First, the exhaust
To date, heap leaching of oxide ore mineral feedstock substantially tractable, in principle, be taken to strengthen the leaching means, even if the ore contains sulphide, arsenic compounds, sulfur dioxide does not occur, a class of arsenic trioxide gas serious environmental pollution . Heap leaching is carried out at room temperature, and there is almost no smoke and exhaust gas from boiler combustion. Certain chemical materials used in the process generally do not have volatile properties. It can be seen that there is no source term for generating a large amount of exhaust gas during the heap leaching process. However, the shower process, when using an acid heap leaching method, will inevitably produce some mist; heap leaching of uranium ore, the ore heap will release oxygen; a gold heap leaching, such as pH controlled, It produces highly toxic hydrogen cyanide. Although these harmful toxic gases do not have a serious impact on the environment, they have an impact on the organisms near the heap leaching site.
Second, wastewater
Although the wastewater generated by heap leaching is only 7% to 20% of the amount of conventional stirred leaching wastewater, wastewater is still the main waste of heap leaching. The toxic and harmful substances in the heap leaching wastewater mainly come from three aspects: 1 lysing agent itself, they are chemical raw materials such as acid, alkali and salt, some are highly toxic, such as sodium cyanide; some are not conducive to the survival of living things. Such as sulfuric acid; some are non-toxic, such as sodium carbonate, but long-term infiltration into the soil will lead to soil salinization. 2 Many toxic substances, such as uranium, radium, arsenic, copper , lead , cadmium , mercury , chromium, etc., are dissolved and dissolved from the ore; some substances are not toxic, such as iron , aluminum , calcium, magnesium, etc., but when they flow into the surroundings In the case of water, hydrolysis and precipitation will occur, affecting the transparency of the water body and changing the appearance color of the river. Calcium, magnesium and sulfate ions and chloride ions will deteriorate the soil and hinder the normal growth of crops. 3 In the process of recovering metal from the leachate, certain organic and ammonium salts are added, resulting in the presence of ammonium and organic matter in the wastewater. Ammonium is a nutrient-rich ingredient that causes plants to grow in water, causing an increase in the chemical oxygen demand and biological oxygen consumption of water bodies, threatening the survival of plankton. Although the organic matter generally used in water has a low solubility in water, it tends to have a pungent odor, and humans and other organisms cannot adapt.
It can be seen that the waste water generated by heap leaching will not bring targeted and effective treatment measures, and let it flow into the water body, which will bring serious consequences to the environment.
Third, waste residue
The heap leaching residue consists of two parts, one is the ore after the leaching is finished; the other is the slag generated in the wastewater treatment. The ore is leached and some of the harmful elements are partially transferred to the leachate. Although the total amount of harmful components in the ore after leaching is reduced, the waste rock may have a greater impact on the environment than the unleaded ore. This is because after the ore has been in contact with the leaching solution for a long time, some minerals are decomposed and corroded. After the leaching, the ore is washed by water. Due to the capillary force, the leaching agent in the ore and ore cannot be completely It is excluded. Therefore, some leaching processes still exist in the waste rock. If these processes include leaching of toxic elements, the waste rock must become a harmful source of three wastes. If after the water is washed, even if the leaching agent in the ore is removed from the bottom, the waste rock at this time is still more harmful than the unleashed ore to the environment, because the waste rock has been immersed. Corrosion of the agent, as well as the oxidation of new air that is constantly being replaced due to the influence of the unsaturated flow, makes the ore easy to be broken, and harmful substances such as oxygen are more easily released.
In the process of treating wastewater, especially in the treatment of acidic wastewater, a slurry of a large amount of flocculent precipitated hydroxide is inevitably produced. The slurry-like slag is bulky and fluid, and if handled improperly, it will cause considerable pollution to the environment.
Fourth, dust
This is also a waste that is inevitably produced by heap leaching. Especially in dry and windy regions and seasons, dust is more harmful. Regarding the hazard of dust, in addition to silicon (矽), it is related to the type of toxic substances in the ore. Of course, the dust problem is mainly in the category of labor (industrial) health because it affects the health of workers. However, when building a heap leaching project in a windy area, it is impossible to consider the impact of dust on the environment from the standpoint of environmental protection.
Five, noise
In a heap leaching project, the environmental impact of noise can be disregarded. Although it may use some equipment that is very noisy, such as a pressure blower. Because the heap leaching sites are far away from residential areas and are operating in open spaces, these few high-noise devices are unlikely to have a significant impact on their surroundings.
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