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铜阳极泥产自粗铜的电解精炼过程，通常含有Se、Au和Ag等稀贵金属，综合利用价值极高。火法流程被大型冶炼厂广泛用于铜阳极泥的处理，然而火法投资大、金银直收率低和铅害严重的缺点限制了其在中小冶炼厂中的使用。相比较而言，焙烧-湿法浸出相结合的流程更加适用于我国铜阳极泥处理行业的现状，硫酸盐化焙烧-浸出流程是最典型的代表。然而，该流程仍存在污染严重、设备腐蚀和高成本等不足。因此，铜阳极泥处理行业的可持续发展迫切需要更加环保、高效和低能耗的处理工艺。本论文以铜阳极泥中有价元素的高效、绿色分离为目标，进行了铜阳极泥中Se、Ag和Au选择性分离及回收的应用基础研究。论文的主要研究内容与结论如下：（1）研究了H2SO4-MnO2浸出体系从铜阳极泥中选择性分离Se、Cu。根据吉布斯自由能判据，确定了浸出反应的热力学可行性，并依据Me-H2O体系的Eh-pH图，分析了浸出过程中主要金属的状态变化。通过研究反应参数对Cu、Se浸出的影响，得出在最优条件MnO2占干基比重60wt%、H2SO4浓度1.0 mol/L、转速650 r/min、浸出温度80 oC下，Se和Cu的浸出率均为100%。H2SO4-MnO2体系氧化浸出Se的机理为：在强酸性条件下，MnO2晶体中的活性位点Mn（IV）被释放出进入溶液，并扩散至阳极泥表面完成氧化反应。对浸出液中的Ag、Se和Cu，依次采用NaCl沉淀Ag+、Cu粉还原Se和萃取分离Cu进行回收，Ag、Se和Cu的回收率分别为99.5%、94.8%和95.5%。在对工艺的成本效益进行分析的基础上，论证了其在工业上的潜在应用前景。（2）研究了碱性硫代硫酸盐法选择性分离铜阳极泥中Ag。针对未预处理铜阳极泥中的Ag2Se和AgSbS2无法溶解于碱性硫代硫酸盐溶液体系和Cu2S导致浸出过程中Ag再沉淀析出的难题，利用H2SO4-MnO2浸出体系对铜阳极泥预处理，将硫化物转化为了SO42-，并将Ag2Se和AgSbS2转化为了易于浸出的Ag2SO4形态。研究了硫代硫酸盐法、亚硫酸盐法和氨浸法选择性分离预处理渣Ag的热力学基础和浸出动力学，发现S2O32-、SO32-和NH3浓度分别为0.035 mol/L、0.4 mol/L和1.4 mol/L时，反应终点时Ag浸出率分别为93.0%、92.4%和80.2%，表明与亚硫酸盐法和氨浸法相比，硫代硫酸盐法具有无污染、试剂消耗量低和浸出率高的优势。探索了电沉积还原法回收浸出液中的Ag，发现贫液循环用于阳极泥中Ag的分离时其浸出率仍高达95.3%，证明了电沉积后的贫液循环利用的可行性。 （3）研究了球磨活化法分离铜阳极泥中的Au。多种氧化剂-NH4Cl组合对Au转化效果表明，只有KMnO4-NH4Cl组合能够得到较高的Au回收率，阳极泥中的Cu2Se会阻碍Au的转化。揭示了球磨活化过程Au的转化机理为：机械能诱发了原位生成具有高反应活性、易扩散的Cl2，扩散至Au表面将单质态Au转化为水溶性AuCl3。对NH4Cl添加量、含水率、球料比、转速、和球磨时间于活化提金的影响进行了研究，在最优条件下反应60 min时，Au的转化率可达到97.45%。球磨活化后的阳极泥水浸实现了Au的选择性分离，阳极泥Sb、Ag、Cu和Ni含量分别是Au含量的96.85、4.18、6.71和4.59倍，但它们的提取率几乎为零，作为对比Au提取率为80%。（4）采用Na2S2O3浸出-Na2S2O4还原流程，进行了500 kg级分金渣回收银放大试验研究。放大试验结果表明：碱性Na2S2O3体系可实现Ag的高效浸出，Na2S2O4可将浸出液中的Ag还原为单质Ag粉。浸出液中Ag还原后，将溶液两次返回用于分金渣中Ag的浸出发现浸出结果均符合生产要求。Na2S2O3浸出-Na2S2O4还原流程与NH3浸出-N2H4还原流程相比，处理1000 kg阳极泥的水耗由7 m3降低至1.45 m3，试剂成本则降低了42%，证明了新流程的工业应用可行性。;Copper anode slime is produced in the process of electrolytic refining of blister copper, which usually contains rare and precious metals such as Se, Au, and Ag. Therefore, the value of copper anode slime is rather high. Conventional pyrometallurgy processes are widely used in the treatment of anode slime by the large smelters. However, the drawbacks of large investment, low direct yield of silver and gold, and serious lead bearing smoke dust restrict its use in the small and medium smelter. As a comparison, the roast-wet leaching processes are more suitable for the current situation of China's copper anode slime treatment industry, of which the sulphatising roast-leaching process is the typical representative. Nevertheless, it still suffers the drawbacks of sever pollution, equipment corrosion, long recovery period, etc. Hence, the sustainable development of the copper anode slime industry urgently requires a more environmentally friendly, efficient and low-energy treatment process. Focusing on the efficient and green recovery of valuable elements from copper anode slime, the applied fundational research of selective recovery of selenium, silver and gold was studied in this paper. The main research contents and conclusions of the thesis are as follows:(1) H2SO4-MnO2 leaching system for the selective recovery of Se and Cu from copper anode slime. The Gibbs free energy criterion confirmed the thermodynamic feasibility of the leaching process, besides, basced on the analysis of Eh-pH diagram of Me-H2O system, the state changes of main metals in copper anode slime during leaching process were identified. Effects of leaching parameters on the recovery of Cu and Se were then explored. Under the optimal conditions of 60wt%(mass ratio of MnO2 to copper anode slime), 1.0 mol/L H2SO4, rotating speed of 650 r/min and leaching solution of 80 oC, extraction rates of Se and Cu were both 100%. Mechanism of oxidative leaching Se with H2SO4-MnO2 system was: under strong acid conditions, the active center Mn(IV) in MnO2 crystal was released into solution, which then diffused to the surface of anode slime to conduct oxidation process. For the recovery of silver, selenium and copper in leaching solution, the Ag+ was firstly separated from the solution by adding NaCl to precipitate Ag+, then, copper powder was added to reduce selenium and Cu2+ in residual solution was separated with extraction. The recovery rates of Ag, Se and Cu were 99.5%, 94.8% and 95.5%, respectively. The cost-benefit analysis of the proposed process also confirmed its potential industrial application prospects.(2) Selective recovery of silver from copper anode slime with alkaline thiosulfate method. Aimed at the problems that Ag2Se and AgSbS2 in the unpretreated anode slime cannot dissolve in alkaline thiosulfate solution, and the dissolved silver in solution re-precipitated in the presence of Cu2S, the H2SO4-MnO2 leaching system was used to successfully convert the sulfide to SO42-, as well as the Ag2Se and AgSbS2 to readily leached Ag2SO4. The thermodynamic basis and leaching kinetics of selective recovery of Ag in pretreated residue by thiosulfate, sulfite and ammonia leaching were studied. It was found that when concentrations of S2O32-, SO32- and NH3 were 0.035 mol/L, 0.4 mol/L and 1.4 mol/L, respectively, the corresponding silver extractions were 93.0, 92.4 and 80.2, respectively, which indicated that the thiosulfate leaching had the advantage of low reagent consumption and high leaching rate compared with sulfite and ammonia leaching. Exploration of silver recovery from thiosulfate leaching solution with electrodeposition was also carried out. A 95.3% recovery rate was obtained by recycling the electrolyte for silver leaching, confirming the feasibility of recycling of lean liquid for silver leaching.(3) Solvent-free mechanochemistry for the recovery of gold from copper anode slime. Results of gold conversion with series of oxidant-NH4Cl combinations showed that only the KMnO4-NH4Cl combination worked. The presence of Cu2Se in anode slime hindered the gold conversion. The mechanism of gold conversion by mechanochemistry approach was revealed, involving the in situ generation of highly reactive, easily diffusible Cl2 gas by mechanical energy, which then diffused to the surface of gold to convert the elemental gold to water soluble AuCl3. Effects of NH4Cl addition, water content, mass ratio of ball-to-batch, rotating speed and milling time on gold conversion were also studied. Under the optimal conditions, the conversion rate of gold can reach 97.45% at 60 min. Assessment on the selectivity of mechanochemistry approach(MA) and hydrometallurgical processes demonstrated that the MA had excellent selectivity for gold, though contents of co-existing metals, including Sb, Ag, Cu and Ni, were 96.85, 4.18, 6.71 and 4.59 times higher than that of gold, respectively, extraction rates of co-existing metals were nearly zero, as a comparison, the gold extraction rate reached 80%.(4) Na2S2O3 leaching-Na2S2O4 reduction process for the silver recovery from de-gold anode slime-500 kg scale-up experiment. Results of the scale-up experiment confirmed the efficient recovery of silver by Na2S2O3 leaching, and the successful reduction of silver ions to elemental Ag by Na2S2O4 in leaching solution. After reduction, the solution was recycled to leaching and the silver extraction rate met the requirements enterprises. Compared with the ammonia leaching- N2H4 reduction process, the proposed process decreased the water consumption from 7 m3 to 1.45 m3 and reduced cost of processing 1000 kg anode slime by 42%, confirming the feasibility of the industry application of new process.
|肖力. 铜阳极泥中硒银金分离的应用基础研究[D]. 中国科学院大学,2019.|
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