Effect of bleaching powder (ClO−) on pulsating HGMS of chalcopyrite from arsenopyrite

Abstract

High gradient magnetic separation (HGMS) is a potential method of separating chalcopyrite from copper-arsenopyrite co-flotation concentrate. However, during the co-flotation process the addition of bleaching powder (ClO−), which has been a common depressant for arsenopyrite, deteriorates their separation selectivity in the subsequent HGMS process, and until today this effect of ClO− is unknown to people. Pulsating HGMS (PHGMS) technology was used to separate a pure chalcopyrite-arsenopyrite mixture containing 16.85 % Cu and 22.44 % As. It was found that when the concentration of ClO− was increased from 0 % to 10 %, the Cu recovery in magnetic chalcopyrite concentrate was increased from 79.07 % to 88.69 %, with its Cu grade decreased from 20.25 % to 17.65 %; and, the As recovery in the concentrate was significantly increased from 26.82 % to 65.50 %, with As grade increased from 9.92 % to 18.83 %. The X-ray photoelectron spectroscopy (XPS) and electrochemical analysis on the chalcopyrite concentrate revealed that ClO− preferentially oxidized the iron sulfides in arsenopyrite to iron oxides; and, the Crystal Field Theory (CFT) analysis revealed that the magnetic moment of Fe in arsenopyrite was increased from 0 to 5.92B.M after these Fe atoms reacted with ClO−, and the number of single electrons in Fe was increased from 0 to 5. As a result, the magnetic susceptibility of arsenopyrite was increased and more arsenopyrite particles were separated into chalcopyrite concentrate during the PHGMS process, deteriorating the separation selectivity of chalcopyrite from arsenopyrite.