The current development status and hazards of mine tailings in my country
The main components of mine tailings in my country are mostly metal sulfides, which are easily oxidized and form acid mine wastewater that poses a serious threat to human health and the ecological environment. If the tailings are not properly treated, it will also cause environmental pollution; strengthening the treatment of tailings is of great significance to the current mining industry and social development.
The source of mineral processing wastewater
Wastewater in tailings, this type of waste water is produced when the tailings are transported to the tailings pond, and then discharged after a long period of clarification or purification. Wastewater from flushing industrial sites, that is, a small amount of mineral washing water and pulp and other wastewater with complex components such as suspended solids, oil, chemicals and solid particles that are washed away when flushing industrial mine sites.
The waste water in the concentrate is the filtrate separated from the concentrate product after passing through the dehydration methods such as thickener dehydration or filter dehydration.
Relevant sanitary wastewater and rainwater during mineral processing. Such wastewater includes a huge number of solid particles, inorganic or organic chemicals and suspended solids and other complex components, but the amount of water is not large and often enters the sewage pool through the trench. It is not suitable for direct discharge or reuse.
Treatment method of beneficiation tailings and beneficiation wastewater
3.1 Treatment measures for mine tailings
(1) Physical isolation method.
The physical isolation method is a treatment method that isolates oxygen and prevents oxidation by covering the surface of mine tailings with materials such as water, sludge, gravel, and wood chip waste. The main purpose is to control the production of acid mine wastewater.
Similarly, in Sweden, Europe, the zinc-copper mine tailings were successfully treated by the water isolation method, and the results also proved that the water isolation has good oxygen barrier and anti-oxidation effects. In addition, it is reported that South Africa has used the method of covering with gravel to treat tailings, and after two years of wind and water volume verification, there is no large loss of stones or residues, so the tailings are oxidized to a great extent. and curb the production of acidic wastewater.
(2) Chemical neutralization method.
Chemical neutralization is a treatment method in which alkaline substances such as carbonate rock and lime are mixed with mine tailings, and a chemical reaction of neutralization occurs after a period of time to reduce the production of acidic mine wastewater.
In actual operation, by adding an appropriate amount of alkaline substances such as lime to the mine tailings to produce a mixed neutralization effect, the pH value of the mine tailings can be increased, and it is the improvement of the pH value. Earth isolates oxygen and reduces the effect of oxidation reactions.
In addition, an appropriate amount of alkaline substances will form a type of metal precipitate deposited on the surface of mine tailings in the mixed neutralization reaction with mineral metal ions, which can largely inhibit the oxidation of mine tailings. As well as the acidic mine wastewater produced after its dissolution, the goal of effectively and scientifically treating mine tailings is finally achieved.
(3) Vegetation restoration method.
In response to the country’s strong emphasis on the guideline of “who destroys, who reclaims”, my country’s tailings reclamation work has also begun in full swing.
At the same time, the emergence of vegetation restoration method has aroused the keen attention of the public. Usually, there are two methods of vegetation restoration: one is to cover the surface of tailings with a certain amount of soil, and then plant plants on the surface.
For example, the actual case of a non-ferrous metal enterprise in Zhongtiaoshan shows that the company covered the tailings pond with the vegetation or changed the fields to make the metal indexes contained in the crops on the tailings surface lower than the national metal content index.
But at the same time, this method also needs to move a larger batch of soil and many related supporting planting techniques, so it has a high operating cost, which also makes its use unable to be widely popularized; on the other hand, through higher technology Optimizing and cultivating relevant plants with resistance and heavy metal corrosion resistance, and directly planting green plants in a suitable specific tailings environment.
However, in actual planting, due to the wide variety of metal elements in tailings, the plants that can absorb multiple metals together are extremely rare, which has also led to the failure of large-scale application of this vegetation restoration method.
The number of tailings generated in the mining industry is also increasing rapidly. In the actual tailings treatment, it is impossible to completely treat the harmless tailings only by relying on the above methods. Therefore, it is necessary to take measures such as comprehensive recovery and utilization of tailings. The method of cooperating with each other can truly accomplish the goal of scientifically treating tailings.
3.2 Treatment of wastewater
(1) flocculation method.
The flocculation method is a method of using the flocculant to remove impurities to achieve the effect of wastewater treatment. It has three processes: coagulation, bridging and settling. During agglomeration, due to the mutual attraction between particles, the agglomerated state is formed after the charge of the particles on the surface undergoes a neutralization reaction;
In the process of bridging, the flocculant plays the role of bridging, which promotes the aggregation of a large number of particles to form larger particle flocs, and there are two types of polymers, negative and positive. Will cause electrical neutralization reaction. If the synthetic particles belong to the middle polymer, the flocculation process will only stay in the bridging stage.
(2) Adsorption method.
The adsorption method is a method of using solid adsorbents to adsorb pollutants to achieve wastewater treatment, and it is also a method that is frequently used in daily life. The reason why it is widely used is that the adsorbent material is relatively cheap, that is, it has the characteristics of low cost; at the same time, it also has a good adsorption effect.
Usually, we divide adsorbents into two types: material adsorbents and biological adsorbents. The example is as follows: when the wastewater of the lead-zinc mine in the southwest was purified, by gradually increasing the powdered activated carbon in the wastewater of the lead-zinc mine in batches, it was found that the phenomenon of bubble generation in the wastewater was also continuously weakened with the increase of carbon content. And most of the CODCr substances in the wastewater are also absorbed.
(3) In addition to the above wastewater treatment methods, the more conventional treatment methods also include biological treatment methods, oxidation methods, flotation methods, etc. In addition, there are a series of unconventional methods that can effectively treat wastewater, such as natural mineral soil treatment, backwashing method, photocatalytic degradation method and modified agent method, etc.
The development of modern industry and technology is inseparable from and relying on the utilization of a large number of metal ore resources, and strengthening the reuse and energy of tailings and the technology of wastewater treatment is conducive to greatly improving mine mineral resources and beneficiation water. The utilization rate of resources is also conducive to the development of mine recycling economy operations and the improvement of mine ecological environment, and finally achieves a coordinated and sustainable development of resources, economy and environment.