Recovery of Gold, Silver, and Copper from Gold Tailings

In the past, due to limitations in mineral processing technology, large amounts of valuable metals such as gold, silver, copper, zinc, and iron were left behind in gold tailings. Secondary recovery of these resources can significantly improve the comprehensive utilization rate of mineral resources, and significant progress has been made in related technological research in recent years. Currently, the three main recovery methods are roasting, leaching, and flotation.

The roasting method is a key technique for the efficient recovery of gold and silver, encompassing processes such as chloride roasting, iodide roasting, and magnetized roasting. Chloride roasting utilizes chlorine gas to react with gold and silver, forming chlorides to achieve separation; the addition of pyrite can enhance this effect, with gold recovery rates reaching 86.93%, with iron content in the roasting residue exceeding 90%. High-temperature chloride roasting can simultaneously recover gold, silver, and copper; under suitable conditions, the volatilization rates for these three metals can reach 98%, 65%, and 90%, respectively, and the process has already been industrialized.

Leaching methods are primarily based on heap leaching, where a solvent is sprayed onto the ore pile to dissolve valuable components, with the leachate collected from the bottom. This method offers advantages such as a simple process, low investment, and high throughput. Carbon-in-leach (CIL) is used for secondary gold recovery from oxidized gold tailings, achieving a gold leaching rate of 56.08% and a gold adsorption rate of 90.48%, thereby enabling the resource utilization of tailings. Future research and development will focus on developing highly efficient and environmentally friendly leaching agents and optimizing leaching processes.

The flotation method relies on differences in mineral surface hydrophobicity for separation. The key is to remove hydrophilic impurities formed by weathering and oxidation, allowing the fresh mineral surfaces to interact with the reagents. Pre-treatment processes such as agitation and grinding can enhance the flotation of old tailings, achieving the separation of desulfurized and sulfur-rich concentrates. Due to the complex composition and low grade of gold tailings, process optimization supplemented by pre-treatment is necessary to efficiently recover valuable metals.