Key Takeaways & Executive Findings
- •• A low-temperature stirring method achieves 77.75% desorption of NaOL from scheelite surfaces, enabling efficient collector recovery and reuse. • Reusing desorbed collectors with only 30% additional NaOL maintains ~95% scheelite recovery in single-mineral flotation, demonstrating cost-effectiveness. • For real scheelite ore, 75% of normal ZL collector dosage suffices to produce a qualified rough concentrate, highlighting industrial applicability. • AFM and molecular dynamics simulations reveal that low temperature weakens collector adsorption, facilitating desorption and supporting the proposed green method.
Abstract
Flotation is the most common method to recover valuable minerals by selective adsorption of collectors on target mineral surfaces. However, in subsequent hydrometallurgy of mineral flotation concentrates, the adsorbed collectors must be desorbed since it can adversely affect the efficiency of metallurgical process and produce wastewater. ZL, as a fatty acid mixture, is a typical industrially used collector for scheelite flotation in China. Sodium oleate (NaOL) has similar fatty acid group as ZL. In this study, the desorption behavior of NaOL/ZL from scheelite surface by a physical method of stirring at a low temperature was investigated. NaOL desorption tests of single mineral showed that a desorption rate of 77.75% for NaOL from scheelite surface into pulp was achieved in a stirring speed of 2500 r/min at 5°C in a neutral environment. Under the above desorption condition, in the pulp containing desorbed collector by adding extra 30% normal NaOL dosage, the scheelite recovery reached about 95% in the single mineral flotation test. Desorption and reuse of ZL collector for the flotation of real scheelite ore showed only a 75% normal dosage of ZL could produce a qualified rough concentrate. The atomic force microscope (AFM) tests showed that after desorption treatment of low temperature and strong stirring, the dense strip-like structure of NaOL on the scheelite surface was destroyed to be speck-like. Molecular dynamics simulations (MDS) demonstrated that the adsorption energy between NaOL and scheelite surface was more negative at 25°C (−13.39 kcal/mol) than at 5°C (−11.50 kcal/mol) in a neutral pH, indicating that a low temperature was beneficial for the desorption of collector from mineral surface. Due to its simplicity and economy, the method we proposed of desorption of collector from mineral surface and its reuse for flotation has a great potential for industrial application.
1. Introduction
Flotation is an efficient approach to separating target minerals and gangue in mineral processing field [1–4]. In the flotation process, the target minerals are hydrophobically floated to form concentrates by changing the physical and chemical properties of the mineral surfaces due to the adsorption of the collectors [5–6]. However, the collectors on the concentrate surfaces can reduce efficiency of concentration and filtration of the concentrates [7]. Besides in the hydrometallurgy, the collectors will poison the ion exchange resin and imperfect quality of final products [8]. Therefore, it is significative for us to develop an efficient way of desorbing collectors on the concentrate and reusing them in the flotation process, which can help to reduce the collector dosage in flotation and the adverse effects in hydrometallurgy.
There are several physical and chemical methods used to desorb collectors from flotation concentrates. The chemical desorption methods, including competitive adsorption and oxidation treatments, are effective in removing reagents chemically adsorbed on mineral surfaces [9–13]. For example, the xanthates adsorbed on the surface of chalcopyrite concentrates can be desorbed in strongly acidic solutions, because they can be decomposed to alcohols and carbon disulfide in strongly acidic environment [14–15]. However, after chemical treatment, the structures of most desorbed collectors are damaged, and cannot be reused in flotation again [16–17]. The physical desorption methods, including activated carbon adsorption, ultrasonic, and stirring [17–19], are efficient at removing reagents unsteadily adsorbed on mineral surfaces. For example, mechanical agitation with a high speed can be used to make the reagents weakly adsorbed on the concentrate surfaces dislodged via rotational high shear forces [20–21]. In addition, our previous work showed that the desorption method of ultrasonic can desorb the most of lead ion (Pb2+) and benzohydroxamic acid (BHA) from mineral surfaces.
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Liming Tao, Wangni Wu, Zihan Zhao, Ruihua Fan, Jianjun Wang, Zhiyong Gao (2025). Highly efficient desorption and reuse of fatty acid collectors adsorbed on mineral surface: A case study of scheelite. Int. Journal of Minerals, Metallurgy and Materials (矿物冶金与材料学报). https://doi.org/10.1007/s12613-024-3059-5
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Frequently Asked Questions
What is the main objective of this study?
The study aims to develop an efficient and economical method for desorbing fatty acid collectors (NaOL/ZL) from scheelite surfaces and reusing them in flotation, thereby reducing collector consumption and mitigating adverse effects in hydrometallurgy.
How was the desorption of collectors achieved?
Desorption was achieved by a physical method involving stirring at a low temperature (5°C) and high speed (2500 r/min) in a neutral environment, which effectively removed the collectors from the mineral surface without damaging their structure.
What were the key results regarding desorption efficiency?
The method achieved a desorption rate of 77.75% for NaOL from scheelite surfaces. When the desorbed collector was reused with an additional 30% of the normal NaOL dosage, scheelite recovery reached about 95% in single-mineral flotation tests.
How does low temperature facilitate desorption?
Molecular dynamics simulations showed that the adsorption energy between NaOL and scheelite is less negative at 5°C (−11.50 kcal/mol) than at 25°C (−13.39 kcal/mol), indicating weaker adsorption at lower temperatures, which facilitates desorption.
What is the industrial significance of this method?
The method is simple, economical, and environmentally friendly, as it allows the reuse of collectors, reducing chemical consumption and wastewater generation. It has great potential for industrial application in mineral processing.
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