Adsorption Of Oleate Research Articles

Deep insight into the effect of smithsonite particle size on surface heterogeneity and adsorption behavior: A case of fatty acid system

The studies for microfine mineral flotation have focused on the two main directions of increasing the apparent mineral particle size and reducing the bubble size, while little research has been reported on the special surface properties and adsorption mechanisms of mineral particles of different sizes. In this study, sodium oleate was chosen as a typical surfactant. The mechanism of the effect of smithsonite particle size on the heterogeneity and adsorption behavior of the mineral surface was explored in depth. Through microflotation experiments, BET area tests, Washburn contact angle tests, particle agglomeration tests, adsorption tests and inorganic carbon analysis, it was pointed out that the smaller the size of the particles, the greater the surface wettability, and the smaller the density and thickness of adsorbed oleate on the surface. The difficulty of encapsulating the mineral surface with a hydrophobic layer of oleate hydrocarbon chains, as well as suboptimal particle aggregation sizes, are key reasons for the poor flotation behavior of fine smithsonite. Furthermore, the inhomogeneity of active sites and charge distribution of surface components of smithsonite with different sizes was revealed from a microscopic point of view by DRIFT spectroscopic analysis, XPS analysis and zeta potential measurements. As the particle size of smithsonite decreases, the positive charge density on the surface is higher and the hydration tendency is more intense, hindering the adsorption of oleate. This work is expected to guide the full particle size recovery of minerals in the flotation from a novel microscopic point of view.

Surface modification of ilmenite with sodium persulfate and its effect on flotation performance

Ilmenite is a challenging mineral to float, making the improvement of its floatability a prominent research focus. This study proposes a novel surface modification method using sodium persulfate (Na2S2O8) activation in the sodium oleate system for ilmenite. The activation mechanism was investigated using micro-flotation, zeta potential analysis, adsorption measurement, contact angle measurement, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), flotation kinetics calculation, and thermodynamic analysis. Flotation tests demonstrated a significant increase in ilmenite recovery after Na2S2O8 activation under weakly acidic conditions, particularly at pH 4.0, where recovery increased from 12.41 % to 67.24 %. Zeta potential, contact angle, and adsorption tests revealed that Na2S2O8 activation positively shifted the surface potential of ilmenite, enhancing sodium oleate adsorption and increasing hydrophobicity. FT-IR, XPS, and thermodynamic analyses showed that Na2S2O8 facilitated the conversion of Fe2+ to Fe3+ on the ilmenite surface. Additionally, activation with sodium persulfate increased the Fe3+ content on the surface from 20.13 % to 43.50 %, leading to the formation of a more stable ferric iron oleate. AFM scans confirmed that Na2S2O8 activation significantly increased the area and thickness of sodium oleate adsorbed on the ilmenite surface compared to unactivated ilmenite.

Impact of Hydrodynamic Cavitation Pretreatment on Sodium Oleate Adsorption onto Diaspore and Kaolinite Surfaces

To investigate how hydrodynamic cavitation (HC) affects the adsorption of sodium oleate (NaOl) on diaspore and kaolinite surfaces, a comparative study on NaOl adsorption was conducted under different conditions. The flotation and separation of the minerals were also examined with and without HC pretreatment of NaOl. The results show that short-term HC pretreatment of NaOl solutions did not induce a measurable change in the chemical structure of NaOl, but produced micro-nanobubbles (MNBs) and resulted in decreases in the surface tension and viscosity of liquids. When MNBs interacted with minerals, their anchor on solids could affect the contact angles, zeta potentials, and surface NaOl adsorption toward minerals. At low NaOl concentrations, the presence of MNBs reduced the NaOl adsorption capacity and particles’ zeta potential while increasing the minerals’ contact angle. At higher NaOl concentrations, the presence of MNBs promoted NaOl adsorption, further increased the minerals’ contact angle, and further decreases the particles’ zeta potential. Additionally, the flotation and separation of minerals can be enhanced at low NaOl concentrations, largely due to the enhanced bubble mineralization through the selective surface-anchoring of MNBs on diaspore. However, the separation efficiency might deteriorate at high NaOl concentrations, though the presence of MNBs amplified the divergences in minerals’ surface wettability and zeta potentials.

Efficient adsorption of sodium oleate from wastewater with graphene oxide/polyethyleneimine composite hydrogel: Performance and mechanism

Sodium oleate (NaOL) is commonly employed as a traditional organic collector during the flotation process of phosphate ore. However, the residual NaOL in mineral processing wastewater not only poses a great threat to the environment, but also reduces the qualities of subsequent flotation products. In this study, an effective adsorbent graphene oxide/polyethyleneimine (GP) composite hydrogel was prepared and applied for the adsorption of NaOL. The successful association between GO and PEI was elucidated through various characterizations. Further to that, the adsorption performance was systematically determined through adsorption isotherm, adsorption kinetics, co-existing ions and reusability experiments. The results clearly demonstrated that the adsorption behavior of NaOL could be well described by both pseudo-second-order (PSO) kinetic and Langmuir isotherm models. GP composite hydrogel was able to achieve superior NaOL adsorption with an excellent adsorption capacity (295.95 mg/g) and a quick kinetic (120 min). The existence of competitive ions, such as CO32−, SO42− and PO43−, had a negative effect on NaOL adsorption. The mechanism investigation suggested that chemical adsorption and hydrogen bonds were central and played imperative roles for the adsorption of NaOL on GP composite hydrogel. Overall, the current work provides a valuable reference for the efficient adsorption of NaOL.

Atomic insights into the interaction mechanism underpinning carbonate ion adsorption in smithsonite flotation

In industrial practice, smithsonite flotation separation and purification are nearly invariably conducted in highly alkaline environments. According to latest studies, sodium carbonate is a cheap, sustainable, stable, and safe substitute pH modifier that additionally assists with deep extraction recovery of smithsonite. In this work, the influence of carbonate as a pH modifier on smithsonite flotation behavior was comprehensively explored through flotation experiments, contact angle tests, X-ray photoelectron spectroscopy (XPS) investigations, and density functional theory (DFT) calculations. In comparison to sodium hydroxide, smithsonite exhibits far better floatability and hydrophobicity in the carbonate system, as demonstrated by the results of micro-flotation and contact angle experiments. XPS demonstrates that the underlying reason of the distinct pH modifications of smithsonite floatability in the carbonate system is the creation of different zinc-containing compounds, with the highly reactive CO32- forming a Zn5(CO3)2(OH)6 complex with Zn atoms at pH 10.5. Comprehensive DFT calculations further demonstrated that the hybridization reactions between Zn 2 s, O 2 s, and O 2p orbitals and the formation of stable Zn-O covalent bonds between OH- and Zn atoms shielded the preferential adsorption of oleate (OL-) on the smithsonite surface. Uniquely, the ionic bonding generated by carbonate is distinguished by the formation of a low-bonding-capacity Zn-O chemical bond, causing it susceptible to breaking during adsorption competition and allowing OL- to adsorb preferentially on Zn sites.

The inhibition mechanism of esterified starch on flotation separation of fluorite and calcite

Herein, the flotation behavior of fluorite and calcite was examined before and after starch esterification through mineral flotation experiments. Moreover, the adsorption action mechanisms on minerals before and after starch esterification were investigated using methods such as solution surface tension measurement, infrared spectroscopy, and extended Derjaguin–Landau–Verwey–Overbeek theory. The results showed that after starch esterification (esterified starch), there was a greater difference in the mineral recovery rate compared to before starch esterification (ordinary starch), with a better inhibition effect on calcite. The interaction between mineral surfaces and ordinary starch was weaker than the interaction between minerals and esterified starch. In particular, after starch esterification, the surface tension increased, two minerals contact angle decreased, the surface potential became more negative, and the difference in the mineral recovery rate was greater than before starch esterification. After the interaction between minerals and esterified starch, calcite particles displayed good dispersibility, while the cohesion between calcite particles and sodium oleate particles decreased; notably, the effect on fluorite was opposite. Calcite and esterified starch exhibited chemical adsorption, impeding the adsorption of sodium oleate onto calcite and resulting in calcite inhibition. The interaction between fluorite surface and esterified starch involved electrostatic adsorption, with sodium oleate chemically adsorbed onto the fluorite surface. Chemical adsorption proved stronger than electrostatic adsorption, enabling sodium oleate to capture fluorite.

STPP and EDTMPS synergistically enhance the flotation separation of scheelite from fluorite and calcite

In this paper, the synergistic effects of sodium tripolyphosphate (STPP) and sodium ethylenediamine tetramethylenephosphonate (EDTMPS) for the flotation separation from fluorite and calcite were investigated. Flotation tests conducted at various scales demonstrated that the combined inhibitor of STPP and EDTMPS can significantly enhance the separation efficiency of scheelite from fluorite and calcite. For low-grade scheelite in Luanchuan, the combined inhibitor can improve the WO3 grade of scheelite roughing concentrate without compromising the recovery of scheelite roughing, thereby reducing the burden of the Petrov process. Based on the results from X-ray photoelectron spectroscopy and atomic force microscopy, coupled with other surface analysis, it’s evident that STPP and EDTMPS are more readily adsorbed onto the surfaces of fluorite and calcite due to the unique in electrostatic repulsion and steric resistance.The co-adsorption of STPP and EDTMPS covers a more extensive mineral surface area, enhancing the hydrophilicity of fluorite and calcite surfaces. This, in turn, heightens the resistance of the mineral surfaces to subsequent sodium oleate (NaOL) adsorption. As a result, the floatability difference among the three calcium-bearing minerals is expanded, optimizing the separation efficiency.

Synergistic catalysis effect of micro-mesoscopic channel for enhanced methyl oleate catalytic cracking to BTX: A molecular simulation study

The hierarchical ZSM-5 zeolite exhibits superior catalytic performance for methyl oleate catalytic cracking to BTX, while the promotion mechanism at the molecular level is still unclear. Herein, the adsorption and diffusion behaviors of reaction species in hierarchical ZSM-5 zeolite, including methyl oleate, C3H6, C4H8 and BTX, were theoretically investigated by Monte Carlo combined with Molecular Dynamics simulation. It is found that the introduction of mesopores exposes the strong adsorption sites (Brønsted acid) without a confinement effect, thereby promoting the adsorption and cracking of methyl oleate. Moreover, the as-formed C3H6 and C4H8 rapidly transfer from mesopore into micropore, enhancing the aromatization reaction to form BTX. Finally, thanks to the adjacent mesopore providing sufficient space for molecule rotation, the desired BTX products easily desorbs from the micropore. Such synergistic catalysis effect of micro-mesoscopic channel increases the BTX yield by decreasing the diffusion coefficient of C3H6 and C4H8 from 13.2 × 10-9 m2/s on the traditional to 6.4 × 10-9 m2/s on the hierarchical ZSM-5. We anticipate that this work could enrich our understanding of the microcosmic mechanism of hierarchical zeolites for prolific aromatics.

Selective adsorption of soluble starch on the cassiterite surface for effective flotation separation of scheelite from cassiterite

Tungsten and tin are important strategic resources. Scheelite and cassiterite have similar physical and chemical properties and face the challenge of flotation separation. This study proposes soluble starch (SS) as an effective depressant for the flotation separation of scheelite from cassiterite. The depression mechanism of SS was investigated using micro-flotation, zeta potential, total organic carbon, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectroscopy. SS exhibited a good selective depressive effect on cassiterite and was able to efficiently separate scheelite from cassiterite. The results of artificial mixed mineral test showed that the recovery of scheelite and cassiterite were 79.35 % and 9.48 %, respectively and the grade were 70.15 % and 8.11 %, respectively at pH 10. The macromolecular organic depressant SS has abundant hydrophilic groups, such as hydroxyl groups, which cause the material to stably adsorb on Sn active sites on the surface of cassiterite and hinder the adsorption of the collector sodium oleate (NaOL, C17H33CO2Na). The selective adsorption of SS on the surface of cassiterite results in efficient flotation separation of the two minerals.

Polyaspartic acid, an eco-friendly regulator for the improvement of coking coal flotation: applications and mechanism

ABSTRACT In this study, a novel approach is to apply polyaspartic acid (PASP) as an eco-friendly regulator for the flotation of coking coal, which is different from the conventional use of oil collectors only. Flotation trails showed that adding PASP contributes to a two-way improvement in the yield and ash content of clean coal. SEM-EDS observations directly revealed that adding PASP significantly reduces the coating of high-ash fine slimes on the surface of low-ash coal particles. Contact angle detections and zeta potential analysis presented that the preferential adsorption of PASP hardly affects the adsorption of sodium oleate (NaOL) on the surface of low-ash coal particles but significantly weakens the adsorption of NaOL on the surface of high-ash fine slimes, leading to a remarkably hydrophobic difference. Particle interaction energy calculations verified that adding PASP enlarges the energy barrier between low-ash coal particle and high-ash fine slime. Hence, it can be arrived that the preferential adsorption of PASP affects the adsorption of NaOL on the surface of high-ash fine slime, widens the hydrophobic difference, enlarges the energy barrier between low-ash coal particle and high-ash fine slime, reduces the high-ash fine slime coating, therefore leading to a better flotation performance of lean coal.

Unveiling the enhancement mechanism of Fe ion for muscovite flotation: Adjustment of surface potential and agent dispersion

Metal ions have been used to improve the flotation recovery of muscovite, while the enhancement mechanism is still unclear. In this paper, density functional theory (DFT) calculations and molecular dynamics (MD) simulations were employed to investigate the adsorption structure of sodium oleate (NaOL) on muscovite surface, and the diffusivity and foaming of NaOL in the pulp system, in presence of Fe3+ at different pH range. DFT calculation results suggested that the adsorption of iron ions, include FeOH2+ and Fe(OH)2+, could change the surface charge from negative to positive, thus enhancing binding performance for OL−. Moreover, MD simulations indicated that the distribution of iron ions in aqueous solution can significantly affect the dispersion of sodium oleate molecules. Specifically, FeOH2+ may lead to the complexation of oleate ions and result in the agglomeration, which is not conducive to its dispersion in solution. However, Fe(OH)2+ can significantly inhibit the aggregation of OL− molecules, and accelerate the dispersion of OL− in flotation pulp. This work reveals atomic-level mechanism of Fe ion on the dispersion and adsorption of sodium oleate in pulp, which is helpful to the understanding of minerals flotation behavior in presence of metal ions.

Enhanced separation of scheelite and calcite by metal-inorganic complex depressant

The effect of metal-inorganic complex depressant composed of aluminum sulfate and sodium silicate (AlSS) on the flotation separation of scheelite and calcite was studied. Zeta potential and adsorption measurements confirmed that the negatively charged colloidal particles composed of Al(OH)4− and SiOm(OH) n4−2m−n tended to be adsorbed on calcite surface, inhibiting the adsorption of sodium oleate (NaOL), while the adsorption of negatively charged colloidal particles on scheelite surface was relatively low, which resulted in the great adsorption capacity of NaOL on scheelite. The contact angle measurements showed that the hydrophobicity of scheelite was significantly better than that of calcite in the NaOL+AlSS solution. XPS measurement results indicated the adsorption of Al and Si on the calcite surface rather than on the scheelite surface. Compared to adding water glass (sodium silicate, SS) only, the depression effect on calcite was significantly enhanced by the combination of AlSS, while scheelite flotation was hardly affected. Scheelite concentrate with WO3 grade of 68.34% and WO3 recovery of 83.14% could be obtained from mixed scheelite and calcite ores by adding AlSS.

In situ adsorption study of carboxymethylcellulose and sodium oleate on quartz using a quartz crystal microbalance with dissipation (QCM-D)

Adsorption kinetics and conformation of sodium oleate and carboxymethylcellulose (CMC) on the quartz surface in real time remain a challenge in the flotation system of CMC /sodium oleate/quartz. In this work, in situ adsorption characteristics of CMC and sodium oleate on quartz surface was investigated by using quartz surface crystal microbalance with dissipation (QCM-D). QCM-D data showed that the conformations and kinetics were critically dependent on pH and degree of substitution (DS) of CMC. As the degree of substitution of CMC increases, the adsorption layer on the quartz surface becomes looser. There was only one adsorption stage at pH 8 and 12, and the adsorption layer was rigid at pH 12. At pH= 10, the conformation of the adsorbed layer changes from loose to rigid and then to loose again. CMC adsorbs less in the early adsorption stage, and the adsorbed layer is loose. As the adsorption proceeds, the adsorption increases, and the adsorbed layer becomes more rigid. At stage III, the adsorbed layer becomes loose, which is considered to be the formation of a hydrated layer. Under different pH conditions, the adsorption of sodium oleate on the quartz surface had only one stage, and when CMC and sodium oleate were adsorbed one after the other on the surface of the quartz surface, two distinguishable adsorption stages appeared, and the conformation of the adsorbed layer gradually changed from rigid to loose. The change of surface free energy of quartz surface before and after CMC adsorption was also calculated by Washburn kinetic equation and the van Oss - Chaudhuri-Good theory. The results showed that the surface free energy reduced and the hydrophobicity increased after the adsorption of CMC on the quartz surface.

Selective adsorption analysis of BAPTA depressants on the surface of carbonate minerals: Insights into flotation behavior and adsorption mechanism

Flotation separation of magnesite and calcite, two carbonate minerals, poses a significant challenge due to their intrinsic surface similarities. In this study, 1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA) was employed as a depressant to selectively regulate the mineral surface property in magnesite-calcite flotation. Micro-flotation experiments demonstrated that successful separation of magnesite-calcite mixtures could be achieved with 40 mg/L BAPTA and 100 mg/L sodium oleate (NaOL). Contact angle measurements and Ultraviolet-Visible absorption spectrum analysis revealed that pre-adsorption of BAPTA selectively hindered the adsorption of sodium oleate onto calcite surface, effectively eliminating the surface hydrophobicity of calcite induced by sodium oleate. The Extended-Derjaguin-Landau-Verwey-Overbeek (EDLVO) theory further indicated a reduced attractive interaction energy between magnesite and calcite particles in the presence of BAPTA. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) simulation elucidated the stronger binding affinity of BAPTA towards calcium ions. Finally, a model was established for the selective formation of cage-like chelating structures on the calcite surface by BAPTA.

A DFT study on the effect of lattice defects on the electronic structures and floatability of spodumene

The influences of lattice vacancies and lattice impurities on the electronic structures and floatability of spodumene were studied by the density functional theory (DFT) through analysis of partial density of states (DOS), Mulliken population, differential charge density, and frontier molecular orbitals. The calculation indicated that the effect of lattice Al, Si, and Li vacancies on the DOS, Mulliken population as well as the interaction between spodumene and oleate was insignificant. Cr, Fe, and Mn impurities caused the shift of Fermi level towards lower energy and the occurrence of peaks of impurity near Fermi level. K and Na impurities contributed little to the lowest unoccupied molecular orbital (LUMO) of spodumene, while Cr, Fe, and Mn impurities had great contribution, suggesting that Cr, Fe, and Mn impurities significantly affected the interaction between spodumene and oleate. The frontier molecular orbitals analysis indicated Cr, Fe, and Mn impurities are in favor of oleate adsorption.

Floatability of Fluorite and Calcite Inhibited by Sodium Hexametaphosphate via Ultrasonic Activation

In order to separate fluorite and calcite inhibited in tungsten tailings, the effect and mechanism of using ultrasonic external field activation to separate fluorite and calcite inhibited by sodium hexametaphosphate in a sodium oleate system were investigated. After pretreatment with an ultrasonic external field with a frequency of 40 kHz and sound intensity of 0.56, 0.50 and 0.40 W/cm2, the flotation recovery of calcite could be increased from 16.08% to about 80%, while the flotation recovery of fluorite was only increased from 7.5% to about 20%, with a difference of 60% between the two flotation recoveries, and the larger the sound intensity, the shorter the pretreatment time and the smaller the ultrasonic input energy. The contact angle of the calcite surface increased, sodium oleate adsorption increased, and zeta potential decreased after ultrasonic pretreatment, while the contact angle, sodium oleate adsorption, and zeta potential of fluorite surface were less changed. The results of heat of adsorption and XPS measurements showed that more heat was released from the interaction between sodium hexametaphosphate and fluorite, and the Ca2p peaks on the surface of fluorite were shifted to a greater extent after the interaction, which inferred that the adsorption of fluorite and sodium hexametaphosphate was relatively easier and stronger. It is presumed that the ultrasonic pretreatment can bring the mineral surface to different degrees of desorption according to the adsorption strength of sodium hexametaphosphate, exposing Ca2+ active sites for sodium oleate adsorption, while expanding the floatability difference between fluorite and calcite.

Insights into the influence of calcium ions on the adsorption behavior of sodium oleate and its response to flotation of quartz: FT-IR, XPS and AMF studies

Assiduous efforts on the high-efficiency flotation of quartz with calcium ion activation have been ongoing, while there is a lack of understanding of its potential mechanism. In this research, insights into the influence of calcium ions on the adsorption behavior of sodium oleate and its response to flotation of quartz were systematically investigated. Micro-flotation experimental results show that addition order of calcium ions influences the quartz flotation. Ca2+/NaOL complexes exhibit higher flotation recovery of quartz (92.18 %) under the recommended conditions. The Zeta potential and Fourier transform infrared spectroscopy results indicate that the adsorption of NaOL onto bare quartz surfaces is extremely difficult, and the addition of Ca2+ promotes the adsorption of NaOL. X-ray photoelectron spectroscopy analysis results confirm that Ca2+/NaOL complexes reinforce the adsorption of NaOL and Ca2+ onto quartz surface by the formation of -Si-O-Ca-OOCR, and the Ca-OOCR content in the total Ca reaches 62.61 %. The adsorption amount results further illustrate that the adsorption amount of Ca2+ and NaOL increase to 18.56 × 10−2 mg/g and 40.83 × 10−2 mg/g, respectively. Additionally, starch slightly decrease the adsorption amount of Ca2+ on quartz surfaces. Atomic force microscope analysis reveal that Ca2+/NaOL components promote the formation of Ca-OOCR colloid precipitates and the transportation of the precipitates to the quartz surface. The main adsorption of Ca-OOCR colloid precipitates contributes to the enveloped bulge image. Notably, the Ca-OOCR colloid precipitates adsorption mechanism exerts more important role in the adsorption of sodium oleate and calcium ion species, as well as its response to flotation of quartz.

Selective depression by using environment-friendly depressant pectin in apatite and dolomite flotation system

The difficulty of apatite and dolomite to be efficiently separated by froth flotation due to similar physical and chemical properties of both minerals in using fatty acid collectors without any depressants. In this study, pectin was explored as an efficient and environment-friendly depressant in flotation to separate apatite and dolomite. In the micro-flotation experiments, pectin displayed an intense depressing effect in dolomite flotation and slightly affected apatite flotation. Quantum chemical calculation was used to predicated the reactive site of pectin, the results demonstrated that oxygen atoms of COO, OH and COC in pectin display the most negative regions. The Zeta potential results indicated pectin was adsorbed on the dolomite surface selectively and depressed the adsorption of sodium oleate on the dolomite surface due to electrostatic repulsion effect. The Fourier transform infrared (FTIR) spectrum measurements uncovered that the selective separation of pectin was due to OH of pectin molecules. The Raman spectrum demonstrated that weak adsorption of pectin on the apatite surface was due to CO of pectin molecule, while the strong adsorption is regard as COO and COC of pectin for dolomite. XPS results indicated that COO of pectin can chelate with Ca2+ and Mg2+ of dolomite surface and depress dolomite flotation. Hence, pectin was be utilised as an eco-friendly and highly selective depressant.

Insights into the desilication mechanism of goethite by anionic reverse flotation from hydroxyl role

This paper mainly investigates the role of hydroxyl on the desilication of goethite by anionic reverse flotation. Accordingly, micro-flotation experiments suggested that the activation effect of Ca(II) on quartz was obviously better than that of goethite in the high alkaline sodium oleate (OL) system.. Furthermore, the Zeta potential also confirmed that the selectivity of Ca(II) ions on quartz surface was better than that on goethite surface. Solution chemical analysis revealed that the dominant species of activator Ca(II) and collector OL were Ca2+ and OL−, respectively. Fourier transform infrared (FT-IR) spectroscopy suggested that OL− could not form an effective adsorption on mineral surfaces in the absence of Ca2+, while OL - had a strong chemisorption in the presence of Ca2+. Density functional theory (DFT) calculations demonstrated that the successful floating of quartz involves three surface modifications, namely the surface hydroxylation, the adsorption of Ca2+ on the hydroxylated surface, and the adsorption of OL− on the Ca2+-activated surface. In this process, hydroxylation is the prerequisite for the subsequent adsorption of Ca2+ and OL−. Besides, the selective adsorption of sodium humate (SHM) causes the flocculation and inhibition of goethite, which also plays a key role in the desilication of goethite.

Effect of sulfuric acid pretreatment on flotation performance of calcite and fluorite

Difficulty in separating calcite and fluorite owing to their similar surface properties is the focus of research in the field of mineral processing. To increase the selectivity difference between these two minerals, sulfuric acid was introduced as a surface pretreatmentand, and aluminium sulfate was used as the flotation depressant. The effects of H2SO4 pretreatment on calcite and fluorite flotation performance and the mechanisms thereof were studied by combining microflotation experiments, solution chemical calculations, scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS), Fourier transform infrared (FT-IR) spectroscopy, and density functional theory (DFT). Microflotation experiments showed that sulfuric acid pretreatment significantly reduced the flotation recovery of calcite to less than 10%, while it had little effect on fluorite, where the recovery reached greater than 80%. SEM-EDS and FT-IR analyses showed that, after sulfuric acid treatment, the surface composition of calcite was converted from CaCO3 to CaSO4, while the fluorite surface remained almost unchanged. DFT calculations showed that CaSO4 was more hydrophilic than CaCO3; therefore, it was more likely to interact with water molecules. The presence of water molecules affected the adsorption of the sodium oleate (NaOL) collector on the mineral surface. Therefore, the calcite surface adsorption ability of NaOL after sulfuric acid pretreatment was weakened, resulting in a significant decrease in flotation recovery.