Selective adsorption of trisodium nitrilotriacetate on calcite and its application for the separation of fluorite minerals

The recovery of fluorite from calcium-bearing carbonate ores by foam flotation is challenging due to low separation efficiency. Herein, we studied the effect of trisodium nitrilotriacetate (TN) addition on the surface properties of calcite and fluorite. For this purpose, we performed micro-flotation tests and carried out zeta potential measurements as well as Fourier transform infrared (FT-IR) and X-ray photoelectron (XPS) spectroscopic measurements to analyze the surface properties of these minerals. The addition of TN as a novel depressor significantly improved the effect of calcite and sodium oleate (NaOl) on the flotation-based fluorite recovery and separation from calcite. TN interacted with fluorite via an electrostatic interaction according to the zeta-potential and XPS analyses. The interaction of TN with calcite was via electrostatic attraction and chemical adsorption. Preferential chemical adsorption of NaOl replaces TN from the fluorite surface. However, calcite preferentially adsorbs TN due to the chemical bonding between carboxyl of TN and the hydrated calcite surface layer, which chemically modifies the original calcite surface. This work also suggests interaction and adsorption mechanisms between TN and calcite.