含金硫化矿碱性氧化提金研究现状与展望

Research Status and Prospect of Gold Extraction by the Alkaline Oxidation of Gold-bearing Sulfide Ore

从热力学、浸出动力学和电化学等方面,对碱法提金过程中硫化物和金的氧化溶出与钝化机理以及工艺的研究现状进行了系统的总结分析。结合自身研究情况,提出自配位同步溶出硫化矿中金和硫的技术思路,即通过充分利用含金硫化矿物中的硫,在碱性体系中直接生成具有氧化和配位能力的多硫化物及硫代硫酸盐来浸出金;在分析推测含金硫化矿地质成因的基础上,指出硫离子很可能是取代氰根浸金的有效途径;对该研究方向尚需解决的关键科技问题进行了探讨,指出碱性氧化体系中硫化物氧化转变为多硫化物溶金离子以及金硫配合物保持稳定的调控机制是该技术需要解决的最为关键的问题;该技术具有环境友好、流程短和成本低等优点,有很好的应用前景。

The pretreatment methods for gold-bearing sulfide ore mainly include roasting,biological oxidation,pressurized oxidation,acid oxidation,alkaline oxidation,etc.The alkaline oxidation process has become a research hotspot in recent years due to its many advantages,such as low requirements for equipment,simple flowsheet,environmentally friendly,low production cost and so on.The authors found that while the sulphide minerals oxidized,gold simultaneously had been dissolved mostly in the process of gold concentrate alkaline oxidation.Through the analysis and research on this phenomenon,the sulfide anions,such as Sx 2-and S2O32-,were thought to play a major role for dissolving gold.Therefore,a technical idea of synchronous gold extraction from gold-bearing sulfide ore by self-coordination of gold and sulfur.So,the author has extensively consulted relevant research materials at home and abroad.These studies have focused on oxidation and passivation of sulphide,leaching and passivation of gold,etc.,and the mechanism of gold leaching in alkaline sulfur-containing solutions were presented from different aspects,including thermodynamics analysis,electrochemical dissolution,and leaching kinetics.Research methods involves SEM,XPS,EQCM,XAFS,etc.The main conclusions drawn from these research materials are as follows:Firstly,in alkaline solutions,sulfide is easily oxidized to polysulfide and thiosulfate,which can solubilize gold.But these polysulfide ions are unstable and will eventually be oxidized to stable forms such as sulfate and sulfite in the presence of oxygen.Secondly,both gold and sulphide can be passivated in the alkaline oxidation process.Sulphide can be oxidized generate Fe(OH)3,FeAsO4 and other precipitates,which forms a passivating layer on the surface of sulfide minerals and gold,preventing the further oxidation decomposition of sulphide and the dissolution and leaching of gold.Passivation inhibition can be reduced or eliminated by mechanical stripping or by adding appropriate dispersants.At present,researches on gold-leaching by the alkaline oxidation of gold-bearing sulfide ores are more,and leaching system involves the NaOH-NaClO-NaCl system,NaOH-NaCN system,NaOH-Na2S-S system,NaOH-Sx 2–system,copper-ammonium thiosulfate system,alkaline thiourea system,etc.Generally,a better gold leaching rate can be achieved in laboratory,but there are problems for industrial application,for example,dosage of lixiviants is high,gold-leaching ions is unstable,the catalyst is needed and so on.How to effectively reduce the useless consumption of lixiviants is the key to the wide application of alkaline sulfide gold leaching technology.The mechanism on dissolution and passivation of sulfide and gold in alkaline goldleaching system were systematically summarized and analyzed.On the basis of own research the authors put forward the technical idea of self-coordination simultaneous dissolution of gold and sulfur from sulfide ore.Namely,we can directly leach gold in alkaline leaching gold system by utilizing the sulfur of gold-bearing sulfide ores,which are oxidized to generate polysulfide and thiosulfate having the ability to oxidize and coordinate for the gold.This technical idea likely is an effective way to solve before-mentioned problems for industrial application.Some data indicate that gold was enriched and precipitated out from sulfide minerals during crustal movement,instead of being transported by metamorphic pyrite.It suggests that in certain magmatic hydrothermalism conditions,sulfur and gold of sulfide ore likely had ever formed some gold-sulfur compounds.On the base of geological form causes analysis for the gold-bearing sulfide ore,the author points out that the sulfide ions are likely to be effective lixiviants to replace cyanide for the gold leaching.The author also discusses the key scientific and technological problems that need to be solved in this field,and points out that oxidizing sulfide to convert into polysulfide and thiosulfate and keeping the stability of the gold-sulfur complexes are the most important problems to be solved in this technique.