Abstract
Hemimorphite and smithsonite are all-important zinc oxide minerals. The beneficiation and separation of them using flotation method is usually considered difficultly. Minerals surface wettability and its regulation are the core issues in the flotation process, which closely correlate with the surface properties of the minerals. Therefore, an in-depth understanding of the surface properties of the two minerals is of great significance for the study of the flotation technology of them. In this study, the surface properties of the hemimorphite (110) surface and the simthsointe (101) surface, and their relationships to the mineral floatability have been investigated by first-principle calculation method based on density functional theory. The calculation results demonstrated that the hemimorphite (110) surface exhibited more obviously surface reconstruction. For the orbital energy level of the surface atoms of two minerals, the O 2p orbital is closer to the Fermi level than the Zn 3d. Chemical bond Mulliken population value indicated that the ionicity of the unsaturated linkage on the smithsonite (101) surface was stronger than that on the hemimorphite (110) surface. The absolute values of the ratios of negative charges to positive charges on the surfaces of hemimorphite and smithsonite were 1.529 and 1.256 respectively. These results implied that the O atoms on hemimorphite (110) surface are more impede collector molecule, such as hydroximic acid, bond with Zn atom, hemimorphite (110) surface is more readily wetted by water. This study provides comprehension at an atomic level to the relationship between surface properties and the floatability of hemimorphite and smithsonite.
Highlights
As an important base metal, zinc is widely used as a raw material in various industries such as electroplating, batteries, automobile manufacturing, etc. [1,2]
Up to present, generalized gradient approximation (GGA) and local density approximation (LDA) are the most widely used method applied in Density functional theory (DFT) study of solid material property
Due to the H+ and OH− ions are the potential determining ions for hemimorphite and smithsonite [30], it can be conjectured that the point of zero charge (PZC) of hemimorphite is lower than smithsonite, which conforms to the experimental results [31], but the eVidence is where future work is needed
Summary
As an important base metal, zinc is widely used as a raw material in various industries such as electroplating, batteries, automobile manufacturing, etc. [1,2]. Hemimorphite [Zn4 Si2 O7 (OH)2 ·H2 O] and smithsonite [ZnCO3 ] are the typical zinc oxide minerals [2,4,5,6]. The traditional technique for treating low-grade zinc oxide ores is hydrometallurgy [3]. Flotation is a separation process that exploits natural and induced differences in surface properties of the minerals. Cleavage is the tendency of a mineral to break along smooth planes parallel to zones of relative weak bonding. In-depth understanding of the nature of the cleavage surface of the hemimorphite and smithsonite is of great significance for the investigation of the flotation behavior of them. The study provides an essential and comprehensive understanding of the cleavage plane properties and the relationship between surface properties and the floatability of hemimorphite and smithsonite
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