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Flowsheet development for the recovery of cadmium and indium from copper flash furnace electrostatic precipitator dust via hydrometallurgical processing
Trouba, Joseph
Trouba, Joseph
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2022
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2023-11-04
Abstract
Copper flash furnace electrostatic precipitator (FF ESP) dusts contain significant
amounts of copper, as well as bismuth, lead, arsenic, cadmium and the critical element indium.
Disposal of dusts results in losing the copper values, but recycling the dusts directly back to the
smelting furnace creates recirculation loads of elements problematic to downstream operations.
Avoiding the reintroduction of such deleterious elements, particularly bismuth, requires
processing the dust. FF ESP dust treatment also presents further advantage, as it provides an
opportunity for the recovery of cadmium and indium used in thin film solar energy generation
essential to the green energy transition.
FF ESP dust is a complex material, with numerous elements in a range of different
phases. The primary economic motivation for dust treatment is the selective leaching of copper
away from bismuth, lead and arsenic. Most previous methods make use of water or sulfuric
acid, achieving varying degrees of success. A novel ammoniacal flowsheet was developed to
selectively leach copper and cadmium away from bismuth, lead, arsenic, iron, and indium.
Treatment of the leachate for copper precipitation and ammonia regeneration necessitates the
use of a bleed stream, from which cadmium is recovered. Combining this cadmium with
tellurium to form CdTe was performed, turning a hazardous metal into a source material for
renewable energy technologies. The residue of ammoniacal leaching contains bismuth, lead,
arsenic, iron, indium, and the remaining copper, which undergoes further treatment with NaCl
and H2SO4. Previous methods using H2SO4 alone recovered bismuth, but the addition of NaCl
enabled to simultaneous removal of lead into the solution. This leachate is the most enriched
indium stream, however further investigation is necessary for indium recovery.
Economic analysis of the process based upon ammoniacal leaching was compared to
an alternative, with cost estimates calculated based upon METSIM process modeling of both
the proposed and previous flowsheets. The ammoniacal flowsheet developed was economically
competitive with the alternative for the conditions evaluated, with the added benefit of providing
an outlet for cadmium recovery and indium enrichment.
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