Copper tailings mineral composition and copper tailings reprocessing technology

With copper resources dwindling and rich ores becoming increasingly scarce, the reprocessing of refractory copper and tailings has become an important channel for resource recovery. Copper tailings contain various valuable components, which can be reused through appropriate reprocessing methods. This article will focus on the valuable components in copper tailings and the reprocessing of copper tailings.

01I. Mineral Elements in Copper Tailings

The valuable components in copper tailings are diverse, including metallic, non-metallic, and rare elemental components. Common ones include:

Copper: Exists in the form of copper sulfide and copper oxide. Copper sulfide often remains due to insufficient dissociation or incomplete reagent action, and its surface is often covered with an oxide film. Copper oxide is often not recovered due to improper pulp pH or inappropriate collector selection, and is dispersed.

Gold and silver: Often exist as fine-grained inclusions within sulfide mineral crystals or adsorbed on the surface of slime. Gold may be encapsulated in pyrite as nano-sized particles, while silver may form solid solutions with chalcocite, making separation difficult using conventional beneficiation methods.

Iron: Commonly found in magnetite, hematite, and pyrite. Magnetite is highly magnetic and easily recovered; hematite is less magnetic and requires strong magnetic separation; iron in pyrite needs to be processed simultaneously with sulfur recovery, and its iron content is related to its sulfur content.

Zinc, lead, and molybdenum: Mostly minor associated components, existing as sphalerite, galena, and molybdenite respectively. Their content is usually low, but accumulated reserves in tailings of specific mining areas have recovery value. Sulfur: Primarily derived from insufficiently recovered pyrite, accounting for 2%-8% of the tailings. Pyrite may contain precious metals such as gold and silver; these metals can be recovered during sulfur recovery.

Silicate minerals: Mainly composed of quartz and feldspar, with a high proportion. After further beneficiation and purification, they can meet the raw material requirements of industries such as ceramics and glass.

Rare earth elements: Some tailings may contain trace amounts of rare earth elements, possibly existing isomorphously in minerals such as feldspar and apatite, or adsorbed on the surface of clay minerals. A concentration of 0.05%-0.3% constitutes a strategic value.

02II. Conventional Copper Tailings Re-concentration Methods

1. Copper Tailings Gravity Separation

Gravity separation recovers elements from copper tailings and is suitable for coarser-grained (0.074-2mm) native gold and copper sulfide minerals. Shaking tables utilize the reciprocating motion of the table surface and lateral water flow to enrich denser coarse particles at the concentrate end; spiral sluices utilize centrifugal force and gravity separation to re-concentrate medium- and fine-grained (0.038-0.5mm) tailings.

2. Magnetic Separation of Copper Tailings

Magnetic separation is mainly used to recover magnetic minerals (magnetite, pseudomorphic hematite), and some magnetic rare metal minerals. Permanent magnetic drum separators or high-gradient magnetic separators are commonly used. The former, when the Oersted magnetic field strength is in the range of 1000-2000, can separate strongly magnetic magnetite; the high-gradient magnetic separator, when the Oersted magnetic field strength is in the range of 8000-15000, can separate weakly magnetic hematite.

3. Copper Tailings Flotation

Copper tailings flotation is suitable for recovering sulfide minerals such as copper, molybdenum, and sulfur, as well as some oxide minerals. Conventional flotation is used for incompletely recovered copper sulfides, achieving re-selection and recovery by adjusting the reagent system; carrier flotation is used for fine-grained copper minerals(<10μm), adding coarse-grained quartz as a carrier to achieve flotation recovery; flocculation flotation is used for ultrafine particles (<10μm), adding flocculants such as polyacrylamide to achieve re-selection and recovery.

Copper Recovery: Butyl xanthate is commonly used as a collector, and sodium carbonate is used as a modifier to maintain the pulp pH at 9-11 for flotation, recovering copper concentrate;

Molybdenum Recovery: In copper flotation tailings, kerosene is used as a collector, and No. 2 oil is used as a frother for flotation of molybdenite under acidic conditions;

Sulfur Recovery: For pyrite-containing tailings, xanthate is used for flotation under weakly acidic conditions.

4. Copper Tailings Acid Leaching/Bioleaching

Acid leaching is generally suitable for recovering soluble or oxidized minerals such as gold, silver, copper, and molybdenum from copper tailings. Specifically, oxidized copper ore is leached with sulfuric acid; the acid-base concentration is adjusted in a stirred leaching tank, and copper can be leached out within a measured reaction time. Low-grade oxidized copper tailings are recovered using heap leaching, with a typical leaching cycle of 30-60 days. Molybdenite is leached with NaOH solution to produce sodium molybdate solution, which is then recrystallized and purified. Sulfide minerals can be leached using bacteria such as *Acidithiobacillus ferrooxidans*.

5. Copper Tailings Cyanide

Cyanide is often used to recover gold and silver from copper tailings, but the high toxicity of cyanide limits its application.

Cyanide Gold Leaching: Gold is leached using sodium cyanide solution, with lime added to control the pH at 10-11. The gold leaching rate can reach 70%-90%, but environmental treatment of cyanide-containing wastewater is required.

Ammonia Leaching: Suitable for oxidized copper ores containing alkaline gangue. In an ammonia-ammonium salt solution, oxidized copper minerals form soluble copper-ammonia complex ions, which have a weak dissolving effect on alkaline gangue. The leachate is extracted and electrowinning to obtain high-purity cathode copper.

The above is an introduction to the valuable elements in copper tailings and methods for copper tailings reprocessing. Copper tailings reprocessing not only creates economic value but also promotes the recycling of mineral resources, making it an important way to achieve "zero-waste mines." With technological advancements, the recovery rate of low-grade, complex-component tailings will continue to improve. So how do you determine the valuable elements in copper tailings and suitable reprocessing methods? It is recommended to consult a professional company for experimental analysis and design. Xinhai Mining Equipment can perform reprocessing operations for various types of copper tailings, providing experimental analysis, beneficiation scheme design, complete reprocessing design, and subsequent operation and maintenance. Please feel free to contact us if you have any needs.