THE EFFECT OF STARCH, AMYLOSE AND AMYLOPECTIN ON THE DEPRESSION OF OXI-MINERALS

In the present study microflotation tests were performed on pure mineral systems involving calcite, apatite, quartz and hematite. For the two first minerals sodium oleate was employed as collector and for the two latter the collector chosen was dodecylamine hydrochloride. Purified potato starch amylose and amylopectin (supplied by B.D.H.) and tapioca starch (commercial grade, from Thailand) were used as depressants in all systems. With the exception of hematite, all other minerals were depressed by the polysaccharides in the following decreasing depression order: tapioca starch (made up of approximately 17% amylose and 83% amylopectin), amylopectin and amylose. For hematite, amylopectin showed stronger depression than tapioca starch and amylose. Another important finding refers to the great differences observed for the ratios of collector to depressant concentrations, which were shown to vary from 1 to 11 for quartz to 3 to 1 for calcite (for a constant depressant concentration of 10 mg/l).