Gold and silver belong to precious metals and are mainly used in jewelry processing, electronics, medical, and construction fields in modern times. In recent years, with the deepening of mining and utilization of gold and silver mines, more and more low-grade oxidized gold and silver mines have become selection targets. This article introduces a comparative experiment on the beneficiation process of oxidized gold and silver ore. Flotation, gravity separation, and full mud cyanide tests were conducted on the ore, and the full mud cyanide method ultimately won.
Firstly, analyze the chemical elements and phases of the original ore. The elements with recovery value in the ore are gold and silver. The content of gold in sulfide is low, while the content of silver is high. Gold mainly exists in oxides.
In terms of mineral composition, the ore has a relatively complex composition, with a low content of primary metal sulfide ore and a high content of oxidized ore. The main metal minerals are limonite and hematite, followed by pyrite and arsenopyrite. There are small or trace amounts of white lead ore, galena, siderite, brass ore, etc. The gangue mainly includes quartz, feldspar, mica, dolomite, tourmaline, and apatite.
In terms of embedding particle size, gold mainly presents as fine or micro particles embedded between limonite particles or encapsulated by clay minerals, while silver ore is mainly composed of natural silver and pyroxenite, with a small amount of angular silver ore. Natural silver is mainly encapsulated and embedded, followed by intergranular embedding. The carrier minerals of gold and silver mainly include limonite, white lead ore, pyrite, etc.
Flotation method is a widely used and applicable mineral processing method with a wide range of ore types. Therefore, first consider the flotation method. During the grinding fineness condition test, it was found that as the grinding fineness increased, the recovery rate of silver increased, while the recovery rate of gold also increased, but the amplitude was not significant. After the grinding experiment, the grinding fineness was determined to be -74 μ M accounts for 85%.
The results of the beneficiation test show that regardless of whether Scheme 1 or Scheme 2 is used, the recovery rate of gold in the obtained concentrate is relatively low.
The results of the flotation test were not ideal. Next, a re selection test was conducted, and the grinding fineness test was also conducted first, determining a grinding fineness of -74 μ M accounts for 80%. After determining the grinding fineness, experimental studies were conducted on the recovery of gold and silver through re selection. The results of the re selection experiment show that compared with the beneficiation indicators obtained by flotation technology, the recovery rate of total gold in the shaking concentrate and intermediate ore is higher, but the recovery rate of silver is lower.
The main process parameters that affect cyanide leaching indicators are grinding fineness, sodium cyanide dosage, pH value, leaching concentration, and leaching time. Therefore, the next step is to examine the trend of the influence of various process parameters on the gold and silver leaching indicators.
Full mud cyanide beneficiation process: at grinding fineness -74 μ Under the condition of m accounting for 85%, with a fixed leaching slurry concentration of 40%, a sodium cyanide dosage of 4 kg/t, a leaching pH of 10.5 (lime dosage of 3.5 kg/t), and a leaching time of 24 hours, the leaching rates of gold and silver are 68.32% and 64.13%, respectively.
Compared with flotation or gravity separation processes, the recovery rate of gold obtained from full mud cyanide is higher, while the recovery rate of silver is comparable. Therefore, it is recommended to use the full mud cyanide process to treat the oxidized gold and silver ore.
