Tailings: Dangerous Wastes or Precious Treasures?
Mining scientists from developed countries such as the UK, Australia, and US have researched a lot of new dressing facilities and have achieved significant economic and social benefits.
More and more minerals are explored
However, in some developing countries, people pay more attention to the management of tailing ponds than tailing reuse, and they even confuse tailings with slags or wastes.
What are tailings? What are the potential dangers existing in tailings? And what are the uses of them? This article will answer your questions in detail.
What are tailings?
Tailings definition: tailings are composed of waste rocks and industrial wastewater produced by mineral processing plants. After processing the minerals by facilities and chemicals and extracted the required products, the remaining minerals are called tailings, mine tailings or mine wastes.
What are tailings?
Tailings' classifications: mining rocks and stones in different types and structures are required to be processed in different beneficiation technologies or mineral dressing ways. And the tailings remained are also different in their particles and shapes.
Different kinds and forms of tailings
The reason why the tailings were not used reasonably is the backwardness of the beneficiation technology, resulting in that the valued minerals cannot be extracted from the tailings.
Therefore, the manufacturer established tailing ponds for the management of the tailings, but many tailings were left unattended after long-term storage so that no one would think about their hiding threatens and values until the tailing dams collapse accident occurred.
Are tailings dangerous?
The answer is YES and the reasons are as follows:
After mining and processing, the disposal of mine tailings always becomes the most terrible problem which threatens the environment abominably.
Some mining resources such as rare earth mine and uranium ore will remain some slags, which contain radionuclide.
After long-term disposal of these slags, their radionuclides can easily enter the groundwater or surface water environment, causing serious damage to the surrounding environment. Radioactive contamination has severe effects on the health of workers and nearby residents.
Heavy metals hazard
Statistically speaking, heavy metals kill more than 50,000 people a year.
After the mineral is processed by beneficiation facility, a small number of heavy metals will remain in the tailings. The heavy metals from the tailing disposal will enter the food chain through the enrichment of crops and continuously accumulate in human beings and animals, posing a serious hazard to human health.
At the same time, heavy metals pollution is persistent and highly toxic, which will also cause great damage to local soil and water quality, and will seriously affect the normal life of residents for a long time.
Chemical agent hazard
In general, a large number of chemical agents remain in the tailings after the beneficiation, and these chemicals are extremely harmful to the human body. Once inhaled, the chemical gas will cause fatal harm.
The disposal of tailings covers the land among residents, which will give off large quantities of chemical gases. For example:
The cyanide used for gold beneficiation is a highly toxic agent. The cyanide is called the "king of poisons". When someone inhales cyanide gas, he will lose consciousness within 2 minutes, get a cardiac arrest and die;
Xanthate, black catching agent and phenolic compounds commonly used in beneficiation emit an unpleasant special smell in water, which is very harmful to humans and animals.
Tailings pollute the environment and endanger health
Tailings dam failures
Tailings is required to be stored in the tailings ponds, and the tailings ponds need to be constantly managed and maintained.
Due to the complex chemical characteristics of tailings and the special construction and operation methods of tailings ponds, the storage of them and management of their ponds should be monitored regularly, which takes a lot of manpower and funds.
And tailings dams have a higher risk of dam break than reservoir dams. Once a dam failure occurs, it must cause a number of deaths. Tailings dam failures are the scariest dangers. The safety of residents near the tailing dams cannot be guaranteed under the current situation.
Scientists conducted a statistical analysis of 3,500 tailings dams worldwide and found that the probability of dam failure is more than 10 times that of reservoir dams.
On July 19, 1985, a dam break at the Stava tailings dam in Italy killed 268 people, which was the worst tailings failure all over the world.
In 2019, VALE Group's tailings dam failure in Minas Gerais killed more than 200 people and deprived over 3,000 residents of their homes. VALE paid $107 million to distressed families and employees affected by the accident.
The accident caused the company's iron ore production capacity to fall severely by more than 40 million tons, and the loss was close to $7.4 billion, and even pushed the global iron ore price to a two-year high.
Video from: Guardian News
Tailings: turning wastes into treasures
Some enterprises have begun to turn their eyes on the development and utilization of tailing resources due to the depletion of the world's mining resources and the promotion of environmental protection measures.
Breakthroughs have been made in the use of tailing wastes. For example, some investors extract metals and non-metal elements in tailings and process them into building materials and soil conditioners, etc.
Tailings can bring more profits
Tailings are re-sorted for concentrates
Limited by technical conditions in the past, the rate of the ore beneficiation was extremely low, and the comprehensive utilization of minerals was insufficient, which makes many valued minerals have been piled up and even being discharged into tailings.
With the advancement of science and technology, some enterprises have begun to redress these tailings and achieved some economic benefits. For example:
1. Some magnetite tailings in China contain 20% iron minerals, which is redressed by strong magnetic separators to obtain iron concentrates with a grade of 60%.
2. An iron ore beneficiation plant in Indonesia used a CTB1024 magnetic separator to re-separate iron ore mine waste, and obtained high-quality iron concentrates with a grade of up to 65.76% and an annual output of 39,200 tons of iron concentrates.
3. Peruvian copper mining companies have improved on-site production processes to increase copper and gold dressing rates. At the same time, a sulfur beneficiation facility is added, which brings an annual output value of 1.8 million U.S. dollars.
Iron tailings beneficiation line designed by FTM
Tailings are used for building materials production
60% of Russian beneficiation plants use tailings to produce building materials. In addition to manufacturing building glass-ceramics and chemically resistant glass, various mineral cementing materials have also been developed.
In the United States, except for the recovery of fluorite, feldspar, and quartz from tailings rocks, most of them are used for concrete aggregates, foundation and asphalt pavement materials, and tailings have been separated to produce bricks with compressive strength of 35 MPa.
Japan uses flotation iron ore tailings and coal tailings as the main raw materials to make sewer clay pipes, and the Japanese Institute of Pollution Data has patented the use of them as lightweight porous material.
China applies iron ore tailings to non-fired bricks, glass, glass-ceramics, fine concrete aggregates, and road bases. Among them, the base of roads requires a large number of filler tailings will bring a significant economic and environmental benefit to road construction.
Turning tailings into building materials
Tailings for fertilizer and soil conditioner
Tailings often contain trace elements such as Zn, Mn, Cu, Mo, V, B, Fe, and P, which are essential for maintaining plant growth and development.
The tailings discharged by some dressing plants in Japan are alkaline. In the rice planting experiment, these tailings neutralize acidic soil and can improve the quality of acidic soil.
Tailings for mines' filler
Backfilling the mine goaf is one of the most effective ways to directly use tailings. Especially for mining enterprises that cannot set up a tailing pond, backfilling the goaf by tailings has greater environmental and economic significance.
The tailings cementation and filling method is a mature technology now, which can increase the rate of underground mining recovery by 20-50%. The ideal filling method can completely avoid surface subsidence and basically avoid disrupting groundwater balance.
There are many uses of tailings, such as for the production of calcium carbonate and silica aerogels, and so on. It is believed that with the advancement of science and beneficiation technology, more treatment of tailings will be gradually discovered.
The successful cases of tailings utilization：
- Reprocessing of gold and uranium tailings in South Africa
- Tailings are used in construction instead of cement
Tailing have become the most important issue which obstructs the global sustainable development. Whether from the perspective of the global or any country, the improvement of tailings facilities is very necessary to the socio-economic and environment.
Tailings are not waste but treasures that are not fully excavated due to current technical and economic conditions.
With the development of science and technology, the improvement of beneficiation techniques, the upgrade of dressing facilities and the simplification of operations, the tailings will become precious resources and bring huge economic benefits to more and more enterprises.