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The flotation of unoxidized and oxidized molybdenite fines is a challenging job worldwide. In this work, dodecylamine (DDA) was developed as a potential collector to improve the flotation of molybdenite fines with and without oxidation. The flotation behaviors and interaction mechanisms were probed through flotation tests, contact angle, Zeta potential, Scanning Electron Microscope-Energy Dispersive Spectrometer(SEM-EDS), and X-ray Photoelectron Spectroscopy (XPS). The flotation tests revealed that DDA improved the flotation of unoxidized or oxidized molybdenite fines efficiently. The results of Zeta potential, contact angle, and SEM-EDS uncovered that a substantial number of DDA species adsorbed on both fresh and oxidized molybdenite faces and edges, thus enhancing their hydrophobicity. XPS analysis further manifested that RNH2 and RNH3+ adsorbed on the S atoms of fresh faces through hydrogen bonding. Meanwhile, RNH2 and RNH3+ mainly adsorbed on fresh edges via chemical bonding between amine groups and Mo sites and electrostatic force. For oxidized molybdenite, RNH2 and RNH3+ interacted with oxidized faces through hydrogen bonding while adsorbed on oxidized edges via hydrogen bonding and electrostatic interaction. [ABSTRACT FROM AUTHOR]

Extracellular polymeric substances (EPS) occur naturally and widely on the surface of microbial cells; their reducibility may play a crucial role in graphene oxide reduction. In this work, the conversion of graphene oxide (GO) into reduction graphene oxide (rGO) with EPS (extracted from Bacillus sp.NT 10) as green reductant had been conducted to explore their potential application for graphene preparation. The results showed the GO could be reduced by EPS, especially in the presence of NH4+, and a synergetic effect was found between EPS and NH4+. Further studies hinted the rGO could be also obtained from GO by EPS reduction even under a mild alkaline condition (pH = 8), lightly higher room temperature (40 °C) and a certain amount of time (24 h). The good reduction performance was found to be ascribed to the real deoxygenation of oxygenous functional groups and restoration of electronic conjugation within GO, according to the analysis of XRD, XPS and FT-IR as well as Raman spectra, while the electron-rich tryptophan-like protein and aromatic protein on the surface of EPS as well as the assistance of NH4+ should account for the deoxygenation and restoration in terms of the detection on Zeta potential, AFM and 3D-EEM. These findings revealed the reduction of GO with EPS would be a green, environment-friendly and promising path to obtain rGO, which may open a novel route for the preparing graphene alternatively. [ABSTRACT FROM AUTHOR]

Chalcopyrite flotability were investigated in four common chloride salts. The results indicated that NaCl, KCl, CaCl2 increased chalcopyrite recovery while MgCl2 decreased its recovery. The monovalent salts played an insignificant role while divalent salts apparently decreased the contact angle of chalcopyrite, regardless of the presence of collectors. Furthermore, the zeta potential was increased in divalent salts and even changed from negative to positive values in MgCl2, highly due to Mg(OH)2 precipitation on chalcopyrite surface. In addition, molecular dynamics simulation indicated that Mg(OH)2 precipitates on chalcopyrite (112) surface stabilized the liquid layer and formed a hydrophilic barrier to inhibit SBX adsorption. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effects of inorganic cations (Na+, Ca2+, and Al3+) with different valences and concentrations on the stability of Na-montmorillonite (Na-MMT) suspension. The stability was studied by turbidity and zeta potential measurements and adsorption thermodynamics. The results showed that the Na-MMT particles coagulated at pH 3-4.8, the stability of which was much inhibited by cations with higher concentration and higher valence. This was caused by the adsorption of cations and the reduction of electrostatic repulsion. Adsorption of Ca2+ on Na-MMT surface fits the Freundlich curve model well. Furthermore, the adsorption reduced the zeta potential of Na-MMT and then the energy barrier between the particles which well obeyed the classic DLVO theory. [ABSTRACT FROM AUTHOR]

Air lime mortar is an important material for restoring ancient buildings, but its application is limited because of its low compressive strength, high shrinkage, and high porosity. In this work, improvement of the compressive strength of lime mortar by adding carboxymethyl cellulose (CMC) solution has been investigated. We characterized fine particles of Ca(OH) and lime mortars by scanning electron microscopy, infrared spectroscopy, the adsorption capacity, and the zeta potential. The experimental results show that the addition of CMC improves the compressive strength of lime mortar. Chemisorption of CMC to Ca(OH) particles leads to CMC bridging Ca(OH) particles, which is the key to form a more compact structure according to the porosity of the lime mortar. It was found that CMC acts as a skeleton in lime mortar because of the bridging effect of the molecules and the extended conformation of the molecules at high pH, which contributes to improvement of the compressive strength of lime mortar. [ABSTRACT FROM AUTHOR]

In this work, a novel method to determine the point of zero net proton charge (PZNPC) of colloidal kaolinite in aqueous solutions was presented through the measurement of zeta potential of the particles in various concentrations of NaCl solution and the mathematic regression of the zeta potential versus pH curves. This method is based on the observation that there are two common intersection points (CIP) in the two curves of zeta potential versus pH of colloidal kaolinite with a low and a high NaCl concentration. The observation might be attributed to that NaCl would compress the electric double layer of kaolinite particles and affect the efficiency of the protonation/deprotonation of the HD-faces. The experimental result showed that the PZNPC of kaolinite is 5.37. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effect of inorganic cations (Na+, Ca2+, Ba2+, Fe3+, Al3+) with different valence and concentration on the swelling behaviors of montmorillonite. Na-montmorillonite, obtained from China, was chosen as experimental objective. It was first characterized through the measurements of swelling capacity and zeta potential. Then, swelling properties of Na-montmorillonite influenced by cation concentration, valence, and hydration analyzed were studied. The results showed that the swelling capacity was much inhibited by cations of higher concentrations, higher valences, or weaker hydration. This work also verified the conclusion that the decreased degree of potential is more significant caused by cations of higher valence. [ABSTRACT FROM PUBLISHER]

Specific adsorption of hydrolyzed chromium species on kaolinite surface was studied. Electrokinetic behavior of kaolinite particles in aqueous solutions in the presence of CrCl3 showed that the hydrolyzed chromium species can adsorb on kaolinite surfaces and reverse its charge. This adsorption reached the maximum near the precipitation pH (ppt) of chromium hydroxide. The adsorption followed Langmuir isotherm and was irreversible. It might be resulted from hydrogen bonding between the hydrolyzed metal species and kaolinite surfaces. A novel chemical adsorption model was proposed between kaolinite surfaces and the hydrolyzed multivalent metal species. [ABSTRACT FROM PUBLISHER]

The relative viscosity of colloidal silica dispersion in aqueous electrolytic solutions as the function of volume fraction of dry particles in the solutions has been experimentally determined in this work, in order to study the effects of pH and electrolytes (Na2SO4 and AlCl3) on the hydration of the silica surfaces in the solutions. The results have shown that the maximum relative viscosity of the silica dispersion and the strongest hydration of the silica in aqueous solutions appeared at neutral pH, while the stronger the acidity and the alkalinity of the aqueous solution, the weaker the hydration. In the presence of the electrolytes (Na2SO4 and AlCl3), the relative viscosity of the silica dispersion reduced and the hydration of the silica in aqueous solutions became weak. The higher the concentration of the electrolytes, the weaker the hydration, indicating that the destabilization of the colloidal silica dispersion in aqueous solutions might be realized through adding the high-valence electrolytes to weaken the hydration of the particle surfaces (hydration forces between the particles). Also, it has been shown that the negative zeta potentials of the colloidal silica in aqueous solutions greatly reduced in the presence of the electrolytes. Therefore, the high-valence electrolytes (Na2SO4 and AlCl3) as the coagulant of colloidal silica in aqueous solutions might be originated from that the presence of the electrolytes simultaneously reduces the electrical double layer repulsive force and the hydration repulsive forces between the particles in aqueous solutions. [ABSTRACT FROM AUTHOR]

The effect of depressant 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) on the flotation separation of smithsonite from calcite was studied by micro-flotation and electro-kinetic tests. The micro-flotation results showed that good floatability of both smithsonite and calcite were achieved in the presence of sodium oleate. The depressant PBTCA selectively depressed calcite without interfering the floatability of smithsonite. The mixed minerals flotation results showed that efficiency separation of smithsonite from calcite was achieved using PBTCA as the depressant. Zeta potential measurements indicated that NaOl was able to adsorb on the PBTCA pre-treated smithsonite surface, but failed to adsorb on the PBTCA pre-treated calcite surface. Unlabelled Image • Both smithsonite and calcite floated well in the presence sodium oleate • Separation of smithsonite and calcite using PBTCA depressant was attempted • Calcite can be selectively depressed by PBTCA • This might be attributed to the matched-degree of PBTCA with calcite [ABSTRACT FROM AUTHOR]

Abstract Effects of sodium chloride on the sulfidization flotation of cerussite (PbCO 3) were investigated by micro-flotation tests, adsorption tests and zeta potential measurements. The micro-flotation test results indicated that sodium chloride effectively improved the sulfidization flotation performance of cerussite. The electrical double layers of cerussite particles were compressed in sodium chloride solution, thus providing more lead sites on the cerussite surface and promoting the adsorption of sulfide ions. In sodium chloride solution, more lead sulfide species were formed on the cerussite surfaces and improved its sulfidization flotation performance. Graphical abstract Unlabelled Image Highlights • Effect of sodium chloride on cerussite sulfidization flotation was investigated. • Sodium chloride improved the sulfidization flotation performance of cerussite. • Electrical double layer of cerussite was compressed by sodium chloride. • More lead sites on cerussite surface enhanced the sulphur ion adsorption. [ABSTRACT FROM AUTHOR]

Graphical abstract The interation of quartz-malachite and calcite-malachite are present by zeta potential distribution. Abstract The role of gangue minerals including quartz and calcite slimes in the sulfidization flotation of malachite was investigated by micro-flotation tests, sedimentation analysis, zeta potential distribution measurements and DLVO calculations. The micro-flotation results showed that calcite slime depressed malachite flotation at pH 9.5 while quartz slime does not appear to influence malachite flotation. Sedimentation tests showed that hetero-coagulation occurred in both of malachite-calcite and malachite-quartz systems. The zeta potential distribution of individual minerals and mixed minerals measurements were used to describe the observed depression of sulfidization flotation of malachite by calcite but not quartz slime addition. DLVO calculation can be explained the hetero-coagulation in malachite-calcite system but not in malachite-quartz system, this may be attributed to the dissolved species of malachite adsorbed on quartz surface in malachite-quartz system. [ABSTRACT FROM AUTHOR]

To reduce the negative effects of lizardite on the flotation of pentlandite, amino trimethylene phosphonic acid(ATMP) was tested as a potential depressant for lizardite. Micro-flotation test results indicated that the flotability of pentlandite restored in pentlandite-lizardite system by the addition of ATMP. The adsorption and ICP results indicated that ATMP interacted with the Mg species of lizardite surface meanwhile a part of the Mg ions were dissolved from lizardite surface. XPS tests illustrated that ATMP changed the surface characteristics of lizardite mineral and the Mg/Si atomic ratio decreased on lizardite surface. Zeta potential measurements demonstrated that the lizardite zeta potential was changed from positive to negative after interacting with ATMP, which caused the electro-steric repulsion between pentlandite and lizardite particles, and thus the pentlandite floatability was restored. [ABSTRACT FROM AUTHOR]

Sylvite (KCl) is a classical soluble mineral with high solubility, endowing the possibility to precisely adjust its surficial structure for flotation recovery. In this work, efforts have been originally made to study flotation behaviors of KCl with (200) and (222) exposing facets. KCl(200) crystals had a higher recovery than that of KCl(222) with octadecylamine hydrochloride (ODA). FTIR and XPS results indicated that interaction force between KCl and ODA was not chemical absorption. Zeta potential results further implied the mechanism that the ODA reacted with KCl by static force and KCl(200) possessed a lower potential than KCl(222) and thus facilitated the flotation process. 2D as well as 3D AFM results provided microscopic details of perfect cubic KCl(200) and octahedron KCl(222) samples where layered growing method of former samples exhibited more edges with hanging Cl bonds, leading to its more negative surficial potential and less hydrophilic property, enhancing flotation recovery. Moreover, adhesion & adsorption force further illustrated that KCl(200) obtained a stronger interaction with bubbles, in coincidence with its better flotation recovery. KCl crystals with (200) exposing faces promoted flotation in comparison with crystal with (222) faces, offering strategy to reserve (200) faces for designing KCl crystals with high recovery. [Display omitted] • Sylvite flotation behaviors connected with exposing facets were firstly investigated. • Sylvite with (002) facet possessed higher flotation recovery than that with (222) facet. • Stronger adhesion of bubbles on (002) facet facilitated flotation recovery. • Interaction between exposing facets and collector was electrostatic adsorption. • Negative surficial potential of (200) facet was originated from edges with hanging Cl bonds during its layered growth. [ABSTRACT FROM AUTHOR]

[Display omitted] • The mixed collectors improve the collecting ability and selectivity of bastnaesite comprehensively. • The BHA and SHA are chemically adsorbed by Ce site on the bastnaesite surfaces. • The two mixed collectors have a stronger adsorption ability on bastnaesite surface than single collectors. • The chelate formed of BHA and SHA on banaesite is most likely to exist in the form of the five-membered ring. Bastnaesite, as one of the most important sources of rare earth elements, are typically separated through flotation. However, the complex association and fine particle size of bastnaesite make it challenging to achieve high flotation recovery and grade. In this study, mixed collectors composed of benzohydroxamic acid (BHA) and salicyhydroxamic acid (SHA) has been developed for the flotation of bastnaesite. Results show that BHA has better collection performance while SHA show better selectivity in the flotation separation of calcite and dolomite. The combination of BHA and SHA in the flotation turn out that the recovery and grade of bastnaesite are simultaneous promoted compared to single collector. Adsorption experiments indicate that bastnaesite has larger adsorption capacity to BHA, while SHA are more selective adsorbed on bastnaesite rather than calcite and dolomite. Zeta potential measurements confirm the stronger adsorption of mixed collector onto the bastnaesite surface compare to single collectors, which agree well with the flotation results. The FTIR analyses show that the mixed collector undergoes a chemical reaction on the bastnaesite surface, facilitating chelation between the collector and bastnaesite. The XPS analyses verified that the newly formed bonds are Ce-O bonds between the collectors and bastnaesite. Overall, this study developed a kind of mixed collector for bastnaesite flotation, the synergistic effect and co-adsorption of BHA and SHA on bastnaesite surface have been demonstrated, which provide new approach to improve the flotation recovery and grade of bastnaesite. [ABSTRACT FROM AUTHOR]

• Pb cations effectively activated wolframite flotation when using BHA as the collector. • Pb(OH)+ was adsorbed onto the wolframite surfaces and played as active sites. • The active Pb sites chemically interacted with BHA on the wolframite surfaces. • BHA-Pb complexes formed in solution could displace the Fe and interact with the Mn on the surfaces. The activation mechanism of Pb(II) on the flotation of wolframite was systematically investigated. Micro-flotation test results showed that Pb(II) effectively improved the flotation of wolframite in the presence of benzyl hydroxamic acid (BHA). Maximum floatability of wolframite was achieved at approximately pH 8.5. Adsorption of the hydrolyzed species of Pb(II) occurred at this pH value, which provided more activated sites on the wolframite surface. As such, BHA-Pb complexes were formed on the wolframite surface, which increased the BHA adsorption. In addition, BHA-Pb complexes were also formed in solution, which replaced the Fe and interacted with the Mn on the wolframite surface. These findings were proved by the results of zeta-potential measurements, adsorption measurements, solution chemistry calculations, Fourier transform infrared spectroscopy (FT-IR) analysis, and X-ray photoelectron spectroscopy (XPS) characterization. [ABSTRACT FROM AUTHOR]

Highlights • Cu2+ and Fe3+ ions strongly depressed the flotation of molybdenite. • pH influenced the depression performance. • The depression mechanism of Cu2+ was apparently different from that of Fe3+. Abstract Cu2+ and Fe3+ are generally inevitable in the flotation of molybdenite. In this work, the effect of Cu2+ and Fe3+ on the flotation of molybdenite was investigated through flotation tests. The influence mechanism was studied by Zeta potential measurement, scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) analysis. The results showed that the flotation of molybdenite was strongly depressed by Cu2+ and Fe3+, and the depression of Fe3+ was more powerful than that of Cu2+. The depression performance of molybdenite was significantly influenced by pH in the presence of Cu2+ and Fe3+, which was due to the adsorption of different hydrolyzed species as pH varied. The depression mechanism involved two different models in Cu2+ solution. In acid media, the depression was mainly contributed to the coverage of less hydrophobic CuS, as well as a small amount of hydrophilic Cu(OH) 2 and Cu2+ on molybdenite surface. While in alkaline condition, the adsorption of Cu(OH) 2 precipitate was the main reason for the depression. In Fe3+ solution, Fe(OH) 3 precipitate was the main component adsorbed on molybdenite surface to make the surface of molybdenite hydrophilic. [ABSTRACT FROM AUTHOR]

In this work, the exfoliation of montmorillonite related with electric charges on the layers in aqueous solutions were investigated through the measurements of zeta potential, turbidity and atomic force microscopy, as well as molecular dynamics simulation. The charge amount on montmorillonite layers was adjusted by blocking or neutralizing the layer charges with tetraethylenepentaminecopper (II) ([Cu(tetren)] 2+ ) through cation exchange reaction. The experimental results have shown that the exfoliation closely correlated to the amount of the layer charges. The larger are the charge amount on montmorillonite layers, the more easily the montmorillonite is exfoliated. This observation might be attributed to the repulsive energy (electrostatic and hydration repulsion) was stronger between the high charged montmorillonite layers than low charged ones. [ABSTRACT FROM AUTHOR]

[Display omitted] • PCP could dramatically improve the flotation of molybdenite fines. • PCP was more favorable to adsorb on molybdenite edges than faces. • PCP complexed with Mo sites on the edge to form strong P-O-Mo bonds. • The targeted adsorption of PCP on edges enhanced its hydrophobicity. The flotation of molybdenite fines is a challenging task during mineral processing worldwide. In this work, potassium cetyl phosphate (PCP) was explored as a novel collector to enhance the flotation of molybdenite fines. The flotation performances were assessed by micro-flotation tests. The adsorption mechanisms were uncovered through Zeta potential, Fourier Transform Infrared Spectrometer (FTIR), X-ray Photoelectron Spectroscopy (XPS), atomic force microscopy (AFM), Tafel curves, cyclic voltammetry, contact angle and density functional theory (DFT) calculations. The flotation tests demonstrated that PCP could efficiently collect molybdenite fines. Zeta potential and contact angle results suggested that the adsorption of PCP significantly improved the hydrophobicity of molybdenite surfaces. AFM, Tafel curves and adsorption energy revealed that PCP had a preferential affinity to edges (E ads = -735.14 kJ/mol) than faces (E ads = 33.5 kJ/mol). FTIR, XPS, cyclic voltammetry and DFT analysis manifested that PCP chemisorbed on the edges via the hybridization of the O 2p orbital of P-O radical within phosphate groups with the Mo 4d orbital, forming two high ionicity bonds, which could replace kerosene to improve the flotation of molybdenite fines. [ABSTRACT FROM AUTHOR]

The adsorption of Pb 2+ at the rutile/water interface has been studied for the activation of rutile flotation with salicyl hydroxamic acid (SHA) as a collector in this work. This study was performed through measurement of the zeta potential, adsorption capacity, calorimetry and X-ray photoelectron spectroscopy. The experimental results showed that the adsorption of SHA on rutile and the flotability of rutile were significantly improved by the addition of Pb 2+ . This improvement was attributed to the specific adsorption of Pb 2+ in the form of PbOH + , which interacted with the Ti-OH at the rutile surface and formed a surface Ti-O-Pb + complex. This adsorption followed the Langmuir model. It reversed the zeta potential sign of rutile at pH 5.5–6.8 and had a heat of adsorption of −46.71 kJ/mol, suggesting the occurrence of a chemiosorptive process. [ABSTRACT FROM AUTHOR]

Montmorillonite (MMT) is easily exfoliated into two-dimensional(2D) nanosheets, which are widely used to prepare functional composites. However, there are few studies on the differences in the performance of MMT nanosheets (MMTNS) with different exfoliation degrees, which seriously limits the further breakthrough in the preparation of high-performance MMTNS based materials. In this work, some representative performance of MMTNS with different exfoliation degrees was investigated, and the performance was closely related with making functional composites. The exfoliation degrees of MMTNS were controlled by different ultrasonic exfoliation powers. The performance of MMTNS was studied by the measurements of atomic force microscopy (AFM), Zeta potential, turbidity, viscosity, scanning electron microscopy (SEM) and molecular dynamics simulation. The results show that MMTNS with high exfoliation degree had more negative electrical sites exposed and stronger repulsive potential energy between particles, which exhibited high surface negative electricity and excellent dispersion stability. Moreover, the MMTNS with high exfoliation degree had better gelling property. It can be seen that the "house-of-cards" structure in the structure after gelation of MMTNS with high exfoliation degree was more intensive. Also, with the increase of MMTNS exfoliation degree, its adsorption capacity for organic matter was better and its reaction with organic was more active. These findings might be helpful to select the suitable MMTNS for making functional composites by controlling its exfoliation degree. [Display omitted] • MMTNS with different exfoliation degree had different properties for making materials. • Highly exfoliated MMTNS had high surface electrical property and dispersion stability. • High exfoliation degree helps MMTNS show excellent gelling property. • The reaction of highly exfoliated MMTNS with organic was more active. [ABSTRACT FROM AUTHOR]

Highlights: [•] Found out that DDA induced a much stronger aggregation in aqueous kaolinite suspensions. [•] Presented a good correlation of kaolinite aggregation with DDA adsorption and surface hydrophobicity. [•] DDA induced hydrophobic agglomeration of colloidal kaolinite was negatively affected by NaCl addition. [Copyright &y& Elsevier]

[Display omitted] Montmorillonite (MMT), having special property of hydration expansion, can be easily exfoliated into two-dimensional (2D) nanosheets, which are the promising blocks for making multifunctional nanocomposites. In this work, the exfoliation performances of MMTs from different region including Inner Mongolia (IM), Zhejiang (ZJ) and Liaoning (LN) were investigated from the perspective of layer charge density. All the MMTs were prepared as Na-MMTs first to avoid the effect of the interlaminar ion. Atomic force microscope (AFM) measurements indicated that the exfoliation performance increased as: IM-MMT < ZJ-MMT < LN-MMT. Alkyl ammonium ion exchanged method was applied to study the layer charge density of the MMTs. It was found that the exfoliation performance decreased with the layer charge density of MMT increased. The characterizations of zeta potential, swelling index and BET specific surface area were used to reveal the effects of layer charge density on the exfoliation performance of MMT. The results showed that with increasing the layer charge density, MMT was with more negative zeta potential, thus leading to the stronger binding forces between the layers. The swelling index of LN-MMT was the highest who had the lowest layer charge density, demonstrated by the largest specific surface area and pore diameter after hydration swelling, which explained the best exfoliation behavior of LN-MMT. This study correlates the exfoliation performances with the layer charge density of MMT, and it will provide a guidance to prepare much thinner and larger MMT nanosheets. [ABSTRACT FROM AUTHOR]

Few literatures pay emphasis on investigating the effect brought out by metal ions on flotation in the case of cationic collector. In this work, the effect of Al(Ⅲ) and Fe(Ⅲ) on rutile floatability using dodecylamine polyxyethylene ether (AC1203) as collector was evaluated. In addition to the flotation tests, zeta potential measurements, solution chemistry calculation, surface tension measurement and XPS analysis were conducted to elucidate the detailed depression mechanism. The results indicate that the floatability of rutile seriously inhibited by Al(Ⅲ) and Fe(Ⅲ), and the depression effect of Al(Ⅲ) is much stronger than that of Fe(Ⅲ). Moreover, on the basis of zeta potential and solution chemistry calculation tests, Al(OH) 3 and Fe(OH) 3 precipitates are believed to be the principal components that act with rutile surface, and the preferential adsorption of Al(OH) 3 precipitate could further deteriorate the interaction of collector with rutile. It is worth mentioning that Al(Ⅲ) and Fe(Ⅲ) are capable of acting with AC1203 to form complexes, consequently affecting the flotation environment. Furthermore, XPS analysis reveals that Fe(OH) 3 precipitate tend to adsorb on rutile surface through physical interaction, while Al(OH) 3 precipitate could react with Os and bridging O on rutile surface to form Ti-O-Al bonds, resulting in less active Ti sites for collector adsorption. [ABSTRACT FROM AUTHOR]

The aggregation state of mineral slurry by coagulant with the presence of clay nanosheets appears similar to a flocculation gel with the absence of flocculant. The interactions between particles in mixed clay and quartz minerals systems are influenced by the interactions of ion correlation and slime coating, which creates zeta potential variation. Particle concentration has a substantial effect on zeta potential, and coal slurry has a relative high particle concentration. To realize an in situ aggregation study, zeta potential measurement of coal slurry was performed using electrokinetic sonic amplitude (ESA) without dilution at different calcium ion concentrations and pH values. The zeta potentials of three minerals commonly occurring in coal slurry (quartz, kaolinite and montmorillonite) with similar particle concentrations were also measured. The result suggests that aggregation of coal slurry by calcium ions in the presence of clay minerals belongs to fluctuation. The ion correlation and slime coating could be detected by ESA with a decrease in zeta potential under high calcium ion concentration conditions. The face-face coagulated clay nanosheets were formed by ion correlation, acting as a "flocculant chain". The adsorption force between the "flocculant" and particles is described as a slime coating. This flocculation process is referred to as "salt-clay-coagulation-flocculation" (SCCF). During ion correlation, rearrangement of the electric double layer between face-face spaces causes a reduction of the zeta potential. The super-fine negatively charged clay nanosheets might coat onto the quartz particle surfaces under the effect of electrostatic attraction force and Ca2+ ion correlation. Quartz and clay minerals were oppositely charged because the special adsorption of calcium ions on the clay basal face was restricted in hexatomic rings. • The aggregation termed as "salt-clay-coagulation-flocculation" (SCCF) can be determined by zeta potential test. • During SCCF, "flocculant chain" is formed by face-face coagulation of clay. • During SCCF, the adsorption force between the "flocculant" and particles is slime coating. • Face-face coagulation is attributing to the ion correlation between the clay basal surfaces. • The zeta potential difference between quartz and clay is discussed. [ABSTRACT FROM AUTHOR]

There is little scientific agreement on the way sodium fluorosilicate (SF) depresses gangue minerals, resulting in a stagnation into in-depth research. Here, we describe a new explanation hoping to advance this step of development. In this study, flotation of rutile from almandine was investigated using SF as the depressant and Styryl phosphonic acid (SPA) as the collector. The study was performed through the measurements of zeta potential, contact angle, and X-ray photoelectron spectroscopy (XPS), in addition to the micro-flotation of single minerals and artificially mixed minerals. The experimental results demonstrated that SF acting in the form of SiF 6 2− at pH 5–6 was a highly selective depressant on almandine, rather than on rutile, leading to a high selectivity for the flotation of rutile. The XPS results revealed a strong interaction between F and active Fe sites on almandine surface, reducing adsorption sites for collector, thereby strongly depressing the flotation of almandine. [ABSTRACT FROM AUTHOR]

In this work, multifunctional MoS 2 prepared by hydrothermal method was studied as an adsorbent for the simultaneous removal of Hg2+, Pb2+ and Cd2+ in aqueous solutions. This study was performed through the adsorption experiments in single- and multi-metal systems. It was shown that MoS 2 exhibited a highest adsorption capacity for Hg2+, and lowest for Cd2+, which was mainly attributed to the different affinities between the S sites and the heavy metals. Based on the results of XPS and Zeta potential, the adsorption mechanisms were investigated in depth, which involved oxidation-reduction between Hg2+ and MoS 2 , electrostatic attraction between positively charged heavy metals and negatively charged MoS 2 , complexation of Hg–S, Pb–S, Cd–S, Hg–O and Pb–MoO 4 and ion-exchange reaction occurred on –SH and –OH. In the coexistence of Hg2+, Pb2+ and Cd2+, the excess MoO 3 generated during the oxidation-reduction between MoS 2 and Hg2+ resulted in a higher adsorption capacity for Pb2+ compared with the condition in single-metal system. However, the adsorption sites of S on MoS 2 would be occupied competitively by the three heavy metals so that it caused lower adsorption capacities for Hg2+ and Cd2+. These findings would make a great significance in the field of water treatment by MoS 2. Image 1 • The co-adsorption on MoS 2 for Hg2+, Pb2+ and Cd2+ has been studied first. • An original adsorption mechanism is come up with in multi-metal system. • The analysis of characteristic and mechanism is productive. [ABSTRACT FROM AUTHOR]