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Click to add WeChatWith the continuous development of comprehensive utilization technology of gold tailings, people have realized that gold tailings are an important secondary resource. Through tailings reselection, a variety of useful components can be comprehensively utilized, and the market potential is huge. At present, the common recycling of gold tailings reselection mainly includes the recycling of gold, the recycling of other associated non-ferrous/ferrous metals, and the recycling of non-metallic minerals.
Early beneficiation technology and beneficiation equipment were low-level, resulting in a large number of gold-bearing tailings resources with a grade of more than 0.3g/t. The gold grade in some stockpiled tailings reached more than 0.5g/t, and the potential for gold recovery from gold tailings is great. Usually, the gold recovery technology in gold tailings mainly includes flotation and cyanide leaching.
Flotation is widely used for the separation of fine and ultra-fine materials, and has been gradually applied to the recovery of gold in gold tailings in recent years.
In the gold tailings reselection process, flotation is mostly suitable for gold-containing tailings with good floatability, which generally require regrinding to ensure the full dissociation of gold-containing minerals. This gold tailings flotation reselection method can achieve efficient dispersion and suppression of gangue minerals.
Usually, the gold tailings are re-grinded to -200 mesh, accounting for about 70-80%, and a single/combined collector (butyl xanthate, butyl ammonium black medicine, isopentyl xanthate, Y89 xanthate), activator (copper sulfate), pH adjuster (sulfuric acid) are used to obtain qualified gold concentrate through roughing, concentrating and scavenging.
When it is difficult to recover gold in tailings by conventional flotation method, cyanide leaching method can be considered to recover gold. This method is suitable for gold-bearing mineral tailings with fine particle size and good dissociation.
Gold-bearing ore is leached in cyanide solution, and activated carbon is used to directly adsorb the dissolved gold from the slurry, and carbon desorbs the electrolytic gold mud to directly separate, purify and smelt. In addition, low-cost heap leaching gold extraction process can also be used according to actual conditions, and the tailings can be pelletized and heap leached or non-granulated chemical loose heap leached.
With the development and progress of mineral processing technology, the lower limit of the recovery grade of useful components has gradually decreased. The reselection and recovery of associated non-ferrous and ferrous metals in gold tailings is also an important way to achieve comprehensive recycling of tailings.
Usually, gold mine tailings are often accompanied by elements such as Cu, Pb, Zn, Fe, and S. From the current production practice, Cu>0.1%, Pb>1%, and Zn>0.5% in gold tailings have comprehensive recovery value.
Usually, flotation methods are used to recover copper, lead, and zinc from gold mine tailings, such as priority flotation, partial mixed flotation, partial priority flotation, mixed-priority flotation, equal flotation, and combined flotation process, etc.
For different gold tailings ore compositions, the flotation separation process adopted is also different. For example:
■ When the gold tailings after cyanide leaching contain high levels of arsenic and copper, the flotation process of direct arsenic suppression and copper selection can be considered;
■ When the cyanide tailings are sulfur concentrates and contain copper, lead and zinc at the same time, the different inhibitory effects of cyanide on copper, lead and zinc minerals in the cyanide tailings can be used to adopt the preferential mixed flotation lead-zinc-sulfuric acid decyanation activation-copper-sulfur separation process, which not only improves the copper recovery rate, but also recovers cyanide.
The recovery process of iron in tailings is relatively simple. Depending on the different forms of iron, weak magnetic, strong magnetic, roasting magnetic separation, gravity separation and other methods can be used. Sulfides in tailings are usually recovered by flotation and gravity separation.
Generally, the mass fraction of non-metallic minerals in gold mine tailings is above 90%. For example, the total amount of the main minerals quartz (50-75%) and feldspar (10-35%) in quartz vein-type and altered rock-type gold mine tailings can reach about 85%. Reselecting and recovering non-metallic minerals from tailings not only alleviates the harm of large-scale storage of tailings, but also increases the economic benefits of mines and meets the needs of related industries, achieving multiple goals at one stroke.
Quartz is a common non-metallic mineral in gold tailings, especially in quartz vein type and altered rock type gold mines, with high content and great comprehensive recovery potential. Flotation is the main method for recovering quartz. Since quartz and feldspar have similar floatability, the focus of quartz separation and purification is to solve the efficient separation of quartz and feldspar.
According to the flotation medium conditions, the separation methods of quartz and feldspar can be divided into hydrofluoric acid method, fluorine-free acid method, neutral medium flotation method and alkaline medium flotation method. Among them, the hydrofluoric acid method and fluorine-free acid method are relatively more mature.
Feldspar is a framework silicate mineral, which often coexists with quartz, mica and other minerals in gold tailings. To recover feldspar, it is mainly necessary to separate feldspar from coexisting minerals such as quartz and mica. Removing iron and other metal compounds is an important part of feldspar purification. Generally, magnetic separation and gravity separation are used to remove iron and other heavy minerals, and then flotation is used for fine selection.
Mica is also one of the main components of gold mine tailings. It has good natural floatability and is mostly recovered by flotation. Depending on the type of collector, the flotation method mainly includes flotation with cationic amine collectors in acidic media and flotation with mixed anionic and cationic collectors in alkaline media.
In addition, due to the flaky structure of mica and its easy distribution in fine particles, the sedimentation rate in the slurry is relatively slow, and some gold tailings can also be enriched with mica by gravity separation and classification.
The above is the process method for gold tailings reselection and recycling. Gold mine tailings are valuable secondary resources. They contain many types of useful components and different ore properties. Therefore, it is recommended to customize a suitable process flow through mineral processing tests, and rationally select a suitable gold tailings reselection and recycling method based on the final mineral processing test report to fully realize the comprehensive utilization of tailings!
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