Topic 3 Utilization and Protection of Metal Resources

Topic 3

Utilization and protection of metal resources

Metal resources on the earth exist widely in the earth's crust and oceans. Except for a few very inactive metals such as gold and silver, which exist in the form of simple substances, the rest exist in the form of compounds.

Industrial extraction of metals from ores that contain metal elements and are valuable for mining. Our country is one of the few countries in the world with a relatively complete range of known minerals, and its mineral reserves are also very rich. Among them, the reserves of bustard, molybdenum, titanium, tin, and sharps rank among the top in the world, and the reserves of copper, aluminum, and abrasion also occupy the largest share in the world. important position.

Nature provides human beings with abundant metal mineral resources, and human beings extract hundreds of millions of tons of metals every year for industrial and agricultural production and other fields. Among them, iron is the most extracted.

1.Iron smelting

As early as the Spring and Autumn Period and the Warring States Period, my country began to produce and use ironware. Since the 1st century, iron has become the most important metal material.

The principle of ironmaking is to use the reaction of carbon monoxide and iron oxide. In the laboratory, experiments can be performed using the setup shown in Figure 8-20. It can be seen from the experiment that the powder in the glass tube gradually turns from reddish brown to black, and this black powder is the reduced iron; the clarified lime water in the test tube becomes cloudy, which proves that carbon dioxide is generated. The chemical equation of the reaction is as follows: Fe2O3+3CO to 2Fe+3CO2

Smelting iron ore into iron is a complex process. Put iron ore, coke and limestone① together into the blast furnace, and at high temperature, use the carbon monoxide produced by the reaction in the furnace to reduce iron from the iron ore.

2. Metal resource protection

On the one hand, human beings have to ask for a large amount of metal mineral resources from nature every year to extract hundreds of millions of tons of metals. On the other hand, according to relevant reports, metal equipment and materials scrapped due to corrosion every year in the world are equivalent to 20% to 40% of the annual output . What an astonishing number! Preventing metal corrosion has become a major problem in the fields of scientific research and technology.

1. Metal corrosion and protection

The process of iron products rusting is actually the process of chemical reaction between iron and oxygen and water vapor in the air. Corrosion of iron products requires conditions, for example, there must be substances that can react, the reactants must be able to contact each other, the products will not hinder the reaction, and so on. The dense aluminum oxide film formed by the reaction of aluminum and oxygen can cover the surface of aluminum, thereby protecting the aluminum in the inner layer from reacting with oxygen; while the rust (mainly composed of Fe2O3-XH2O)produced by the reaction of iron with oxygen and wateris very loose and cannot prevent the iron in the inner layer from continuing to react with oxygen, water, etc., so all iron products can be rusted.

Knowing the corrosion conditions of iron products, we can find ways to prevent iron products from rusting according to these conditions.

2. Metal resource protection

Mineral reserves are limited and cannot be regenerated. According to the proven reserves of some minerals and the current consumption rate of these metals, some people estimate that some minerals can be mined

How to protect metal resources?

In addition to preventing the corrosion of metals discussed above, another effective way to protect metal resources is metal recycling. It is estimated that recycling an aluminum beverage can is 20% cheaper than making a new one, and it also saves metal resources and 95% energy. At present, more than 50% of iron and more than 90% of gold in the world have been recycled.

Recycling of scrap metal can also reduce environmental pollution. For example, used batteries contain lead, iron, cadmium, mercury, etc. If the used batteries are discarded at will, the leakage of these metals will cause groundwater and soil pollution, threatening human health. Recycling these metals can not only save metal resources, but also reduce environmental pollution, which is a good thing that kills two birds with one stone. For example, in the current production of lead, the secondary lead from the used lead-acid batteries of automobiles occupies a large proportion.

The third effective way to protect metal resources is to mine minerals in a planned and rational way, and to strictly prohibit random mining regardless of national interests. There are other ways to find metal substitutes. With the development of science and technology, new materials emerge in an endless stream. For example, plastics have been widely used to replace steel and other alloys in pipes, gears and auto parts.

After studying this topic, you should know

1.Smelting iron ore into iron is a complicated process. The main reaction principle is that at high temperature, carbon monoxide captures the oxygen in the iron ore and reduces the iron:

Fe2O3+3CO to 2Fe+3CO2

2.In actual production, the raw materials or products used generally contain impurities. When calculating materials and output, attention should be paid to the problem of impurities.

3.The main condition for iron to rust is direct contact with air and water (or water vapor). If the air and water are isolated, the iron and steel can be prevented from rusting to a certain extent. Oiling, painting, plating wear-resistant and corrosion-resistant inscriptions on the steel surface and making corrosion-resistant alloys such as stainless steel can prevent steel from rusting.

4.Effective ways to protect metal resources are to prevent metal corrosion, recycle scrap metal, mine minerals reasonably and effectively, and find metal substittes.