难选碳质金矿石中碳质物劫金机理及新型浸金药剂研究

The refractory gold-bearing ores have gradually become the main resource for China’s gold industry. As a major type of refractory ores, the carbonaceous gold ores, which contain sulphur, arsenic and carbon impurities, accounts for over 20% of the total gold reserve in China. How to improve the gold recovery efficiency from the carbonaceous gold ores, especially in a green way, has always been one of the critical technical issues encountered by the global gold industry. However, up until now there is still a lack of systematic and in-depth fundamental research in this area. In this research project, the surface chemical properties of the mineral crystals in the carbonaceous gold ores will be characterised comprehensively, such as the occurrence of sulphur, arsenic and carbon, and etc. Based on the property characterisation and the theory of metal-organic coordination chemistry, the molecular structure design will be carried out to develop a new and highly-efficient cyanide-free leachant. By means of experiments, modern detection technology and the molecular simulation, the adsorption behaviour between the gold ion complexes and the various types of carbonaceous matter in the ores will be studied to find out the physic-chemical nature of their interactions; thus the “preg-robbing” mechanism by carbonaceous matter can be explained by the combination of the electrostatic adsorption theory, the valence bond theory and the crystal field theory. On the basis of the proposed mechanism, a “preg-robbing” inhibitor will be designed aiming to block the contact of gold-leachant complex ions onto the surface of the carbonaceous matter. Hence the recovery rate of gold from the carbonaceous gold ores can be increased. This research project is of great theoretical and practical significance for improving the leaching efficiency of gold from the carbonaceous ores and moreover for the sustainable development of China’s gold industry.

难处理金矿石已经逐渐成为我国黄金生产的主要资源，其中含硫、含砷、含碳的碳质金矿占我国总金矿储量的20%以上。采用非焙烧法（环保要求）提高碳质金矿中金的浸出率一直是黄金产业的一大技术难题，但目前针对该问题，缺乏系统而又深入的基础研究。本项目拟对碳质金矿中硫、砷、碳元素赋存形式等矿物晶体表面化学特性进行系统表征，并基于对碳质金矿中主要矿物晶体表面化学活性的研究及金属有机配位化学理论，进行碳质金矿的非氰浸金药剂的分子结构设计，研制新型、高效无氰浸金药剂。采用浸出试验、机理分析、MS模拟相结合方式，系统研究碳质金矿中各碳质组分对金离子配合物吸附作用的物理化学本质；再结合静电吸附、价键及晶体场理论，揭示金矿中碳质物的“劫金”机理，研制出能够阻隔碳质物与载金配合物发生吸附作用的药剂，提高难处理碳质金矿中金的浸出率。本研究将对提高碳质金矿的浸金效率，促进我国黄金产业的可持续发展，具有重要理论及实际意义。

对于世界黄金产业，采用环保手段（非焙烧法）提高碳质金矿中金的浸出率一直是一大技术难题。本项目基于某难处理碳质微细粒浸染型金矿石，探明了金的赋存状态及工艺矿物学特征，表征了矿石中主要矿物的晶体化学特性、主要矿物晶面断裂键的类型和数量、主要解理面等。进行了碳质物提取及劫金试验，证实了具有劫金能力的碳质组分主要为石墨类及腐殖酸类，且石墨类对金的吸附能力更强。考察了一系列表面覆盖抑制剂对碳质物表面活性的抑制效果，研究结果发现DS-1与DS-3以2:1比例复配，对碳质物的抑制效果最佳，金的浸出率从9.29%提高到45.08%。借助红外光谱检测以及Material-Studio(8.0)模拟计算，认为DS-1与DS-3在腐殖酸表面发生物理吸附，且与DS-3发生了微弱的磺化反应。使用Material studio8.0计算两个药剂在石墨晶体表面的作用能分别为-56.90kcal/mol和-28.72kcal/mol，说明这两种药剂可以与石墨之间发生吸附作用。在浸出之前，加入该复配抑制剂，碳质物的活性位点被药剂优先占据，进而减弱其对金的吸附能力。在新型浸金药剂方面，对7种低氰药剂进行浸金条件试验。结果显示，在适宜的用量条件下，DZL-1与DZL-4能够达到85%以上的浸金效率，其余药剂浸金效果较差。DZL-1与DZL-4均为新型低氰药剂，较氰化钠安全且环保，其中DZL-4的氰含量更低。此外，研究发现对于非碳质微细粒浸染型金矿，新型非氰浸金剂DZL-8使用过程中能够释放出二氧化氯，是一种环保、经济、高效的新型浸金药剂。因其强氧化性，能够先将铁矿和砷黄铁矿氧化成离子状态，使被硫化矿包裹的金暴露出来，再利用与金的氧化还原电位差异将金氧化成稳定的Au(Cl)4–络离子，实现金的浸出。在最佳的浸金条件下，Fe、As、Sb的氧化率分别达到67.01%、90.64%和85.27%，金的浸出率达到91.02%。本研究还创新性地提出了超临界二氧化碳技术浸金，利用ScCO2-H2O体系酸性，使被硅酸盐及硫化矿包裹的金暴露出来，改变石墨类碳质物的表面性质与孔道结构，减弱其对金络离子的吸附能力，进而提高浸金效率。对比直接氰化浸金，该方法证实对提高浸金效率有效，但对于提高程度以及作用机理还需进行进一步深入研究。