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Extraction of magnesium from the mechanochemically activated talc samples was conducted at 298 K and 333 K using 0.5 mol/dm3 H2SO4 or 0.5 mol/dm3 HCl solutions. Talc is transformed from crystalline state into disordered one by dry grinding within about 30 minutes in a planetary ball mill. The structural change is accelerated by the prolonged grinding. This structural change means that the environmental structure around magnesium in the talc crystalline is drastically changed by grinding, while silicon tetrahedra remain unchanged. Therefore, the disordering of the structure leads to an easy magnesium extraction and preferentially by the acid solutions. 30 minutes leaching is enough time to extract magnesium from the talc samples. The magnesium yield is significantly increased to about 40 % as the grinding progresses up to 30 minutes. Leaching of the 180 minutes ground sample using the H2SO4 and HCl solutions of 298 K enables us to extract magnesium at about 70% and 63%, respectively. On the contrary, the yield of silicon is supressed below about 3 %.

Leaching of chalcopyrite concentrate having specific surface area of about 3 m2/g in 0 .5 mol/dm3 HCl solution was conducted at 333 K using hematite (Fe2O3) and ferric chloride (FeCl3) powders , respectively. The leaching of the concentrate with Fe2O3 powder permits to achieve about 75 % copperextraction within 24hours, while about 65 % copper is extracted by the leaching with FeCl3 powder. Theyield of copper in the leaching with Fe2O3 powder is twice or more higher than that without the promoters . High copper extraction can be achieved when much of the elemental sulfur is formed on the solid residue after the leaching . Especially, the presence of Fe2O3 powder gives us the elemental sulfur precipitates more than that of FeCl3 powder . Therefore, Fe2O3 can be an effective promoter in the leaching of chalcopyrite concentrate using HCl solution .