Leaching process of low grade zinc oxide ore of Lanping in NH3-(NH4)2SO4 system

The leaching process of low grade zinc oxide ore of Lanping in the system of NH3-(NH4) 2SO4 was studied. The influences of pH, total ammonia concentration, ratio of solid to liquid, temperature, particle size of ore, stirring speed on the leaching behavior of zinc and the main impurity elements were investigated. The low grade zinc oxide ore was leached by two-stage counter-current process under the condition of low pH and total ammonia concentration. The results show that the main parameters for the recovery of zinc and impurities are pH, total ammonia concentration, and ratio of solid to liquid, and the concentration of Si, Fe, Cd, Pb in lixivium is low. The optimum leaching conditions are found to be the total ammonia concentration 3 mol/L, pH 9.60, ratio of solid to liquid 4, and the leaching time 4 h. More than 90% of zinc is extracted, and pH of lixivium is less than 9.0 in the two-stage counter-current process, which satisfies the requirement of the subsequent solvent extraction process.