Embrapa studies Amazon tree to replace mercury in gold mining – 05/22/2023 – Vaivém

The use of mercury in gold extraction may have its days numbered. Research shows that leaves from a plant from the Amazon region could be the solution. In addition to solving a series of problems left by the use of mercury, the plant will recompose areas removed by the mines themselves.

Researchers from Embrapa, a miners’ cooperative, three universities and even the jewelry sector are focused on this project, which aims to obtain an extract from the leaves of the balsa tree (“Ochroma pyramidade”). The tree, leafy, with fast growth and that can reach 30 meters, has several popular names, such as balsa stick, raft stick, hare paw and others, depending on the region of the country.

“We are not inventing the wheel, but trying to improve it”, says Marina Morales, a researcher at Embrapa Florestas and responsible for conducting the studies. The speech makes sense, because the use of the balsa wood leaf already occurs, although in an artisanal way, in the Chocó region, in Colombia.

What is being sought now is to obtain a bioextract, taken from the leaves of the tree, so that it can be a bioextractor of gold and, if competitive, a possible substitute for mercury. In Colombia, the plant showed viability as a substitute for mercury in gold extraction, when done in the open.

Morales still foresees many challenges within the laboratory. The path traced by the group, however, has great chances of obtaining a production in scale. The research is being well accepted, but she believes that she will still have to take a lot of people out of their comfort zone as the project unfolds.

The first part of the study, which began in 2020, aimed to increase the potential of what is already being done, with the chemical characterization of the leaves of the balsa tree. The objective is to look for an extractor that is more competitive than mercury, or at least the same, says the researcher.

This year, the study enters the second phase, with the aim of improving the bioextract. Through Coogavepe (Cooperativa dos Garimpeiros do Vale do Rio Peixoto), in the region of Peixoto de Azevedo (MT), samples will be collected for comparison between the traditional extraction with mercury and that with the bioextractor from the leaf of balsa wood . The cooperative brings together 150 small-scale mines released for mining.

The extraction of gold in the open sky is done by removing the soil and using jets of water to separate the ores, generating the “concentrate”. The next step is to use mercury to separate gold from other minerals.

In this last step, the researchers are going to use the balsa wood bioextractor, instead of mercury. In the first phase of the project, four possible formulations were determined, which will be tested and improved to see which best replaces mercury.

The Embrapa researcher says that the objective is to have a competitive non-toxic bioextractor, so that it can be used not only by hand but also by small mining, with indication of toxicity and cytotoxicity analyses.

The tests on the new formulations will indicate the toxicity of the product. The performance of the bioextractor on small crustaceans will be measured and chemically scanned to assess possible interference. Cytotoxicity measures the effects of the product in both animal and plant models.

The bioextractor, in its final stage and already improved, will be put in contact with plant roots —in this case, the onion— to check for any aberrations. In the animal model, the test will be on fish.

Fine adjustments are normal in the course of a survey, but Morales believes that from 2025 onwards the laboratory phase will move on to tests in small-scale mines. In an ideal scenario, a new stage of the process would be undertaken, that of producing balsa wood trees in an area close to the mines.

The proximity of tree planting to the mines has several positive factors. It allows the assembly of a biofactory in the region itself, avoiding the transport of leaves and reducing costs. The planting serves to revegetation of the areas already used by the mines and for the commercial exploitation of the wood of balsa wood. Lightweight and resistant, wood has many uses, ranging from propellers for wind power generators to handicrafts and toys.

The introduction of balsa wood in gold extraction will bring a series of benefits, ranging from protecting the health of workers and the riverside population to greater environmental and economic sustainability.

The use of mercury in specific handling areas in legal mining can reduce the release of this metal into the environment, which does not occur in illegal mining. The biggest problem with mercury is that it is cumulative, says the researcher. It goes down the chain and brings serious risks to health and the environment, and may lead, in the human case, to a neurodegenerative syndrome.

In addition to Embrapa Florestas, Embrapa Agrossilvipastoril, Coogavepe, UFMT (Federal University of Mato Grosso), UEM (State University of Maringá) and Unicamp (State University of Campinas) participate in the extract development studies. The preliminary study was financed by Raquel de Queiroz, jewelry designer.