Abstract
Process flowsheets for the recovery of zinc, indium and gallium from La Oroya zinc ferrite residue (19˙5%Zn, 26˙6%Fe, 0˙052%Ga, 0˙075%In) using Na2CO3 roasting are proposed. While several leaching flowsheets are discussed, the flowsheet where zinc ferrite is roasted with Na2CO3 and MnCO3, followed by two stages of leaching (hot water and H2SO4), iron reduction and precipitation of In and Ga as hydroxides, Fe as FeOOH and zinc as basic zinc sulphate from solution appears to be the most promising option for metals recovery from this material using Na2CO3 roasting. Sulphuric acid for leaching may be regenerated using either Na2SO4 metathesis or solvent extraction/ion exchange and Na2CO3 can be recovered for recycle to roasting from solution using precipitation and calcination of NaHCO3. Future research on these potential flowsheets is required, including possible methods for the recovery of iron, silver and gallium from the various process streams.
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