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Foaming cleaner - Spray-on treatment clears asbestos

点击量:   时间:2017-05-13 01:02:12

By Andy Coghlan ASBESTOS can now be eliminated from buildings by simply spraying foam on it. Acidic chemicals in the foam destroy the asbestos, converting it into harmless minerals. Chemists who developed the foam believe it will cut the cost of decontaminating buildings by as much as 75 per cent, because the process is less labour-intensive than the traditional technique of removing asbestos mechanically. “The building is not out of action for so long,” says Leon Petrakis, head of the team at the Brookhaven National Laboratory in Upton, New York, which developed the foam with W. R. Grace, a chemicals company in Boca Raton, Florida. An added advantage is that the original material need not be replaced, since the converted coating is fireproof. In the US alone, the Environmental Protection Agency estimates that at least 730 000 public and commercial buildings and 100 000 schools still need treating. This could cost up to $150 billion using conventional methods. The new treatment works on coatings containing asbestos that have been spread on structural beams and columns in buildings. These coatings, which are normally a few centimetres thick, contain up to 15 per cent by weight of chrysotile, or white asbestos—the most common type of asbestos. The remainder is an inert mixture of gypsum and a silicate. At present, the fireproofing has to be scraped off after sealing off the area in depressurised tents to prevent fibres from escaping. The asbestos is then disposed of in special landfill sites and the building fireproofed. The chemical method is simpler and safer—the workers simply spray on the foam. “It looks just like shaving cream,” says Petrakis. Over the next two days, the foam soaks into the fireproofing, selectively attacking and destroying asbestos fibres. Petrakis will not disclose the precise ingredients of the foam until patents are granted, but he says the main components are acids and fluoride ions. Asbestos fibres are made of hollow tubes built up from magnesium and silicon oxides. “We attack the structure where there are magnesium oxide and silicon oxide units sharing single oxygen atoms,” says Petrakis. Once the tubes have been destroyed, the oxides are converted into inert minerals that blend with the original fireproofing material. Petrakis says workers are unlikely to breathe in fibres while using the foam. “It’s such a gentle application,” he says. In tests, levels remained well below the federal safety limit of 0.1 fibres per cubic centimetre of air. Independent tests on the treated material by researchers at the Underwriters Laboratories in Northbrook, Illinois, showed it was just as effective at fireproofing beams and columns as asbestos. Grace is preparing to license the treatment to companies that strip asbestos out of buildings. “We would supply the chemicals, as well as pumps, a mixing unit, air to blow up the foam and nozzles to dispense it,” says Len Ciesluk, the commercial project manager at Grace. Terry Jago, chief executive of the Asbestos Removal Contractors’ Association in Britain,