Change of carcinogenic chrysotile fibers in the asbestos cement (eternit) to harmless waste by artificial carbonatization: Petrological and technological results

摘要

Asbestos cement materials, mainly the eternit roof ceiling, being widely applied in the past, represent a serious environmental load. The solar radiation, rain and frost cause the deliberation of cement from the eternit roofing and consequently the wind contaminates the surrounding area by the asbestos (chrysotile) fibers. In combination with other carcinogens (e.g. smoking), or at reduced immunity of a man, they may cause serious respiratory diseases and lung cancer. The article presents the procedure and experimental results of artificial carbonatization, applied in the asbestos cement (eternit). The wet crushed and pulverized asbestos cement was thermally modified at 650 ℃ and then the chrysotile fibers easily and completely reacted with the mixture of CO_2 and water, producing new Mg-rich carbonates - hydromagnesite and magnesite: 2Mg_3Si_2O_5(OH)_3 + 5CO_2 + nH2O → Mg_5(CO_3)_4(OH)_2 · 4H_2O + MgCO_3 + 4SiO_2 · nH_2O ; n = 3 ÷ 9thermally modified chrysotile hydromagnesite magnesite in amorphous phase Applying this methodology, the asbestos-bearing waste can be stabilized and environmentally friendly permanently deposited. Finding a way of neutralizing of extreme pH values (around 12) at large eternit dumps represents also an asset of presented research. Simultaneously, the artificial carbonatization of chrysotile asbestos, applying CO_2, offers an alternative way for permanent-liquidation of a part of industrial CO_2 emissions, contributing to multiple benefit of this methodology.