Surface Properties and Floatability Comparison of Aegirite and Specularite by Density Functional Theory Study and Experiment

Abstract

Understanding the differences in surface properties between aegirite and specularite is of great significance to study their separation. In this work, the surface properties of aegirite and specularite, as well as their relationships to floatability, have been explored by first principle calculation, flotation, and Zeta potential measurement. The surface relaxation indicated that the specularite (001) surface appeared to show more surface reconstruction. The unsatisfied bond properties, Mulliken bond population, and surface charge showed that the floatability of specularite was superior to that of aegirite. The flotation results showed that the hydrophobicity of specularite was higher than that of aegirite with dodecylamine (DDA) as the collector. It is infeasible to separate specularite from aegirite by flotation using starch as the depressant, and research of effective reagents with high affinity to the element Si is the subclinical breakthrough point of specularite/aegirite separation.Minerals 2019, 9, 782 2 of 15 flotation with amines. They also found that starch was not a selective depressant for magnetite in the process of the reverse cationic flotation of iron ores when iron-containing silicates as amphiboles are present in the flotation system [8]. Carboxymethyl cellulose, an effective depressant for iron oxide, was also found to be a depressant for chlorite [14].The novel high-efficiency depressants or collectors are considered to be an effective method to solve the unsatisfactory separation problems [15,16]. These depressants and collectors are targeted for making a sufficient hydrophilic and hydrophobic state of the mineral and gangue surface, respectively. Therefore, they are profoundly inseparable from understanding the surface properties of the minerals in the novel depressant or collector molecule design and their adsorption mechanism on the mineral surface.In recent years, with the rapid developments of theoretical and computational chemistry, a density functional theory (DFT) calculation can be adopted to visually investigate the surface properties and floatability of minerals and to predict possible novel reagents [4,17]. The wettability of the mineral surface and its regulation have always been the core issues of the flotation process [18][19][20]. Thus, further research of the nature of the cleavage surface, especially of the main cleavage surface, is of great significance for investigating the floatability of the minerals. For example, Han et al. [21] calculated the surface properties of the hemimorphite (110) surface and the simthsointe (101) surface by the first-principle calculation method to investigate their relationships to the mineral floatability, which implied that hemimorphite (110) surface is more readily wetted by water, while the O atoms on hemimorphite (110) surface are more impeding of collector molecules. He et al. [22] calculated the properties of spodumene and revealed that the O atoms in spodumene are the most active, while the Li atoms are inactive, so an activator is nece...

Carbonation of calcium-magnesium pyroxenes: Physical-chemical controls and effects of reaction-driven fracturing

“…The fact that the theoretical value of γ for augite calculated using Eq. ( 11) is nearly identical to the surface energy value of 1.2 J m -2 reported for aegirine (Li et al, 2019) give us confidence about the reliability of our calculation method. Note that augite and aegirine are isostructural and form a solid solution, so it is not unexpected for their surface energy values to be very similar.…”

Study of the Effect of Absorbed Cu Species on the Surface of Specularite (0 0 1) by the DFT Calculations

“…The unit cell parameters were a = b = 5.03 Å, c = 13.75 Å, α = β = 90 • , and γ = 120 • . Li et al [27] studied the surface energy of several specularite crystal surfaces through DFT calculations, and the results showed that the (0 0 1) surface of specularite has the lowest surface energy. Therefore, the (0 0 1) surface was constructed according to the overall structure of specularite.…”

Flotation separation of specularite from chlorite using propyl gallate as a collector

“…18 The (001) surface was the most stable surface of chlorite and specularite, which was modelled for further adsorption calculation. 7,19 The bottom atoms xed mineral face was geometry optimized using the smart algorithm method under 0.001 kcal mol À1 convergence accuracy. The Ewald summation procession was applied to calculate van der Waals force and electrostatic energy.…”

“…It is difficult to separate in mineral processing due to the existence of the iron element in iron-containing silicates and iron ores, which leads to similar magnetic and oatability properties of targeted minerals and gangues. 6,7 It has been proven that the chlorite depressed by starch could not be oated effectively in reverse otation route using anionic collector sodium oleate, and the addition of sodium alginate could improve the separation efficiency. 8 Besides, the sodium oleate also is invalid for the separation of hematite and aegirite; for example, the recovery of aegirite maintained around 80% while hematite around 90% with sodium oleate 1 Â 10 À4 mol L À1 at pH ¼ 4-9.…”

“…9 Meanwhile, as for specularite and aegirite separation, these two minerals showed similar oatability when cationic collector dodecylamine was used. 7,10 Moreover, traditional depressants, including starch and carboxymethyl cellulose, were ineffective of selective depressing iron-containing silicates for the otation separation of iron ores from amphibole or chlorite. 1,6,10,11 Hence, effective otation reagents are urgently needed to solve the vexing beneciation problems.…”