Lead and silver extraction from waste cake from hydrometallurgical zinc production

This paper presents the experimental results of the extraction of lead and silver from a lead-silver waste cake obtained in the process of hydrometallurgical zinc production. While controlling the pH value, the lead-silver cake was leached at a temperature close to boiling point in different concentrations of aqueous calcium chloride solutions. The experiments were performed applying different ratios between the mass of cake and the volume of the leaching agent under different durations of the process. It was concluded that at the optimal process parameters (pH 2.0-2.5; CaCl 2 concentration, 3.6 mol dm -3 ; temperature, 95 °C; solid/liquid ratio, 1:5), the leaching efficiency of lead and silver could reach the approximate value of 94 %. Applying the same optimal process parameters, the method was applied to the leaching of a lead-silver cake in a magnesium chloride solution, but with significantly lower efficiencies. The results show that leaching of lead and silver in a calcium chloride solution could be a prospective method for increasing the recovery of lead and silver during hydrometallurgical zinc production.