Abstract
Calcium ions are common in flotation process water, and have a significant effect on the molybdenite floatability, making separation of molybdenite from other minerals more difficult. Therefore, to improve the separation selectivity, the research of how calcium ions affect the molybdenite surface properties is of great significance. In this study, various methods including flotation tests, contact angle measurements, batch adsorption tests and Density Functional Theory (DFT) simulations were carried out to understand the adsorption characteristics and mechanism. Results of the contact angle measurements showed that the inhibition effects of calcium ions on molybdenite flotation kinetics were mostly attributed to the decrease of the edge surface hydrophobicity, as the contact angle of the edge surface decreased more than the face surface after treatment with calcium ions. While fitting the results of batch adsorption tests with adsorption kinetics and isotherm models, it was found that the Lagergen pseudo-first-order equation and the Freundlich isotherm model nicely follow the experimental trend. Moreover, DFT calculation results indicated that both Ca2+ and CaOH+ preferentially adsorb on the molybdenite (100) surface, particularly the edge surface, which was consistent with the contact angle results. Ca2+ adsorbed on the Mo-top site on the S-(100) surface by forming Ca-S bonds, transferring electrons from Ca 3d orbitals to S 3p orbitals. CaOH+ adsorbed on the S-top site of Mo-(100) surface by forming a strong covalent Mo-O bond and S-Ca bond. The results provide a basis for understanding and improving the separation effect of molybdenite from other minerals in the presence of calcium ions.
Highlights
Molybdenite is the principal ore from which molybdenum metal is extracted
In order to enhance the separation performance, this study investigated the adsorption mechanism of calcium ions on molybdenite surfaces through flotation tests, contact angle, batch adsorption tests and first-principles simulation calculation of calcium ions on the face and edge surfaces based on Density Functional Theory (DFT)
Thetests, object of this study was to analyze surfaces several methods including flotation kinetic contact angle tests, batch the adsorption characteristics and mechanism of The calcium ionskinetic on different molybdenite adsorption tests and simulation works based on DFT
Summary
Due to the natural hydrophobic property of molybdenite, flotation is commonly used for its processing. Molybdenite has closely paragenetic relationships with chalcopyrite. In practical Cu-Mo separation processes, molybdenite is collected as the froth product and the chalcopyrite is depressed [2]. Flotation is a water-intensive process, and the surface properties of the minerals and the function of the reagents may be significantly affected by various ions in the process water. Flotation of the molybdenite is strongly depressed by ions, while chalcopyrite recovery is slightly lower under the same conditions [3]. If the wettability of molybdenite is depressed more, the separation process will be more difficult. Studying the effect of ions on molybdenite flotation and mechanism is important for practical Cu-Mo separation
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