Zeta potential of the surface of ultrafine sulfides and floatability of minerals

The results of experimental investigations into the zeta potential of ultrafine sulfides (chalcopyrite, tennantite, galenite, sphalerite, pyrite, and pyrrhotine), the floatability of monomineral fractions of sulfides of the floatation coarseness (–0.1 + 0.05 mm) in a mechanical flotation machine, and the floatability fine particles of sulfide (–0.044 + 0.010 mm) in the Hallimond tube are presented. The preparation procedure of ultrafine powders and sulfhydril collectors to measure the zeta potential is presented. Zeta potentials of the surface of mineral particles and insoluble forms of sulfhydril collectors are investigated in the pH range from 2.0 to 12.5 (an acidic medium was formed by using H₂SO₄ and basic one by using NaOH or Ca(OH)₂), and various values of zeta potentials are found for sulfides in the sodium hydroxide and lime medium. Zeta potentials for all sulfides are negative in the NaOH medium at pH > 9.5, they are positive (1–18 mV) in the Ca(OH)₂ medium at pH > 11, and zeta potentials for chalcopyrite are positive in the studied range \(p{H_{Ca{{\left( {OH} \right)}_2}}}\) 9.0–12.5. The values of the isoelectric point in the medium of sulfuric acid and sodium hydroxide are as follows: for chalcopyrite—pH 6.5 and 8.8, for tennantite—pH 3.0, for sphalerite—pH 5.1 and 6.4, for pyrite—pH 3.1 and 8.9, and for pyrrhotine—pH 7.0. In the lime medium, the value for tennantite and sphalerite pH 12.0, for galenite—pH 11.2, for pyrite—pH 9.5 and 11.2, and for pyrrhotine—pH 9.5 and 12.1. Measurements of zeta potentials of ultrafine sulfide particles give the opportunity to refine the interaction mechanism of sulfhydril collectors with sulfides and associate the nonselective recovery of final tailings of sulfides in the highly alkaline lime medium with the contribution of the electrostatic component during the adhesion of ultrafine sulfide particles on bubbles and their mechanical carryout into the froth product.