Effects of Interfacial Hydroxylation Microstructure on Quartz Flotation by Sodium Oleate

Abstract

Quartz, a common inorganic nonmetallic mineral, is usually removed or purified by beneficiation, normally flotation. Given the strong polarity of the quartz surface, it is easy to hydrate to form a hydroxylation layer, which makes it impossible to float quartz with sodium oleate (OL) used alone. An ideal flotation method for quartz is preactivation with Ca2+, followed by collection with OL. Herein, the effects of surface hydroxylation on the adsorption of the anionic collector OL on the quartz surface before and after Ca2+ activation are systematically investigated by density functional theory (DFT) calculations. The results show that the displacement adsorption of surface hydroxyl substituted by OL– is not feasible in thermodynamics, and the OL– can only bind to the H atoms of the hydroxylated quartz surface via hydrogen bonds, namely, hydrogen binding adsorption. Due to the electrostatic repulsion and steric hindrance effect induced by the surface hydroxylation structure, the adsorption ability of OL– on the quartz surface mediated by hydroxyl bridges is very weak, which is insufficient to realize quartz floating. However, Ca2+ ions are easily adsorbed on the hydroxylated quartz surface, providing favorable active sites for subsequent adsorption of OL–, thus becoming a credible solution for the industrial flotation of the strong hydrophilic mineral quartz. These findings shed some new insights for accurately understanding the flotation mechanism of strongly hydrophilic oxide minerals and are beneficial to promoting the development of mineral flotation fundamentals.

Progressive Hydrophilic Processes of the Pyrite Surface in High-Alkaline Lime Systems

“…In addition, it is worth mentioning that the presence of numerous hydroxyls disrupts the electrical neutrality of the periodic system, and here, we use the counterion H anions to retain the charge balance of the system. Considering that the presence of numerous counterions in the system can cause difficulties in DFT calculations, the treatment was that the practice of placing the counterions at the bottom of the slab was adopted, allowing them to relax to the unsaturated coordinated anions . This avoids the interaction of numerous counterions with the adsorbate in the finite vacuum box, which may lead to a large error in the calculated adsorption energy.…”

“…Considering that the presence of numerous counterions in the system can cause difficulties in DFT calculations, the treatment was that the practice of placing the counterions at the bottom of the slab was adopted, allowing them to relax to the unsaturated coordinated anions. 33 This avoids the interaction of numerous counterions with the adsorbate in the finite vacuum box, which may lead to a large error in the calculated adsorption energy.…”

Emerging Trends of Computational Chemistry and Molecular Modeling in Froth Flotation: A Review

“…Quartz surface activation with Ca 2+ or Ca­(OH) + repels water molecules from the surface, bridging α-BLA – to it and leading to a significant promotion of quartz floatability. DFT calculations further revealed that the preactivation of hydroxylated quartz surface with Ca 2+ introduces favorable active sites for subsequent adsorption of sodium oleate, making direct flotation of quartz industrially feasible …”

“…DFT calculations further revealed that the preactivation of hydroxylated quartz surface with Ca 2+ introduces favorable active sites for subsequent adsorption of sodium oleate, making direct flotation of quartz industrially feasible. 351 MD simulations based on the Universal force field parameters and Mulliken partial charges were conducted to assess the hydrophilicity of Cu 2+ activated sphalerite surface. 352 The wettability of the pristine and the Cu 2+ -activated sphalerite was compared by calculating the contact angle, water number density distribution, water dipole orientation, and water residence time, among other things.…”

Probing the Interaction Mechanism of Sodium Oleate and Dodecyl Amine with Quartz Surfaces in the Presence of Ca2+ Ions by AFM Force Measurement

“…15 For the Ca 2+ -activated quartz anion flotation process, two possible mechanisms have been reported by Zhang et al through first-principles calculations. 16 One process is the preadsorption of Ca 2+ ions on the quartz surface, which offers reaction sites for the NaOL anion collector's subsequent interfacial adsorption. The other mechanism is that the NaOL anion collector preassembles with Ca 2+ ions to form a calcium dioleate colloidal precipitate and works on the mineral surface to achieve hydrophobic floating of quartz.…”