In this work, selective flotation separation of microfine apatite and chlorite was achieved by using sodium oleate (NaOL) as a collector with a low dosage of acidified sodium silicate (ASS) as a depressant. The optimum ratio of sodium silicate to sulfuric acid for ASS was 5:3, and a good separation effect was also achieved in the mixed ore system. Compared to the deionized water system, the ions of Na⁺, Ca²⁺ and Mg²⁺ in seawater adsorbed on the surfaces of apatite and chlorite, which made the zeta potential of the two minerals shift positively. This presented a challenge to the selection of reagents for mineral separation. The addition of ASS changed the pH value of the pulp from weak alkalinity caused by seawater to weak acidity, which allowed the metal ions adsorbed on the mineral surface to desorb. Meanwhile, ASS can selectively adsorb on the desorbed chlorite surface in the form of Si(OH)₄, which hindered the action of NaOL, leading to the depression of chlorite. NaOL adsorbed well on the desorbed surface of apatite and increased the apatite particle size from 27 μm to 229 μm, with a hydrophobic agglomeration effect, thus enhancing the flotation of microfine apatite.

A gold mine located in western China is facing the problem of a low concentrate grade, significantly hindering its economic benefits. Preliminary assessments indicate that this is caused by gangue minerals that are prone to floating and sliming, necessitating suppression in the flotation process. The effect of fenugreek polysaccharide gum (FGM) upon the flotation separation of arsenopyrite (representative of Au-bearing minerals) and pyrophyllite (a typical gangue mineral) was investigated; its industrial potential was verified through actual ore flotation and pilot plant testing. Additionally, the selective inhibition mechanism of FGM on pyrophyllite was elucidated. The flotation tests of pure minerals indicated that pyrophyllite has a high natural floatability; thus, it cannot be separated from arsenopyrite at low alkaline pH (7–9); smaller pyrophyllite particle sizes, especially −0.038 mm fractions, significantly decreased the arsenopyrite recovery; FGM can eliminate this adverse effect to a large extent through its selective depression of the flotation of pyrophyllite. For real ore systems, FGM also exhibited superior performance compared with the commonly used silicate and SHMP; closed-circuit flotation tests showed that the gold grade of the concentrate increased by 3.90 g/t and the enrichment ratio increased by 2.53 with the addition of FGM. As of now, FGM has increased the profits by USD 1.715 M in the past two years by improving concentrate grade and recovery efficiency. According to the results of contact angle, zeta potential, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), the selective adsorption of FGM onto the pyrophyllite surface was the reason for the positive effect; the interaction primarily involved the Al sites on the pyrophyllite surface and the –OH on FGM molecules.

Due to the influence of the clay minerals, the grade of the concentrate from a gold concentrator in Northwest China is low, which significantly compromises product valuation and market competitivenes. This study evaluated the industrial potential of fenugreek polysaccharide gum (FGM) as a depressant to enhance the flotation through pilot-scale testing. Results showed that the FGM system effectively upgraded the concentrate grade by 4.7 g/t, while slightly increasing recovery by 0.37%. The application of FGM has generated an additional $1.715 million profit over the past two years. These findings suggest that FGM holds significant potential for large-scale industrialization in the flotation of high-clay-content sulfide ores.