Zhen Wang

To solve the problem of mechanical entrainment and slime coating of fine sericite and chlorite hindering the flotation separation of gold-bearing pyrite in low-grade gold ores, ethylenediamine-N,N’-disuccinic acid (EDDS) was innovatively used as a selective and eco-friendly depressant. A systematic set of tests, including micro-flotation, artificial mixed mineral flotation, zeta potential measurement, adsorption capacity test, solution chemistry analysis and X-ray photoelectron spectroscopy (XPS) characterization, was conducted to explore its flotation performance and action mechanism. The results showed that pH 8 and 200 mg/L EDDS were the optimal conditions under which EDDS reduced the recoveries of sericite and chlorite to ~20% and ~15%, respectively, while restoring pyrite recovery to ~80% with a notable upgrade in concentrate grade. EDDS exhibited strong chemical adsorption on sericite and chlorite via chelating their active Al/Mg sites, significantly enhancing their hydrophilicity. In contrast, it only undergoes weak physical adsorption on pyrite, with negligible observed influence on its hydrophobicity and the adsorption of (sodium butyl xanthate) SBX. At pH 8, EDDS mainly existed as HEDDS³⁻ (~90%), whose triple negative charge strengthened electrostatic interaction with positively charged gangue surfaces, boosting selective adsorption. This study confirms EDDS as a highly efficient depressant for pyrite–sericite/chlorite flotation under pure mineral and artificial mixed mineral conditions. Since the present study is based on pure minerals and artificial mixtures, further validation using real ore samples is still required before practical industrial application. This research expands the application of EDDS in mineral processing and provides a novel eco-friendly technical approach for the laboratory-scale separation of fine gold-bearing pyrite from low-grade gold ores with high clay gangue content.

To elucidate the refractory depression of serpentine in a Jinchuan copper-nickel ore (Located in Gansu Province), this study compared the effects of serpentine from Gansu and Liaoning on chalcopyrite flotation via single/mixed mineral flotation, zeta potential, micro-polarity detection, XPS, ToF-SIMS, and EPMA. Single mineral flotation showed chalcopyrite recovery reached ~90% at pH < 8 with 60 mg/L DDTC, while Gansu serpentine had slightly higher recovery than Liaoning serpentine. In mixed mineral flotation, chalcopyrite recovery dropped to ~70% (pH = 8), and Gansu serpentine recovery rose to ~45% (vs. ~35% for Liaoning). When 40 mg/L CMC inhibitor was added, chalcopyrite recovery restored to ~80%, and both serpentines’ recovery fell below 20%—but serpentine (Gansu) still had marginally higher recovery. The zeta potential and micro-polarity experiments collectively indicate that the collector exhibits selective adsorption on the surface of chalcopyrite; compared between the two serpentine samples, the collector adsorption is stronger on the surface of Gansu serpentine. In contrast, the depressant shows selective adsorption on the surface of serpentine, but when comparing the two serpentine samples, the depressant adsorption is stronger on the surface of exotic serpentine. This finding to a certain extent explains the reason why Gansu serpentine is difficult to depress. EPMA showed Gansu serpentine had lower MgO (38.668% vs. 41.012% for Liaoning), and XPS exhibited smaller Mg 1s shifts (1.93 eV vs. 4.46 eV) with CMC. This study explains Gansu serpentine’s poor depressibility, providing critical support for optimizing Cu-Ni ore flotation reagents and processes, gradually bridging to industrial application. This work provides a universal framework for global low-grade copper-nickel ores with silicate gangues.

This study investigated the flotation performance of W8, a blended xanthate collector containing ethyl, butyl, propyl, and amyl xanthates, combined with ammonium dibutyl dithiophosphate (ADD) for treating low-grade arsenopyrite-type gold ore from Golmud, Qinghai. Real ore flotation tests demonstrated the superior efficacy of the W8 + ADD system, achieving 84.06% gold recovery with 0.34 g/t tailings, outperforming conventional sodium amyl xanthate (SAX) + ADD and sodium propyl xanthate (SPX) + ADD systems. Systematic studies on pure arsenopyrite revealed a significant synergistic effect in the mixed SPX-SAX system (1:4 ratio), representative of W8 composition. At pH 9, the mixed collector achieved 73.5% recovery, substantially higher than individual SPX (37.5%) or SAX (45.8%). This enhanced performance was attributed to improved surface hydrophobicity (contact angle 47.68° vs. 36.92° for SAX), greater adsorption density (4.97 × 10⁻⁷ mol/g under depressant conditions), and extensive formation of molecular aggregates observed via AFM, which increased surface roughness to 28.95 nm. Flotation kinetics further confirmed the advantage of W8 + ADD, which reached 72.1% cumulative recovery in 420 s, exceeding both mixed SPX/SAX (69.5%) and single SAX (65.5%) systems. The synergistic interaction among different xanthate components in W8 enables efficient recovery of gold from this refractory ore.

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.

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.

The aim of the study was to compare the effects and mechanism of tetrasodium pyrophosphate (TSPP) and sodium tripolyphosphate (STPP) as dispersants on the selective flotation of arsenopyrite from muscovite. The results of single-mineral flotation showed that the recovery of arsenopyrite was 81.4% when no dispersant was added. The recovery of arsenopyrite slightly decreased with increasing dosage of TSPP. When the dosage of STPP was 6 × 10⁻⁵ mol/L, the recovery of arsenopyrite was only 28.6%. Neither of the dispersants had significant influence on the muscovite flotation (<10%). However, in a mixed-mineral system, the recovery of arsenopyrite dropped significantly, and then under the action of dispersants, its recovery back up. The RPM results showed that the dispersion effect of TSPP was superior to that of STPP. The electrokinetic potential showed that the potential change value of muscovite with TSPP was −17.37 mV, while that of muscovite with STPP was −8.33 mV (pH = 8). The adsorption of TSPP onto muscovite was stronger than that of STPP. FTIR and XPS analysis confirmed that dispersants exhibited chemical adsorption with the Al atoms on muscovite and that dispersant STPP exhibited stonger adsorption than TSPP on arsenopyrite, which was consistent with flotation experiments.