Key Takeaways & Executive Findings
- •• Gum Arabic (GA) is introduced as a novel, eco-friendly depressant for selective flotation separation of chalcopyrite from molybdenite. • At pH 8.0 with 20 mg/L GA, chalcopyrite recovery in mixed mineral flotation was 67.49% higher than molybdenite, demonstrating strong selectivity. • GA adsorbs onto molybdenite via chemical chelation, hydrogen bonding, and hydrophobic interactions, while showing weak interaction with chalcopyrite, preserving its floatability. • Pre-adsorbed GA prevents butyl xanthate adsorption on molybdenite, and GA primarily adsorbs on the 'face' rather than 'edge' of molybdenite, offering a promising Cu–Mo separation strategy.
Abstract
The environment-friendly and efficient selective separation of chalcopyrite and molybdenite poses a challenge in mineral processing. In this study, gum Arabic (GA) was initially proposed as a novel depressant for the selective separation of molybdenite from chalcopyrite during flotation. Microflotation results indicated that the inhibitory capacity of GA was stronger toward molybdenite than chalcopyrite. At pH 8.0 with 20 mg/L GA addition, the recovery rate of chalcopyrite in the concentrate obtained from mixed mineral flotation was 67.49% higher than that of molybdenite. Furthermore, the mechanism of GA was systematically investigated by various surface characterization techniques. Contact angle tests indicated that after GA treatment, the hydrophobicity of the molybdenite surface significantly decreased, but that of the chalcopyrite surface showed no apparent change. Fourier transform-infrared spectroscopy and X-ray photoelectron spectroscopy revealed a weak interaction force between GA and chalcopyrite. By contrast, GA was primarily adsorbed onto the molybdenite surface through chemical chelation, with possible contributions from hydrogen bonding and hydrophobic interactions. Pre-adsorbed GA could prevent butyl xanthate from being adsorbed onto molybdenite. Scanning electron microscopy–energy-dispersive spectrometry further indicated that GA was primarily adsorbed onto the “face” of molybdenite rather than the “edge.” Therefore, GA could be a promising molybdenite depressant for the flotation separation of Cu–Mo.
1. Introduction
Copper and molybdenum are essential metallic resources for electronics, construction, and industrial manufacturing. Approximately 50% of molybdenum and 70% of copper reserves in the world originate from porphyry Cu–Mo ores, which are formed by the natural combination of chalcopyrite and molybdenite. However, the separation of chalcopyrite and molybdenite poses a challenge in mineral processing. Chalcopyrite and molybdenite exhibit similar floatability, making their effective separation crucial. For technical and economic reasons, froth flotation is currently the primary method for separating chalcopyrite and molybdenite. Cu–Mo flotation separation typically consists of two stages: Cu–Mo bulk concentrates are obtained in the first stage, followed by the addition of selective depressants for the separation of chalcopyrite and molybdenite.
The separation of Cu–Mo bulk concentrates is primarily achieved by inhibiting chalcopyrite using inorganic copper depressants, such as sodium sulfide/hydrosulfide, cyanides, and sodium thioglycolate. However, these chalcopyrite depressants are toxic and volatile, posing health risks to on-site workers and causing ecological damage due to toxic gas emissions with extensive use. Therefore, exploring additional depressants for Cu–Mo separation is essential. In recent decades, extensive research has focused on depressants for chalcopyrite, such as l-cysteine, 3-amino-5-mercapto-1,2,4-triazole, rosin-3-acetic acid, ferrate, n-thiourea-maleic acid, and 2,3-disulfanylbutanedioic acid. However, these novel chalcopyrite inhibitors still face challenges, including high pollution and harsh separation conditions. Some studies reported the inhibition of molybdenite in the reverse flotation separation of Cu–Mo bulk concentrates, revealing that most molybdenite inhibitors are nontoxic, biodegradable, and widely available. Yuan et al. successfully achieved the separation of chalcopyrite and molybdenite using humic acid, which demonstrated selective adsorption on the molybdenite surface rather than the chalcopyrite surface. Yang et al. found that pectin was primarily adsorbed on the surfaces of molybdenite and chalcopyrite through hydrophobic interactions and electrostatic attraction; sodium butyl xanthate can replace the pectin adsorbed on the chalcopyrite surface but not that adsorbed on the molybdenite surface. Zeng et al. investigated the mechanism of tannic acid in the separation of chalcopyrite and molybdenite, revealing that the hydrophobic interaction of tannic acid with the molybdenite surface was more favorable for adsorption than its chemical interaction with the chalcopyrite surface. Although the aforementioned molybdenite inhibitors exhibited favorable selectivity and have achieved flotation separation of Cu–Mo bulk concentrates in laboratory settings, research in this area remains limited, and the reaction mechanisms require further investigation. Therefore, the development of a highly selective and eco-friendly molybdenite depressant and in-depth studies are needed.
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Tao Chen, Runqing Liu, Wenchao Dong, Min Wei, Wei Sun (2025). Differential adsorption of gum Arabic as an eco-friendly depressant for the selective flotation of chalcopyrite from molybdenite. Int. Journal of Minerals, Metallurgy and Materials (矿物冶金与材料学报). https://doi.org/10.1007/s12613-024-2979-4
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Frequently Asked Questions
What is the main contribution of this study?
The study introduces gum Arabic (GA) as a novel, eco-friendly depressant for the selective flotation separation of chalcopyrite from molybdenite, demonstrating high selectivity and providing mechanistic insights.
How does gum Arabic selectively depress molybdenite?
GA adsorbs onto molybdenite surfaces via chemical chelation, hydrogen bonding, and hydrophobic interactions, significantly reducing its hydrophobicity, while showing weak interaction with chalcopyrite, thus preserving its floatability.
What are the optimal conditions for using gum Arabic in Cu-Mo separation?
The optimal conditions include pH 8.0 and a GA concentration of 20 mg/L, under which the recovery of chalcopyrite in the concentrate was 67.49% higher than that of molybdenite.
Why is an eco-friendly depressant needed for Cu-Mo flotation?
Traditional chalcopyrite depressants like sodium sulfide and cyanides are toxic and volatile, posing health and environmental risks. Eco-friendly alternatives like GA are biodegradable and safer.
What techniques were used to investigate the adsorption mechanism?
The study employed contact angle measurements, Fourier transform-infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy–energy-dispersive spectrometry (SEM-EDS) to analyze the adsorption mechanism.
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