Theory And Experimental Study On Ammonium - Amine Salt Enhanced Vulcanized Malachite Flotation

Copper oxide ore is an important copper ore resource, and malachite is one of the main copper oxide minerals. Sulfuration-xanthate flotation is the primary method of recovery of copper oxide minerals. This recovery method has been widely used in industry. Previous studies have proposed numerous sulfuration-xanthate flotation theories based on current research. However, the depth of research on sulfuration-xanthate flotation is not satisfactory, and some questions regarding the sulfuration-xanthate flotation mechanism remain because of the complexity of flotation systems. Previous studies have focused on the reactions between the minerals and flotation reagents as well as the reaction products; molecular-level investigations are rare. Therefore, it is necessary to further study the mechanism of intensified sulfuration-xanthate flotation of copper oxide by ammonium-amine salt to better understand this reaction.In this study, malachite and copper oxide ore served as the main research subjects. Density functional theory (DFT) calculations and atomic force microscopy were used to investigate the bulk and surface properties of malachite such as its geometric and electronic structure. The related mechanisms of sulfuration and reinforced sulfuration of malachite were studied using DFT calculations, which allowed new mechanisms of sulfuration and reinforced sulfuration of malachite to be proposed. The interaction between IX and malachite after sulfuration and reinforced sulfuration was also studied by DFT calculations. The dissolution of malachite was investigated under different conditions through flotation solution chemistry theory and inductively coupled plasma-mass spectrometry measurements. The surface properties of malachite samples exposed to different sulfuration conditions were characterized by zeta potential, scanning electron microscopy-energy-dispersive X-ray (EDS) and X-ray photoelectron spectroscopy (XPS). Lastly, reinforced sulfuration flotation experiments of both pure mineral malachite and copper oxide ore by ammonium-amine salt were carried out, which verified the results of theoretical calculations and mechanism investigations.The discovery that malachite is a mineral with a layered structure was further confirmed. Handstand symmetry exists between layers and the electric density between adjacent layers is relatively weak because it is dominated by intermolecular forces. The Fermi level intersects with the conduction band, so malachite exhibits good conductivity. The region near the Fermi level is primarily contributed by Cu 3d and O 2p orbitals. Compared with other atoms, Cu and O have relatively high reactivity. The (-201) surface of malachite crystals is the dominant cleavage surface, and the new surface of malachite relaxed during grinding, which results in surface reconstruction.Based on the stratified structure and DFT calculations of malachite crystals, the adsorption configuration of S7 in the malachite surface is complicated. We find that S2 acts as a bridge between adjacent layers of Cu atoms, and interacts with Cu atoms in the adjacent layer to form Cu-S-Cu adsorption configurations. This links adjacent layers through chemical bonding rather than just intermolecular forces, which contributes to the stability of the overall structure of malachite crystals. That interlayer sulfuration exists in Sz sulfurated malachite is a new discovery in malachite sulfuration theory. Compared with the Cu 3d orbital peak before vulcanization, the sulfuration and reinforced sulfuration of the malachite surface shift the orbital peak closer to the Fermi level. It is likely that the latter process strengthens the peak of the Cu 3d orbital; namely NH4+ and en enhance the activity of Cu atoms on the malachite surface, increasing the density of S2 and producing a reinforced sulfurated malachite surface. We propose a new curing mechanism to explain the reinforced malachite surface reactivity of Cu atoms upon addition of a combination of NH4+ and en.Our DFT calculations reveal that the adsorption of xanthate on the malachite surface is unstable because of the weak force between layers. Interlayer sulfuration of malachite increases the forces between layers by forming Cusurface-S-Cusubaltem adsorption configurations. This enhances the activity of Cu atoms in the surface layer, which leads to stronger xanthate adsorption on the malachite surface after reinforced sulfuration. NH4+ and en increased the reactivity of Cu atoms and the adsorption strength between the surface layer or layers and S2- strengthening the interaction between the layers and making the structure more stable. Highly efficient curing also made the adsorption of xanthate on the malachite surface more stable. From these results, we propose a new stable adsorption mechanism using NH4+ and en together to enhance the reactivity of the Cu atoms of the malachite surface.The dissolution of malachite in ammonium-amine salt and sodium sulfide solution was compared. The solubility variation of malachite under different conditions indicates that CCu in sodium sulfide solution is two orders of magnitude smaller than that in pure water, and CCu in ammonium-amine salt solution is also two orders of magnitude smaller than that in pure water. Meanwhile, CCu in ammonium-amine salt and sodium sulfide solution is one order of magnitude lower than that in pure water. This indicates a substantial decrease of CCu after reinforced sulfuration of malachite.The negative shift of the potential of malachite over time indicates that the ammonium-amine salt could effectively strengthen the sulfuration effect of the malachite surface. Semi-quantitative EDS analysis showed that the S content of malachite ranged from 1.62% to 14.64% after direct sulfuration. The S content of the malachite surface increased after reinforced sulfurized. XPS analysis revealed that the 2p electron binding energy of Cu atoms decreased after sulfuration and intensified sulfuration, so the reactivity of copper atoms will be enhanced. The ratios of the areas of S 2p3 and 2 peaks after strengthening sulfuration were 5.06% and 3.88%, respectively, which are greater than those after direct vulcanization of 3.50% and 2.66%, respectively. Therefore, the adsorption amount of sulfur after sulfuration is greater than that after direct vulcanization. These findings further confirm that ammonium-amine salt could effectively strengthen the vulcanization of malachite.Based on flotation tests are carried out with application of pure mineral malachite and actual copper oxide so as to verify and optimize the best flotation reagent system and processes. For the malachite sulfide flotation, the optimal PH value in the range of 9 to 11, the best dosage of sodium sulfide reagent system of 4×10-3 mol/L and iso-amyl xanthate dosage of 9.64×10-3 mol/L, and the maximum recovery is 51.64%. Comparing the effects of intensified vulcanization between combination of ammonium salts and single ammonium salt, the recovery of malachite increase by nearly 20% that significantly improved cure efficiency among which the best combination of ammonium hydrogen carbonate and phosphoric acid Ethylenediamine. The flotation results of combination of ammonium-amine salt improved sulfide-xanthate of the actual copper oxide show that it could improve the concentrate grade of 4.88% and concentrate recovery rate of 12.83%, tailings grade is decreased significantly and achieve efficient recovery of copper that is a strong verification for conclusions of the theoretical researches.