New technology makes it easier to extract gold from e-waste

E-waste is the fastest growing solid waste category in the world. In 2019, 54 million tons of devices became trash – 21% more than five years earlier. Simple calculations show that roughly 7 kg fall on every inhabitant of the planet.

According to forecasts, by 2030, this indicator will reach 74 million tons, which means an almost two-fold growth in 16 years. It should be noted that telephones, laptops and televisions are predominant in the garbage, but these days electronics can be found even in sneakers, writes Forbes.

The most e-waste (almost 25 million tons) in 2019 was generated in Asia. America and Europe follow (13 and 12 million tons respectively). E-waste is also piling up in Africa and Oceania. If it continues to become cheaper, its quantity will increase rapidly in poor countries.

One of the reasons for the rapid accumulation of junk is the fact that mobile devices usually last only a few years. Then they become unusable or unable to cope with the growing demands for speed and memory. Since repairing and refurbishing a smartphone is comparable in price to buying a new one, the old one goes in the bin.


Processing

In 2019, only 17% of e-waste was collected and processed. All the rest are in landfills or burned in garbage plants along with their contained gold, silver, platinum, copper, etc.

According to conservative estimates, the total value of metals in e-waste in 2019 reached 57 billion dollars. According to the International Monetary Fund, this figure exceeds the nominal GDP of 112 out of 194 countries.

Currently, the manufacturing industry is booming in developing countries. In search of precious metals, people manually disassemble or shred electronics and burn them. Such dangerous substances as mercury and lead fall into the air, water, soil and body of self-made people. These are toxic elements that are released into the environment by electronics that accumulate in landfills. Often the latter are not specially equipped landfills, but just a pile of garbage somewhere.


The hardest materials on the planetSimply put, when we talk about stiffness, we mean the ability of a material to withstand varying degrees of external force


Why is e-waste both valuable and dangerous, yet hardly recycled?

Because their processing is unprofitable. If we divide $57 billion by 54 million tons, we get that each kilogram of e-waste contains about a dollar worth of precious metals. At the same time, the cost of processing this kilogram of high-tech equipment, and in view of all environmental norms, is rather even higher.

Experts have long debated what financial, legal and organizational measures are needed to remedy the situation. One of the key mechanisms is through extended producer responsibility. It obliges him or the importer of the goods to take care of the disposal or pay for its collection. In one form or another, this concept has been adopted in many countries around the world, but it aims to cover the whole world.

Another effective way for mass processing of waste is new technologies.


The Philosopher’s Stone?

Scientists from China and Great Britain have taken an important step in this direction. They have developed a simple and scalable technology to extract the most valuable component – gold – from e-waste.

The key element of this know-how is graphene, or two-dimensional carbon.

The co-author of the development is Andre Geim, the discoverer of graphene, who received the 2010 Nobel Prize in Physics for his discovery (together with Konstantin Novoselov).

Graphene is a flat sheet of carbon one atom thick. Such an unusual structure gives the material unique properties that are sought after in many fields, from water filtration to next-generation electronics. Often groups of foreign atoms, including oxygen, are embedded at the edges of the carbon lattice or inside it. This form of graphene is called oxide. Graphene oxide has been produced commercially for over a decade.


What is the new technology?

It looks very simple. The electronic waste is dissolved in acid and a sheet of graphene oxide is immersed in this solution. Without any additional reagents, catalysts or energy consumption, gold is deposited on graphene. The metal can then be isolated by simply burning the graphene.

One gram of graphene allows you to extract from a solution containing 0.1, 1 and 10 parts per million gold, respectively 690, 1180 and 1850 mg of gold. A noticeable release of the precious metal was observed even from a solution of 10 parts per trillion of gold, which is comparable to its content in wastewater.


The miracle material that can accelerate the fight against climate changeGraphene, which consists of multiple layers of carbon atoms bonded in a repeating hexagonal pattern, is the thinnest known material

If an old processor is dissolved in acid, not only the gold will be in the solution, but also 13 other metals in concentrations from one to hundreds of parts per million.
On the graphene will be deposited not only 90% of the gold contained in the solution, but also 99% of the tin, 53% of the chromium, 52% of the aluminum, 30% of the calcium, 26% of the lead, 7% of the nickel and 4% of the copper.

From the point of view of gold mining, these are unnecessary impurities. Tin or aluminum, for example, are too cheap to extract from the chips. Therefore, the authors somewhat complicate the technology by changing the acidity of the solution. They try two ways to do this. The first allows to extract 99% of the gold in the solution with slight extraction of copper and aluminum (less than 3%). The second extracts 93% of the gold and less than 2% of the nickel. The remaining metals are not isolated from the solution.

The authors emphasize that in the extraction of gold, graphene outperforms other materials both in terms of selectivity and the ability to extract the precious metal from low-concentration solutions.


The article is in bulgaria

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