Synthesis of a novel dithiocarbamate collector and its selective adsorption mechanism in galena flotation

Abstract

The high consumption of depressants in the flotation separation of sulfide lead-zinc ores would cause serious environmental problems, and conventional dithiocarbamate collectors suffered from the drawbacks of low flotation activity and poor selectivity. Hence, it’s urgent to develop efficient collectors for the separation of galena and sphalerite. In this study, a novel morpholine dithiocarbamate propylene ester (MDPE) was designed and synthesized by the introduction of morpholine structure containing the C-O-C group, aiming to improve the surface activity and selectivity of the molecule. Surface tension tests indicated that MDPE exhibited a higher surface activity and stronger hydrophobicity than conventional collector N,N-diethyl dithiocarbamate propiononitrile ester (Ester-105) due to the introduction of morpholine structure. Microflotation experiments revealed that compared with Ester-105, higher flotation recovery of galena (90.75%) with significantly improved flotation selectivity against sphalerite by using MDPE of 2 × 10−4 mol/L at low alkalinity (pH=8.5) was obtained. Surface wettability measurements displayed that MDPE enhanced the hydrophobicity of galena surfaces more obviously than sphalerite. UV–vis spectra showed that MDPE preferred to interact with Pb2+ rather than with Zn2+. Adsorption experiments elucidated that the adsorption capacity of MDPE for galena was stronger than that for sphalerite. FTIR spectra and XPS proved that MDPE might chemically adsorb on the surface of galena through the formation of C-S-Pb structure. DFT calculations were conducted to demonstrate that the introduction of morpholine structure improved the chemical activity of the molecule.