Selective flotation separation of smithsonite and calcite using sodium dodecyl phosphonate as a collector: Flotation performance and adsorption characteristics

Abstract

Smithsonite stands as a representative zinc oxide ore and is frequently found co − occurring with calcite. These two minerals possess similar physical and chemical characteristics, which consequently pose difficulties in their separation. To tackle the problem of separating smithsonite from calcite, this research employs sodium dodecyl phosphinate (NaDDP) as an effective and eco − friendly collector for the selective flotation of smithsonite and calcite. The obtained zinc concentrate features a Zn grade of 42.97 % and a recovery rate of 93.65 %, along with a Ca grade of 6.10 % and a recovery rate of 12.51 %, achieving an efficient flotation separation of the two minerals. Total Organic Carbon (TOC) analysis and Inductively Coupled Plasma (ICP) spectrometry reveal that a substantial amount of NaDDP is consumed by the Ca²⁺ released from calcite, leading to a restricted effective adsorption capacity of the reagent on the mineral surface. Nevertheless, the solubility of smithsonite is lower than that of calcite, and the quantity of NaDDP consumed in the solution is small, whereas the amount of the reagent adsorbed on the mineral surface is large. X-ray Photoelectron Spectroscopy (XPS), Zeta potential, time − of − flight secondary ion mass spectrometry (ToF − SIMS), and Density Functional Theory (DFT) calculation and analysis demonstrate that the interaction ability of NaDDP with Zn sites is stronger than that with Ca sites. When both are present at the same time, NaDDP reacts preferentially with Zn. This gives rise to adsorption differences between the two minerals for this reagent, resulting in variations in flotation behavior.