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In all kinds of gold minerals, the carlin type gold is a finely disseminated gold deposit mainly occurring in carbonate rocks. The gold grade of this kind of gold ore is low, large metallogenic scale and fine gold dissemination. The main gangue minerals include quartz, calcite, barite, kaolin and etc. It is a gold mineral that is difficult to recover. Among the arsenic, mercury and other harmful elements are easy to cause environmental pollution, if the treatment is not standard. In this passage, we will discuss the difficulties and methods of carlin type gold recovery.
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The carlin type gold deposit itself is more complex. The content of arsenic, carbon and mercury in the ore is higher. And the grain size of the chimeric gold deposit is finer. Therefore, the recovery difficulties are mainly about the points as follows: First, the lower grain size increases the difficulty of ore grinding; Second, the carbon could absorb gold in the pregnant solution, which is difficult to recover; Besides, the toxic minerals such as arsenic and mercury in the ore interfere with the recovery of gold. So compared with ordinary sulfide gold mine, carlin type gold recovery technology is more complicated.
According to the characteristics and nature of ore, after crushing and grinding, the carlin type gold recovery technology mainly includes flotation, biological oxidation or roasting, cyanidation leaching, etc. In the following, we will mainly focus on carbon ore, arsenic ore, silicon-sulfide ore, and silicon-refractory ore respectively.
The organic carbon in the carbonaceous ore comes from the early Marine algae, and the organic carbon is converted into oil parent rock. Compared with coconut shell charcoal, which is often used in carbon leaching, the carbon in the mineral has a higher adsorption capacity of dissolved gold, which leads to the gold ore in the ore can not be normally retained in the cyanide solution, which is often called "gold robbery". To avoid the “gold robbery”, from the perspective of dressing method, this kind of ore first needs to be neutralized through oxidation, which can be adopted including roasting, oxidation, biological oxidation, etc., and then gold recovery by cyanide leaching method, so as to obtain a more effective recovery effect. Besides, because of the good flotability of carbon, it can be separated by terpenic oil or kerosene. It can effectively reduce the carbon content in the ore.
Arsenic in the ore may react with pyrite to form arsenopyrite, resulting in its inability to interact with collectors, so it is difficult in gold recovery. Due to the fine grain size of gold in the carlin type gold deposit, and the close symbiosis of pyrite and arsenopyrite as the carrier minerals of gold, flotation separation will be difficult. The following methods can be adopted from the separation method: Firstly, aeration before flotation promotes ore oxidation and can remove arsenic minerals from the surface of arsenopyrite. The flotation effect of fine gold and gold-bearing material can be improved by using strong collecting agents, such as BK903G, BK302A or MA. In addition, the addition of copper sulfate, lead nitrate and other activators to improve the floatability of gold carrier minerals is also a feasible method.
Because both pyrite and silicon can encase gold particles, they can cause hard-to-pick properties. The cyanide may react with the sulfide rather than gold, which influences the gold recovery rate. The gold recovery of this kind of ore can be high-pressure leaching or roasting.
When gold particles are coated with poorly permeable silicon, it is difficult for them to be recycled directly, a phenomenon known as "silicon locking". Compared with the ores containing carbon and sulfide, the gold recovery of this kind of ore is simple. The recovery rate of gold can be improved by increasing the fineness of the grinding at the grinding stage, followed by flotation or leaching.
The above is the difficulties and methods of carlin type gold recovery. According to different kinds of minerals, there are different compositions, so are the extraction technologies and technology flows. Therefore, it is necessary to carry out the ore dressing test before formulating the ore dressing process, and determine the ore dressing process according to the test, so as to obtain the reliable ore recovery index by scientific and reasonable methods.