Tailings waste from a mineral processing plant of a fluorite and galena mine is characterized by the release of F together with heavy metals such as Zn, Pb, Cd and Cu. Leaching tests carried out on the tailings waste show that the concentrations of F and Pb exceed the legal Italian limits for characterisation as inert material. To avoid the risk of spreading to areas not directly affected by mining activities and to obtain inert products suitable for reuse as construction material or as backfill in the mine, stabilization has been investigated using potassium dihydrogen phosphate singly or combined with calcium hydroxide. In order to assess the effectiveness of the additives for the stabilization of pollutants, reactor batch tests have been carried out by adding different proportions of these additives to the tailings material. The mixture, with a liquid/solid ratio equal of 10, was agitated for 24 hours and, at the end of the test, the eluate was filtered through a 0.45 µm membrane and analysed. The results show that the use of potassium dihydrogen phosphate in combination with calcium hydroxide allows for the immobilization of F and Pb by formation of stable or poorly soluble compounds. In addition, solidification of the thus inertized material using 10 % cement produces a material of which the leachate is in accordance with the regulatory limits for discharge in groundwater, allowing for its use as backfill in the mine.
Stabilization of mining tailings containing fluospar and heavy metal using potassium dihydrogen and calcium hydroxide
SERCI, ANTONELLO;
2013-01-01
Abstract
Tailings waste from a mineral processing plant of a fluorite and galena mine is characterized by the release of F together with heavy metals such as Zn, Pb, Cd and Cu. Leaching tests carried out on the tailings waste show that the concentrations of F and Pb exceed the legal Italian limits for characterisation as inert material. To avoid the risk of spreading to areas not directly affected by mining activities and to obtain inert products suitable for reuse as construction material or as backfill in the mine, stabilization has been investigated using potassium dihydrogen phosphate singly or combined with calcium hydroxide. In order to assess the effectiveness of the additives for the stabilization of pollutants, reactor batch tests have been carried out by adding different proportions of these additives to the tailings material. The mixture, with a liquid/solid ratio equal of 10, was agitated for 24 hours and, at the end of the test, the eluate was filtered through a 0.45 µm membrane and analysed. The results show that the use of potassium dihydrogen phosphate in combination with calcium hydroxide allows for the immobilization of F and Pb by formation of stable or poorly soluble compounds. In addition, solidification of the thus inertized material using 10 % cement produces a material of which the leachate is in accordance with the regulatory limits for discharge in groundwater, allowing for its use as backfill in the mine.
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