The activation of magnesia in serpentine by calcination and the chemical utilization of asbestos tailings—a review

CIM Bulletin, Vol. 73, No. 824, 1980

M. NAGAMORI, A.J. PLUMPTON and R. Le HOUILLIER, Centre de Recherches Minérales, Ministere de I'Energie et des Ressources, Gouvernement du Quebec, Sainte-Foy, Quebec

Asbestos tailings are a typical serpentine, hydrated magnesium silicate, consisting primarily ofantigorite and a few per cent of unrecovered fibrous chrysotile. Serpentine has unique thermal properties in that dehydroxylating calcination at 600 to 700°C can yield an amorphous structure in which most of the magnesia is liberated from the original bond with silica and thereby rendered chemically active. The amount of activated magnesia can be quantified by selective leaching with a weak acid such as acetic acid. Many wet processes have been proposed to extract magnesium values from calcined or natural serpentine by means of various acids and their ammonium salts. However, the only commercial utilization of serpentine today is found in dry processes such as the production of fused magnesium phosphate fertilizer.The present paper reviews the physical chemistry of the dehydroxylation of serpentine and also various wet and dry processes in order to provide a general view regarding the chemical transformation of asbestos tailings.
Keywords: Industrial minerals, Asbestos tailings, Magnesia, Serpentine, Calcination, Decomposition, Leaching.