Effects of Interfacial Hydroxylation Microstructure on Quartz Flotation by Sodium Oleate

Correlation between Clay Minerals, Rheology, and Flotation in the Desulfurized Pulp of High-Sulfur Bauxite

Eliminating the adverse influence of clay minerals on the flotation separation of pyrite from high-sulfur bauxite has always posed a challenge. In this study, the correlations among rheology, clay minerals, and flotation in desulfurized pulp of high-sulfur bauxite were explored after the mineralogical characteristics were understood. The fine pyrite particles were closely intergrown with kaolinite, Illite, and diaspore. A total of 73.74% of the Illite and 65.60% of the kaolinite were liberated when the high-sulfur bauxite was ground to -0.075 mm, accounting for 79.33% by a ball mill. The influence on the apparent viscosity and yield stress of the pulp followed the order of kaolinite > Illite > pyrite. However, heterocoagulation occurred in the case of pyrite mixed with kaolinite and Illite, resulting in the formation of a network structure characterized by a higher apparent viscosity and greater yield stress. Generally, pulp rheology and the flotation index were negatively correlated, with the sulfur grade (S grade) in the flotation products decreasing as the apparent viscosity and yield stress increased. A strategy to mitigate the adverse effects of clay minerals on the rheological properties of high-sulfur bauxite pulp involves the addition of sodium hexametaphosphate (SHMP) to destroy this network structure. For kaolinite-pyrite mixed pulp, the S grade and sulfur recovery (S recovery) of the sulfur concentrate (S concentrate) increased by 1.36% and 6.93%, respectively, when the mass fraction of kaolinite was 60% and the apparent viscosity (or yield stress) decreased to 0.00616 Pa·s (or 0.33 Pa) from 0.00679 Pa·s (or 0.4239 Pa). This study provides valuable insights for enhancing the flotation desulfurization performance of high-sulfur bauxite through rheological regulation.

Construction of cellulose-based dual-gradient heterogeneous bilayer membranes with optimized directional moisture transport property for enhancing moisture-electricity generation

Moisture-electricity generation (MEG) offers a promising strategy for sustainable energy conversion by harvesting ambient moisture to generate electricity. However, cellulose-based MEGs (CMEGs) are limited by inefficient proton migration and disordered moisture transport. To address these issues, we propose a dual-gradient heterogeneous bilayer cellulose-based membrane (CA@CF/CANPF) for Bi-CMEGs. The pore size gradient regulates water adsorption and diffusion, effectively guiding directional transport within the membrane, while the gradient of oxygen-containing functional groups improves hydrophilicity and facilitates ion exchange, accelerating proton migration. This Bi-CMEGs design achieves an open-circuit voltage of approximately 665.2 mV, a short-circuit current of 11.2 μA/cm2 and an effective power density of 1.24 μW/cm2, demonstrating excellent adaptability and stability across varied temperature and humidity conditions. Compared to recent advancements in CMEGs, the dual-gradient structure significantly enhances moisture transport and proton migration, overcoming key efficiency and scalability limitations. Notably, an amplified voltage of approximately 2516.7 mV is achieved by integrating the Bi-CMEG units in series, which is sufficient to directly power an LED for over 6 h under typical laboratory conditions. This work emphasizes the dual-gradient structure of Bi-CMEG, providing an efficient and unique design concept for sustainable cellulose-based moisture-electricity generation devices.

Hydrophilic Modification of Macroscopically Hydrophobic Mineral Talc and Its Specific Application in Flotation

Sodium diethyldithiocarbamate (DDTC), a common collector used to enhance the hydrophobicity of minerals in froth flotation, nevertheless weakens the hydrophobicity of the talc surface. To rationalize this anomaly, the interactions of a hydrophobic alkyl group and hydrophilic mineralophilic group (-NCS2-) of heteropolar surfactant DDTC, and a water molecule with the talc (001) surface, were investigated. Herein, DFT simulations found that the talc (001) surface features natural hydrophobicity determined by the competition between adhesion (surface water) and cohesion (water-water interactions). The interaction of the hydrophobic alkyl group of DDTC with the talc surface is more favorable compared to that of the -NCS2- group and H2O, favoring the hydrophilic modification of the talc surface. Additionally, adsorption isotherms, time-of-flight secondary ion mass spectrometry (ToF-SIMS), microflotation tests, and contact angle measurements also indicate that the differences in adsorption orientation of the heteropolar surfactant DDTC on the talc surface enhance the hydrophilicity of the talc surface, leading to a decreased recovery of the talc. This study provides crucial surface chemistry evidence for the selective adsorption of heteropolar surfactants and contributes to the understanding of the mechanism for the efficient flotation separation of molybdenite from talc.

New Low-Temperature Collector for Flotation Separation of Quartz and Hematite after Reduction Roasting and Its Mechanism

It is an effective method to separate hematite by converting it to magnetite by reduction roasting and then separating it by magnetite separation. However, quartz will partially remain in the concentrates. Therefore, it is significant to separate quartz from the concentrates to produce high-quality iron concentrates. In this work, N-{3-[(2-propylheptyl)oxy]propyl}propane-1,3-diamine (PPPDA) was synthesized and served as a collector for low-temperature flotation to separate quartz from magnetite that was generated by reduction roasting of hematite. The flotation experiment and principle of the PPPDA collector on quartz and the new generated magnetite surface were studied by flotation experiments, ζ potential measurement, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations. Flotation data showed that, in the pH range of 5-9, when PPPDA dosage was 15 mg/L and temperature was 10-30 °C, PPPDA has good collecting ability on quartz minerals, which could make the recovery difference between quartz and the new generated magnetite reach more than 95%. Artificial mixed ore experiments at a low temperature of 10 °C yielded a concentrate with an iron grade of 64.41% and an iron recovery of 78.98%. The data of ζ potential, FTIR spectrum, and XPS and DFT calculations confirmed that PPPDA could not be adsorbed on the new generated magnetite, and the adsorption principle between PPPDA and quartz was mainly electrostatic adsorption and hydrogen bond adsorption.

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

Quartz is a key raw material in high-tech fields (such as photovoltaics and semiconductor microelectronics), and the most efficient extraction method of quartz is mineral flotation. Quartz activation plays a crucial role in mineral flotation. However, the mechanism underlying the process remains unclear, and the role of additional metal ions is controversial. In this study, the interaction forces between the quartz surface, the dodecylamine (DDA) cation/sodium oleate (NaOL) anion mixed collectors, and Ca2+ were analyzed using atomic force microscopy in order to systematically explore the activation process of quartz flotation. The results confirmed that the activation process was initialized from NaOL, which was adsorbed on the surface of a calcium-covered quartz surface. The existence of DDA inhibited the binding of Ca2+ to NaOL so that more Ca2+ was adsorbed on the quartz surface to provide the adsorption site for NaOL. Moreover, the best adsorption condition of Ca2+ + NaOL + DDA mixed solution was analyzed by quartz crystal microbalance with dissipation, and it demonstrated that the most stable chemisorption environment on the quartz surface was at pH 11.0. In these circumstances, Ca2+ could first adsorb in a point-like manner on the quartz surface, which was then adsorbed with a mixture of NaOL and DDA. This result showed that, at a specific pH, Ca2+ could encourage the coadsorption of cationic/anionic mixed collectors on quartz. This work provides an important new understanding of the intermolecular interactions that take place during complex mineral flotation processes between chemical additives and mineral surfaces. The methodology used in this study can be easily adapted to different interfacial processes, including water treatment, membrane technology, bioengineering, and oil production.

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.

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

Pyrite, as a disturbing gangue mineral in the beneficiation of valuable sulfide minerals and coal resources, is usually required to be depressed for floating in flotation practice. Specifically, the depression of pyrite is achieved by causing its surface to be hydrophilic with the assistance of depressants, normally with inexpensive lime used. Accordingly, the progressive hydrophilic processes of the pyrite surface in high-alkaline lime systems were studied in detail using density functional theory (DFT) calculations in this work. The calculation results suggested that the pyrite surface is prone to hydroxylation in the high-alkaline lime system, and the hydroxylation behavior of the pyrite surface is beneficial to the adsorption of monohydroxy calcium species in thermodynamics. Adsorbed monohydroxy calcium on the hydroxylated pyrite surface can further adsorb water molecules. Meanwhile, the adsorbed water molecules form a complex hydrogen-bonding network structure with each other and with the hydroxylated pyrite surface, which makes the pyrite surface further hydrophilic. Eventually, with the adsorption of water molecules, the adsorbed calcium (Ca) cation on the hydroxylated pyrite surface will complete its coordination shell surrounded by six ligand oxygens, which leads to the formation of a hydrophilic hydrated calcium film on the pyrite surface, thus achieving the hydrophilization of pyrite.