| Zinc is widely used in industry for its good corrosion resistance property and alloy performance. The domestic consumption of zinc concentrates is tremendous with the rapid development of zinc smelting industry. Therefore, it is necessary to exploit all sorts of zinc resources to keep the sustainable and healthy development of zinc metallurgical industry. Resourceful zinc ores are found in southwest of China, a great part of which are high-iron sphalerite and low-grade zinc oxide ore. As a result, it is difficult to extract valuable metals economically by traditional smelting technology. Therefore, the development of new process to deal with the refractory zinc ore is imperative. Ammonia immersion method has significant technical advantages and economic benefits for its low energy consumption, simple purification, less pollution and strong adaptability.The leaching processes of low grade zinc oxide ore from Lanping and high-iron sphalerite in the system of NH3-(NH4)2SO4 have been studied in this paper. The effect of various factors on the leaching behaviors was investigated.42L-scale expanded experiment of low grade zinc oxide ore has been accomplished in laboratory. And the mechanism of mechanical activation during the ammoniacal oxidation leaching process of high-iron sphalerite was also studied.The leaching experimental results of low-grade zinc oxide ore showed that the main parameters for the leaching of zinc and impurities are pH, total ammonia concentration, and liquid/solid ratio. The optimum leaching conditions were found to be the total ammonia concentration 3 mol/L, pH 9.60, liquid/solid ratio 4, leaching time 4 h. More than 90% of zinc was extracted, and pH of lixivium was less than 9.0 in the two-stage counter-current process, which is satisfied with the requirement for the subsequent solvent extraction process. In the expanded experiment of low grade zinc oxide ore, the total leaching ratio exceeded 90%, the concentration of zinc and pH of lixivium were about 13 g/L and 8.90-9.00 respectively, which is suitable for the predetermined qualification of "ammonia leaching-purification-extraction-electro-winning" technique. The mechanical activation could accelerate the extraction of high-iron sphalerite. The activation time, pH of solution, dosage of NaClO, grinding atmosphere were the main factors to the leaching of high-iron sphalerite. With the increase of activation tine, the particle size of the ore grains decreases first and then increases, the lattice strain ratio rises, and the crystalline turns into amorphous during the process of mechanical activation. Combining the changing tendency of particle size, crystallite size and lattice strain with the experimental phenomena that the zinc leaching ratio increases gradually with the prolongation of activation time, it indicates that brittle crush and plastic deformation occurs with the mechanical grinding. The increase of zinc recovery ratio is attributed to the increase of the specific surface area and lattice disorder. When the stored energy of surface reaches the ultimate state, the particle size doesn't decrease but increase, and the promotion of mineral dissolution is mainly determined by the lattice distortion. |
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