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Ammonia leaching of zinc depth simulation electrolyte purification and removal of organics

Author: LiJian
Tutor: ChenQiYuan
School: Central South University
Course: Physical and chemical
Keywords: zinc ammoniacal leaching solution purification cementation organics removal absorption resin
CLC: TF813
Type: Master's thesis
Year: 2011
Downloads: 48
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Abstract


With the daily exhaustion of the resources of zinc sulfide ore and sharp decrease of grade of zinc ore, the development and utilization of low-grade zinc oxide ore become imperative. The mineral deposit of Lanping region in Yunnan Province is the largest low-grade zinc oxide ore deposit in China. But the oxidation of the ore is complete, the content of alkality gangue is high, the mineral composition is complex, which has various mineral species. It is hard to treat economically and efficiently if conventional acid leaching process is adopted. Therefore, "ammonia leaching-extraction-electrowinning" process is undoubtedly better than acid leaching process for zinc oxide ore with high-alkality gangue.The presence of inorganic and organic impurities markedly decreace the current efficiency and increase energy consumption, embrittle the cathode zinc, and even plate-burning appears in the electrowinning of zinc hydrometallurgy, which is not beneficial to the production of high grade zinc. Therefore, the zinc ammoniacal leaching solution should be deeply purified and organics in the electrolyte must be removed before the electrowinning. this study was to explore the effects of relative amount of metallic impurities, dosage of zinc dust, purification time, purification temperature, pH and total ammonia concentration of zinc ammoniacal leaching solution on the purification of this zinc ammoniacal leaching solution. meanwhile, the effect of the concentration of organics on the zinc electrowinning was studied and the adsorption property and reusage property were compared among several kinds of absorption resins in the hope of seeking for a sorbent with excellent adsorption property and reusage property.The results indicated that total ammonia concentration of the zinc ammoniacal leaching solution had little effect on the cementation and the relative amount of metallic impurities, dosage of zinc dust, purification time, purification temperature and pH of the zinc ammoniacal leaching solution were the main factors which influenced the cementation. Maintaining copper-cadmium mole ratio of approximate 0.5 or less than 0.2 were beneficial to the cementation of cadmium and copper, and maintaining nickel-cadmium mole ratio of approximate 0.40 or less than 0.07 were also beneficial to the cementation of cadmium and nickel. Nevertheless, the presence of cobalt was bad for the cementation of cadmium and cobalt. All metallic impurities can be brought down to acceptable levels under optimized conditions of zinc dust dosage:2g/L, purification time: lh, purification temperature:35℃, pH of the zinc ammoniacal leaching solution: 9.03.The purified solution obtained by one-stage purification which contained Cu≤50μg/L, Cd≤300μg/L, Co≤100μg/L, Ni≤100μg/L Pb≤40μg/L met the requirements of zinc electrowinning. The difference of cementation of cobalt between acidic and ammoniacal medium was also analysed, and it was found that the difficulty of cobalt removal in acidic medium was owing to the greater velocity of hydrogen evolution; on the contrary, the velocity of hydrogen evolution was less obviously than the reduction rate of cobalt in ammoniacal medium. The presence of organics not only decreaced the current efficiency, but also badly changed the deposit morphology and orientation. Compared with active carbon, SD300 showed excellent adsorption property and reusage property, and the adsorption efficiency was maintained about 65% after adsorbing five times.

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CLC: > Industrial Technology > Metallurgical Industry > Nonferrous metal smelting > Heavy metals smelting > Zinc
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