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Aluminum can be more present in your daily life than you think

Image: Bernard Hermant in Unsplash

Aluminum is one of the most abundant, important and present metals in modern society. If you look around, it's going to be hard to find an object that doesn't have at least one part made of aluminum. But after all, what is aluminum? Get to know the environmental impacts of aluminum, the reasons why it is so used, learn how to recycle it and what its properties are.

Aluminum

the chemical element Al, aluminum, when pure, has the form of a silver metal, light and odorless. Aluminum is considered the third most abundant chemical element in the earth's crust and the most abundant among metallic elements. However, it is not found in metallic form as we know it, but in various minerals and clays.

Aluminum extraction process

The main raw material of metallic aluminum is Alumina. Alumina is extracted from a class of rocks called bauxite through the Bayer process. It is estimated that the world reserves of bauxite total about 34 billion tons - Brazil has 10% of this total (around 3.6 billion tons).

After obtaining alumina, which is an aluminum oxide (Al2O3), it is necessary to obtain pure metallic aluminum. This happens through a process called electrolysis, in which an electrical current passes through the alumina, causing it to transform into metallic aluminum, the primary aluminum.

Watch the video that explains in a simplified way the production of aluminum, from the extraction of bauxite.

Aluminum properties

When aluminum is presented in a pure metallic format, it has some characteristics that allow its application in several areas. Among its properties are:

• Strength and high melting point (660°C);
• Low density (almost four times lighter than metallic copper);
• High corrosion resistance;
• Good electrical conductivity (about 60% of the conductivity of copper, being suitable for higher volume fixed installations, such as electrical transmission installations, as it is lighter and cheaper);
• It has the ability to reflect light;
• Easy to be processed and molded;
• Waterproof, odorless and non-flammable (except powdered aluminum);
• Possibility of adding other elements to the material, thus forming alloys with varied properties;
• Extremely abundant in the environment;
• 100% Recyclable.

Aluminum, not only in its metallic form, is extremely used in several areas, such as in constructions, materials, ceramics, industrial processes, food, pharmaceuticals, cosmetics, water treatments, packaging, vehicles, domestic utensils and airplanes, among others.

Aluminum is also very important to the gemstone market. Ruby, Sapphire, Garnet (garnet), jade and topaz have aluminum in their compositions.

Aluminum was and is very important for the development of modern society. Despite being considered a practically inexhaustible natural resource, its constant and growing exploitation affects the environment, in addition to presenting risks to human health.

Profile of the Brazilian aluminum industry

Currently, Brazil occupies the fourteenth place in the ranking of countries that produce the most primary aluminum and is in fourth place among the largest alumina producers in the world. In addition, the Brazilian aluminum industry has a significant share of the country's GDP, representing around 4.9% of the Industrial GDP.

Environmental impacts of aluminum

Energy consumption

Due to the fact that aluminum is a very stable metal, the energy required for its production is extremely high, reaching 16.5 kWh for each kilo of aluminum produced. Translating this data: a kilo of aluminum produced by means of alumina consumes energy, on average, to keep a computer running for 8 hours, every day, for a month.

For each ton of aluminum produced in Brazil, the industry consumes an average of 14.9 megawatt/hour (MWh) of electricity per year. This amount of energy represents 6% of all electricity generated in the country. The energy used to transform bauxite and alumina into aluminum is such that this branch of industry leads the ranking of the largest industrial consumers of electricity in the country.

Thanks to this extreme energy consumption, the industrial plant that will transform alumina into aluminum must have exclusive power generation stations for its production. Depending on the type of energy conversion, this can have even more impacts on the environment. Often, these power stations are hydroelectric, which, contrary to what many people think, are not considered a totally “clean” energy source.

• What is hydropower?

Emission of polluting gases

The production of aluminum, from the extraction of bauxite to the transformation of alumina into aluminum, generates some pollutant gases, such as carbon dioxide (CO2) and perfluorocarbons (PFCs). The frequent emission of these gases into the atmosphere contributes to the greenhouse effect and intensifies the global warming process. Importantly, PFC gases are 6,500 to 9,200 times more powerful than carbon dioxide (CO2) in creating the greenhouse effect.

• Carbon equivalent: what is it?

red mud

Red mud is the popular name for the insoluble waste generated in the production of alumina during the clarification step of the Bayer process. The composition of the red mud varies depending on the composition of the bauxite used in the process. The most common elements present in red mud are iron, titanium, silica and aluminum which cannot be successfully extracted.

Red mud is made up of very fine particles and is extremely alkaline (pH 10~13). Due to the high pH, ​​this mud can cause burns on contact with the skin. Literature data show that a variation between 0.3 and 2.5 tons of red mud is generated for each ton of alumina produced. Each year, around 90 million tons of this waste are produced in the world. Its disposal needs to be done in adequate places, generally disposal ponds, built with high cost techniques, which make it impossible to leach its components and the consequent contamination of surface water bodies and groundwater.

THE Environmental Protection Agency (EPA), the US Environmental Protection Agency, does not consider red mud to be a toxic waste. However, since it is an extremely rich residue in metals and has a very high alkalinity, the slurry can have a very strong influence on the environment, altering its properties and stability.

As in the case of iron ore tailings dams, tailings from aluminum production can also cause serious accidents. In 2010, a red mud spill left nine dead and a scene of devastation in a village in Hungary. Check out the result of this accident in the video.

The particles present in the red mud are very fine, which makes them have a vast surface area, a very interesting characteristic for technological applications. Several researches are carried out to search for possible uses of red mud, such as in the ceramic industry, civil construction, surface treatment and effluent treatment, among others.

Aluminum recycling

Aluminum is considered a 100% recyclable material, as it does not degrade in the recycling process. If a kilo of aluminum is recycled, theoretically a kilo will be recovered. In addition, to recycle a ton of aluminum, it takes only 5% of the energy that would be needed to produce the same amount of primary aluminum, ie, recycling aluminum saves 95% of electricity. Thus, Brazil has a prominent position in the list of countries that most recycle aluminum cans.

Among the advantages of recycling aluminum are:

• Ability to be recycled infinite times without losing its properties;
• Recycling a kilo of aluminum consumes only 5% of the energy needed to produce a kilo of aluminum from scratch;
• Each ton of recycled aluminum saves nine tons of CO2 (each ton of CO2 is equivalent to driving around 4800 km);
• Each ton of recycled aluminum preserves five tons of bauxite.
• Each recycled aluminum can saves enough energy to leave a TV on for 3 hours.

The aluminum recycling process basically consists of heating until it is completely melted, when the aluminum becomes liquid. It is then put into molds for ingot generation and then cooled until solidified. For the recycling of cans, first an inspection is necessary to remove papers, plastics and any materials other than aluminum. After inspection, the cans are squashed to take up less space and be “melted” quickly.

There are some legends about recycling aluminum. One of them concerns the composition of the ring. According to the story, if you filled a PET bottle of one or two liters with the rings from the cans, it would be worth more than 100 reais, as the ring would contain precious metals, such as gold or silver. This is false information. In fact, the ring is worth less than the can itself, as its composition is low in aluminum. That's why some institutions receive large quantities of rings and sell the material as a set, using the money to buy wheelchairs. This is another of the stories that circulate and generate doubts, but it is not a legend. In fact there are projects engaged in this type of donation.

• Learn more in the article: "Can seal: remove or not remove from aluminum can".

Aluminum in your daily life

Aluminum is very present in the daily lives of society. Currently, it would be impossible to maintain the pace of industrial development without this element. It makes up a large part of the objects we use and consume: soda cans, antiperspirants, bulletproof glass, water purification mechanisms, airplane wings, as well as kitchen utensils such as cutlery and pans. The electronic equipment you are using to read this text is sure to have aluminum in some of its parts.

In the case of food, aluminum reacts with air and forms a protective layer with oxygen, preventing the transfer of aluminum to food. It is noteworthy that it is not recommended to sand or wash the inside of aluminum pans with the rough part of the sponge, as this can break this protection, leaving the aluminum exposed. If this has occurred, boil water for a few minutes, remove the water and, without drying the pan, heat it until it is completely dry.

toxicity

Aluminum is the only abundant element in nature that has no vital function for any biological system of the organism, which is strange from an evolutionary point of view, since nature generally chooses the most abundant elements as vital for biological systems. “We don't have any evidence that any organism actively uses aluminum for any beneficial purpose”, comments Christopher Exley, professor of bioinorganic chemistry and expert in aluminum ecotoxicology, from Keele University in the United Kingdom.

The US Food and Drug Administration (FDA), the Brazilian Aluminum Association (ABAL) and the European Aluminum Association (European Aluminum) claim that aluminum has no toxicity for healthy people, since the metal has low intestinal absorption - the small part that is absorbed enters the circulatory system, being later eliminated by the renal system.

However, people with impaired kidney function or chronic kidney failure and premature babies can accumulate aluminum in their bodies. In bone tissue, metal "exchanges" with calcium, causing osteodystrophy, and in brain tissue it can cause encephalopathy. The FDA classifies aluminum salts in foods and vaccines as "generally recognized as safe (GRAS)". In some vaccines, the FDA considers aluminum salts to be additives that enhance the desired effects.

Some scholars and scientists do not agree with these statements and try to prove the direct link of aluminum with various reactions and diseases. Although to date there is no direct proof, there is much evidence linking aluminum to various allergies, breast cancer and even Alzheimer's. Studies show that the presence of aluminum is much higher than normal in these cases (the normal thing would be not to have aluminum), but no study has proven that aluminum is directly related to the onset of these diseases, or if the high levels of aluminum in these patients they are a consequence of the disease.