铅锌冶炼次氧化锌中提取锗的基础研究

Lead and zinc ores produced from many mines in south China are rich in germanium. In conventional lead and zinc smelting, germanium is enriched in secondary zinc oxide, which is obtained by fuming zinc leaching residue and lead smelting slag. Currently, the process of leaching-germanium precipitation by tannin has been used industrially for recovering germanium from the secondary zinc oxide. However, the process has some severe problems: first, the leaching efficiency of germanium is as low as 60-80%; second, the consumption of tannin for precipitating 1 mol of germanium is as high as 56-80 mol; third, the process results in a great amount of tannin together with its decomposition products accumulation in the solutions of zinc hydrometallurgy, deteriorating the purification and electrowinning processes of zinc sulfate solutions.. In respond to the above problems, this subject carries out research on following aspects from the perspective of application foundation: first, the mineral occurrence modes and leach behavior of germanium in the secondary zinc oxide are planed to study by using process mineralogy method and detection technologies, for example, EPMA, combined with leaching tests; second, the forms of Ge(IV) ions in the solutions of zinc sulfate under different conditions will be studied by using PHREEQC software, associated with ion chromatography and other analytical methods; third, the mechanism and process optimization of germanium precipitation by tannin are planed to study through NMR and other organic structure analysis methods using purified precipitation products as samples, associated with precipitation experiments; fourth, the solution extraction of germanium in zinc sulfate solutions, which contain such impurities as iron, arsenic, copper, silicon, etc., will be studied.

中国南方多地铅锌矿富含锗。冶炼中，锗富集于锌浸出渣和炼铅炉渣烟化产物次氧化锌中。现行含锗次氧化锌锗回收工艺为浸出—丹宁沉锗，存在如下问题：一，锗浸出率低至60-80%；二，沉淀1mol锗消耗56-80mol丹宁；三，丹宁及其分解产物积聚于湿法炼锌溶液中，恶化溶液净化和电积过程。针对上述问题，本项目从应用基础研究角度，开展以下几方面研究，旨在为铅锌冶炼次氧化锌中锗的高效提取奠定基础：一，采用工艺矿物学研究方法，综合运用电子探针微区分析等检测技术，结合浸出试验，查明锗在次氧化锌中赋存形态及浸出行为；二，运用PHREEQC软件，结合离子色谱等分析方法，研究不同条件下，Ge(IV)在硫酸锌溶液中存在形态；三，纯化丹宁与Ge(IV)沉淀产物，采用核磁共振等有机物结构分析方法，结合沉淀试验，对丹宁沉锗机理进行研究并优化过程；四，研究硫酸锌溶液中锗与锌、铁、砷、铜、硅等离子的溶剂萃取分离。

针对硫酸浸出-单宁沉淀法从次氧化锌中回收锗存在的问题，本项目以国内某厂产出的次氧化锌为研究对象，从次氧化锌及其硫酸浸出渣中锗的赋存状态、单宁沉锗过程中单宁与锗及其他金属离子的相互作用和硫酸锌溶液中锗的N235高效萃取分离三方面开展工作，并最终实现了次氧化锌中锗的高效分离回收。次氧化锌中，锗无独立矿物，弥散分布于铅、锌的矿物中，但部分方铅矿中锗含量较高；赋存于方铅矿、纤锌矿和铅矾等难溶矿物中的锗，在常规浸出中难以浸出，导致锗浸出率低；同时，金属铅包裹和铅矾共沉淀作用，难以避免地造成锗的损失；采用氧化浸出技术，可将锌锗浸出率提高10~15 %。pH 为0~6.5时，溶液锗主要以电中性的锗酸分子形态存在；单宁沉锗过程中，降低pH、提高锗浓度、添加锌离子利于提高锗的沉淀率；单宁酸与锗形成可溶配合物，单宁酸水解，单宁酸与非锗金属配位，单宁酸与锌、铁等共沉淀是单宁耗量大的原因。对比研究了N235、N235-TBP和N235-TOP体系分离锗的性能，N235和N235-TBP体系对砷的共萃显著，引入TOP后，可将砷的共萃控制在1 %左右；采用N235-TOP体系，在优化条件下，可实现锗的高效分离，负载有机相经NaOH反萃，可实现砷、锗的完全反萃；经化学计量分析，确定N235-TOP体系萃取锗的萃合物为R3NHGe(OH)3C4H4O6·TOP0.3。提出了“常规/MnO2氧化两段浸出—N235-TOP直萃/再萃”新工艺，可以提高N235体系适应的水相酸浓度，而“一段MnO2氧化浸出—预酸化N235-TOP萃取”工艺流程则更短；采用氧化浸出、N235-TOP萃取法分离次氧化锌浸出液中的锗，可实现次氧化锌中锗的高效回收，并将溶液中有机质的量控制在较低水平，具有一定的应用潜力。