Key Takeaways & Executive Findings
- •• Konjac glucomannan (KGM) acts as a highly selective depressant for calcite in scheelite flotation, achieving a recovery difference of 82.53% at 50 mg/L. • KGM selectively adsorbs on calcite surfaces via chemical interactions, blocking sodium oleate adsorption and enhancing separation efficiency. • The eco-friendly and cost-effective nature of KGM offers a sustainable alternative to traditional depressants like sodium silicate. • DFT simulations corroborate experimental findings, confirming strong adsorption of KGM on calcite, providing a mechanistic basis for its use.
Abstract
This study investigated the effect of konjac glucomannan (KGM) on the flotation separation of calcite and scheelite. Micro-flotation tests showed that under the action of 50 mg/L KGM, the floatability of calcite notably decreased, while the impact on scheelite was negligible, resulting in a recovery difference of 82.53%. Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM) analyses indicated the selective adsorption of KGM on the calcite surface. Test results of the zeta potential and UV-visible absorption spectroscopy revealed that KGM prevented the adsorption of sodium oleate on the calcite surface. X-ray photoelectron spectroscopy (XPS) analysis further confirmed the chemical adsorption of KGM on the calcite surface and the formation of Ca(OH)2. The density functional theory (DFT) simulation results were consistent with the flotation tests, demonstrating the strong adsorption performance of KGM on the calcite surface. This study offers a pathway for highly sustainable and cost-effective mineral processing by utilizing the unique properties of biopolymers such as KGM to separate valuable minerals from gangue minerals.
1. Introduction
Tungsten is a valuable and scarce metal resource with notable strategic importance. Scheelite (CaWO4) plays a crucial role as a major source of tungsten, contributing approximately 30% of the global tungsten reserves, which are estimated at 3.5 million tons [1–2]. Calcium-containing minerals often exhibit comparable surface characteristics and flotation behavior [3–4]. The difficulty in separating scheelite and its accompanying minerals through flotation [5] necessitates the application of appropriate reagents and techniques.
Flotation is a prevalent technique for separating scheelite from its gangue minerals due to differences in surface wettability. Notably, sodium oleate (NaOL) can facilitate the formation of hydrophobic regions on the surface through chemical adsorption. However, NaOL has an affinity for calcite, particularly under weakly alkaline conditions, compromising the selectivity and efficiency of the scheelite flotation process. Depressants or modifiers such as sodium silicate are necessary to suppress the adsorption of NaOL on the calcite surface and enhance mineral separation. Sodium silicate forms an adsorption layer that diminishes the surface adsorption sites of NaOL, typically inhibiting calcite flotation. However, sodium silicate has certain disadvantages, such as low selectivity and negative effects on scheelite when used excessively. Recent advancements have introduced new depressants, such as polycarboxylates, chelating agents, and polyols, which have demonstrated promising results in improving the separation efficiency and selectivity of these minerals [6–9]. These inhibitors offer certain advantages, such as a low dosage requirement and effective dispersion. However, they still have several drawbacks, including high costs and, in some instances, an unclear mechanism of action.
In this paper, the application of the biopolymer konjac glucomannan (KGM) in the flotation processes of scheelite and calcite, as well as its underlying mechanism, are investigated. KGM is a biopolymer isolated from the tuber of the konjac plant. The structure of KGM is characterized by a primary chain of β-(1→4)-linked D-mannose and D-glucose units, with a molar ratio of approximately 1.6:1. Additionally, KGM possesses branched chains located at the C-3 position of D-glucose and D-mannose residues and a minimal amount of acetyl groups situated at the C-6 position on the main chain (roughly one acetyl group per 17 sugar residues) [10]. This research investigated the influence of KGM on the flotation performance and surface adsorption of the two minerals by employing micro-flotation tests, surface wettability tests, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and other characterization techniques. The findings reveal the selective inhibition of calcite flotation by KGM without affecting scheelite flotation, which is conducive to their separation. This study presents a novel approach for the inhibition of certain calcium-bearing gangue minerals, introducing an environmentally friendly and sustainable method for preventing calcium-bearing gangue minerals in mineral flotation.
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Zhenhao Guan, Ying Zhang, Shuming Wen, Qi Zuo, Yu Wu, Xiaokang Li (2025). Flotation separation of scheelite and calcite using the biopolymer konjac glucomannan: A novel and eco-friendly depressant. Int. Journal of Minerals, Metallurgy and Materials (矿物冶金与材料学报). https://doi.org/10.1007/s12613-024-2964-y
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Frequently Asked Questions
What is the main finding of this study?
The study demonstrates that konjac glucomannan (KGM) acts as a highly selective depressant for calcite in scheelite flotation, achieving a recovery difference of 82.53% at a concentration of 50 mg/L, without significantly affecting scheelite recovery.
How does KGM selectively depress calcite?
KGM selectively adsorbs on the calcite surface through chemical interactions, as confirmed by FTIR, XPS, and DFT simulations. This adsorption blocks the attachment of sodium oleate, thereby preventing calcite from becoming hydrophobic and floating.
What are the advantages of using KGM over traditional depressants?
KGM is a natural, eco-friendly, and cost-effective biopolymer. Unlike sodium silicate, it offers higher selectivity and does not adversely affect scheelite flotation, making it a sustainable alternative for mineral processing.
What techniques were used to investigate the mechanism?
The study employed micro-flotation tests, Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), zeta potential measurements, UV-visible absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) simulations.
What is the significance of this research for the mining industry?
This research provides a novel, environmentally friendly method for separating scheelite from calcite, which is a challenging task due to their similar surface properties. The use of KGM could lead to more sustainable and cost-effective mineral processing practices.
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