Selective flotation of scheelite from calcite using Al-Na2SiO3 polymer as depressant and Pb-BHA complexes as collector

Abstract In previous studies, by regulating the Pb/BHA ratio and pH, lead complexes of benzohydroxamic acid (Pb-BHA) have been proven to be selective for the separation of scheelite from calcium minerals. In this study, sodium silicate (Na 2 SiO 3 ) and Al-Na 2 SiO 3 polymer were used as depressants for the further separation of scheelite from calcite. Flotation results indicated that both scheelite and calcite were depressed by Na 2 SiO 3 , while Al-Na 2 SiO 3 polymer gave good selectivity. The depressing ability of Na 2 SiO 3 for calcite was significantly improved due to the formation of some Al-Na 2 SiO 3 species with aluminum ions, while the reverse was true for scheelite. Zeta potential results indicated that both colloidal Na 2 SiO 3 and Al-Na 2 SiO 3 particles were negatively charged and difficult to adsorb on the negative scheelite surface through electrostatic attraction, especially for Al-Na 2 SiO 3. X-ray photoelectron spectroscopy analysis results showed that the Al-Na 2 SiO 3 adsorbed amount on the scheelite surface was less than the Na 2 SiO 3 adsorbed amount, while the reverse was true on the calcite surface. Binding energy analysis results indicated that calcium cations of scheelite and calcite surfaces could bond to oxygen atoms of Na 2 SiO 3 /Al-Na 2 SiO 3 through chemisorption. However, compared with Na 2 SiO 3 , Al-Na 2 SiO 3 showed weaker chemisorption on the scheelite surface, but adsorbed more powerfully onto the calcite surface. Therefore, Al-Na 2 SiO 3 showed excellent selectivity for scheelite and calcite, which has been successfully applied at the Shizhuyuan mine.