Dehydroxylation of the serpentinite before its chemical treatment

摘要

The thermal treatment of serpentine from the locality Ljeskovac, Croatia, was studied in order to reach optimum characteristicsfor the inorganic acid leaching process. The fine and pure hydromagnesite and silica powder are main final products of the serpentineleaching. The dominant mineral constituent of used serpentine was lizardite Mg3[Si2O5](OH)4. The first step was milling of serpentineto the fine powder with the particle size less than 175 μm, followed by heating at the temperature of crystal lattice degradation. FromTG and DTA curves, the optimum parameters were found: the heating time of 180 minutes and the temperature of 660 °C. Afterthe serpentine thermal decomposition, a Mg and Si mixed oxide is formed rather than separated MgO and SiO2 phases. Only the freeoxides allow the adequately successful acid leaching with pure and high quality magnesium oxide and silica powder as final products.