As a major gold producer, China produces a large amount of tailings during the large-scale gold mining process every year. However, due to the backward technology in the early days, some useful gold will be discharged with the tailings, and this gold still has recoverable value. Recycling through reasonable process methods can not only improve resource utilization, but also reduce environmental pollution. Generally speaking, the process methods for gold recovery in gold tailings mainly include gravity separation, flotation and cyanide leaching.
Gravity separation is a cost-effective and easy-to-operate mineral processing technology, especially suitable for processing gold tailings with high density and coarse particle size. It uses the difference in specific gravity between gold and gangue minerals to achieve the separation of coarse and fine gold in the fluid medium.
The shaking table gold separation is aimed at gold tailings with a particle size of 2-0.037mm. Through the asymmetric reciprocating motion of the bed surface and the flushing effect of the thin layer of water flow, the minerals are layered and separated according to density. It is stable and reliable to select gold, with high separation accuracy, and can obtain high-grade concentrate.
The spiral chute is the main equipment for chute gold selection. It is suitable for processing gold tailings with a coarse particle size in the range of 2-0.02mm. It uses the combined forces of inclined water flow and ore particle gravity to effectively separate ore particles with different specific gravities.
In addition, gravity separation is often used in combination with flotation or chemical mineral processing methods. Especially when sulfide and gangue are intergrowths in flotation tailings, gravity separation can effectively recover coarse gold that is difficult to recover by flotation.
Flotation is a technology widely used in gold mine tailings recovery. It effectively separates useful minerals from gangue minerals by utilizing the differences in physical and chemical properties of mineral surfaces. For tailings containing precious metals with large specific gravity such as gold and silver, even if the content is low, regrinding to -200 mesh accounts for about 60-80%, which can ensure that the minerals are fully dissociated, thereby increasing the recovery rate of gold. During the flotation process, by using activators such as copper sulfate and efficient collectors (such as butyl xanthate, butylammonium black drug, isopentyl xanthate, Y89 xanthate), combined with pH adjusters (such as sulfuric acid), Carry out rough selection, selection and sweeping to achieve effective activation of gold-bearing minerals and efficient dispersion and suppression of gangue minerals. This method is not only suitable for gold-containing mineral tailings with good floatability, but also can significantly improve recovery efficiency and obtain high-quality gold ore concentrate through comprehensive optimization and process adjustment.
Cyanide leaching is a process used to recover gold from gold tailings when traditional flotation or gravity separation methods are not applicable. This method is suitable for gold-bearing tailings with fine particle size and good dissociation. Gold, silver, etc. are dissolved from the tailings through the affinity of cyanide and precious metals. The leached gold is then adsorbed by activated carbon, and the gold mud is separated and purified through carbon desorption and electrolytic deposition processes, and finally smelted. The concentration and reaction time of the cyaniding agent must be strictly controlled during the cyanidation process to avoid environmental pollution. In addition, in order to reduce costs, heap leaching processes can also be used, which include granulation heap leaching or chemical loose heap leaching without granulation. Cyanide leaching can improve the recovery rate of gold and optimize economic benefits while ensuring environmental safety.
The re-selection process of gold tailings involves a variety of methods, each of which has its own unique advantages and applicable conditions. When selecting a re-selection process, it is necessary to comprehensively consider factors such as the mineralogical characteristics of the tailings, the types and contents of metals and non-metals contained, and economic benefits. According to the tailings with different characteristics, appropriate methods are selected or used in combination with other processes to achieve efficient recovery of gold in gold tailings.
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