Acid dissolution of mine waste – a new environmentally friendly way to extract metals

New research shows that magnesium and other metals in mine waste can be solubilized and recovered thanks to acid-producing bacteria. Researcher Nathan van Wyk believes this method has great potential to reduce environmental pollution, extend the life of mines and provide raw materials for industry.

Each year, more than 3 billion tons of metals are produced for use in a variety of products. However, the metal content of ores is decreasing due to development, making the metals more difficult to obtain. As a result, metal prices have increased and hazardous waste has increased. Additionally, there is an increasing demand for so-called rare earth elements, which are often present in very low concentrations and can generate large amounts of mining waste.

Mine waste is often disposed of in large fields at mines. Metals in waste can leach into groundwater, windblown fine waste can spread contaminants, and some chemicals used to extract metals can also cause contamination. This is an environmental hazard because it can cause But this waste is also an opportunity.

The waste still contains significant amounts of several useful metals. Therefore, if we can extract metals from waste, we can reduce environmental pollution and produce more raw materials, says ecology researcher van Wyk.

acid dissolution

In his doctoral thesis, Van Wyk investigated how to extract metals from waste using acids produced by bacteria. The wastes he investigated were primarily bauxite residues, minerals containing aluminum and used in aluminum production, and some wastes resulting from magnesium production.

Studies have shown that acids extracted nearly 100% of magnesium from magnesium-rich waste. And as for the bauxite residue, some metals were extracted by acid. 68% of aluminum, 80% of calcium, 59% of titanium, and some rare earth elements were extracted, and 42% of yttrium was also solubilized.

“Acid dissolution of mine waste is a promising way to utilize valuable resources. It reduces the amount of waste, protects the environment, generates raw materials for industry and extends the life of mines.” Applying this method, while advancing ‘green’ technology, has many benefits rather than just leaving waste behind,” says van Wyk.

Debris can be used as concrete

A positive advantage of this method is that the residual material can be combined with inexpensive additives to produce a type of quick-hardening concrete.

“The waste from the process can be used to produce construction materials such as concrete. Our concrete does not need to be calcined (an energy-intensive process) during production because the energy has already been consumed. There is no.

“More than 7% of all energy used by industry worldwide is used in the production of concrete and cement. Therefore, by utilizing this waste, we can achieve zero solid waste from magnesium mining. , we can reduce global energy consumption to some extent,” says Van. Wike.

Van Wyk believes that the acid dissolution method will require some development to achieve large-scale production, but that laboratory-scale research has revealed a sophisticated and effective process that will We hope that this method will be adopted in the mining industry.

“We have developed a new technology that has several applications within the mining industry. Through this technology, some mining operations can be transformed into zero-waste facilities,” van Wyk said. I say.