1752 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
phosphate ions and precipitate as ferric phosphate (FePO4)
(Eq. (8)).
To confirm the formation of FePO4 coating on the arse-
nopyrite surface, untreated and ME-treated arsenopyrite
samples were analyzed by XPS (Figure 4). The Fe 2p spec-
trum of untreated arsenopyrite showed Fe2+ peak assigned
to Fe—AsS of arsenopyrite, while no peak was observed
in the P 2p spectrum. On the other hand, ME-treated
arsenopyrite showed that Fe3+ as well as PO43– peaks were
detected, which indicate that FePO4 coating was formed
on the surface of arsenopyrite by ME using ferrous and
phosphate ions.
Effect of Microencapsulation Treatment on Gold
Extraction from Gold/Arsenopyrite Mixture by
Thiosulfate Leaching
As confirmed earlier, arsenopyrite showed a detrimental
effect on gold extraction in thiosulfate leaching due to
the enhanced decomposition of thiosulfate that is, gold
extraction decreased from 99% (without arsenopyrite) to
~10% (with arsenopyrite) (Figure 2(a)). When ME treat-
ment was applied prior to thiosulfate leaching, gold extrac-
tion efficiency was improved to ~52%. This improved gold
extraction is most likely attributed to the formation of
FePO4 coating that limits the contact between thiosulfate
and arsenopyrite, resulting in the reduction of thiosulfate
decomposition. Although ME treatment showed a positive
result, gold extraction efficiency was only half of that with-
out arsenopyrite. This result implies that arsenopyrite was
not fully coated by FePO4 precipitates, so some portion of
thiosulfate was still decomposed through uncoated arseno-
pyrite parts. To further improve the efficiency of thiosulfate
leaching in extracting gold in the presence of arsenopy-
rite, it is necessary to optimize ME treatment conditions
Figure 3. The changes in dissolved Fe and P concentrations
after microencapsulation treatment
Figure 4. XPS spectra of untreated and ME-treated arsenopyrite
phosphate ions and precipitate as ferric phosphate (FePO4)
(Eq. (8)).
To confirm the formation of FePO4 coating on the arse-
nopyrite surface, untreated and ME-treated arsenopyrite
samples were analyzed by XPS (Figure 4). The Fe 2p spec-
trum of untreated arsenopyrite showed Fe2+ peak assigned
to Fe—AsS of arsenopyrite, while no peak was observed
in the P 2p spectrum. On the other hand, ME-treated
arsenopyrite showed that Fe3+ as well as PO43– peaks were
detected, which indicate that FePO4 coating was formed
on the surface of arsenopyrite by ME using ferrous and
phosphate ions.
Effect of Microencapsulation Treatment on Gold
Extraction from Gold/Arsenopyrite Mixture by
Thiosulfate Leaching
As confirmed earlier, arsenopyrite showed a detrimental
effect on gold extraction in thiosulfate leaching due to
the enhanced decomposition of thiosulfate that is, gold
extraction decreased from 99% (without arsenopyrite) to
~10% (with arsenopyrite) (Figure 2(a)). When ME treat-
ment was applied prior to thiosulfate leaching, gold extrac-
tion efficiency was improved to ~52%. This improved gold
extraction is most likely attributed to the formation of
FePO4 coating that limits the contact between thiosulfate
and arsenopyrite, resulting in the reduction of thiosulfate
decomposition. Although ME treatment showed a positive
result, gold extraction efficiency was only half of that with-
out arsenopyrite. This result implies that arsenopyrite was
not fully coated by FePO4 precipitates, so some portion of
thiosulfate was still decomposed through uncoated arseno-
pyrite parts. To further improve the efficiency of thiosulfate
leaching in extracting gold in the presence of arsenopy-
rite, it is necessary to optimize ME treatment conditions
Figure 3. The changes in dissolved Fe and P concentrations
after microencapsulation treatment
Figure 4. XPS spectra of untreated and ME-treated arsenopyrite
