The presence of galena, sphalerite (cleiophane), and Carbonaceous Material (CM) in sulphide ore complicates the application of a direct-differential flotation flowsheet due to increased mutual interactions between both marketable concentrates and final tailings. Flotation tests, measurements of electrokinetic (zeta) potential, adsorption of sulphydric collectors, and colorimetric indicators were employed to elucidate the cause-and-effect relationships underlying the reduction in contrast of the flotation properties of galena and cleiophane surfaces. It was established that galena and cleiophane exhibit comparable flotation responses when using diesel oil within a pH range of 6–8. While high galena recovery is anticipated, the similar recovery of cleiophane is attributed to the ZnS zeta potential approaching zero in this pH interval. Experimental results demonstrated a distinct difference in the flotation behavior of galena and cleiophane, both with natural surface oxidation and following the removal of sulphoxy films. The application of Carbonaceous Material depressants derived from wood processing by-products (lignin-sulphonates) resulted in a significant decrease in sphalerite recovery. Although the flotation rate constant for Carbonaceous Material in the presence of lignin-sulphonate-based depressants decreases, the overall recovery to concentrate increases over time. The implementation of a bulk-differential flowsheet, involving the preliminary removal of CM prior to the bulk Pb-Zn flotation of lead-zinc sulphide ore, has been demonstrated to be effective.

The novelty of this study lies in the first comparative characterisation of five carbonaceous materials: three monophase carbons (wood charcoal, carbon, graphite) and two ore-derived CM samples from polymetallic sulphide and oxidised lithium ores. The methodology included IR spectroscopy, XPS, acid–base adsorption centres identified by colour indicators, chemical composition analysis, and kinetic flotation tests. Bulk and surface compositions differed significantly: although the ash content of ore-derived CM reached 84.4%, XPS revealed carbon-enriched surfaces with thin films of about 1–2 nm. IR spectra confirmed multiphase structures with carbonate, silica, and aluminosilicate bands, and showed an identical composition of CM from different industrial ore types. Flotation kinetics confirmed high floatability (recoveries 80%–99%, k up to 1.95 min⁻¹). Even with sodium lignosulphonate at 500 mg/L, recovery only decreased from 83.02% to 52.54%, showing the limited efficiency of depressants. These results provide a basis for the preliminary removal of CM prior to rough (bulk) flotation in the processing of different ore types, improving concentrate quality, reducing reagent consumption, and lowering metallurgical losses.