Tailings are components with low content of valuable parts produced in beneficiation operations that cannot economically be used for industrial production and are also the main components of industrial solid waste. Currently, the output of metal ores, non-metallic ores, coal, clay, etc., mined in various countries in the world is huge every year, and the amount of tailings produced is also huge.
Why Should Tailings Be Comprehensively Utilized?
Tailings have seriously hampered the mining industry’s green and sustainable development and have also become an essential factor that damages the environment and endangers safety. By comprehensively utilizing it, we can solve all the problems caused by tailings and increase the profit and income of mining enterprises.
1. Recyclable components are abundant in tailings
China’s main types of ore are co-associated ores, which account for 80% of the total mineral resources and are difficult to separate. In addition, the beneficiation and smelting technology of the early mines was relatively backward, and the economic conditions in different periods were also other. Usually, it could recover only one or some minerals in the ore. It makes non-ferrous, rare, precious metals, and many non-metallic minerals that remain in the tailings. They can be recycled and utilized with the current beneficiation technology to supplement the increasingly depleted mineral resources.
2. Non-metal resources are abundant in tailings
Due to erosion, the tailings contain a large amount of quartz, feldspar, amphibole, pyroxene, calcite, dolomite, silicate minerals, and magnesium. The main chemical components are silicon, aluminum, calcium, and magnesium. etc., in which the content of silicon and aluminum is higher. Therefore, it is essential to fully use tailings resources, especially the non-metallic resources contained in them.
3. Tailings have serious hazards
Presently, the primary method of tailings disposal is tailings storage, which will occupy a large amount of agricultural and forest land and destroy the allocation of land resources in the area where it is located. In addition, some mining processing plants in remote areas or small-scale processing plants in towns will discharge tailings directly into the natural environment, causing significant environmental damage. It is urgent to consume tailings through various comprehensive utilization methods.
4. The comprehensive utilization of tailings has high economic benefits
To protect mineral resources, maintain ecological balance, and implement a virtuous circle, the industrially developed countries in the world have begun to build “secondary raw material industries” and have achieved remarkable results. The tailings stockpiled in my country generally have higher grades, especially the tailings in the 1950s and 1960s, which have greater development and utilization value. Moreover, compared with developing new veins, the exploration cost of tailings is lower, and the exploration results are more accurate. At the same time, the transportation around the tailings pond is convenient, and the infrastructure is relatively complete, which can make a large investment in infrastructure. The tailings in the tailings pond are relatively loose and fine in particle size. Only a small amount of crushing and grinding operations are required, the energy consumption is low, and the production cost is low.
What Are The Comprehensive Utilization Methods of Tailings?
1. Secondary separation of tailings
The total amount of tailings is large, and there are many types. The following takes iron tailings, copper tailings, lead-zinc tailings, and rare earth tailings as examples to introduce:
For the secondary separation of iron tailings, there are already relatively mature processes to recover the iron minerals in them and obtain iron concentrates of better quality. Because of the weak magnetic properties of iron tailings, pre-concentration-magnetic separation-reverse flotation and magnetization roasting-magnetic separation processes have become popular secondary separation methods for iron tailings. These two methods have low TFe grades. , The treatment effect of iron tailings with fine embedded particle size is relatively significant, the iron grade of the obtained concentrate products is generally between 55% and 67%, the recovery rate of metallic iron is high, and the products have high economic value.
For copper tailings, the secondary separation methods include reducing agent reduction roasting-grinding-magnetic separation process, flotation, and leaching process. The reduction roasting-grinding-magnetic separation process reduces metals such as copper and iron in the copper tailings into metal elements by reducing agents, grinding them to be fine, and finally, using magnetic separation for recovery. Flotation can achieve secondary separation of valuable components in copper tailings using different procedures and reagents. The chemical leaching process can realize the recovery and utilization of various valuable metals in copper tailings.
The grades of lead, zinc and other metals in lead-zinc tailings are relatively high and have high recovery values, so their secondary sorting is meaningful. There are many types of secondary beneficiation methods for lead and zinc tailings. In addition to the traditional beneficiation process, there are many new technologies. Such as:
- The magnetic roasting-magnetic separation process. This process can effectively recover metallic iron and has a certain enrichment effect on other metals.
- Centrifugal heavy medium separation technology. It can divide lead and zinc tailings into light and heavy parts. The heavier part contains the most valuable minerals, which can be processed and recovered later.
- Chemical leaching. It is a traditional leaching process that can achieve all the recovery of lead and zinc.
- Microbial leaching. It is a new process of leaching lead-zinc tailings by bacteria. The leaching rate is lower than chemical leaching, but the secondary pollution is less.
Rare earth is an important national strategic resource, and rare earth tailings contain many valuable minerals, especially REO, which must be recovered as much as possible. The secondary separation methods of rare earth tailings include traditional beneficiation processes and new technologies. The traditional beneficiation processes include single flotation, flotation agglomeration magnetic separation, and flotation-magnetic separation-gravity separation combined process. The new technologies include supergravity-roasting, magnetization roasting-magnetic separation, etc. These processes can effectively recover valuable components such as REO in rare earth tailings.
Generally, the secondary sorting of tailings can sort out the valuable metals in tailings as much as possible and realize the resource utilization of tailings. At the same time, the secondary separation of tailings can dissipate a large number of tailings and turn waste into treasure.
2. Tailings are used as raw materials for building materials
Elements such as Si and Al contained in tailings are essential components for the production of building materials so that they can use tailings as raw materials for building materials production.
Currently, the state advocates equipment-type construction, prohibits quarrying in the mountains, and proposes the resource utilization of solid waste to promote efficient use. Using tailings as raw materials for building materials can achieve bulk consumption of tailings, solidify/stabilize harmful substances in tailings, and prevent the migration of toxic substances. It mainly uses tailings as raw materials for building materials such as concrete and ceramics.
Because the components contained in tailings can meet the requirements of building materials manufacturing, building materials that meet the relevant national standards can be obtained only after some process treatments, such as sintering, curing, etc. An excellent way to realize the comprehensive utilization of tailings. Using tailings to prepare building materials can absorb many tailings and realize high-value utilization of tailings.
3. Application of tailings in agricultural production
There are three main applications of tailings in agriculture: the preparation of chemical fertilizers, the use of soil amendments, and the reclamation of tailings.
The tailings usually contain trace elements necessary for plant growth, such as Zn, Mn, Cu, Mo, V, B, Fe, P, etc. After a series of treatments, the tailings can be made into chemical fertilizers, improving soil structure and increasing soil fertility, enabling crops to thrive and increase agricultural yields.
The main principle that tailings are used as soil conditioners is that the components contained in tailings can react with harmful substances in the soil. It prevents the migration of harmful substances in the soil, effectively repairs the polluted soil, and reduces the migration of pollutants. While restoring the environment, it also eliminates tailings and realizes the use of waste to treat waste.
Tailings reclamation is also an essential application of tailings in agricultural production. At present, the reclamation of tailings often adopts the biological method or microbial method. Using these two methods can reduce the content of soluble heavy metals in soil and realize the stabilization of heavy metals. In foreign countries, biological or microbial methods are often used to reclaim/remediate tailings, and the reclamation rate can reach up to 80%. The tailings reclamation/remediation in China started late, but the development is still relatively rapid. State departments have issued relevant regulations, which have greatly promoted the development of tailings reclamation.
4. Tailings backfill
Tailings backfilling can dissipate many tailings and is an extremely effective tailings reduction and utilization technology. There are many types of tailings backfilling techniques, among which the most commonly used is cemented backfilling technology. This technology is to mix inert materials such as fine sand and an appropriate amount of gel material with water to make backfilling materials, which can improve the recovery rate of ground mining. In tailings backfilling, tailings are often prepared with other solid wastes to prepare filling materials, which are backfilled into goaves of mines or other underground voids due to engineering construction.
Backfilling the mined-out area with tailings can replace the original cement-bonded filler. This method can absorb a large number of tailings and reduce the cost of backfilling. At present, tailings are often mixed with active industrial wastes such as smelting slag to prepare backfilling mortar. It can realize complete tailing cement filling, meet the technical requirements of backfilling, and comprehensively utilize industrial wastes. It has development prospects. It has achieved some success in filling goaves with tailings as a cementitious material.