Investigating the performance of a novel polyamine derivative for separation of quartz and hematite based on theoretical prediction and experiment

Investigating the Mechanism of Diethylenetriamine Pentamethylene Phosphonic Acid as a Depressant for Calcite Flotation of Fluorite

Fluorite and calcite have been attracting research attention for a long time. This paper reports on an investigation of the use of diethylene triamine pentamethylphosphonic acid (DTPMPA) as a chelating inhibitor. DTPMPA was used as a chelating inhibitor to study the flotation, separation, and adsorption behaviors of fluorite and calcite minerals. The microflotation experiment showed that the maximum separation of fluorite and calcite can be achieved with a DTPMPA dosage of 1.5 × 10-4 mol/L under weakly alkaline conditions (pH = 8). Zeta potential measurement, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy were used to confirm that DTPMPA was adsorbed on the surface of calcite, inhibiting NaOl adsorption. Additionally, density functional theory calculations showed that oxygen in the DTPMPA phosphate group formed the most stable bidentate binuclear adsorption configuration by chelating with calcium on the calcite surface. Through detection analysis and simulation calculations, the results showed that DTPMPA exhibited significantly weaker adsorption on fluorite compared to that on calcite, highlighting its selective inhibition ability on calcite.

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

Froth flotation is the most versatile process in mineral beneficiation, extensively used to concentrate a wide range of minerals. This process comprises mixtures of more or less liberated minerals, water, air, and various chemical reagents, involving a series of intermingled multiphase physical and chemical phenomena in the aqueous environment. Today's main challenge facing the froth flotation process is to gain atomic-level insights into the properties of its inherent phenomena governing the process performance. While it is often challenging to determine these phenomena via trial-and-error experimentations, molecular modeling approaches not only elicit a deeper understanding of froth flotation but can also assist experimental studies in saving time and budget. Thanks to the rapid development of computer science and advances in high-performance computing (HPC) infrastructures, theoretical/computational chemistry has now matured enough to successfully and gainfully apply to tackle the challenges of complex systems. In mineral processing, however, advanced applications of computational chemistry are increasingly gaining ground and demonstrating merit in addressing these challenges. Accordingly, this contribution aims to encourage mineral scientists, especially those interested in rational reagent design, to become familiarized with the necessary concepts of molecular modeling and to apply similar strategies when studying and tailoring properties at the molecular level. This review also strives to deliver the state-of-the-art integration and application of molecular modeling in froth flotation studies to assist either active researchers in this field to disclose new directions for future research or newcomers to the field to initiate innovative works.

Substituent Effects in Kaolinite Flotation Using Dodecylamine: Experiment and DFT Study

The molecular structure of cationic surfactants is closely related to their flotation performance. In this paper, three cationic surfactants with different head group structures were selected as collectors of kaolinite, and the substituent effects were studied by the DFT method. The DFT calculation results showed that increasing the number of substituents in the dodecylamine head group can significantly increase its surface and head group charge. Dodecylamine has the lowest LUMO orbital energy, so dodecylamine has the strongest electron attraction ability and the strongest interaction with kaolinite. Electron density differential showed that there was an area of electron aggregation between the collector and the surface of the kaolinite. The interaction energy of DDA on kaolinite surfaces was greater than that of the other two collectors, indicating that the adsorption of DDA on the surface of kaolinite was more stable. Flotation results showed that higher a kaolinite yield was obtained in the presence of dodecyl dihydroxyethyl methyl ammonium chloride. The calculated results of the solvent-accessible surfaces, the head group charge, and the number of bonds between the collector and the kaolinite show good consistency with the actual flotation results of the three collectors, which can be used as a screening index for kaolinite flotation collectors.

Effects of the Goethite Surface Hydration Microstructure on the Adsorption of the Collectors Dodecylamine and Sodium Oleate

Dodecylamine (DDA) and sodium oleate (OL) are commonly used collectors in the reverse flotation and the direct flotation of goethite. However, the flotation mechanisms of DDA and OL on the goethite surface remain unclear. In this study, the first-principles density functional theory calculations were used to reveal the role of the hydration of the goethite surface and its effects on flotation reagents from a microscopic perspective. The calculation results showed that DDA was adsorbed on the surface of goethite by hydrogen bonds in the absence of hydration. However, the existence of the hydration microstructure hindered the formation of hydrogen bonds and made it difficult for DDA to be adsorbed on the goethite surface. In the OL system, oleate ions are chemically adsorbed on the surface Fe sites of goethite in the absence of hydration, while in the presence of hydration, the oleate ions were adsorbed on the H-terminal hydration surface of goethite by hydrogen bonds. This work sheds new light on the roles of the hydration microstructure and the adsorption mechanism of the flotation reagent on the oxide minerals.

Experimental and Molecular Dynamics Simulation Study on the Effects of the Carbon Chain Length of Gemini Surfactants on the Inhibition of the Acid-Rock Reaction Rate

A series of gemini surfactants were synthesized to examine their adsorption properties. The properties of gemini surfactants, including critical micelle concentration, electrostatic potential distributions, charge, occupied volume, lowest unoccupied molecular orbital (LUMO), and highest occupied molecular orbital (HOMO), were evaluated using conductivity and density functional theory (DFT) calculations. The calculation results indicated that the electrostatic potential distributions were similar among the four gemini surfactants. Moreover, surfactants with longer carbon chains are more likely to be oblique on the rock surface according to the energy gap between the HOMO of the surfactants and the LUMO of the calcite surface. Experimental tests and molecular dynamics (MD) simulations were conducted to analyze the calcite-surfactant interactions. Combined with the free energy (ΔG) based on the contact angle and adsorption energy (E) based on MD simulation, the adsorption ability increases as the carbon chain length decreases. MD simulation is used to understand the form of surfactant molecules on the calcite at an atomic scale at different times. An obvious aggregation of gemini surfactants was found with an increase in the carbon chain length, which reduces the adsorption density and covered area of the surfactant. The adsorption behavior of the gemini surfactant is beneficial for isolating H⁺ transfer and retarding the acid reaction with the rock. The retarding ability and etching morphology were studied by acid etching. The acid-rock reaction rate showed that 12-4-12 had the best inhibition performance. Meanwhile, the uneven surface pattern following 12-4-12 etching is beneficial for maintaining the acid fracturing conductivity.

Collecting Agent–Mineral Interactions in the Reverse Flotation of Iron Ore: A Brief Review

Froth flotation has been widely used in upgrading iron ores. Iron ore flotation can be performed in two technical routes: direct flotation of iron oxides and reverse flotation of gangue minerals with depression of iron oxides. Nowadays, reverse flotation is the most commonly used route in iron ore flotation. This review is focused on the reverse flotation of iron ores, consisting of reverse cationic flotation and reverse anionic flotation. It covers different types of collecting agents used in reverse iron ore flotation, the surface characteristics of minerals commonly present in iron ores (e.g., iron oxides, quartz, alumina-bearing minerals, phosphorus-bearing minerals, iron-bearing carbonates, and iron-bearing silicates), and the adsorption mechanisms of the collecting agents at the mineral surface. The implications of collecting agent–mineral interactions for improving iron ore flotation are discussed.