Flotation separation of different minerals is based on the selective modulation of mineral surface properties by flotation reagents. However, a quantitative understanding of the facet-dependent interaction mechanism of different functional groups in typical flotation reagents still remains elusive, resulting in the challenge in accurate modulation of surface interaction in mineral separation processes. Herein, taking a typical serpentine-pyrite flotation system, the chemical force microscopy technique was used to quantitatively measure the intermolecular interactions of various self-assembled monolayers (i.e., OH-SAM, COOH-SAM, and PO 4 -SAM) with different serpentine planes (i.e., SiO basal, MgOH basal, and MgSiO edge) and pyrite surface in aqueous solution at the nanoscale. It was found that all the functional groups exhibited the attractive force with MgOH plane of serpentine during surface approach due to electrostatic double layer interaction, while a pure repulsion was detected on SiO and edge planes at both pH 5.5 and 8.5, indicating that MgOH plane was the dominant facet for reagent adsorption. At the typical flotation condition of pH 8.5, the strong adhesion was observed for –COOH groups interacting with both MgOH plane and pyrite surface during retraction attributed to the metal complexation, while –OH groups were much more adhesive on pyrite surface than that on MgOH plane. In contrast, a strong adhesion on MgOH plane (21.09 ± 0.25 mN m −1 ) and relatively weak adhesion on pyrite (14.93 ± 0.64 mN m −1 ) were respectively observed for −PO 4 groups, which implied the excellent selectivity of −PO 4 groups. Density functional theory (DFT) simulation also indicated the stronger adsorption energy of −PO 4 group with MgOH plane (−73.7 kcal mol −1 ) than pyrite surface (+62.7 kcal mol −1 ). Moreover, the excellent separation performance of phosphoric acid-based reagents was further confirmed during serpentine-pyrite flotation experiments. This work provides quantitative information on molecular interaction mechanisms underlying the adsorption of functional groups on different mineral planes at the nanoscale, which also helps develop a molecular design principle for chemical additives to achieve the selective modulation of target mineral planes in complex mineral pulps.
The large amount of mineral processing wastewater generated during the extraction of rare earth elements, especially the organic flotation reagents inside, has posed great environmental threats. In this work, a facile method to prepare tubular micromotors based on CuS and MnO 2 was proposed, followed by further integration of Bi 2 MoO 6 on the micromotor surface to enhance the photocatalytic activity. The resulting Bi 2 MoO 6 @MnO 2 @CuS tubular micromotors which could realize autonomous motion by the generation of abundant micro/nanobubbles were employed for the removal of salicylhydroxamic acid (SHA), a commonly used reagent in rare earth ores flotation, via photo-assisted Fenton-like processes. The incorporation of Bi 2 MoO 6 in the tubular structure increased the SHA removal efficiency under visible light by 32.51 %. Moreover, the synergistic effect between photocatalysis and Fenton-like processes contributed to a SHA removal efficiency of 95.51 % within 30 minutes. A possible mechanism was proposed to explain the enhanced catalytic activity of the tubular micromotors. This study provides a way to fabricate tubular micromotor with low-cost and stable materials in batches, which may shed light on the treatment of rare earth ore processing wastewater.
A novel compound 4-amino-5-mercapto-1,2,4-triazole was first synthesized, and its selective adsorption mechanism on the surface of chalcopyrite was comprehensively investigated using UV–vis spectra, zeta-potential, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy measurements (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and first principles calculations. The experimental and computational results consistently demonstrated that AMT would chemisorb onto the chalcopyrite surface by the formation of a five-membered chelate ring. The first principles periodic calculations further indicated that AMT would prefer to adsorb onto Cu rather than Fe due to the more negative adsorption energy of AMT on Cu in the chalcopyrite (001) surface, which was further confirmed by the coordination reaction energies of AMT-Cu and AMT-Fe based on the simplified cluster models at a higher accuracy level (UB3LYP/Def2-TZVP). The bench-scale results indicated that the selective index improved significantly when using AMT as a chalcopyrite depressant in Cu−Mo flotation separation.
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