The flotation of bastnaesite, as a major mineral source of rare earth elements, attracting much attention in the mineral processing field, is challenging owing to the natural flotability of calcium-bearing minerals. To promote the application of flotation, we systematically investigated the flotation behavior of bastnaesite, barite, and calcite, with salicylhydroxamic acid (SHA) as the collector through micro-flotation experiments, zeta-potential measurements, Fourier transform infrared (FT-IR) analyses, X-ray photoelectron spectroscopy (XPS) analyses, and solution chemistry analyses. Micro-flotation experiments confirm that the flotability of bastnaesite is high at pH 6.5–8.5, while calcite floats at pH 8.0–9.5, and barite has little flotation response. The results of FT-IR, XPS, and zeta-potential measurements indicate that there is chemical adsorption of SHA on the bastnaesite surface, and physical adsorption also occurs. However, as for barite and calcite, there is only physical adsorption of SHA on the surfaces. The solution chemistry results show that SHA anions can interact with RE³⁺, REOH²⁺, and RE(OH)₂⁺ on bastnaesite surfaces in aqueous suspensions, resulting in bastnaesite flotation.

The study of the depression effect of non-toxic depressants on the flotation separation of chalcopyrite from galena is of great importance for both industrial applications and theoretical research. The mixed depressant (D_Final) of four common inhibitors—sodium carboxymethyl cellulose, sodium silicate, sodium sulfite, and zinc sulfate—exhibited high selectivity during the separation of chalcopyrite from galena. Flotation tests on an industrial copper–lead bulk concentrate showed that using this depressant mixture can achieve highly efficient separation of chalcopyrite from galena at the natural pH of the pulp. Copper and lead concentrates were produced at grades of 21.88% (Cu) and 75.53% (Pb), with recoveries of 89.07% (Cu) and 98.26% (Pb). This showed a similar performance of D_Final with dichromate, which is a depressant that is widely used in industry, but without the environmental risks or the need for pH control. Zeta potential and Fourier transform infrared (FT-IR) results showed that interaction between the surface of the chalcopyrite and the mixed depressant was prevented by pre-treatment with a composite thiophosphate collector (CSU11), while the mixed depressant could expel/replace the composite thiophosphate on the surface of galena by chemical adsorption, depressing its flotation. This is the reason why this non-toxic depressant achieved the selective depression of galena from chalcopyrite, leading to efficient flotation separation.

Effective flotation of fine particles is a problem for mineral processing. In this paper, a flocculant mostly used in heavy metal ion treatment was used in an arsenopyrite flotation system. The adsorption behavior and flotation performance of PEI on the xanthate flotation of arsenopyrite were investigated through zeta potential and adsorbed amount measurements, XPS and size distribution detections, and micro-flotation tests. Zeta potential results showed that the adsorption of 40 mg/L polyethyleneimine (PEI) caused an increase in the zeta potential of arsenopyrite, and had only a slight depression on the further adsorption of SBX, which was further confirmed by the results of the adsorbed amount measurements. However, when the dosage of PEI was 150 mg/L, the adsorption of SBX was strongly depressed. This was because moderate PEI only bridged different arsenopyrite particles, and most of the active sites for the SBX adsorption were still exposed; when PEI was in excess, the mineral particles would be covered so that there were not enough active sites for SBX adsorption. Fe and As on the mineral surface were the adsorption sites for the PEI molecules, which were resolved from the chemical shifts in the As/Fe peaks of the XPS spectra. PEI can increase particle size, and moderate PEI dosage can make the particle size suitable for flotation with SBX where bridging and hydrophobic effects take place. The flotation results showed that −20 μm arsenopyrite particles had poor flotation recovery with the SBX collector alone, but when they were treated with 40 mg/L PEI, the recovery largely increased. PEI can serve as an effective flocculant for the flocculation flotation of fine arsenopyrite. A comparison model, showing the possible interactions among reagents, particles, and bubbles in the pulp with different PEI dosages, is proposed.

Silicate minerals with a certain degree of flotability are often easy to mix into sulfide ore concentrate in mineral processing industry. In this paper, the adsorption of yeast dextran (YD) on clinochlore and its application in pyrite/clinochlore separation were investigated. The adsorbed amount...