Ammonia Leaching Of Low-grade Zinc Oxide Ore And Zinc Ion-exchange Membrane Electrolysis

The ammonia leaching-process is usually used to deal with the low grade zinc oxide ore containing high alkaline gangue. However, ammonia is unfavorable for the zinc electrolysis. It is necessary to study the electrolytic process and the related influence factors in order to realize the direct electrolysis of zinc ion in ammoniacal solution.The leaching process of the low grade zinc oxide ore from Yunnan Nanping had been investigated by use of ammonia-ammoniacal sulfate system, and the effects of grain size of ore, ammonia concentration, temperature, leaching time, liquid/solid ratio and stirring rate have been discussed. The results indicate that the leaching ratio of zinc is72.5%under the conditions of the particle size of12-24#, ammonia concentration of6mol/L,temperature of40℃, leaching time of3h and liquid/solid ratio of5:1. Moreover, the effect of ammonia concentration and liquid/solid ratio on the leaching rate of zinc is more evident than the temperature and stirring rate.The direct electrolysis of zinc ion in ammoniacal solution had been studied by using the home-made double-fluid electrolytic cell. The static experiments had been performed to evaluate the effect of cell voltage, electrolysis time, electrode spacing and temperature on the electrolysis process of zinc when using zinc ammonia solution as catholyte and sodium hydroxide as anolyte. The results indicte that the smooth and sound zinc plates can be obtained under the conditions of zinc concentration of10g/L, cell voltage of3V, electrolysis time of1h, electrode spacing of4cm and temperature of40℃. The purity of zinc plates is95.36%and the current efficiency is95%. Furthermore, the effect of zinc concentration on the current efficiency is more evident than the temperature and cell voltage. Based on the obtained results above, a kind of enlarged electrolytic cell, in which multi-anode chamber can be hanged and the electrolyte can be recycled, had been designed and used for dynamic experiments of zinc electrolysis. It was found that the zinc plates of high quality can be obtained and the recovery of zinc reaches to84.3%under the conditions of flow rate of catholyte of20mL/min and electrolysis time of4h, and keeping the other conditions constant. The lean catholyte can be recycled for the leaching process.