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mining engineering

The salvation of the mineral

Process reduces the dispersion of asbestos fibers and avoids diseases caused by handling the product

Much used over the last few decades, asbestos has become a serious public health problem, when used as a raw material in industrial products like roofing, water tanks and components of automobile brakes. The dust that originates from this mineral has caused lung diseases in workers who have manipulated this material, both in factories and in the mines. Banned or used with restrictions, in many countries, asbestos may get a break from a new process that inhibits the dispersion of particles from its fibers. The novelty comes from researchers of the Photonic Materials Group from the Chemistry Institute (IQ) of the São Paulo State University (Unesp), in Araraquara. “We used a substance called coacervate, formed from an inorganic polymer of sodium polyphosphate and calcium chloride. It is like a gel, and it can be spread over the surface of the asbestos to coat and immobilize its fibers, in such a way that they get suspended in the air during handling”, explains Professor Younes Messaddeq, the project’s coordinator.

Developed in a similar way as others that are also arising in Europe, the product is applied to the internal walls of the mines with brushes or sprays, before the mineral is extracted, which lessens the dispersion of fibers and particles. Applying this gel, though, is not enough to avoid problems with fibers during the transport and manipulation of asbestos, because when they are dry, they start dispersing once again. To be completely immobilized, heat treatment is needed, also developed by the researchers from Araraquara, which has resulted in a patent, financed by FAPESP and filed with the National Institute for Industrial Property (INPI).

The method consists of treating the asbestos fibers with a solution of sodium polyphosphate at different temperatures, in a way that innovates over the similar techniques developed abroad. The current processes for destroying the fibers of this mineral call for high temperatures (between 1,800 and 2,000º C), at a cost of around US$ 1,200.00 per ton. By the new method, they are destroyed at 300º C. “This reduces costs by 75%, compared with the traditional process”, says Messaddeq. “In Europe, in a similar process, researchers reached 1,200º C.”

Adopting the complete process may result in new materials for the building industry. “They are vitroceramics (crystallized materials that resemble glass in their visual aspect) with a high thermal and mechanical stability, which keeps the main qualities of asbestos, although with the fibers immobilized”, says Messaddeq. Another advantage is that the technique may be used in recycling products made with asbestos, such as roofing and water tanks, besides being useful in immobilizing other inorganic fibers that offer risks to health when inhaled, like glass fiber.

The Photonic Materials Group began to work in this area in 1999, after a debate with French researchers, during an international event on special glasses. The first work on this theme was a postdoctoral project of chemist Marco Antonio Utrera Martines, which opened up a new line of research for the group. The postdoctoral studies by Veronique Andries and studies for a master’s degree by Daniela Grando were also carried out with scholarships from FAPESP. In the same area, with a scholarship from the National Council for Scientific and Technological Development (CNPq), Francisco Audísio Dias Filho is working towards his doctorate. Martines’s project was carried out between 1999 and 2001, with the participation of Pierre Vast, from the Lille University, In France, who produced the first researches with coacervate.

With the new technique, workers will be able to stop inhaling the particles of the fibers that come adrift from the mineral and over the course of time build up in the lungs and cause such diseases such as asbestosis and lung cancer. In the case of asbestosis, the fibers are lodged in the pulmonary alveoli. To defend itself, the organism deposits over them a protein similar to cement, that heals the alveolus by preventing it from filling with air. This process, which is repeated over the years, can make the lungs fibrous and without any elasticity, resulting in respiratory difficulties.

Besides being cheap and easy to extract, asbestos has some special physical and chemical properties: high mechanical resistance, low thermal conductivity, resistance to chemical products, and stability at different levels of acidity, besides providing for electrical and acoustical insulation and protecting against fire. For presenting this set of properties, it was a raw material used intensively in the 20th century in many industrial products. Nowadays, asbestos has been banned from practically the whole world, although it is still used, with restrictions, in several countries, such as China and Russia.

Laws modified
In Brazil, the states of São Paulo, Rio de Janeiro, Mato Grosso do Sul and Rio Grande do Sul approved projects of law banning the product in public works to start with. But the Federal Supreme Court (STF), in a decision taken on 8 May this year, judged as unconstitutional the state laws that prohibited trading in and using asbestos in São Paulo and Mato Grosso do Sul. The São Paulo law laid down that importing, extracting, processing, trading, manufacturing and installing materials containing asbestos would be prohibited in the state, from January 2005 onwards. The lawsuit that resulted in the decision of the STF was taken out by Goiás, the state where the only mine in operation in Brazil is to be found, at Cana Brava, in the municipality of Minaçu. With it, Brazil occupies the place of fourth largest producer in the world, behind only Russia, Canada and China.

The Project
Process for Immobilizing and Destroying Asbestos Fibers (nº 01/08350-3); Modality Intellectual Property Support Program (PAPI); Coordinator
Younes Messaddeq – IQ-Unesp; Imvestment R$ 6,000.00