Chloride leaching of silver and lead from a solid residue after atmospheric leaching of flotation copper concentrates

Recovery of silver and lead by means of chloride leaching of solid residue after atmospheric leaching of the copper concentrate from Lubin Concentrator (KGHM) was investigated. The effect of leaching temperature, chloride concentration, Fe(III) and oxygen presence, solid-to-liquid ratio and feed preleaching with NaOH on the silver and lead recovery was analyzed. Chloride leaching appeared to be very effective for recovery of lead, whereas satisfactory recovery of silver was observed after chemical pretreatment of the leaching feed with alkali solution of NaOH in order to liberate Ag entrapped in the jarosite structure. It was found that to achieve the satisfactory recovery of Ag and Pb leaching had to be performed in acidified 4 M chloride concentration at temperature of 90 oC. The presence of oxidants, that is O2 and iron(III) ions, was beneficial in the initial stage of the process. The maximum recovery of Ag and Pb was found for the solid-to-liquid ratio of 1:10 after 10 hours leaching.