Research On Acid-controlled Oxidation Leaching Process And Industrial Application Of Germanium-containing Zinc Oxide Dus

The germanium-containing zinc oxide dust produced output from lead-zinc smelting industry is the main raw material for extracting germanium.Currently,the zinc oxide dust treatment process widely suffers from the problem of low zinc and germanium direct recovery rates,and the presence of complex germanium compounds in zinc oxide dust is one of key factors limiting the direct recovery of germanium and zinc.This issertation focuses on the characteristics of germanium-containing zinc oxide dust in a lead-zinc enterprise.It proposes a new process of acid-controlled oxidative leaching-neutralization-reduction is proposed by controlling the acidity at different leaching stages and simultaneously using the synergistic effect of oxidants.With the aim of improving the extraction rates of germanium and zinc,the research mainly focuses on the mechanism,process parameters,and process optimization of the controlled acid oxidation leaching process for germanium-containing zinc oxide dust.The whole process of continuous experiment,continuous expansion experiment and industrial experiment has been carried out,and industrial application has been realized,achieving the following main results:（1）The elemental states of germanium-containing zinc oxide dust were investigated.The zinc in zinc oxide dust containing germanium mainly exists as Zn O,and the lead mainly exists in the form of Pb S;the germanium mainly exists in the silicate and sosoloid（zinc ferrite）,in which the germanium distribution rate in silicate accounts for 69.74%,and that of sosoloid accounts for 18.42%;whereas the germanium distribution rate in the oxides and sulphides are lower,at 7.89%and 3.95%respectively.The decomposition of silicate and solid solution is the key to restrict the efficient leaching of germanium.（2）The thermodynamic analysis of acid leaching process of zinc oxide dust containing germanium was carried out.Ge O in the dust can dissolve in acidic or alkaline solutions,with better solubility in acidic solutions than alkaline solutions.The acid leaching of Ge O₂ is more difficult than that of Ge and Ge O,requiring higher acidity for dissolution.The efficient leaching of germanium in the dust depends on the acidity of the leaching system.In the acid leaching process,the role of oxidizers is to oxidize and convert the metal sulfides in the zinc oxide dust into soluble metal sulfates that are not insoluble in sulfuric acid.（3）The effect of acidity on metal leaching rate in dust containing germanium and zinc oxide under different oxidant conditions was studied.The higher acidity is beneficial for the leaching of zinc and germanium in the dust.Compared to others,the addition of oxidizers has a positive effect on the zinc leaching rate,while it has no significant effect on the germanium leaching rate.The influence of acidity on the germanium leaching rate is more pronounced.The acidity of the leaching system,the type and amount of oxidants added has an important impact on the oxidation state of iron in the acid leaching solution.Under low acidity and strong oxidation conditions,the concentration of Fe³⁺ions in the acid leaching solution tends to increase,which is unfavorable for subsequent neutralization treatment.Controlling the concentration of Fe³⁺ions in the acid leaching solution can be achieved by controlling the solution p H at 0.3-0.5 and using oxygen as the oxidant to reduce the tendency of Fe²⁺ions to oxidize to Fe³⁺ions.By regulating the acidity and oxidant,efficient leaching of germanium and zinc,as well as control of iron concentration and oxidation state in the solution,can be achieved.The total iron concentration（TFe）and Fe³⁺ions concentration can be controlled below 5 g/L and 0.5 g/L,respectively.（4）The leaching difficulty of germanium in different phases was studied.Germanium in oxides and sulfides is relatively easy to leach,with a leaching rate of 85%-90%.However,germanium in silicates and sosoloid is relatively difficult to leach,with a leaching rate of 80%-85%.The correlation between germanium leaching and the content of elements such as Fe,Si,S,Pb in zinc oxide dust was studied.High Fe and Si content in the dust will restrict the efficient leaching of germanium,while Pb and S content have no significant inhibitory effect on germanium leaching.It was found that Si in the dust follows a pattern of dissolution followed by precipitation,and increasing the leaching temperature is an effective method to reduce the Si concentration in the acid leaching solution of zinc oxide dust.（5）A new process of acid controlled oxidation leaching-neutralization reduction was proposed.Under the conditions of a temperature of 90℃,a time of 4 hours,a stirring speed of 400 r/min,and a liquid-to-solid ratio of 7 m L/g,the zinc leaching rate can exceed 92%,and the germanium leaching rate can exceed 89%.The concentration of TFe in the neutralization and reduction filtrate is 1.7-2.0 g/L,and the concentration of Fe³⁺ions is less than 0.5 g/L.The expansion experiment showed that using the controlled acid oxidation leaching-neutralization reduction process,the leaching rate of germanium in low iron and low silicon zinc oxide dust can exceed 88%.However,the leaching rate of germanium in high iron and high silicon zinc oxide dust was only 78.64%.The iron and silicon contents and their phases limit the leaching of germanium.（6）The industrialization application of the acid controlled oxidation leaching-neutralization reduction has researched.The transformation and design of key equipment such as oxygen distributor were carried out,by which the oxygen was dispersed in solution in the leaching tank.Industrial application indicate that the leaching rate of zinc and germanium was89.29%and 81%.Compared to the original process,the zinc leaching rate increased by 10.19%and the germanium leaching rate increased by 16%.