Copper ion mobility in sphalerite activation

Migration of Cu from the surface into the bulk has been reported in the cas e of sphalerite. The phenomenon was examined here by X-ray photoelectron sp ectroscopy (XPS) and by determining the effect of time delay between Cu add ition and xanthate (collector) addition on collector adsorption and flotati on recovery. Delay time had no effect at pH 3 and 6but at pH 9.2, collector adsorption decreased after a time delay of 20 min. However, sphalerite rec overy was not affected in part due to a collectorless flotation response in duced by oxidation promoted by Cu. XPS measurements showed the surface Cu c oncentration decreased with time but no corresponding increase in sub-surfa ce concentration was detected. Addition of collector at zero delay time sho wed no decrease in the surface Cu concentration. These observations are att ributed to a portion of the adsorbed Cu being in a colloidal Cu(OH), form. With delay time, some of the colloidal portion is lost to solution resultin g in the decrease in surface Cu and collector uptake. The early addition of xanthate, by reacting with all forms of Cu present, prevents the loss. Cop per mobility does not seem to be a factor in flotation practice. (C) 2001 E lsevier Science B.V. All rights reserved.