Application of hydroxyethylidene diphosphonic acid as a depressant for efficient pyrite separation from serpentine: a performance and mechanistic study

Abstract

Hydroxyethylidene diphosphonic acid (HEDP) is an industrial environmental reagent, often used as a chemical raw material in industrial water treatment, household cleaning products and personal care products. In this work, the effort to use HEDP to the flotation of pyrite containing fine-grained serpentine was conducted, and the selective separation of serpentine and pyrite was accomplished. During the flotation process, the introduction of 30 mg/L HEDP resulted in a rapid increase and recovery of 89% pyrite recovery at pH 9 under deteriorated conditions. The results of the micro-flotation method showed how well HEDP was selectively inhibited in the pyrite-serpentine flotation separation process. On the basis of a number of measures, including ICP-OES tests, Zeta potential testing, Scanning electron microscopy (SEM) characterization, and X-ray photoelectron spectroscopy (XPS) analysis, it was discovered that a substantial amount of HEDP was selectively adsorbed on the serpentine surface by chemically chelating with the Mg active site. In contrast, the adsorption of HEDP on the surface of pyrite was almost negligible. HEDP prefers to adsorb on the positively charged serpentine surface in the form of H5C2P2O73- negative charge, while accelerating the release of Mg from the serpentine surface into the solution by forming Mg3[H5C2P2O7]2 hydrophilic chelate. Both of these effects remarkably contribute to the reversal of the serpentine surface potential to a negative potential. Due to electrostatic repulsion, the hetero-coagulation of negatively charged serpentine and negatively charged pyrite was broken, and the selective collecting capability of the PBX collector on the surface of pyrite was regained, allowing for the selective separation of pyrite and serpentine minerals. The application of HEDP in the actual ore (Peru copper ore BM1-type sample) sorting further demonstrated its good selective inhibition effect, and HEDP was able to enhance the grade and recovery of Cu and S in the concentrate while ensuring the reduction of Mg grade and recovery.