Optimization and kinetics study of zinc extraction from zinc containing leaching residue in sulfuric acid solution

In this paper, the acidic leaching kinetics of the leach residue containing 6.5% Zn, 3.5% Pb and 2.5 % Fe in sulfuric acid solution was studied. Leaching temperature, holding time, liquid-solid ratio (volume/weight) (L/S), stirring speed and pH (sulfuric acid concentration) were determined as an affecting parameter on the leaching process. The Central Composite Design (CCD) was used for the experimental plan with the five variables (parameters) on Zn recovery. The leaching recovery of Zn was checked through experiments. Statistical analysis confirms the optimum conditions obtained by the experimental results. The 85 % of Zn was obtained under optimal condition: leaching temperature 70 ˚C, holding time 90 min, liquid-solid ratio 10:1, stirring speed 750 rpm and pH = 2. It was found that leaching kinetics follows the kinetic law of shrinking-core model. The results show that diffusion through product layer is the leaching kinetics rate controlling step. The calculated apparent activation energy of the process is 10 k j/mole, which is characteristic for a diffusion- controlled process.

Keywords:

optimization , zinc , acidic leaching , kinetics , low grade leach residue