LEACHING OF SILVER FROM MECHANOCHEMICALLY PRETREATED OF COMPLEX SULPHIDE CONCENTRATE
Abstract
The hydrometallurgical processing of complex concentrates represents an ecologically attractive alternative with respect to classical pyrometallurgical technologies. The intensification of the thiourea leaching of silver from a silver-bearing Peruvian concentrate (deposit Casapalca) using mechanochemical alkaline leaching as the pretreatment step was investigated. The leaching of as-received concentrate with the acid thiourea solution afforded only 5 % Ag into leach. The mechanochemical pretreatment resulted in up to 71 % of tetrahedrite degrading and an increase in the specific surface area of the concentrate from the original value 0.26 m2g-1 to a maximum value of 15.73 m2g-1. These physico-chemical changes in the concentrate as a consequence of mechanochemical pretreatment had a pronounced influence on the subsequent silver extraction. The mechanochemical pretreatment of the concentrate was performed in attritor using the method of experiment design by application a 22 factorial experiment extended by use of a second order polynomial for the adsorption specific surface area response. These chosen parameters of the attritor as variables were studied time of milling and weight of the sample. The optimum results obtained by mechanochemical pretreatment and subsequent leaching of the concentrate with thiourea were achieved by using milling time 30 min and weight of sample 30 g. In this case the 99 % recovery of Ag was reached already after ten minutes of leaching.
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