Surface Properties Of Minerals Research Articles

Application of exopolysaccharides synthesized by Xanthomonas campestris in an efficient separation system of refractory chalcopyrite and molybdenite

Bacterial polysaccharides get an abundance of attention owing to their distinctive biological activity and promising applications. Recent research found that the specificity of the molecular structure of exopolysaccharides (EPS) can be used to accomplish selective regulation of the physicochemical properties of mineral surfaces. The development and application of novel microbial EPS as a flotation reagent for chalcopyrite and molybdenite separation possesses a promising development prospect. Consequently, we attempted to create effective and sustainable molybdenite depressants in this work by optimizing the strain's fermentation settings and identifying the molecular structure of the generated EPS. Fermentation condition tests revealed patterns of influence of fermentation parameters on EPS yield, the viscosity average molecular weight, and biomass during the fermentation process, and optimized the optimal fermentation conditions. Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), and ion chromatography (IC) analyses clarified the structure of the EPS in terms of monosaccharide composition, glycosidic bonding, and functional groups. Mixed mineral flotation tests proved that a low dosage of polysaccharide reagent (100 mg/L) at pH 10 effectively inhibited molybdenite and achieved separation targets of 21.96% Cu and 2.63% Mo in the concentrate, with separation efficiencies (SE) of 72.67% and 55.78% for Cu and Mo, respectively.

Enrichment and fractionation of rare earth elements (REEs) in ion-adsorption-type REE deposits: Constraints of an iron (hydr)oxide–clay mineral composite

Abstract Ion-adsorption-type rare earth element (REE) deposits are the source of more than 90% of global heavy REEs (HREEs). Thus, understanding the ore genesis of REEs, particularly the distribution characteristics and enrichment mechanisms of HREEs, is vital for efficient exploration and mining of ion-adsorption-type REE deposits worldwide. The characteristics and petrogenesis of bedrock, and the aqueous mobility of REEs, are known to be important factors controlling REE accumulation and fractionation in the weathering crust of REE deposits. However, the effect of REE adsorption on secondary minerals, which is a crucial step in deposit formation, remains poorly understood. This problem was addressed by the study described herein, which involved a systematic analysis of the complete weathering profile (78 m) of the Renju ion-adsorption-type REE deposit in South China and a simulated adsorption experiment. Clay minerals and iron (Fe) (hydr)oxides are the dominant REE adsorbents in the weathering crust and most are micro-to-nanosized particles. Thus, the fine particle fraction (< 2 μm) was separated from field samples, to better disclose their effects on the concentration and redistribution of REEs. Phase compositions and morphologies were characterized by X-ray diffraction, Mössbauer spectrometry, and scanning/transmission electron microscopy (SEM/TEM), which revealed that various clay minerals and Fe (hydr)oxides form composites along the profile of the deposit. Composites of ferrihydrite–kaolinite, goethite–kaolinite/halloysite, and hematite–kaolinite/halloysite were found to be distributed in the semi-weathered, completely weathered, and topsoil layers, respectively, with different sizes and shapes. The concentrations and partition patterns of REEs in different occurrence states were distinguished after sequential extraction. Ion-exchangeable-REEs were the major state and enriched in the upper completely weathered layer. These species were found to be adsorbed onto kaolinite and halloysite via electrostatic attraction, without obvious fractionation. Fe (hydr)oxides were determined to comprise ca. 20% of REEs at most depths and over 50% of REEs in the topsoil and semi-weathered layer. It was found that Fe (hydr)oxides scavenge REEs through complexation and oxidation, resulting in HREE enrichment and a positive cerium (Ce) anomaly, respectively. In addition, compared with crystalline Fe (hydr)oxides, amorphous Fe (hydr)oxides immobilize more REEs but exhibit weaker preferential adsorption of HREEs. The above-described findings are consistent with the results of simulated experiments for REE adsorption onto a clay mineral–Fe (hydr)oxide composite (Bt-60), which was obtained from hydrothermal processing of biotite. Furthermore, the distributions and stabilities of LREEs and HREEs were distinguished by TEM–energy–dispersive spectroscopy (EDS) of Bt-60 before and after REE extraction by ammonium sulfate. The phase transformation pathways of clay minerals and Fe (hydr)oxides, and their different enrichment and fractionation characteristics in REEs, were also discussed in terms of the structure and surface properties of minerals, adsorption mechanisms, and variations in chemical properties across the REE group. The results shed new light on how clay minerals and Fe (hydr)oxides affect the enrichment and fractionation of REEs in ion-adsorption-type deposits.

Effects of alkali pretreatment on the flotation of spodumene and feldspar

The surface chemistry and morphology of minerals produced by alkali pretreatment affects their flotation behaviors. This study systematically investigated the impact on the mineral surface dissolution using NaOH as a modifier, which could modify the surface properties of minerals and improve the floatability difference between spodumene and feldspar. Various characterizations including flotation experiments, flotation kinetics analysis, SEM analysis, microcalorimetry analysis, zeta potential measurements, XPS analysis and ICP-MS analysis were conducted. Single minerals and actual ore flotation experiment results were in good agreement, and the flotation grade and recovery of Li2O in spodumene concentrates increased by 1.11 % and 6.99 %, respectively, after NaOH pretreatment. The flotation kinetics results demonstrated the cumulative recoveries of spodumene exhibited the best agreement with the first-order kinetic model and the flotation kinetic constant was improved after alkali pretreatment. Microcalorimetric results indicated the absolute values of the reaction heat for spodumene were higher than that of feldspar reacted with collectors after the alkali pretreatment. XPS and ICP results demonstrated the amounts of Al active sites on the spodumene surface was significantly increased after alkali pretreatment compared to that on the feldspar surface, improving the selective adsorption of NaOL.

Artificial formation of alpha recoil tracks using an americium source

Alpha recoil track (ART) is a lattice defect formed by the alpha decay of 238U, 235U, 232 Th, and their daughter products. The age since the start of ART accumulation can be estimated using the number of ARTs and the uranium and thorium concentrations, given the known decay constants of uranium and thorium. It is necessary to investigate mineral surface properties, appropriate etching conditions, and the ART annealing characteristics upon heating to apply ART observation to the dating and thermal history study of various minerals. This study aims to develop a method for artificially forming ART so that the shape and properties of etched ART in various minerals can be studied in the future. A 300 Bq americium source was used to irradiate muscovite, in which the ARTs were well observed in previous studies, for time intervals of 1 h, 3 h, 6 h, 12 h, 2 days, 4 days, and 1 week after annealing treatment to erase all naturally occurring ARTs, and the samples were observed using phase contrast microscopy after chemical etching. The ART areal density formed on the sample surface and the irradiation time has a linear relationship for the samples with irradiation time up to 12 h. However, the size distribution of the formed artificial ARTs showed a different distribution from that of the naturally observed ARTs. Several samples of muscovite irradiated for 3 h were prepared and annealed at different temperatures (100 °C, 150 °C, and 200 °C) and times (30 min, 1 h, 3 h, 5 h, 10 h, 20 h, 100 h, and 352 h) to determine the stability of ARTs under geological conditions. Given the uniform size distribution of natural ARTs, the results of this annealing experiment indicate that the smaller size of natural ARTs may be indicative of annealing at ambient temperature for an extended period (108–109 yrs), or ARTs may have been annealed in the recent past at a slightly higher temperature (150 °C–200 °C). We cannot rule out the possibility that the observed natural ART-like tracks were formed by the bombardment of smaller nuclei (e.g., move of major atoms by cosmic ray irradiation), assuming that the track size reflects the energy and mass of nuclei. Further detailed studies of annealing behavior and track formation processes by various atoms are required to reach a definitive understanding.

Facet engineering of minerals for effective oil-water separation

Minerals have been growing as an emerging ‘hot’ topic in separating water-in-oil emulsions. Whether the intrinsic structure of minerals could precisely regulate water–mineral interactions for enhancing emulsions separation efficiency is still ambiguous. Here, taking half-hydrated gypsum as a case, this study reveals the crystal facet-dependent potential mechanism of minerals in water-in-oil emulsions separation. We show that the (204) facet of half-hydrated gypsum is more susceptible to water-induced degradation and hydration reaction. With combined experimental and theoretical studies, the facet-dependent mechanism for oil–water separation are revealed; the (204) facet that exhibited weak internal hydrogen bond and strong binding energy with water accelerated the dissolution and recrystallization of half-hydrated gypsum, thus enhancing oil–water separation efficiency. Through engineering, half-hydrated gypsum with a higher surface fraction of the (204) facet achieved much higher separation efficiency (99.9%), surpassing those of minerals in disclosed literature. This investigation not only contributes significantly to the comprehension of interactions at the minerals-water interface but also illuminates novel perspectives and avenues for the utilization of facet engineering in advancing research on mineral surface properties.

The Effect of Aloe Vera Bioreagent as a Frother and Collector in the Gold Ore Flotation Process on Increasing Grade and Recovery

One of the concentration processes in processing sulfide gold ore is the flotation technique which takes advantage of differences in mineral surface properties by adding chemical reagents. The addition of chemical reagents to the flotation process can cause environmental problems. Therefore, efforts are needed to replace chemical reagents with more environmentally friendly materials. In this research, an attempt was made to replace chemical reagents with a commonly found plant extract, namely aloe vera, as a bioreagent. Bioflotation experiments on a laboratory scale were carried out using a Denver flotation cell with an aloe vera reagent as a frother. This gold mineral bioflotation experiment was carried out on a 150 mesh size fraction. The results of increasing concentrate levels by flotation indicate that the aloe vera reagent as a frother is able to produce biosurfactants which replace chemical reagents as a more environmentally friendly biofrother and biocollector. This can be concluded based on flotation experiment data with bioreagent which has been tested showing an Au content value of 10.09 and a recovery of 96.15%, while flotation using chemical reagents shows an Au content value of 10.50 and a recovery of 95.96%. So the use of aloe vera as an environmentally friendly bioreagent in the flotation process releasing low sulfidation gold is more effective than the use of chemical reagents because it is indicated that there is a biosurfactant content in aloe vera.

Surface properties of clinker phases and clay minerals characterized by inverse gas chromatography (IGC) and their link to reactivity

This paper presents a preliminary study of the characterization of the surface energy properties of clinker phases (C3S and C3A), kaolin and metakaolin by Inverse Gas Chromatography (IGC). For this, a reliable measurement methodology was developed. By looking at changes in the whole series of results (dispersive surface energy, specific polar interaction parameter, acid and base constants, morphology index, nanoroughness and adsorption energy distribution function), it is possible to discern changes between the same powders with different surface treatments. A promising correlation between surface properties and the reactivity of studied materials have been found. However, based on the IGC characterization, the increased reactivity of metakaolin compared to the raw kaolinite seems to be strongly linked to the change in local order rather than significant changes in the surface energetics, although a change in the acid/base nature of the surface has been observed.

Electrical Responses of Modified Mineral Surfaces as Observed With Spectral Induced Polarization and Atomic Force Microscopy

AbstractAtomic force microscopy (AFM) and spectral induced polarization (SIP) are widely used to investigate the electrical properties of mineral surfaces at vastly different scales of measurement. We compare AFM and SIP measurements made on two different materials (glass beads and silica gel) subjected to etching, deposition of iron oxide particles, and inclusion of calcite grains. We found that the treatments produced qualitatively consistent behaviors in the AFM and SIP data. Direct AFM measurements of surface charge density for silica and calcite surfaces were quantitatively compared to values estimated from the SIP results using a grain polarization model. No statistically significant difference (at a 95% confidence level) was found between the surface charge density of silica estimated by AFM (2.3 ± 6.6 mC/m2 for glass beads and 1.6 ± 0.1 mC/m2 for silica gel) versus SIP (5.4 ± 4.4 mC/m2 for glass beads and 1.6 ± 0.5 mC/m2 for silica gel). The surface charge density for calcite determined by AFM (43.5 ± 12.9 mC/m2) was approximately 19 times higher than that found for silica. While the charge density of calcite surfaces determined by SIP was also generally higher than that found for silica, different treatments produced significantly different values between 4.7 and 258 mC/m2 (with a maximum 95% CI of ±8.7 mC/m2). Several possible explanations exist for the range of the observed SIP measurements, including aging of the calcite surfaces. Overall, this study suggests the potential for the complementary use of AFM and SIP measurements to constrain future investigations of polarization mechanisms in porous media.

SBSNet: selective branch segmentation network of coal flotation froth images

ABSTRACT Flotation is a physical and chemical process that uses the difference between mineral surface properties to separate valuable minerals from worthless minerals through the attachment of bubbles. The visual information of the flotation foam surface can reflect the flotation effect and will be closely related to the flotation conditions, directly indicating the degree of mineralization of the foam layer. Considering the problem that coal slurry foam images are difficult to segment due to the mutual adhesion of bubbles and fuzzy boundaries, in this work, we proposed a new and effective segmentation algorithm for extracting coal slurry flotation foam edge information. Based on the encoder and decoder structure, a selective multi-branch input segmentation deep neural network model was designed. We evaluated the proposed method and model using a self-built coal slurry foam image segmentation dataset. The intersection over union, mean intersection over union, and PA evaluation indicators of this method increased by 12.8376%, 7.2716%, and 1.457%, respectively, compared with those of the U-Net model. The experimental results showed that the selective branch segmentation network model had high accuracy and robustness in extracting coal slurry bubble edge information, and it could effectively solve the problem of difficult segmentation of coal slurry foam images. This study provided a foundation for optimizing flotation process parameters and realizing intelligent flotation site parameters.

Facet-Dependent Charge Density of Serpentine: Nanoscopic Implications for Aggregation and Entrainment of Fine Particles.

Deciphering the facet-dependent surface properties of clay minerals holds vital significance in both fundamental research and practical engineering applications. To date, the anisotropic local charge density of serpentine surfaces still remains elusive, and thus, the interaction energies and associated aggregate structures between different crystal planes of serpentine cannot be quantitatively determined. In this work, different crystal planes of serpentine (i.e., SiO basal, MgOH basal, and edge) were selectively exposed, and their surface potentials and charge densities were determined using atomic force microscopy (AFM) force measurements coupled with Derjaguin-Landau-Verwey-Overbeek (DLVO) theory fitting. The SiO and edge planes consistently exhibited a permanently negative surface charge, whereas the point of zero charge (PZC) on the MgOH plane was estimated to be pH 9.0-11.0. Based on the interaction energy calculation between different serpentine planes, the aggregation structures of serpentine were predicted. Combined with scanning electron microscopy observation of freeze-dried samples, SiO-MgOH and MgOH-edge associations were found to dominate the aggregate structures at pH ≤ 9.0, thereby resulting in a stacking or "card-houses" structures. In contrast, all of the plane associations exhibited the repulsive interaction energy at pH 11.0, which led to a completely dispersed system, ultimately causing the most severe fine particle entrainment during froth flotation. Our work provides quantitative clarification of facet-dependent surface properties and aggregate structures of serpentine under different pH conditions, which will help improve the fundamental understanding of colloidal behaviors of clay minerals.

Cleaning and upgrading of low-rank coal using a novel rotary triboelectric separator with the polyvinyl chloride as friction medium

In this work, a novel laboratory rotary triboelectric separator was designed for the beneficiation of low-rank coal using polyvinyl chloride as the friction medium. The friction charge polarity of the different components in the low-rank coal was determined by charge-to-mass ratio measurements. The separation performance of the rotary triboelectric separator was investigated by separating the simulated materials. The surface properties of the simulated minerals were analyzed using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The influence of different conditions on the separation of low-rank coal was studied using rotation speed, feed rate and plate voltage as variables. Under the optimum operating conditions, the ash removal rates of 0.25–0.5 mm, 0.125–0.25 mm and −0.125 mm low-rank coals were 50.05 %, 61.88 % and 25.56 %, respectively. Inductively coupled plasma mass spectrometry (ICP-MS) analysis of the separated products indicated that several harmful trace elements (i.e., Cd, Cr, Pb and Sb) were removed distinctly. Our results will provide an effective way for the separation and upgrading of low-rank coal.

Sodium metabisulfite as a copper depressant in the selective flotation of copper-molybdenum concentrate using seawater

The main challenge for the selective flotation of copper and molybdenum (Cu-Mo) sulfide minerals in seawater is the formation of colloidal precipitates in strongly alkaline conditions. These precipitates hinder the selective separation of copper from molybdenum minerals in seawater by lowering the floatability of Cu-Mo sulfide minerals. The present study aimed to examine the direct utilization of seawater in the selective flotation of Cu-Mo sulfides. Additionally, the effectiveness of sodium metabisulfite (Na2S2O5) as a copper depressant for selective flotation of Cu-Mo sulfides in seawater was studied under weakly acidic, neutral, and moderately alkaline conditions. A complex Cu-Mo concentrate that largely consisted of chalcopyrite and molybdenite, as well as a tiny amount of pyrite and quartz, was used in the flotation tests. The flotation results revealed that treatment with 3.6 kg/t Na2S2O5 in seawater at pH 5.5 significantly lowered the copper recovery from 97% to 11% and caused a modest reduction in the molybdenum recovery from 98% to 94% with a Cu-Mo separation efficiency of 83%. These flotation results demonstrate that Na2S2O5 treatment in seawater selectively depresses the floatability of copper minerals. Consequently, molybdenum can be separated from copper minerals under a weakly acidic condition in seawater. In addition, this study discusses the effects of various pH conditions and dosages of Na2S2O5. The surface properties of Cu-Mo minerals were studied using X-ray photoelectron and infrared spectroscopies, and a mechanism to explain the selective flotation of Cu-Mo using Na2S2O5 treatment in seawater is proposed.

Rheological properties of rare earth minerals flotation pulp in the presence of anions

Water quality has been found to significantly influence the flotation operations due to the alteration of surface properties of minerals. The effect of cations on the flotation of RE minerals has been studied, however, there are still very limited information regarding the effect of anions. The present study examined the impact of specific anions such as Cl−, SO42−, and HCO3− on the flotation performance of rare earth (RE) ore. This study integrates flotation experiments, rheology measurements, entrainment experiments, zeta potential measurements and settling experiments. It is observed that an increase in the concentration of these anions lead to a decrease in the recovery of RE minerals and an increase in the recovery of FeO minerals and thus negatively affecting flotation efficiency. This adverse effect is most pronounced with Cl− and least noticeable with HCO3−. An increase in the non-selective entrainment of gangue minerals is observed when the flotation pulp has higher viscosity. The reduction in the zeta potential of fine particles in the presence of these results in a higher pulp viscosity due to increased attractive forces between particles. These findings were verified by settling experiments and calculations based on the DLVO theory.

Investigation on flotation separation of bastnaesite from calcite with a novel collector: Octylamino-bis-(isobutanohydroxamic acid)

Bastnaesite is an important mineral resource, usually associated with calcite and other minerals, flotation is one of the most widely used methods in the selection process. Collector is the key to achieve flotation separation of bastnaesite from gangue mineral. The effect of a new hydroxamic acid collector with two functional groups: Octylamino-bis-(isobutanohydroxamic acid) (OIBHA), on the flotation separation of bastnaesite from calcite was investigated. The Single mineral and artificial mixed ore flotation results revealed that OIBHA exhibited better collecting ability and selectivity compared with the conventional hydroxamic acid collector octanohydroxamic acid (OHA). Effective separation between bastnaesite and calcite can be realized. The concentrate with 68.82 % REO grade and 90.23 % REO recovery was obtained with 3 × 10−4 mol/L OIBHA. Fourier transform infrared (FTIR) analysis, zeta potential measurements and quantum chemical calculations were used to investigate the selective adsorption mechanism of OIBHA. The results of FTIR analysis and zeta potential measurements showed that OIBHA was strongly adsorbed on the surface of bastnaesite, but did not interact with calcite. Quantum chemical calculations results indicated OIBHA matched well with bastnaesite surface, thereby improved the selectivity. The results in this paper are instructive for the study of the spatial matching properties of collectors and mineral surfaces.

Effect of energy input on surface properties and dispersion of diaspore and kaolinite in flotation process

Fluid strengthening and interfacial regulation are two important means to improve the flotation recovery of fine minerals. The fluid strengthening process often affects the surface properties of minerals and thus the dispersion of minerals. The effects of energy input on the dispersion and surface properties of kaolinite and diaspore were investigated in this work. The dispersion of minerals was examined through optical observation, turbidity measurement, and particle size analysis. The surface properties of minerals were characterized by measuring the zeta potential and the contact angle. Micro-flotation was used to test the effect of energy input on flotation performance. The findings revealed that increasing energy input resulted in improved particle dispersion, reduced hetero-coagulation, modified surface properties of minerals, and facilitated the separation of kaolinite and diaspore. This research would provide theoretical and technical support for the flotation of diasporic bauxites.

Performance of Thermal-, Acid-, and Mechanochemical-Activated Montmorillonite for Environmental Protection from Radionuclides U(VI) and Sr(II)

Low-cost sorption materials based on the clay mineral of the smectite group—montmorillonite—were used for the removal of radionuclides uranium (VI) and strontium (II) from contaminated water. A wide range of industrial methods such as thermal treatment, acid activation, and mechanochemical activation were applied. Complex methods, such as SEM microscopy analysis, X-ray powder diffraction (XRD), thermal analysis, and nitrogen adsorption–desorption at −196 °C, were used to assess the characteristics of the structure of the obtained materials. The thermal treatment, acid activation, and mechanochemical activation resulted in changes in the surface properties of the clay minerals: specific surface area, porosity, and distribution of active sites. It was established that the mechanochemical activation of montmorillonite significantly increases the sorption characteristics of the material for U(VI) and Sr(II) and the acid activation of montmorillonite increases it for U(VI). The appropriateness of the experimental adsorption values for U(VI) and Sr(II) on modified montmorillonite to Langmuir and Freundlich models was found. Independently of the changes induced by acid attack, calcinations, or milling, the sorption of U(VI) and Sr(II) ions on treated montmorillonite occurs on a homogeneous surface through monolayer adsorption in a similar fashion to natural montmorillonite. Water purification technologies and modern environmental protection technologies may successfully use the obtained clay-based sorbents.

Adsorption features of pigments onto iron oxides: Co-effect of the molecular structure of adsorbates and the varied surface properties of minerals

The knowledge about the adsorption properties of pigments onto different iron oxide minerals is still limited. The adsorption behaviors of three typical pigments, including amaranth (AR), tartrazine (TA), and brilliant blue (BB), onto three iron oxides (ferrihydrite, goethite, and hematite) were investigated. The primary mechanism of their interactions was the electrostatic attraction. The affinities of iron oxides toward any pigment were generally in the sequence of ferrihydrite > goethite > hematite (e.g., the maximum adsorption amounts (qmax) of AR onto the three iron oxides were 35.5 mg/g, 11.6 mg/g, and 4.2 mg/g, respectively), which was related to the differences in physicochemical properties of minerals (e.g., specific surface area, surface hydroxyl density, and crystal structure). Interestingly, for a given iron oxide, the pigment-binding capacity of the mineral was in the order of AR > TA > BB. This effect was attributed to variations in pigment molecular sizes and electrostatic interactions between pigments and minerals. The pigment-binding capabilities of iron oxides changed as the solution pH varied. Hydrogen-bonding and electrostatic interactions were the main mechanisms below and above pH > pHPZC (pH value at zero point charge), respectively. Furthermore, adding Cu2+ facilitated pigment adsorption, mainly stemming from the surface-bridging effect. Pigments also enhanced Cu2+ adsorption onto iron oxides due to the decreasing electrostatic repulsion between Cu2+ and particles as well as the complexion between Cu2+ with pigment molecules adsorbed on mineral surfaces. The insightful information demonstrates that ubiquitous iron oxide minerals can affect the fate of pigments in natural environments.

Effects of surfactant with different injection times on asphaltene adsorption behaviors on the kaolinite surfaces: A molecular simulation study

The adsorption behavior of asphaltenes on the mineral surfaces seriously reduces oil recovery, which is dependent on the molecular structure, surface properties of the inorganic minerals, and the injection time of chemicals. In the present study, the molecular dynamics (MD) simulation is performed to construct the asphaltene-kaolinite adsorption systems and the 3-(N,N-Dimethyloctadecylammonio) propane sulfonate (DOPS) surfactant flooding systems to explore the effect of DOPS injection times on the detachment of asphaltene aggregates with discrepant adsorption characteristics. The number density distribution and the interaction analysis between asphaltene and kaolinite are employed to evaluate the adsorption behaviors of asphaltene on the kaolinite-liquid interfaces. The radial distribution function (RDF) describes the relative positions of the surfactants and asphaltene aggregates. The effective free energy and the independent gradient model based on Hirshfeld partition (IGMH) method further illustrate the microscopic mechanism of asphaltene detaching by the surfactant. The simulation results indicate that intensely polar carboxylate groups and polyaromatic rings with π-conjugated structures dominate the adsorption behavior of asphaltenes. The DOPS surfactants injected after the water flooding are difficult to produce effective ways of detaching asphaltenes, while the introduced DOPS surfactants during water flooding can generate DOPS-ASPn combinations to detach asphaltene from the kaolinite surfaces. This work first investigates the effects of surfactants with different injection times on the oil detachment efficiency at a molecular scale, further deepening the understanding of oil detachment process via surfactant flooding.

Chitosan as an Eco-Friendly Alternative for Silicate Depressant in Phosphate Flotation

The quest for environmentally friendly reagents in froth flotation processes has gained significant importance for minimizing ecological impacts. This research investigates the utilization of chitosan polymer as a green depressant for silicate minerals in the direct flotation of phosphate minerals. To understand the behaviour of the flotation feed, zeta potential measurements were conducted to assess the electrical properties of mineral surfaces in the presence and absence of chitosan polymer. Furthermore, the effects of chitosan dosage, pulp pH, and flotation time on the flotation recoveries and concentrate grade of phosphates were studied. Comparative analyses were performed by comparing the flotation recoveries of phosphate minerals achieved using chitosan polymer with those obtained when employing a commercial silicate dispersant, sodium silicate. The findings revealed that at a dosage of 300g/ton, the recovery of phosphate minerals reached approximately 70% when using chitosan polymer, whereas the recovery was only around 40% with the same dosage of sodium silicate dispersant. These outcomes demonstrate the potential of chitosan as an effective and sustainable silicate depressant in the phosphate flotation process under specific conditions.

The surface dissolution process of smithsonite and its effect on flotation behaviour

Previous studies have shown that the dissolution alters the static intrinsic properties of mineral surfaces, such as changing the surface components or active sites, which in turn affects the floatability. In this work, the dissolution process of smithsonite with different particle sizes and its influence on the flotation behaviour were systematically investigated from a dynamic perspective of the dissolution of ions on the mineral surface. Micro-flotation experiments revealed the inhibition of the flotation of smithsonite during the early phases of dissolution, particularly in the case of the fine particle. Inductively coupled plasma optical emission spectroscopy (ICP-OES) tests, Inorganic carbon (IC) tests, and X-ray photoelectron spectroscopy (XPS) analysis indicated that the early phases of the dissolution process of smithsonite exhibited a more rapid rate of zinc ions. However, as the dissolution progressed and a state of saturation was reached, the further dissolution of carbonate inhibited that of zinc ions. Subsequent adsorption measurements and Fourier transform infrared (FTIR) analysis illuminated the transformation in flotation behaviour resulting from the surface dissolution of smithsonite, primarily by affecting the stability of the adsorption of agents. The rapid dissolution rate of ions on the surface of smithsonite led to decreased adsorption stability of (sodium oleate) NaOL and diminished floatability. This phenomenon was particularly discernible on the surface of fine particle smithsonite. This investigation advances a novel mechanism for comprehending the impact of the surface dissolution processes on the flotation behaviour of smithsonite of different particle sizes, providing a theoretical and practical reference for the flotation of fine particles and marginally soluble minerals.