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Leaching Behavior Of Secondary Zinc Oxide Dust In Ammonia Solutions

Posted on:2012-06-10Degree:MasterType:Thesis
Country:ChinaCandidate:W J WangFull Text:PDF
GTID:2211330335491616Subject:Iron and steel metallurgy
Abstract/Summary:PDF Full Text Request
Secondary zinc oxide dust, is a kind of zinc containing second resource, which is made by reductive volatilization from zinc containing wastes. Secondary zinc oxide dust is the intermediate product in zinc recycling process, can be used to prepare many zinc based products, such as zinc salts and active zinc oxides. Leaching secondary zinc oxide dust is an important process in recovery of zinc from solid wastes. The main leaching methods are acid leaching and ammonia leaching. Acid leaching usually uses sulfuric acid as the leaching agent. Ammonia leaching is based on ammonia as a leaching agent, meanwhile adding ammonium bicarbonate. Compared with acid method, ammonia leaching has been accepted as a more promising method for zinc leaching because of its many advantages such as simple process, low cost and less waste water.However, the zinc leaching behavior with ammonia is insufficiently and the controllability of the leaching process is not strong. The leaching ratio will change when the properties of raw material change. Different samples have different leaching behavior, and their solution chemical behavior is still not clear so far. Therefore, research on the leaching behavior of secondary zinc oxide dust in ammonia solutions is of great importance for optimization and better controllability of the process.On the basis of study on dissolve of pure ZnO in ammonia solutions, the leaching behaviors of two secondary zinc oxide samples in ammonia leaching systems were investigated in this paper. Their best leaching technological parameter were studied systematically. Influence of [NH3]T: ZnT ratio and relationship between [NH3]T:ZnT ratio and [NH3]T:[Zn2+]T ratio were investigated. Meanwhile, the leaching behaviors of impurities and influence of impurities to zinc leaching were also studied in this paper.The results indicated:The [NH3]T:ZnT ratio in leaching process is relate to raw materials. Compare with pure ZnO, secondary zinc oxide leaching needed high [NH3]T:ZnT ratio. [NH3]T:ZnT ratio in solution can be characterized by the ease of leaching zinc. The smaller [NH3]T:ZnT ratio, the more zinc dissolved in units ammonia. When [NH3]T:ZnT= 6.4, the [NH3]T:[Zn2+]T ratio reaches a lowest value. In the ammonia leaching system, zinc in solution mainly exists as [Zn(NH3)4]2+. Ammonia in solution mainly exists as dissociated ammonia, dissociated ammonia accupy the proportion of total ammonia reached 90%. Cu and Cd are the main impurity factor for zinc leaching ratio of pure ZnO, while Fe and Pb are not.
Keywords/Search Tags:zinc oxide, secondary zinc oxide dust, ammonia leaching, zinc leaching
PDF Full Text Request
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