Application of an Amino-Polycarboxylic Acid Grinding Aid in Grinding-Flotation System for Magnesite and Dolomite: Separation Behavior and Adsorption Mechanism

Abstract

Low-grade magnesite has not been effectively utilized because of its high vein content. A large number of discarded low-grade magnesite will cause waste of resources and serious environmental pollution. In the grinding process, magnesite and calcium-bearing vein mineral dolomite are prone to surface dissolution. The dissolved metal ions will be adsorbed on the surface of the minerals, making their surface properties convergent, leading to flotation separation difficulties. Based on this, polycarboxylic acid grinding aid (EGTA) was used to optimize the grinding-flotation system of magnesite. Grinding tests show that EGTA can increase the content of –74+23 μm  and decrease the content of –23 μm in magnesite grinding products. However, EGTA significantly enhanced the content of dolomite with a particle size of –23 μm. Flotation test responded that adding EGTA in the grinding process can improve the flotation separation effect of magnesite and dolomite. The mechanism study reflected that EGTA can selectively adsorb on the Ca sites on the surface of dolomite, which increased the hydrophilicity of dolomite, In addition, EGTA had stronger chelating effect on Ca2+ in the slurry, which improved the chemical environment of the slurry. At the same time, EGTA can promote the dissolution of dolomite and increase the difference between the surface element contents of magnesite and dolomite. Therefore, EGTA has great potential for application in magnesite flotation process.

Keywords: Low-grade magnesite, dolomite, Grinding aid EGTA, Grinding-flotation system, Surface properties, Slurry environment