482 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
adhesion energy found was less than 5 mJ/m2, much less
than the 20–40 mJ/m2 found in the literature. With respect
to contact angle measurements, plasma cleaned silica and
mica displayed contact angle of ~8 and ~7 degrees, respec-
tively. TCOD-treated surfaces of silica and mica showed
contact angles of ~107 and ~96 degrees, respectively.
AKNOWLEDGEMENTS
This work was supported by U.S. National Science
Foundation grants DMR-2150356, and CBET-1805550.
The focused ion beam work was made possible by NSF
grant ECCS-2018626.
REFERENCES
Bleiwas, D. L., 2012. Estimated water requirements for the
conventional flotation of copper ores: U.S. Geological
Survey Open-File Report 2012–1089, 13 p., http://
pubs.usgs.gov/of/2012/1089/.
Chelgani, S. C., and Neisiani, A. A. 2022. Dry Mineral
Processing. Zurich: Springer.
Dorobantu, L. S., Bhattacharjee, S., Foght, J. M., and Gray,
M. R. 2009. Analysis of force interactions between
AFM tips and hydrophobic bacteria Using DLVO the-
ory. Langmuir 25(12): 6968–6976
Grierson, D. S., Flater, E. E., and Carpick, R. W. 2005.
Accounting for the JKR–DMT transition in adhesion
and friction measurements with atomic force micros-
copy. Journal of Adhesion Science and Technology. 19(3–
5): 291–311.
Jin X, and Kasal B. 2016. Adhesion force mapping on
wood by atomic force microscopy: influence of surface
roughness and tip geometry. Royal Society Open Science.
3: 160248.
Jogikalmath, G., Stuart, J. K., Pungor, A., and Hlady, V.
1999. Adhesion mapping of chemically modified and
poly(ethyleneoxide)-grafted glass surfaces. Colloids and
Surfaces A: Physicochemical and Engineering Aspects.
154(1–2): 53–64.
Kappl, M., and Butt, H.-J. 2002. The colloidal probe tech-
nique and its application to adhesion
force measurements. Part. Part. Syst. Charact. 19: 129–143.
Karoussi, O., and Hamouda, A.A., 2008. Macroscopic
and nanoscale study of wettability alteration of oil-wet
calcite
surface in presence of magnesium and sulfate ions. Journal
of Colloid and Interface Science. 317: 26–34.
Malhotra, D., Taylor, P., Spiller, E., Lavier, M. (Editors).
2009. Recent Advances in Mineral Processing Plant
Design. Littleton, CO: Society for Mining, Metallurgy,
&Exploration.
Marti, O. 2000. Measurement of adhesion and pull-off
forces with the AFM. in Bhushan, B. (Ed.) Handbook
of Modern Tribology. Boca Raton, FL: CRC Press.
Sansao B., Kellar, J., Cross, W., Schottler, K., Romkes, A.
2021a. Comparison of surface energy, and adhesion
energy of surface-treated particles. Powder Technology.
384: 287–275.
Sansao, B.M.B., Kellar, J.J., Cross, WM, Romkes, A.
2021b. Separation of particles of different surface ener-
gies through control of humidity. Minerals Engineering
160: 106680.
Sansao, B.M.B., Cross, W.M., Romkes, A. Kellar, J.J. 2002.
Influence of substrate roughness on particle adhesion
and concentration. Mining, Metallurgy &Exploration
39: 3–12.
Sansao, B.M.B., Kellar, J.J., Romkes, A., Cross, W.M.
November 7, 2023. Separation of particles of differ-
ent surface energies through control of humidity, Patent
number: 11806657.
Sauerer, B., Stukan, M., Abdallah, W., Derkani, M. H.,
Fedorov, M., Buiting, J., and Zhang, Z. J. 2016.
Quantifying mineral surface energy by scanning force
microscopy. Journal of Colloid and Interface Science
472: 237–246.
USGS Minerals Yearbook. 2020. Table T2 https://www.usgs
.gov/centers/national-minerals-information-center
/copper-statistics-and-information.
Wang, A., and Butte, M.J. 2014. Customized atomic force
microscopy probe by focused-ion-beam-assisted tip
transfer. Applied Physics Letters 105: 053101.

Previous Page Next Page

Extracted Text (may have errors)

482 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
adhesion energy found was less than 5 mJ/m2, much less
than the 20–40 mJ/m2 found in the literature. With respect
to contact angle measurements, plasma cleaned silica and
mica displayed contact angle of ~8 and ~7 degrees, respec-
tively. TCOD-treated surfaces of silica and mica showed
contact angles of ~107 and ~96 degrees, respectively.
AKNOWLEDGEMENTS
This work was supported by U.S. National Science
Foundation grants DMR-2150356, and CBET-1805550.
The focused ion beam work was made possible by NSF
grant ECCS-2018626.
REFERENCES
Bleiwas, D. L., 2012. Estimated water requirements for the
conventional flotation of copper ores: U.S. Geological
Survey Open-File Report 2012–1089, 13 p., http://
pubs.usgs.gov/of/2012/1089/.
Chelgani, S. C., and Neisiani, A. A. 2022. Dry Mineral
Processing. Zurich: Springer.
Dorobantu, L. S., Bhattacharjee, S., Foght, J. M., and Gray,
M. R. 2009. Analysis of force interactions between
AFM tips and hydrophobic bacteria Using DLVO the-
ory. Langmuir 25(12): 6968–6976
Grierson, D. S., Flater, E. E., and Carpick, R. W. 2005.
Accounting for the JKR–DMT transition in adhesion
and friction measurements with atomic force micros-
copy. Journal of Adhesion Science and Technology. 19(3–
5): 291–311.
Jin X, and Kasal B. 2016. Adhesion force mapping on
wood by atomic force microscopy: influence of surface
roughness and tip geometry. Royal Society Open Science.
3: 160248.
Jogikalmath, G., Stuart, J. K., Pungor, A., and Hlady, V.
1999. Adhesion mapping of chemically modified and
poly(ethyleneoxide)-grafted glass surfaces. Colloids and
Surfaces A: Physicochemical and Engineering Aspects.
154(1–2): 53–64.
Kappl, M., and Butt, H.-J. 2002. The colloidal probe tech-
nique and its application to adhesion
force measurements. Part. Part. Syst. Charact. 19: 129–143.
Karoussi, O., and Hamouda, A.A., 2008. Macroscopic
and nanoscale study of wettability alteration of oil-wet
calcite
surface in presence of magnesium and sulfate ions. Journal
of Colloid and Interface Science. 317: 26–34.
Malhotra, D., Taylor, P., Spiller, E., Lavier, M. (Editors).
2009. Recent Advances in Mineral Processing Plant
Design. Littleton, CO: Society for Mining, Metallurgy,
&Exploration.
Marti, O. 2000. Measurement of adhesion and pull-off
forces with the AFM. in Bhushan, B. (Ed.) Handbook
of Modern Tribology. Boca Raton, FL: CRC Press.
Sansao B., Kellar, J., Cross, W., Schottler, K., Romkes, A.
2021a. Comparison of surface energy, and adhesion
energy of surface-treated particles. Powder Technology.
384: 287–275.
Sansao, B.M.B., Kellar, J.J., Cross, WM, Romkes, A.
2021b. Separation of particles of different surface ener-
gies through control of humidity. Minerals Engineering
160: 106680.
Sansao, B.M.B., Cross, W.M., Romkes, A. Kellar, J.J. 2002.
Influence of substrate roughness on particle adhesion
and concentration. Mining, Metallurgy &Exploration
39: 3–12.
Sansao, B.M.B., Kellar, J.J., Romkes, A., Cross, W.M.
November 7, 2023. Separation of particles of differ-
ent surface energies through control of humidity, Patent
number: 11806657.
Sauerer, B., Stukan, M., Abdallah, W., Derkani, M. H.,
Fedorov, M., Buiting, J., and Zhang, Z. J. 2016.
Quantifying mineral surface energy by scanning force
microscopy. Journal of Colloid and Interface Science
472: 237–246.
USGS Minerals Yearbook. 2020. Table T2 https://www.usgs
.gov/centers/national-minerals-information-center
/copper-statistics-and-information.
Wang, A., and Butte, M.J. 2014. Customized atomic force
microscopy probe by focused-ion-beam-assisted tip
transfer. Applied Physics Letters 105: 053101.

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XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 481
surface interacting with the FIB manufactured silica tip.
The adhesion map in Figure 5 shows that the plasma clean-
ing may have left some material behind as evidenced by the
dark regions of low adhesion strength. Figure 6 resembles
Figure 4 except that the adhesion force is much greater in
Figure 6.
Table 2 summarizes the data gathered using the stan-
dard AFM tip and the FIB manufactured silica tip and a sil-
ica disk substrate. The plasma-cleaned substrate values are
approximately as expected from our previous work. For the
TCOD and TMPA treated silica disk surfaces, the adhesion
values found are lower than expected although the ratio of
the values for the silicon tip are close to what was expected
from Sansao et al.’s previous research [Sansao et al., 2021a,
2021b, 2022]. We are unsure why this has occurred. The
ratio of the surface treated materials adhesion energies is
similar but the absolute values are much lower in the AFM
adhesion measurements. Given that the untreated surface
adhesion energies are similar to the literature values, the
AFM technique does not seem to be the issue. Thus, the
issue seems more likely to be related to the surface treat-
ment and is under investigation.
Overall, using the AFM to measure adhesion is a useful
technique that does not require the building of a new setup
to measure the adhesion. The use of the FIB manufactured
tip offers a method by which mineral pieces can be utilized
for better understanding adhesion in mineral processing
systems.
CONCLUSION
This research represents, to our knowledge, the first time
a focused ion beam manufactured AFM tip has been used
for adhesion measurements on a mineral system, although
mineral surface energy had been measured with this method
by Sauerer et al. (2016). Performing AFM adhesion mea-
surements worked reasonably well with plasma cleaned
surfaces, although less well with surfactant treated sur-
faces. For the plasma cleaned surfaces the adhesion energy
found was 30–40 mJ/m2 as compared to literature values
of 48.5 mJ/m2. For surface treated silica substrates, the
Table 2. AFM adhesion data for silica substrate
Treatment
Humidity,
%
DMT Adhesion,
mJ/m2
JKR
Literature
Value*
Silicon Tip
Plasma Cleaned 50 40 48.5
TCOD 35 1.1 21.6
TMPA 40 2.6 40.1
FIB Silica Tip
Plasma Cleaned -31.8 48.5
TCOD -3.5 21.6
*Literature values are from Sansao et al., 2021b
Figure 6. Force-displacement curve on a plasma-cleaned silica substrate with a FIB
manufactured quartz tip

Previous Page Next Page

Extracted Text (may have errors)

XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 481
surface interacting with the FIB manufactured silica tip.
The adhesion map in Figure 5 shows that the plasma clean-
ing may have left some material behind as evidenced by the
dark regions of low adhesion strength. Figure 6 resembles
Figure 4 except that the adhesion force is much greater in
Figure 6.
Table 2 summarizes the data gathered using the stan-
dard AFM tip and the FIB manufactured silica tip and a sil-
ica disk substrate. The plasma-cleaned substrate values are
approximately as expected from our previous work. For the
TCOD and TMPA treated silica disk surfaces, the adhesion
values found are lower than expected although the ratio of
the values for the silicon tip are close to what was expected
from Sansao et al.’s previous research [Sansao et al., 2021a,
2021b, 2022]. We are unsure why this has occurred. The
ratio of the surface treated materials adhesion energies is
similar but the absolute values are much lower in the AFM
adhesion measurements. Given that the untreated surface
adhesion energies are similar to the literature values, the
AFM technique does not seem to be the issue. Thus, the
issue seems more likely to be related to the surface treat-
ment and is under investigation.
Overall, using the AFM to measure adhesion is a useful
technique that does not require the building of a new setup
to measure the adhesion. The use of the FIB manufactured
tip offers a method by which mineral pieces can be utilized
for better understanding adhesion in mineral processing
systems.
CONCLUSION
This research represents, to our knowledge, the first time
a focused ion beam manufactured AFM tip has been used
for adhesion measurements on a mineral system, although
mineral surface energy had been measured with this method
by Sauerer et al. (2016). Performing AFM adhesion mea-
surements worked reasonably well with plasma cleaned
surfaces, although less well with surfactant treated sur-
faces. For the plasma cleaned surfaces the adhesion energy
found was 30–40 mJ/m2 as compared to literature values
of 48.5 mJ/m2. For surface treated silica substrates, the
Table 2. AFM adhesion data for silica substrate
Treatment
Humidity,
%
DMT Adhesion,
mJ/m2
JKR
Literature
Value*
Silicon Tip
Plasma Cleaned 50 40 48.5
TCOD 35 1.1 21.6
TMPA 40 2.6 40.1
FIB Silica Tip
Plasma Cleaned -31.8 48.5
TCOD -3.5 21.6
*Literature values are from Sansao et al., 2021b
Figure 6. Force-displacement curve on a plasma-cleaned silica substrate with a FIB
manufactured quartz tip

483
Optimising Tribocharger Designs for Separating Granular
Material Using the Discrete Element Method
Joshua N. Rasera, Jan J. Cilliers
Imperial College London
Kathryn Hadler
European Space Resources Innovation Centre
ABSTRACT: The optimisation of tribochargers using the discrete element method for the separating granular
materials, essential for dry mineral beneficiation, is studied. Various tribocharger designs are compared an
optimum is identified. The suitability of the design for charging other materials is considered. We extend our
analysis to simulate the conditions on the Moon, adapting the tribocharger design its unique environment.
We highlight the versatility of our modelling approach and its potential for mineral processing on Earth and
in space, particularly in the context of space resource utilisation. We provide insights into the adaptability and
effectiveness of tribocharging technologies under diverse conditions.
INTRODUCTION
Space Resource Utilisation (SRU) is integral to human
exploration and habitation of space. A critical first step for
SRU is the production of oxygen from lunar regolith, as it
can sustain human life and fuel space vehicles. Lunar min-
erals, comprising about 40% oxygen by mass, offer a rich
resource for this purpose (French et al., 1991). Utilising
space materials for water, fuel, and building supplies could
significantly reduce the launch mass and overall cost of
space missions.
Mineral beneficiation employs physical property dif-
ferences like density, surface chemistry, or electromagnetic
characteristics for separation (Wills &Finch, 2015 Rasera
2020). Dry processing techniques have been considered
for several mineral processing applications at lab- and
pilot-scale (Wills &Finch, 2015 Kelly and Spottiswood,
1989a, b, c Manouchehri et al., 2000a, b Trigwell et al.,
2003 Dwari et al., 2009 Bittner et al., 2014 Bilici et al.,
2011 Brands et al., 2001 Ballantyne &Holtham, 2010,
2014 Ireland 2010a, b, 2012 Ireland &Nicholson, 2011
Lawver 1973 Dwari et al., 2007). However, industrial-scale
dry processing technologies for terrestrial applications have
been limited to the use of high-tension roll separators for
the separation of ilmenite and rutile from zircon in beach
sands operations (Bittner et al., 2014 Dwari 2007 Wills
&Finch, 2015 Lawver 1973). For the majority of mining
applications, water-driven technologies, such as froth flota-
tion and spiral concentrators, have been favoured (Wills &
Finch, 2015).
Tribocharging, the frictional imparting of electrostatic
charge, is a millennia-old phenomenon (Lacks 2012),
yet its underlying mechanisms remain elusive (Lacks &
Levandovsky, 2007 Waitukaitis et al., 2014 Zhao et
al., 2003). Factors influencing charge transfer and reten-
tion include humidity, temperature, impact velocity, and

Previous Page Next Page

Extracted Text (may have errors)

483
Optimising Tribocharger Designs for Separating Granular
Material Using the Discrete Element Method
Joshua N. Rasera, Jan J. Cilliers
Imperial College London
Kathryn Hadler
European Space Resources Innovation Centre
ABSTRACT: The optimisation of tribochargers using the discrete element method for the separating granular
materials, essential for dry mineral beneficiation, is studied. Various tribocharger designs are compared an
optimum is identified. The suitability of the design for charging other materials is considered. We extend our
analysis to simulate the conditions on the Moon, adapting the tribocharger design its unique environment.
We highlight the versatility of our modelling approach and its potential for mineral processing on Earth and
in space, particularly in the context of space resource utilisation. We provide insights into the adaptability and
effectiveness of tribocharging technologies under diverse conditions.
INTRODUCTION
Space Resource Utilisation (SRU) is integral to human
exploration and habitation of space. A critical first step for
SRU is the production of oxygen from lunar regolith, as it
can sustain human life and fuel space vehicles. Lunar min-
erals, comprising about 40% oxygen by mass, offer a rich
resource for this purpose (French et al., 1991). Utilising
space materials for water, fuel, and building supplies could
significantly reduce the launch mass and overall cost of
space missions.
Mineral beneficiation employs physical property dif-
ferences like density, surface chemistry, or electromagnetic
characteristics for separation (Wills &Finch, 2015 Rasera
2020). Dry processing techniques have been considered
for several mineral processing applications at lab- and
pilot-scale (Wills &Finch, 2015 Kelly and Spottiswood,
1989a, b, c Manouchehri et al., 2000a, b Trigwell et al.,
2003 Dwari et al., 2009 Bittner et al., 2014 Bilici et al.,
2011 Brands et al., 2001 Ballantyne &Holtham, 2010,
2014 Ireland 2010a, b, 2012 Ireland &Nicholson, 2011
Lawver 1973 Dwari et al., 2007). However, industrial-scale
dry processing technologies for terrestrial applications have
been limited to the use of high-tension roll separators for
the separation of ilmenite and rutile from zircon in beach
sands operations (Bittner et al., 2014 Dwari 2007 Wills
&Finch, 2015 Lawver 1973). For the majority of mining
applications, water-driven technologies, such as froth flota-
tion and spiral concentrators, have been favoured (Wills &
Finch, 2015).
Tribocharging, the frictional imparting of electrostatic
charge, is a millennia-old phenomenon (Lacks 2012),
yet its underlying mechanisms remain elusive (Lacks &
Levandovsky, 2007 Waitukaitis et al., 2014 Zhao et
al., 2003). Factors influencing charge transfer and reten-
tion include humidity, temperature, impact velocity, and