Mineral Surfaces Research Articles

Thermodynamic conditions for the presence of physically sorbed collectors on a mineral surface in an elementary act of flotation

Thermodynamic conditions for the presence of physically sorbed collectors on a mineral surface in an elementary act of flotation

Sorption of 32Si and 45Ca by isotopic exchange during recrystallisation of cement phases

The uptake kinetics of 32Si and 45Ca on cement minerals including C-S-H phases, portlandite, AFm phases, ettringite, and aged hardened cement paste were determined through batch sorption experiments. A two-step uptake kinetics was observed, with a fast initial step during ∼1 day followed by a much slower second step, not yet completed after one year. The working hypothesis that the fast uptake is caused by exchange of the radioisotopes with stable isotopes adsorbed on the mineral surface, whereas the slow uptake step is due to uptake in the crystal lattice during recrystallisation, was tested with the help of phenomenological models that combine surface adsorption and homogeneous recrystallisation. The experimental data could be reproduced satisfactorily using a refined version of the formerly published continuous homogeneous recrystallisation (CHOR) model, supporting the working hypothesis and allowing equilibrium sorption coefficients (Rd; L kg−1) for these radionuclides to be calculated on a mechanistic basis. This provides insight into the intrinsic rates and mechanisms of interaction between cementitious materials and their pore fluids which contain dissolved calcium and silicon.

The carbon activation of electric furnace ferronickel slag and its utilization in cement-based materials

The high annual emissions and low utilization rate of electric furnace ferronickel slag (EFS) have brought enormous impacts on environment. This work intends to propose a methodology for the carbon activation of EFS to improve its resource utilization. To this end, the exfoliation-carbonation (i.e., hybrid aqueous carbonation) was developed and compared with CO2 bubbling carbonation (i.e., direct aqueous carbonation). The carbonation process of EFS and the hydration and mechanical strength of activated EFS blended cement-based materials was evaluated. Experimental results indicated that mechanical pre-treatment could disorder forsterite crystal and promote the dissolution of Mg to form Si enriched mineral surface. The direct aqueous carbonation led to the formation of passivation layer which could be striped by hybrid aqueous carbonation to facilitate further carbon mineralization. Increase in temperature significantly improved the decomposition of forsterite and accelerated the carbon mineralization kinetics. The activated EFS could accelerate the hydration and promote the mechanical strength of cement-based materials. Carbon mineralization is an effective method to strengthening the activity of EFS.

Synergistic adsorption of ethyl xanthate and butyl xanthate on pyrite surfaces: A DFT study

AbstractPyrite is the most widely distributed sulfide mineral with a wide range of uses, and pyrite is mainly recovered by means of flotation in practical production, and the commonly used flotation collectors are mainly xanthates with good flotation performance. The adsorption behavior of commonly used collectors ethyl xanthate and butyl xanthate on the surface of pyrite is investigated by using the density functional tight bounding theory (DFTB). The results show that when a single reagent acts on the pyrite surface, butyl xanthate has a stronger effect than ethyl xanthate, and the adsorbed mineral surface shows obvious hydrophobicity. The interaction between ethyl xanthate and butyl xanthate had a stronger effect than that of a single reagent, and the simulation of the flotation environment at ordinary temperature using molecular dynamics revealed that the synergistic adsorption of the two different reagents on the surface of pyrite was more hydrophobic, that is, the synergistic adsorption of the combined collector of ethyl xanthate and butyl xanthate on the surface of pyrite was stronger. The results of the study are of great significance for the synergistic effect between the combined collector and the mineral.

Geochemical drivers of manganese removal in drinking water reservoirs under hypolimnetic oxygenation

Manganese (Mn) is a naturally occurring contaminant commonly found in drinking water supplies. In lakes and reservoirs, water authorities increasingly use in situ treatment by hypolimnetic oxygenation (HOx) systems to remove metals such as Mn from the water column. HOx systems introduce dissolved oxygen (DO) to the bottom waters (hypolimnion) to promote oxidation and subsequent removal of metals from the water column. Previous laboratory studies have shown the importance of individual geochemical drivers (pH, alkalinity, mineral surfaces) on Mn oxidation, but few studies have examined the influence of these drivers of Mn removal in concert. In this study, we conducted field monitoring and laboratory experiments to examine how pH, alkalinity and the presence of mineral particles influence Mn removal at two drinking water reservoirs in southwest Virginia, both with HOx systems: Falling Creek Reservoir (FCR) and Carvins Cove Reservoir (CCR). Both reservoirs have had historical issues with elevated (>0.05 mg/L) Mn concentrations during seasonal stratification (May–October). Watershed geology contributes to differences in pH and alkalinity between the reservoirs, with FCR having lower historical medians of hypolimnetic pH and alkalinity (6.6 and 18 mg/L CaCO3, respectively) than CCR (7.2 and 62 mg/L CaCO3, respectively).Results of laboratory experiments examining the influence of pH on Mn removal showed substantial Mn loss within 14 days only under high pH (10) conditions. Mn removal did not occur at pH 6 or 8 over the same 14-day period. In experiments with pH 10 and alkalinity >70 mg/L CaCO3, near-total Mn removal occurred within 2 h. Mn removal occurred concurrently with precipitation of microscopic (<5 μm) particles, followed by formation of macroscopic (>100 μm) particles. Particles of both size classes were identified as Mn oxides (MnOx). These observations suggest that increasing pH and alkalinity promotes Mn oxidation and subsequent removal from solution. Results of experiments with pH 10 and alkalinity >70 mg/L CaCO3 suggest that heterogeneous oxidation by MnOx partially drives rapid Mn removal. Thus, initial formation of MnOx creates a positive feedback loop that can enhance additional Mn loss. In experiments using water collected from FCR and CCR, we observed rapid Mn removal in unfiltered water (0.002–0.05 d−1) but no significant removal of Mn in filtered water. These results, in combination with results of analysis of particles collected from reservoir water, suggest that minerals present in the water column likely catalyze MnOx formation. Together, our experimental results suggest that heterogenous oxidation is an important process of Mn removal, while pH and alkalinity variations of the range expected in natural freshwaters contribute less to differential Mn removal. The formation of MnOx particles during in situ oxygenation, as well as the presence of suspended minerals that occur naturally in water columns, play an important role in promoting Mn oxidation and should be accounted for in Mn removal treatment strategies.

A novelty strategy for AMD prevention by biogas slurry: Acetate acid inhibition effect on chalcopyrite biooxidation and leachate

With the widespread application of anaerobic digestion technology, biogas slurry become the main source of organic amendments in practice. Comprehensive studies into the inhibitory effects of low molecular weight (LMW) organic acids, essential components in biogas slurry, on the sulfide minerals biooxidation and its bioleaching (AMD) have been lacking. In this study, acetic acid (AA) served as a representative of LMW organic acids in biogas slurry to investigate its impact on the inhibition of chalcopyrite biooxidation by Acidithiobacillus ferrooxidans (A. ferrooxidans). It was shown that AA could slow down the chalcopyrite biooxidation and inhibit the jarosite formation on the mineral surface. Compared with the control group (0 ppm AA), the sulfate increment in the leachate of the 50 ppm, 100 ppm, and 200 ppm AA-treated groups decreased by 36.4%, 66.8%, and 69.0%, respectively. AA treatment (≥50 ppm) could reduce the oxidation of ferrous ions in the leachate by one order of magnitude. At the same time, the bacterial concentration of the leachate in the 50 ppm, 100 ppm, and 200 ppm AA-treated groups decreased by 70%, 93%, and 94%, respectively. These findings provide a scientific basis for new strategies to utilize biogas slurry for mine remediation and contribute to an enhanced comprehension of organic amendments to prevent AMD in situ in mining soil remediation.

Stability and transformation of jarosite and Al-substituted jarosite in an acid sulfate paddy soil under laboratory and field conditions

Jarosite, a prominent mineral in oxidised acid sulfate soil, is known to sorb and incorporate a variety of elements, including Al. However, to understand the role that jarosite plays in regulating element cycles, it is crucial to understand the stability and transformation pathways of jarosite in an acid sulfate soil under dynamic biogeochemical conditions. In this study, we observed the transformation of unsubstituted jarosite and Al-substituted jarosite, collectively referred to as ‘jarosite’, in an acid-sulfate rice paddy topsoil and subsoil from Thailand. Jarosite was incubated in flooded paddy topsoils and subsoils for up to sixteen weeks, both in laboratory mesocosms and in the field, using bags made of polyethylene terephthalate mesh. One set of mesh bags contained jarosite that was not mixed with any other minerals, and referred to as ‘pure mineral’ incubations. Mineral transformations occurred under the influence of the soil porewater only and were primarily followed by X-ray diffraction analysis. A parallel set of mesh bags contained soil with 57Fe-labelled jarosite enrichment (Fe enriched in soil by a factor of 1.3 but 57Fe enrichment factor of 12.5–13.6), which allowed jarosite transformation to occur in close association with the soil matrix. Mineral transformations in 57Fe-jarosite-enriched soil were followed using 57Fe Mössbauer spectroscopy. In laboratory mesocosms and in the field, jarosite transformed most quickly in topsoil, whereas jarosite underwent limited transformation in subsoils, especially in laboratory mesocosms where Fe reduction was slow. The chemical environment around the jarosite affected the outcome of the transformation processes. Crystalline Fe oxyhydroxides, such as goethite, dominated the products in mesh bags where jarosite was not mixed with soil, whereas short-range-ordered or non-mineral Fe phases, such as Fe(II) sorbed to mineral surfaces or complexed with organic ligands, were dominant transformation products of jarosite when mixed in soil. Furthermore, Al substitution in jarosite caused contrasting effects in mesh bags containing pure minerals or mineral-enriched soil. Aluminium substitution slowed the transformation of jarosite in pure mineral mesh bags, but Al-substituted and unsubstituted jarosite showed similar transformation rates and pathways when incubated as a mixture with soil. The contrasting rate of transformation in topsoil and subsoil, the contrasting products of transformation in pure mineral mesh bags and 57Fe-jarosite-enriched soil, and the contrasting effect of Al substitution in pure mesh bags or jarosite-enriched soil, all demonstrate that the rate and products of jarosite transformation are defined by a balance between competitive transformation pathways that affect the transforming minerals.

Hydrothermal carbon reduction in the absence of minerals

Abiotic synthesis of CH4 in seafloor hydrothermal fluids is generally assumed to occur via heterogeneous reactions on mineral surfaces. Stepwise homogeneous reduction of CO2 has, however, been suggested as an alternative (but sluggish) abiotic pathway to CH4, potentially via metastable species of intermediate oxidation states. In this study, we examine the effect of two temperature-dependent methylated species − methanol (CH3OH) and methanethiol (CH3SH), on homogeneous CH4 formation rates under long-term simulated hydrothermal conditions. Aqueous solutions containing formic acid (H13COOH, generating 13CO2 and H2) were heated with and without H2S at 300–325 °C (35 MPa) in a flexible Au reaction cell over several years without added minerals. Substantial 13C-labeled CH4 and CH3OH production from 13CO2 was observed over 4.3 yr, with aqueous CH4 formation varying with CH3OH abundance – a strong function of dissolved H2 abundance and, inversely, temperature. CH4 production was slower at 325 °C with lower CH3OH concentrations (in equilibrium with CO2 and H2), and faster at 300 °C, accompanying an equilibrium-controlled increase in CH3OH. Fastest CH4 production occurred at 300 °C following injection of H2S and H13COOH, which led to rapid formation (<4 days) of 13C-labeled CH3SH that subsequently decomposed over a further 0.8 yr, partly to 13CH4. Heating aqueous 13CH4 to 345–387 °C (33–35 MPa) in the presence of an oxidizing hematite-magnetite-pyrite assemblage, however, yielded no detectable CH3SH after 112 days indicating the reverse reaction is inhibited under favorable thermodynamics. Neither direct reduction of CO2 to CH3SH nor CO2-CH3SH equilibrium were evident at 300 °C, implying CH3SH and CH3OH play disparate roles in homogeneous carbon reduction to CH4. Longer chain hydrocarbons (C2+ alkanes) remained low throughout the experiments.CH3SH abundances previously reported in vent fluids at the Von Damm hydrothermal field correlate strongly with demonstrably abiotic HCOOH there, suggesting the reduction of HCOOH to CH3SH observed in this study may also occur in vent fluids. A comparison of mineral-free 13CH4 production rates reported here with 13CO2 reduction experiments involving minerals indicates that homogeneous reduction proceeds at similar rates to purported transition metal-catalyzed 13CH4 production, and is generally faster than experiments with either added olivine or ultramafic rock. Previous claims of substantial mineral-catalyzed abiogenic CH4 production are therefore not supported by our study. Homogeneous CO2 reduction may be a significant source of methylated compounds and CH4 in hydrothermal fluids characterized by decadal (or longer) residence times, such as those found in mineral-hosted inclusions or occluded fractures in igneous basement, requiring only moderate temperatures and abundant H2 to proceed.

Efficient sulfidization-free flotation of chrysocolla enabled by specific synergistic effects of ammonium sulfate and octyl hydroxamic acid

Due to its poor sulfidization effect and environmental issues, the traditional sulfidization–xanthate method faces challenges in chrysocolla flotation. Addressing these, our study pioneers a sulfidization-free approach using ammonium sulfate as an activator in an octyl hydroxamic acid (OHA) collector system. This innovation propels flotation recovery from 34.10 % to an impressive 98.43 %. Infrared spectroscopy and adsorption tests confirm that ammonium sulfate improves OHA’s adsorption on chrysocolla. X-ray photoelectron spectroscopy (XPS) analysis reveals a significant rise in C–C and C-N bonds related to OHA on the mineral surface post-activation. Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDS) analysis shows a rougher mineral surface with filamentous precipitates and a higher surface nitrogen atom concentration. Density Functional Theory (DFT) calculations elucidate NH3′s role in disrupting the hydration layer, exposing more Cu sites for enhanced OHA attachment. The Cu 2p shift observed on the mineral surface, along with state density analysis, further confirms the chemical adsorption of OHA on chrysocolla’s Cu sites facilitated by ammonium sulfate. This study introduces a novel NH3-enhanced OHA adsorption method, offering a promising strategy for the efficient flotation of chrysocolla.

Iron minerals enhance Fe(II)-mediated abiotic As(III) oxidation

The abiotic oxidation of As(III) is simultaneously mediated by the oxidation of Fe(II) in microaerobic environment, but the role of Fe minerals in the Fe(II)-mediated As(III) oxidation have been neglected. This work mimicked the microaerobic environment and examined the mechanisms of Fe(II) mediated the As(III) oxidation in the presence of Fe minerals using a variety of iron minerals (lepidocrocite, goethite, etc.). The results indicated the Fe(II) and As(III) oxidation rate were improved with Fe minerals, while As(III) oxidation efficiency increased by 1.3–1.8 times in comparison to that without minerals. Fe(II) mediated the As(III) oxidation happened on Fe minerals surface in the presence of Fe minerals. The As(III) oxidation efficiency increased with increasing Fe mineral concentrations (from 0.5 to 2 g L−1) but decreased with increasing pH values. Reactive oxygen species (ROS) that play a crucial role in As(III) oxidation were Fe(IV) and ·O2−, accounting for 42.7%–47.9% and 24.1%–29.8%, respectively. The Fe minerals facilitated the oxidation of As(III) by ROS and stimulated the release of ROS through the adsorbed-Fe(II) oxidation, both of which favored As(III) oxidation. This work highlighted the potential mechanisms of Fe minerals in promoting Fe(II) mediated the As(III) oxidation in microaerobic environment, especially in terms of As(III) oxidation efficiency, shedding a valuable insight on optimization of arsenic contaminated wastewater treatment processes.

Formation and survival of clay-mediated protocell membranes composed of single-chain amphiphiles in aqueous solutions

Protocell compartments composed of simple amphiphilic molecules could have survived on the clay mineral surfaces which can serve well as plausible sites for prebiotic chemistry on the early Earth. Herein we chose four common single-chain amphiphiles (SCAs), including the anionic surfactant sodium dodecyl sulfate (SDS) and sodium dodecylbenzenesulfonate (SDBS), the cationic surfactant dodecyltrimethylammonium bromide (DTAB) and the zwitterionic lauryl sulfobetaine (LSB)), as model constituents of early membranes to establish a tentative model for protocell compartment. Positively charged Mg2Al-/Mg2Fe-layered double hydroxides (LDHs) and FeS2 are viewed as models of clay minerals. We demonstrate by comprehensively experimental study that unconventional vesicles can be easily promoted in a SCA aqueous micellar solution in the presence of model particles. Morphology evolutions are traced by collecting samples from mixtures of LDHs and SCA aqueous solutions and then recording at different incubation times via negative-staining or cryo-transmission electron microscopy (NS-TEM or cryo-TEM) and dynamic light scattering (DLS). Additionally, the stability of SCA bilayer membranes under possible prebiotic environment are tentatively studied. This work not only offers a robust yet versatile approach for the fabrication of novel vesicles but also provides new insights into the origin of cellular life.

Molecular dynamics study on hydration characteristics of expansive clay minerals by temperature and inorganic salts

Most strata rock minerals have hydrophilic characteristics and the mineral surface is negatively charged. It can adsorb water molecules to form hydration layers on the mineral surface. The existence of hydration layer will reduce the effective pore diameter of rock pore microchannel. Thus, the development efficiency of crude oil is affected. Hydration layer compared to free water, water molecules are arranged in a highly ordered manner, with higher density and more stable toughness. Therefore, it is very important to study the structure of hydration layer adsorbed on rock wall and its influencing factors. Four different rock and mineral types are selected in this paper: Na-montmorillonite, quartz, kaolinite, calcite. Molecular dynamics method was used to simulate different temperature conditions and adding different inorganic salts. Study the influence of temperature and inorganic salts on the hydration layer structure of rock wall. The simulation results show that the increase of temperature and the addition of inorganic salts of different components have a great influence on the adsorption of water molecules on the rock wall, and it changes the original structure of the hydration layer. The adsorption of water molecules on different rock surfaces and the effect of different rock walls on the adsorption of hydration layer are described in molecular form. This study explains the mechanism of temperature and inorganic salts inhibiting water molecules from a microscopic perspective. It is of great significance to study the physical properties of hydration layer. It provides a theoretical basis for the field well wall stability research.

Stability and characteristics of kerosene-in-water emulsions with xanthate surfactants: Influence of hydrophilic-lipophilic balance and molecular weight

The understanding of emulsion stability is important for several industrial applications including foods, pharmaceuticals, petroleum, personal care products, and in our case mineral processing. Xanthate functional surfactants may be useful to improve mineral recovery through froth flotation by delivering oil to valuable mineral surfaces as they may be used to stabilize kerosene-in-water emulsions. The eco-friendly nature of naturally derived reagents such as vitamin E-based xanthates would be beneficial to the mineral processing industry. In this study, conventional (potassium amyl xanthate (PAX)) and novel xanthate functional surfactants such as α-tocopherol polyethylene glycol 400 succinate (TPGS) xanthates which we synthesized from Vitamin E were investigated as emulsifiers. The creaming and oil phase separation of the kerosene-in-water emulsions produced with the xanthate surfactants were studied. The influence of hydrophilic-lipophilic balances (HLBs) and molecular weights (MWs) of the water-soluble xanthates and other commercial surfactants including polyoxyethylene fatty acid esters (Tweens), sorbitan fatty acid esters (Spans), and polyoxyethylene fatty ethers (Brijs) on the characteristics of the kerosene-in-water emulsions was examined. The experimental results showed that the TPGS xanthate formed the most stable emulsion among the xanthate surfactants considered. The results indicated that HLB is not the only factor influencing the emulsifying properties of surfactants. The chemical structure, particularly the molecular weight of the surfactant has a significant impact on its emulsifying properties. Thus, an emulsion stability chart incorporating the HLB and molecular weight of surfactants is proposed. This stability chart can be used for a better classification of the emulsifying properties of commercially available surfactants and novel reagents.

The occurrences and mobility of shale oil in the pore space of terrestrial shale

Movable oil, the critical factor for shale oil enrichment and effective production, is influenced by the pore structure and shale oil occurrence state. However, the pore spaces storing movable oil, the occurrence state of shale oil, and the lower flowing pore size for shale oil remained unclear. To address this knowledge gap, we chose the lacustrine organic-rich Chang7 shale of the Ordos Basin as the research target. By combining gas adsorption techniques (nitrogen and carbon dioxide) with Soxhlet Extraction, we investigated the pore structure alteration of Chang7 shale after Soxhlet Extraction. Based on a comprehensive analysis of mineralogical composition, TOC, and shale oil components, we discussed the pore space in which shale oil exists. Then, we established a slit-shaped clay model and clarified the occurrence state of multi-component shale oil in the pore space with the help of molecular simulation. Our investigation revealed that (1) Chang7 shale can be categorized into three distinct types. Type I, characterized by a high clay mineral content, possesses the greatest SSA and PV and has the highest abundance of movable oil, partially filling the “ink-bottle”-type pores. Shale oil in Type II and III shales mainly exists within slit-type pores. (2) The pore space of Chang7 shale is primarily comprised of mesopores rather than micropores. Moreover, mesopores’ PV and SSA are predominantly governed by clay minerals rather than organic matter. (3) A threshold pore size of 10 nm significantly impacts the occurrence state of shale oil in the Chang7 shale. Beyond this threshold, free oil accounts for over 80% of the total. Chang7 shale oil within micropores (<2 nm) is predominantly asphaltene, existing in an adsorbed state. Within pores sized 2 to 10 nm, shale oil is present in both adsorbed and free states, and the proportion of free-state shale oil increases with the pore size. Free-state shale oil prevails in pores exceeding 10 nm, with a smaller fraction adsorbed onto organic matter and mineral surfaces. Thus, we recommend adopting 10 nm as the lower flowing pore size limit for Chang7 shale.

Surface Hydroxylation-Induced Electrostatic Forces Thicken Water Films on Quartz.

Aqueous films on mineral surfaces control the physical, chemical, and biological transport processes in the atmosphere, soil, and rocks. Despite the importance of thin films for various research and engineering fields, there are still unanswered questions regarding the roles of the different forces affecting the nature of water films. One of these, the focus of this study, is the development of abnormally thick water films on quartz surfaces. In this study, we developed a density-functional-theory-based model to describe the time-dependent evolution of water films and identify the governing forces responsible for thickening films. We simulated the diffusion of water vapor from ambient air toward mineral surfaces and the formation and thickening of water films at various relative humidity values. Our model predicts an abnormal water film thickness on a hydroxylated quartz surface compared to a surface free of hydroxylation, which explains experimental observations. We further used the model to understand the key interaction forces at different stages of water film formation and thickening. Our model suggests that the attractive hydrogen bonding and van der Waals forces initiate a seed layer of water, and the electrostatic forces, generated by the hydroxylated and thus charged surface, lead to the thickening of water films. This generalizable model can provide insights into the peculiarities of water film development on various mineral surfaces.

Assessment of factors and mechanism contributing to groundwater depressurisation due to longwall mining

Assessment of mining impact on groundwater is one of critical considerations for longwall extension and sustainability, however usually constrained by limited data availability, hydrogeological variation, and the complex coupled hydro-mechanical behaviour. This paper aims to determine the factors and mechanism of groundwater depressurisation and identify knowledge gaps and methodological limitations for improving groundwater impact assessment. Analysis of dewatering cases in Australian, Chinese, and US coalfields demonstrates that piezometric drawdown can further lead to surface hydrology degradation, while the hydraulic responses vary with longwall parameters and geological conditions. Statistical interpretation of 422 height of fracturing datasets indicates that the groundwater impact positively correlates to panel geometry and depth of cover, and more pronounced in panel interaction and top coal caving cases. In situ stress, rock competency, clay mineral infillings, fault, valley topography, and surface–subsurface water interaction are geological and hydrogeological factors influencing groundwater hydraulics and long-term recovery. The dewatering mechanism involves permeability enhancement and extensive flow through fracture networks, where interconnected fractures provide steep hydraulic gradients and smooth flow pathways draining the overlying water to goaf of lower heads. Future research should improve fracture network identification and interconnectivity quantification, accompanied by description of fluid flow dynamics in the high fracture frequency and large fracture aperture context. The paper recommends a research framework to address the knowledge gaps with continuous data collection and field-scale numerical modelling as key technical support. The paper consolidates the understanding of longwall mining impacting mine hydrology and provides viewpoints that facilitate an improved assessment of groundwater depressurisation.

Synergism mechanism of the combined NaOL-SDBS collector at solid-liquid interface and its response to flotation separation of ilmenite from pyroxene

Recovering ilmenite efficiently through froth flotation is challenging. In this research, a novel binary system of sodium oleate (NaOL) and sodium dodecyl benzene sulfonate (SDBS) was applied to promote the flotation performance of ilmenite. Using a total dosage of 90 mg/L combined NaOL-SDBS (4:1) collector, the highest flotation recovery rate of ilmenite was 91.55% at pH 5.0. Furthermore, the artificially mixed ore tests produced a concentrate with a TiO2 grade of 43.55% and a TiO2 recovery of 84.07%, confirming the promising separation performance of the combined collector. Results indicated positive synergism between NaOL and SDBS in ilmenite flotation. The synergism of the binary collector at the solid-liquid interface was identified by the analyses of adsorption amount, contact angle, surface tension, atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS). Insights into the synergistic effect between NaOL and SDBS on the ilmenite flotation were mainly attributed to a significant decrease in the surface tension of solid-liquid interface, and the strong adhesion forces of co-adsorption between the combined NaOL-SDBS collector and the mineral surface.

Critical roles of low-molecular-weight organic acid in enhancing hydroxyl radical production by ferrous oxidation on γ-Al2O3 mineral surface

Recognizing the pervasive presence of alumina minerals and low-molecular-weight organic acids (LMWOAs) in the environment, this study addressed the gap in the interaction mechanisms within the ternary system involving these two components and Fe(II). Specifically, the impacts of LMWOAs on hydroxyl radicals (•OH) production and iron species transformation during Fe(II) oxidation on γ-Al2O3 mineral surface were examined. Results demonstrated that adding 0.5 mM oxalate (OA) or citrate (CA) to the γ-Al2O3/Fe(II) system (28.1 μM) significantly enhanced •OH production by 1.9-fold (51.9 μM) and 1.3-fold (36.2 μM), respectively, whereas succinate (SA) exhibited limited effect (30.7 μM). Raising OA concentration to 5 mM further promoted •OH yield to 125.0 μM after 24 h. Deeper analysis revealed that CA facilitated the dissolution of adsorbed Fe(II) and its subsequent oxygenation by O2 through both one- and two-electron transfer mechanisms, whereas OA enhanced the adsorption of dissolved Fe(II) and more efficient two-electron transfer for H2O2 production. Additionally, LMWOAs presence favored the formation of iron minerals with poor crystallinity like ferrihydrite and lepidocrocite rather than well-crystallized forms such as goethite. The distinct impacts of various LMWOAs on Fe(II) oxidation and •OH generation underscore their unique roles in the redox processes at mineral surface, consequently modulating the environmental fate of prototypical pollutants like phenol.

Flotation separation of hematite from quartz with dodecyl trimethyl ammonium chloride and sodium dodecyl sulfonate collector

Through a series of testing methods, including micro-flotation tests, contact angle test, ζ-potential analysis, FTIR, and XPS, the behavior and mechanism of flotation separation of hematite and quartz by mixed anionic-cationic collectors (Dodecyl Trimethyl Ammonium Chloride (DTAC) and Sodium Dodecyl Sulfonate (SDS), DS for short) were investigated. Additionally, the froth performance of the mixed collector was examined through froth stability experiments. The study revealed that the inclusion of DS collectors significantly enhanced the flotation separation efficiency of quartz-hematite, with the addition of SDS leading to a reduction in the foam viscosity of DTAC. Notably, at a pH of 7 and with a DTAC to SDS mass ratio of 2:1, the mixed collector demonstrated exceptional performance in the flotation separation of quartz and hematite, achieving a quartz recovery of 91.85 % and a hematite recovery of 11.45 %. This efficacy was corroborated by ζ-potential measurements, FT-IR analysis, and XPS analysis, which confirmed the physical adsorption of DS on the mineral surfaces. Importantly, the adsorption dynamics were found to be influenced by the different surface charge characteristics of quartz and hematite. Specifically, the higher negative charge on the surface of quartz resulted in unaffected DTAC adsorption in the presence of SDS, while on hematite surfaces, the DTAC interaction with SDS led to the partial desorption of DTAC. Consequently, the adsorption of DTAC on hematite surfaces was reduced, facilitating the selective separation of quartz and hematite.

Understanding the Adsorption Mechanism of BTPA, DEPA, and DPPA in the Separation of Malachite from Calcite and Quartz: DFT and Experimental Studies

The relationship between the structure of bis (2,4,4-trimethylpentyl) phosphinic acid (BTPA), diethyl phosphinic acid (DEPA), and diphenyl phosphinic acid (DPPA) on the flotation performance of malachite was investigated. Through a series of flotation experiments, density functional theory (DFT) calculations, and surface analysis methods, we aimed to deeply understand the microscopic mechanism of the interactions between these collectors and the malachite surface. The experimental results showed that BTPA exhibited excellent selectivity and flotation performance for malachite in the pH range of 5.0–11.0, significantly better than DEPA and DPPA. Surface analysis evidence from X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) further confirmed the chemical adsorption characteristics of BTPA on the malachite surface. DFT calculations revealed that the adsorption capacity of BTPA on the malachite surface exceeds that of DEPA and DPPA. Electron transfer analysis, especially through frontier molecular orbital theory, differential charge density, PDOS, and COHP analysis, indicated that the charge transfer process from the s orbitals of oxygen atoms in the collectors to the d orbitals of copper atoms on the mineral surface is the decisive factor for the adsorption strength.