天然铁锰氧化物负载金银规律性研究

The Gold and Silver Loading Behavior Study of Natural Iron-Manganese Oxides

铁锰氧化物由于其胶体成因特征,在自然体系中是多种有价金属,如金、银、铜、镍、钴、钨、锡、铅等的载体矿物。褐铁矿和硬锰矿等天然铁锰复合氧化矿物所负载的有价金属具有相当的复杂性,难以用物理方法解离或暴露于表面而被浸出,这些有价金属的回收提取一直是选冶技术共性难题。以云南北衙铁金多金属矿氧化带矿石为研究对象,采用X射线衍射光谱(XRD)、自动定量分析(MLA)、激光烧蚀-电感耦合等离子体质谱(LA-ICP-MS)和扫描电子显微镜(SEM)等分析测试手段研究了天然铁锰氧化矿物负载金、银的差异和规律性。研究结果表明,该矿石中金、银的赋存状态具有多样化的特征,矿石中79%的金为游离金,以明金形式存在于褐铁矿的溶蚀孔洞中,褐铁矿中金粒结晶后边缘形成或大或小至极微细收缩孔隙,这些溶蚀孔及结晶收缩孔为氰化浸出金银提供过液通道。矿石中82%的银赋存于硬锰矿中,这部分银主要进入硬锰矿晶格中的大尺度隧道结构中,少数银以螺状硫银矿形式存在于褐铁矿溶蚀孔洞中。为此,北衙氧化矿的选冶研究摒弃"金细则细磨"的常规思维,根据矿物磁性和金、银赋存状态差异,提出分流分选新理念,在粗磨条件下,分出磁铁精矿、褐铁精矿和非磁三股矿物流,在富银含锰的褐铁精矿中采用弱酸体系中选择性还原解离硬锰矿中银,在控制pH值抑制褐铁矿溶解的前提下,还原释放锰矿物晶体结构中的银离子,实现银的化学解离。该研究成果揭示了氧化带金、银的赋存规律,成因机制以及影响金、银冶金提取的深层次的矿物学因素,为氧化矿金银的选冶研究提供了理论依据。

Iron-manganese oxides are carrier minerals of many valuable metals,such as gold,silver,copper,nickel,cobalt,tungsten,tin,lead,etc.The valuable metals loaded by these minerals,such as limonite and psilomelane,are quite complex and difficult to be leached by physical separation or exposure to the surface.In this paper,the oxidized zone of Beiya iron and gold polymetallic ore in Yunnan province was studied by means of XRD,MLA,LA-ICP-MS and SEM.The results showed that the occurrence of gold and silver in the ore had diversified characteristics.About 79%of the gold in the ore was free gold and existed in the dissolution holes of the limonite in the form of visible gold.Extremely small to large shrinkage voids were formed at the margins of gold grains after crystallization,which could provide a passage for cyanide leaching of gold and silver.82%of the silver in the ore occurred in psilomelane.The silver entered into the large-scale pore structure in the lattice of psilomelane as isomorphism,with small amount of it existed in the limonite dissolution holes as acanthite.Therefore,the conventional thinking of"fine grinding of gold rules"has been abandoned in the research of smelting and processing of Beiya oxidation mine.According to the difference of mineral magnetism and the occurrence state of gold and silver,a new idea of shunt sorting was put forward to separate magnetite concentrate,limonite-manganese concentrate and non-magnetic product stream under the condition of rough grinding.The selective reduction and dissociation of silver from psilomelane in a weak acid system was used in the silver rich limonitemanganese concentrate.On the premise of controlling pH value to inhibit the dissolution of limonite,silver ions in the crystal structure of manganese minerals were reduced and released.The research results revealed the occurrence characteristics,the formation mechanisms of gold,silver and copper,and the mineralogical factors affecting the extraction of gold,silver and copper in the oxidation zone,which provided a theoretical basis for the gold,silver and copper smelting research of oxidized ore.