With the increasing exploitation of copper resources, copper emissions are also increasing. Copper tailings are composed of fine silt particles left after copper ore is crushed and cleaned. It contains a large number of metal ores and non-metallic useful components that can be re selected. It is of great significance to select an appropriate re concentration process to recover them for the comprehensive utilization of copper tailings resources. In the actual production process, different types and properties of copper tailings require different beneficiation processes. In the following, the physical and chemical properties of copper tailings are mainly introduced, as well as two common copper methods: sulfide flotation method and leaching method.
The physical morphology of copper tailings is similar to that of sand, but the mineral composition is more complex than that of sand, because it contains more metal minerals than sand. The chemical composition of copper tailings is relatively complex, which contains a large number of valuable elements such as silicon, sulfur, calcium, aluminum and iron. The main minerals are quartz, feldspar, calcite, mica, chalcopyrite, pyrrhotite, etc. Most copper tailings contain more SiO2 (silicon dioxide) and CaCO3 (calcium carbonate), and a certain amount of FeS2 (iron disulfide) and other sulfides.
The essence of sulphide flotation method is to sulfurize the fine oxidized copper ore pulp by adding sulphide, and then add xanthate collectors for flotation. Copper oxide minerals in sodium sulfide solution adsorb HS - and S2 - ions, forming a copper sulfide coating on the mineral surface. Xanthate adsorption on the surface of sulfurized copper oxide is just like the adsorption on the surface of copper sulfide minerals.
In the actual production process, the amount of tailings is far greater than the amount of concentrate. If the copper tailings are directly recovered by sulfide flotation, it will not only affect the yield, but also waste a lot of reagents. Therefore, before the sulfide flotation method is used to treat copper tailings, the original tailings need to be preconcentrated, and a large number of gangue minerals need to be discarded in advance to reduce the subsequent treatment, avoid reagent waste and improve the flotation grade.
In the process of copper tailings re concentration, high grade copper concentrate can be obtained by sulfide flotation, and the recovery effect is good. However, due to the high technical requirements and large investment in the vulcanization process, this method is mostly applicable to large-scale copper tailings concentrators.
The leaching of copper tailings is to convert the copper compounds in the solid phase into copper ions in the liquid phase, and then extract the metal copper in the leaching solution. According to different leaching agents, it can be divided into acid leaching, ammonia leaching, bacterial leaching and electrochemical leaching. Next, two common methods are introduced: acid leaching and ammonia leaching.
Acid leaching method: generally, dilute sulfuric acid is used as the leaching agent, which is suitable for treating oxidized copper ore mainly containing acid gangue. This method has the advantages of high copper leaching rate, low price of leaching agent and simple process and operation. However, its application scope is relatively narrow, and it is only suitable for handling simple copper oxide ores, and requires low calcium, magnesium and impurity iron content, and poor leaching selectivity.
Ammonia leaching method: the ammonia leaching method can directly treat copper tailings, or the tailings can be reduced and roasted before ammonia leaching. Ammonia leaching method is applicable to the treatment of oxidized copper ores with high alkali gangue content and more mud and sand. Ammonia leaching method has high selectivity for copper and alkaline gangue components, and there are few impurity metal ions in the leaching solution. However, this method requires high equipment and energy consumption.
In addition, copper tailings contain many other valuable elements. According to the composition of copper tailings, many useful ingredients such as gold, iron, silver, wollastonite and fluorite can be selected from them. In the process of copper tailings re concentration, sulfide flotation method and leaching method can be used for copper tailings re concentration. In the actual production process, it is necessary to select appropriate re concentration process and equipment according to the nature of copper tailings, and recover copper, gold, silver, iron and other useful metal and non-metallic elements from waste rocks and tailings again, so as to achieve efficient utilization of resources.
