The size of the gold particles is a major factor in determining the rate of gold dissolution. Assuming that the dissolution rate of gold is 3 mg cm (cm 2 ·h), it takes 14 hours for the spherical gold particles having a diameter of 44 μm (325 mesh) to be completely dissolved, and 48 hours for the spherical gold particles having a diameter of 149 μm (100 mesh). To this end, coarse gold must first be removed prior to cyanidation to increase gold recovery and minimize cyanide operation time.
In the cyanidation process, the gold particles are generally classified into three sizes according to the characteristics of the cyanidation operation: larger than 74 μm (200 mesh) is coarse gold, and 37 to 74 μm (200 to 400 mesh) is fine gold. Less than 37 μm (400 mesh) is fine particle gold. For the convenience of operation, gold particles larger than 495 μm (32 days) are sometimes referred to as extra coarse gold.
Coarse and extra coarse gold are very slow to dissolve in cyanidation and take a long time to dissolve completely. For such gold particles, it is often uneconomical to use extended cyanide time because the gold in most gold ores is mainly fine particles and particles. The method of recovering coarse and extra coarse gold in the recovered ore used in many cyanidation mines at home and abroad is often carried out by mixing or re-selecting the mercury before cyanidation, so as to avoid the loss of undissolved coarse gold in the tail. In the mine.
Fine gold is well soluble during normal cyanidation operations. This is because most of the dissociation is monomeric gold at the corresponding grinding particle size.
The fine gold particles are often dissociated from the monomer during the grinding operation, and most of them are still in the package of other minerals or gangue. Particulate gold in sulfide minerals is often subjected to oxidative roasting prior to cyanidation. The fine-grained gold coated with quartz gangue is difficult to leach during cyanidation. The recovery of such particulate gold by cyanidation usually requires the ore to be finer to increase the degree of dissociation of the gold particles. This will increase the grinding cost and bring difficulties to the solid-liquid separation of the cyanide slurry, increasing the loss of cyanide and dissolved gold. For some particulate gold ore, it is often impossible to use cyanidation because the ore grinding size is not fine enough.
Therefore, it can be considered that the size of gold in the ore is often one of the important factors determining whether cyanidation can be used.
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