Surface chemistry in the flotation of trona and other soluble carbonate salts.

摘要

Recent studies have shown that the flotation method can be used for preprocessing of trona ore to remove insoluble mineral contaminants prior to chemical treatment and production of soda ash. However, there is little fundamental study about the flotation chemistry of trona. In this regard, first, the applicability of flotation for the treatment of trona ore was further investigated. Then, fundamental details of the surface chemistry for the flotation of insoluble gangue minerals were studied. Finally, the solution chemistry for the trona system was studied in greater detail.;Flotation results showed that the developed new flotation technology for the separation of insoluble minerals from trona is possible by proper control of the flotation conditions. The experimental results for insoluble gangue minerals indicate that the surface charge/collector colloid adsorption theory may be used to explain their flotation behavior. In addition to the studies of insoluble gangue mineral flotation, the studies with carbonate minerals suggest that certain important factors can affect the flotation response of these soluble carbonate salts from their brines, including thermodynamic stability of the salt, viscosity of the brine, and interfacial water structure. Based on the interfacial water structure studies, Na2CO3 and K2CO3 were found to act as strong water structure makers, whereas NaHCO3 and NH4HCO3 act as weak water structure makers. In addition, there is a considerable agreement between the changes in the OD band parameters (bandwidth and the peak wavenumber) of carbonate and bicarbonate salt solutions and the viscosity characteristics of their solutions. Surface tension experiments revealed that carbonate ions are more hydrated than bicarbonate ions which cause a greater increase in the surface tension of carbonate solutions when compared to that of bicarbonate solutions. The air/brine interface was also investigated using sum-frequency vibrational spectroscopy (SFVS) and molecular dynamics simulations (MDS) to provide further understanding of soluble salt interfacial phenomena at the molecular level. Contact angle measurements confirmed the strong interaction of water at the salt surfaces. Bubble attachment experiments also suggest that collector adsorption takes place at the surface of NaHCO3 for flotation this is not the case for Na2CO3. Finally, it was concluded that due to the structure making effect of Na2CO 3 in the brine and at the trona surface, the direct flotation of trona from its brine is difficult.