peaks
of 1043 cm–1 is due to the bending vibration of -OH the
peaks of 868 cm–1 is due to the out-of-plane bending vibra-
tion of CO32–and the peaks of 750 cm–1 and 725 cm–1 are
due to the in-plane bending vibration of CO32–.
Figure 10 also shows the ATR-FTIR spectra of a mala-
chite surface after it contacts 1×10–4 M OHA solution at
pH 6 for 1 hour. On the spectra, On the spectra, the main
peaks shown at 3406 cm–1 and 3308 cm–1 are due to the
stretching vibration of hydroxyl group (-OH) the strong
doublet shown at 2955 cm–1 and 2871 cm–1 are due to the
stretching vibrations of –CH3 the strong doublet shown
at 2925 cm–1 and 2850 cm–1 are due to the stretching
vibrations of –CH2– the peaks of 1507 cm–1 is due to the
asymmetry bending vibration of –OH the peaks shown
at 1490 cm–1 and 1384 cm–1 are due to the asymmetric
stretching vibration of CO32– the peaks of 1096 cm–1 is due
to the symmetric stretching vibration of CO32– the peaks
of 1046 cm–1 is due to the bending vibration of -OH the
peaks of 868 cm–1 is due to the out-of-plane bending vibra-
tion of CO32–and the peaks of 765 cm–1 and 725 cm–1 are
due to the in-plane bending vibration of CO32–.
DISCUSSION
Adsorption of OHA on Malachite Surface
Figure 1 is the surface image of a bare malachite surface
obtained in air, which shows that the solid surface is quite
smooth with only some scratch lines on the sample surface
due to surface polishing, and it confirms that the polished
malachite surface is appropriate for an AFM imaging study.
Figure 2 is the surface image of a bare malachite sur-
face soaked in water. It shows that when malachite contacts
water, there is some change in morphology on malachite
surface, with some grains with clear boundary showing up.
Figure 9. The detach force (F) measured between an AFM probe and a malachite plate soaked
in solutions at pH 6 as a function of the separation (H) between the probe and the plate by
applying an AFM force measurement. (O) in air (◊) in water (Δ) in 1×10–5 M OHA solution
adsorbate is physically not “oily soft” in nature and the
detachment of the AFM probe from the mineral surface
takes little effort.
AFT-FTIR Results
Figure 10 shows the ATR-FTIR spectra of malachite surface
before and after it contacts OHA solution. The assignment
of the peaks on the spectra is listed in Table 1. For the case
of bare malachite surface, on the spectra, the main peaks
shown at 3400 cm–1 and 3300 cm–1 are due to the stretch-
ing vibration of hydroxyl group (-OH) the peaks shown
at 1490 cm–1 and 1384 cm–1 are due to the asymmetric
stretching vibration of CO32– the peaks of 1096 cm–1 is due
to the symmetric stretching vibration of CO32– the peaks
of 1043 cm–1 is due to the bending vibration of -OH the
peaks of 868 cm–1 is due to the out-of-plane bending vibra-
tion of CO32–and the peaks of 750 cm–1 and 725 cm–1 are
due to the in-plane bending vibration of CO32–.
Figure 10 also shows the ATR-FTIR spectra of a mala-
chite surface after it contacts 1×10–4 M OHA solution at
pH 6 for 1 hour. On the spectra, On the spectra, the main
peaks shown at 3406 cm–1 and 3308 cm–1 are due to the
stretching vibration of hydroxyl group (-OH) the strong
doublet shown at 2955 cm–1 and 2871 cm–1 are due to the
stretching vibrations of –CH3 the strong doublet shown
at 2925 cm–1 and 2850 cm–1 are due to the stretching
vibrations of –CH2– the peaks of 1507 cm–1 is due to the
asymmetry bending vibration of –OH the peaks shown
at 1490 cm–1 and 1384 cm–1 are due to the asymmetric
stretching vibration of CO32– the peaks of 1096 cm–1 is due
to the symmetric stretching vibration of CO32– the peaks
of 1046 cm–1 is due to the bending vibration of -OH the
peaks of 868 cm–1 is due to the out-of-plane bending vibra-
tion of CO32–and the peaks of 765 cm–1 and 725 cm–1 are
due to the in-plane bending vibration of CO32–.
DISCUSSION
Adsorption of OHA on Malachite Surface
Figure 1 is the surface image of a bare malachite surface
obtained in air, which shows that the solid surface is quite
smooth with only some scratch lines on the sample surface
due to surface polishing, and it confirms that the polished
malachite surface is appropriate for an AFM imaging study.
Figure 2 is the surface image of a bare malachite sur-
face soaked in water. It shows that when malachite contacts
water, there is some change in morphology on malachite
surface, with some grains with clear boundary showing up.
Figure 9. The detach force (F) measured between an AFM probe and a malachite plate soaked
in solutions at pH 6 as a function of the separation (H) between the probe and the plate by
applying an AFM force measurement. (O) in air (◊) in water (Δ) in 1×10–5 M OHA solution