High‐temperature chlorination of gold with transformation of iron phase

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Abstract
Gold in cyanide tailings from Shandong Province is mainly encapsulated by hematite and magnetite at distribution rates of 76.49 % and 10.88 %, respectively. Chlorination–reduction one‐step roasting of cyanide tailings was conducted under the following conditions: calcium chloride dosage of 6 %, bituminous coal dosage of 30 %, calcium oxide dosage of 10 % (all dosages are vs. the mass of cyanide tailings) at 1000 °C of roasting temperature. X‐ray diffraction (XRD), scanning electron microscopy (SEM), and chemical‐phase analysis were performed to investigate the effects of iron phase transformation on the high‐temperature chlorination of gold. Results indicate that the lattice structure of hematite undergoes expansion, pulverization, and reorganization when hematite is reduced to magnetite, which leads to 42.03 % gold exposure, and the high‐temperature chlorination rate of gold is 41.17 % at the same time. The structure of wustite formed by the reduction in magnetite is porous and loose, and thus 44.02 % of gold is exposed. The high‐temperature chlorination rate of gold is increased by 41.98 percentage points. When wustite is reduced to metallic iron, 4.42 % of gold is exposed, and the high‐temperature chlorination rate of gold is increased by 3.38 percentage points. Accordingly, the high‐temperature chlorination of gold mainly occurs in two stages, in which Fe 2 O 3 is reduced to Fe 3 O 4 , and Fe 3 O 4 is reduced to Fe x O finally.
Funding Information
  • National Natural Science Foundation of China (51474018)
  • National Natural Science Foundation of China (51474018)

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