Hydrophobic Agglomeration Research Articles

Impact of acid surface pretreatment on the hydrophobic agglomeration of micro-fine ilmenite and titanaugite in flotation

Acid surface pretreatment was employed to realize the selective hydrophobic agglomeration of micro-fine ilmenite in flotation. Microflotation and artificially mixed mineral experiments manifested that after acid surface pretreatment, the recovery of micro-fine ilmenite with the increase of NaOL concentration and the floatability difference of micro-fine ilmenite and titanaugite increased significantly. Zeta potential and contact angle analyses suggested that acid surface pretreatment intensified the adsorption of NaOL on ilmenite surfaces while reducing it on titanaugite surfaces. Turbidity, optical microscope, and EDLVO theory analyses attested that the hydrophobic attraction dominated in a short particle spacing in NaOL solution. Following acid surface pretreatment, the hydrophobic agglomeration between micro-fine ilmenite particles enhanced in NaOL solution due to increased hydrophobic attraction. In contrast, the hydrophobic attraction and agglomeration between micro-fine titanaugite particles as well as between micro-fine ilmenite and titanaugite particles weakened. Overall, acid surface pretreatment improved the selective adsorption of NaOL and the selective hydrophobic agglomeration of micro-fine ilmenite, resulting in enhanced separation efficiency and recovery of micro-fine ilmenite.

Flotation behavior and mechanism of microfine apatite and illite in different electrolyte solution systems

The deep sea is rich in mineral resources, and due to the scarcity of freshwater resources, the use of seawater is becoming more widespread. However, the presence of a large number of electrolyte ions in seawater can pose a challenge to mineral flotation and the effects of different electrolytes vary. This study investigated the effects of common chloride (Cl-) electrolyte solutions of Na+, Mg2+ and Ca2+ on the flotation behavior of microfine apatite and illite using sodium oleate (NaOL) as the collector and acidified sodium silicate (ASS) as the depressant. The results showed that ASS can selectively adsorb to the surface of illite as Si(OH)4, hindering the action of NaOL but having little effect on apatite. The electrolyte solution improved the foaming performance of the slurry. It also reduced the critical micelle concentration (CMC) of NaOL and promoted the formation of NaOL micelle, which promoted the adsorption of NaOL on the surface of apatite. However, the reaction of free Mg2+ and Ca2+ in the slurry with oleic anion consumed the effective components of the collector, which was not conducive to mineral flotation. After NaOL interacted with apatite, it had hydrophobic agglomeration effect, which strengthened the flotation recovery of microfine apatite and the separation efficiency from illite.

Preparation of TiO2–SiO2–CaCO3 composite opacifier by hydrophobic agglomeration and mechanism of inhibiting glaze yellowing

This study investigates the preparation of TiO2–SiO2–CaCO3 composite opacifier (Ti–Si–Ca) and its application in sanitary ceramic glazes. This approach involved hydrophobic agglomeration through surface-induced hydrophobic modification of TiO2, SiO2 and CaCO3 particles, along with the interactions between the hydrophobic carbon chains of modifiers. The Ti–Si–Ca formed a uniform coating with well-dispersed TiO2 and SiO2 particles on the CaCO3 surface and strong bonds formed among TiO2, SiO2 and CaCO3 through interpenetration of the organic carbon chains on the surface. The Ti–Si–Ca was added to the basic glazes of sanitary ceramics at a proportion of 15.5 % and fired at 1125 °C for 4 h. The resulting white ceramic glazes had chromaticity values of L*, a*, and b* at 93.76, −0.73, and 3.89, respectively, demonstrating superior glaze opacity and whiteness compared to glazes made with a ZrSiO4 opacifier (L* 90.30, b* 4.50). Glass and titanite phase make up the majority of the Ti–Si–Ca ceramic glazing layer of, with titanite serving as the opacified phase. Elimination of organic groups in Ti–Si–Ca during glaze firing formed interfacial chemical bonds among TiO2, SiO2 and CaCO3, which facilitated the synthesis of titanite from the three components at high temperatures. The Ti–Si–Ca was a highly opaque glaze without yellowing because the organic groups of Ti–Si–Ca were removed and interfacial chemical bonds formed among the TiO2, SiO2 and CaCO3 in the low-temperature stage of glaze firing. This transformed the three phases into titanite at high temperature and eliminated free TiO2. The formation of rutile TiO2, which has a yellow hue, at high temperatures was inhibited. This study provides a novel approach for low-energy preparation of TiO2–SiO2–CaCO3 composite opacifiers and addresses the challenge of replacing ZrSiO4 with TiO2 in ceramic opacifiers.

Hydrophobic agglomeration flotation of fine cassiterite induced by kerosene and sodium oleate

In this study, the effect of kerosene and sodium oleate (NaOL) on inducing hydrophobic agglomeration flotation of fine cassiterite was investigated through the micro-flotation tests, particle size distribution and morphological analysis, zeta potential and contact angle measurements. The results indicated that adding kerosene before NaOL could obtain a higher recovery than adding NaOL before kerosene. The agglomerates induced by adding kerosene before NaOL was dense and regular in structure with larger particle size distribution and stronger surface hydrophobicity, which jointly contributed to its higher flotation recovery. Furtherly, the extended DLVO theory calculation was carried out to explain the agglomeration behaviour of fine cassiterite under different reagents. The results convinced that under the reaction of NaOL before kerosene or kerosene before NaOL, hydrophobic interaction and sufficient kinetic energy input were necessary to form agglomerates, and the attraction effect between cassiterite particles under the reaction of kerosene before NaOL was the strongest.

Effect of Acidified Sodium Silicate on the Flotation Separation of Microfine Apatite from Chlorite in Seawater

In this work, selective flotation separation of microfine apatite and chlorite was achieved by using sodium oleate (NaOL) as a collector with a low dosage of acidified sodium silicate (ASS) as a depressant. The optimum ratio of sodium silicate to sulfuric acid for ASS was 5:3, and a good separation effect was also achieved in the mixed ore system. Compared to the deionized water system, the ions of Na+, Ca2+ and Mg2+ in seawater adsorbed on the surfaces of apatite and chlorite, which made the zeta potential of the two minerals shift positively. This presented a challenge to the selection of reagents for mineral separation. The addition of ASS changed the pH value of the pulp from weak alkalinity caused by seawater to weak acidity, which allowed the metal ions adsorbed on the mineral surface to desorb. Meanwhile, ASS can selectively adsorb on the desorbed chlorite surface in the form of Si(OH)4, which hindered the action of NaOL, leading to the depression of chlorite. NaOL adsorbed well on the desorbed surface of apatite and increased the apatite particle size from 27 μm to 229 μm, with a hydrophobic agglomeration effect, thus enhancing the flotation of microfine apatite.

Mechanistic insight of hydrophobic agglomeration of rhodochrosite fines Co-enhanced by Oleic-Kerosene emulsion and static magnetic field

Efficient enrichment of fine rhodochrosite is key to purifying manganese carbonate ore and reducing the discharge of electrolytic manganese slag at the source. Enhancing the agglomeration of rhodochrosite fines is important for efficient flotation separation. In this study, we investigated the agglomeration mechanism of rhodochrosite fines co-enhanced by oleic-kerosene emulsion and static magnetic field using agglomerate and surface properties analysis, electrical conductivity and atomic force microscopy measurements, and extended Derjaguin, Landau, Verwey, and Overbeek theoretical calculations. The results showed that the agglomerate size and regularity degree increased with increasing shearing time, achieving the maximum values of the average size at 20 min with magnetic field and at 40 min without magnetic field. Larger-sized and tighter agglomerates can be formed in a shorter time by the Lorentz force in magnetic field. As magnetic field was applied, the surface electronegativity of rhodochrosite in emulsion solution was stronger and positively correlated with magnetic field intensity. In addition, due to the higher solubility of oleic acid, the adsorption capacity and net heat of emulsion increased, resulting in a stronger hydrophobicity of rhodochrosite with a shorter hydrophobization time. Interestingly, almost no attraction existed between particles with magnetic field in aqueous solution, while a larger attraction existed without magnetic field in emulsion solution, and the attraction and action distance both increased markedly with increasing magnetic field intensity. However, the magnetic attraction was much smaller than hydrophobic attraction. As a result, agglomeration of rhodochrosite fines could be enhanced by stronger hydrophobic attraction under the synergy effect of magnetic field and oleic-kerosene emulsion. This research will be conducive to in-depth insight into the enhancement mechanisms of rhodochrosite agglomeration and will provide a basis for flotation regulation.

Investigating agglomeration of kaolinite particles in the presence of dodecylamine by force testing and molecular dynamics simulation

Kaolinite, one of the main components of clay minerals, is detrimental to slime water sedimentation. Sedimentation, adsorption, surface tension, contact angle, and interaction force measurements were conducted to study the hydrophobic agglomeration mechanism in kaolinite particles in the presence of dodecylamine (DDA). The results showed that DDA could be adsorbed on the kaolinite surface, improving the surface hydrophobicity and promoting hydrophobic particle agglomeration. Kaolinite hydrophobic sedimentation was enhanced with increased DDA concentration. The settling velocity and the adsorption of DDA on slurry particles were optimal when the DDA concentration was 14 × 10-4 mol/L. The shape and size distribution significantly affected the particle-surface interaction. Reliable force data could not be obtained from colloidal probes made of actual clay particles. Therefore, silica-silica and silica-alumina systems were used to replace clay mineral particles for force testing. AFM results showed that electrostatic repulsion existed in silica-silica and silica-alumina particles in ultrapure water. With DDA addition, the electrostatic repulsive force in silica-silica and silica-alumina particles decreased, the hydration film was destroyed, and an adhesion force was generated. In addition, the silicon-oxygen (001) surface of kaolinite adsorbed DDA more easily than the aluminum-oxygen (001̅) surface. The adsorption behavior of DDA+ on the kaolinite (001) and (001̅) surfaces was calculated by molecular dynamics simulation to explore the adsorption mechanism of DDA on kaolinite surfaces. The results suggested that the DDA+ polar head groups were adsorbed on the kaolinite surface, whereas the non-polar groups faced the solution. DDA+ adsorbed more easily on the (001) surface than on the (001̅) surface.

Hydrophobic agglomeration behavior of rhodochrosite fines Co-induced by oleic acid and shearing

• Agglomeration of rhodochrosite markedly depended on oleic acid concentration and pH. • Hydrophobic attraction drove agglomeration correlated with adsorption of oleic acid. • Large and dense agglomerates formed with increasing stirring rate until 500 rpm. • Excessive shearing could break agglomerates with large-scale fragmentation mechanism. • The broken fragments regrew incompletely as reducing stirring rate to initial value. Efficient separation of fine-disseminated rhodochrosite is a challenge in the purification of manganese carbonate ore and a key to reduce the discharge of electrolytic manganese slag. The agglomeration behavior of the fine particles is of importance for flotation separation. In this study, we investigated the agglomeration behavior and aggregate properties of rhodochrosite fines co-induced by oleic acid (OA) and shearing using particle size and structure analysis, surface properties measurement, extended DLVO (EDLVO) theoretical calculation and shear fracture model analysis. The results showed that rhodochrosite fines agglomerates obviously with the increasing OA concentration and pH value, and the average particle size reaches the maximum at the initial OA concentration of 1 × 10 -3 mol/L and pH of 6. The monolayer physical and chemical saturation adsorption of OA cause stronger hydrophobicity of rhodochrosite. Meanwhile, the hydrophobic attractive force between particles is stronger than electrostatic repulsive force, resulting in hydrophobic agglomeration. The moderate stirring rate is conducive to forming larger-sized and denser agglomerates with the critical rate of 500 rpm. However, intensive shearing will cause significant damage to the formed agglomerates. Besides, the volume concentrations of 10–30 μm and 30–45 μm particles increased with the increase of stirring rate after breakage and with a lower value of γ’ than 0.5, suggesting that the agglomerates breakage is mainly controlled by large-scale fragmentation mechanism. Interestingly, as recovering shearing from the higher rate to the initial rate, a secondary agglomeration is achieved by the regrowth of core (30–45 μm particles) and attach of branches and coatings (some < 10 μm and 10–30 μm particles) under the synergy of hydrophobic attraction and shearing. However, it did not fully recover back to the original balanced state before fragmentation, which was due to irreversible damage caused by excessive shearing. This research will be beneficial for in-depth understanding of agglomeration mechanisms of rhodochrosite fines and provide a basis for subsequent efficient flotation separation.

Mechanistic Insight of Hydrophobic Agglomeration of Rhodochrosite Fines Co-Enhanced by Oleic-Kerosene Emulsion and Static Magnetic Field

Mechanistic Insight of Hydrophobic Agglomeration of Rhodochrosite Fines Co-Enhanced by Oleic-Kerosene Emulsion and Static Magnetic Field

Hydrophobic agglomeration flotation of oxidized digenite fine particles induced by Na2S and butyl xanthate

Secondary copper sulfide mineral fine particles are easily oxidized, and their effective recovery by froth flotation is extremely challenging. This study investigated the roles of sodium sulfide (Na2S) and sodium butyl xanthate (SBX) in the hydrophobic agglomeration flotation of oxidized digenite fine particles. The microflotation experiments of the study showed that the simultaneous addition of Na2S and SBX is beneficial for improving the floatability of heavily oxidized digenite fine particles. In addition, the recovery at pH 7.0 was apparently higher than that of the unoxidized digenite fine particles, indicating that hydrophobic agglomeration of digenite fine particles may occur. The results of the zeta potential measurements, X-ray photoelectron spectroscopy analyses, and contact angle measurements suggested that negatively charged hydrogen sulfide ion and xanthate ion respectively hydrolyzed from Na2S and SBX adsorbed on the surface of digenite. Moreover, they significantly decrease the amount of hydrophilic copper sulfate and oxides/hydroxides on the surface, thus improving the surface hydrophobic degree of digenite. The results of the optical microscopy analysis, particle size analysis, and extended Derjaguin–Landau–Verwey–Overbeek theory calculations provided strong evidence for the roles of Na2S and SBX in promoting the hydrophobic agglomeration of the digenite fine particles. After treatment with Na2S and SBX, the total interaction energies between the digenite fine particles were negative, indicating that the strong hydrophobic attractive forces promote the formation of large-sized agglomerates, enabling the digenite fine particles to be more easily captured by bubbles than those without the treatment. Therefore, effective recovery of heavily oxidized digenite fine particles can be realized by the hydrophobic agglomeration flotation technology induced by Na2S and SBX.

Determination of the Conditions for Agglomeration of Molybdenite Fines in the Presence of Kerosene Emulsion Through the Extended DVLO Theory

The hydrophobic agglomeration of fine particles of molybdenite in the presence of kerosene emulsion, has been studied in this paper. The results obtained in the investigation as; zeta potential of kerosene emulsion(?emulsion), zeta potential of the molybdenite sample (?MoS2), hydrophobicity of molybdenite represented by the contact angle (?MoS2) varying the pH, were used to calculate the total potential energy through the extended DVLO theory. Diagram containing curves total potential energy vs. separation distance of the particles, indicate that increasing the pH, also increases the energy barrier to overcome to achieve agglomeration and viceversa, which translates to a high probability of agglomeration in the pH range 5 to 8, with greater effect as the pH is increased in the acidic region.

Determination of the Conditions for Agglomeration of Molybdenite Fines in the Presence of Kerosene Emulsion Through the Extended DVLO Theory

The hydrophobic agglomeration of fine particles of molybdenite in the presence of kerosene emulsion, has been studied in this paper. The results obtained in the investigation as; zeta potential of kerosene emulsion(ζemulsion), zeta potential of the molybdenite sample (ζMoS2), hydrophobicity of molybdenite represented by the contact angle (θMoS2) varying the pH, were used to calculate the total potential energy through the extended DVLO theory. Diagram containing curves total potential energy vs. separation distance of the particles, indicate that increasing the pH, also increases the energy barrier to overcome to achieve agglomeration and viceversa, which translates to a high probability of agglomeration in the pH range 5 to 8, with greater effect as the pH is increased in the acidic region.

Influence of Terpenic Oil on Flotation Behavior of Sphalerite and Implication for the Selective Separation

Terpenic oil (TO) is commonly used as a flotation frother for the selective separation of sulfide minerals. As a frother, most reports have mainly focused on its effect on froth stability and froth entrainment, whereas its influence on the floatability of sulfide minerals has received little attention. In this work, the influence of TO on the flotation behavior of sphalerite was investigated by using microflotation tests, contact angle and zeta potential measurements, and FT-IR and SEM-EDS analyses. Microflotation tests conducted in a modified Hallimond tube indicated that compared with the collector potassium butyl xanthate (KBX), the flotation recovery of sphalerite was significantly increased when TO was added to the pulp, but the recovery of Cu-activated sphalerite with the addition of TO was lower than that with the addition of KBX. Contact angle measurements demonstrated that the contact angle of sphalerite was distinctly increased by the addition of TO, but the contact angle of sphalerite treated with TO was lower than that treated with KBX after Cu activation. Zeta potential measurements demonstrated that the zeta potential of sphalerite particles was slightly decreased when treated with TO, and the isoelectric point (IEP) was decreased from 3.3 to 3.1 due to the interaction of TO with sphalerite particles. FT-IR and SEM-EDS confirmed that TO could be adsorbed on the sphalerite surface on the formation of the oil film due to its low solubility, thereby increasing the surface hydrophobicity of the sphalerite. In addition, the TO absorbed on the surface acts as a bridging role and promotes the hydrophobic agglomeration of sphalerite particles. These results suggest that except for froth entrainment, the influence of TO on the flotation behavior of sphalerite may be another reason for the misreporting of sphalerite in concentrates.

Systematic exploration of quaternary ammonium salt adsorption on oxidized coal based on experiments and MD simulations

To explore the hydrophobic modification mechanism of quaternary ammonium salts on oxidized coal surface, the surface hydration of oxidized coal and the adsorptions of different quaternary ammonium salts on oxidized coal surface were investigated in this study, involved a series of experiments and MD simulations. The results of adsorption, contact angles, and agglomeration observation show that quaternary ammonium salts can adsorb on the oxidized coal surface to improve its surface hydrophobicity. Furthermore, the adsorption quantity of quaternary ammonium salts on oxidized coal surface and their ability to improve surface hydrophobicity increase when the carbon chain length increases. However, quaternary ammonium salts cannot effectively promote the formation of the hydrophobic agglomeration of oxidized coal particles. MD simulation results show that water molecules can undergo strong hydration on oxidized coal surfaces by forming hydrogen bonds with the oxygen-containing functional groups. The OTAC+ cations mainly accumulate on oxidized coal surfaces through the dispersive force occurring between the non-polar carbon chains of OTAC+ and non-polar aromatic rings of oxidized coal, and there is a strong self-agglomeration occurs between OTAC+ cations. The dispersion force between non-polar carbon chains and coal molecules dominates the adsorption of quaternary ammonium salt on oxidized coal surface, which is a very weak force and difficult to ensure the stable adsorption of quaternary ammonium cations on oxidized coal surface in aqueous solution.

Hydrophobic Agglomeration of Fine Pyrite Particles Induced by Flotation Reagents

Flotation reagents can change the surface properties of minerals, leading to differences in the interaction between mineral particles and affecting the mutual aggregation or dispersion of particles. In this work, we studied the role of activator copper sulfate, collector butyl xanthate and frother terpineol in adjusting the potential energy of pyrite particles from the perspective of the interfacial interaction. We evaluated the surface characteristics using contact angle analysis and zeta potential measurements under different reagents. A microscope was used to observe aggregation state of particles. The hydrophobic agglomeration kinetics of pyrite was studied through the turbidity meter measurement, and the interaction energy between pyrite particles was calculated using the extended-Derjaguin-Landau-Verwey-Overbeek (extended-DLVO) theory. The results showed that the repulsive potential energy is dominant among pyrite particles in aqueous suspensions and that the particles are easy to disperse. Flotation reagents can effectively reduce the repulsive energy between pyrite particles and increase the attraction energy between particles, which is conducive to the hydrophobic agglomeration of fine pyrite. Reagent molecules can greatly reduce the electrostatic repulsion potential energy of the pyrite particles’ interface, increase the hydrophobic attraction potential energy between the particle interfaces, and its size is 2 orders of magnitude larger than the van der Waals attraction potential energy, which is the main reason for induced the agglomeration of fine pyrite and is conducive to the flotation recovery of fine pyrite. Generally, the order in which the reduction of pyrite agglomeration was affected by the additions of flotation reagents was butyl xanthate &gt; terpineol &gt; copper sulfate.

Hydrophobic agglomeration of rhodochrosite fines in aqueous suspensions with sodium oleate

Hydrophobic agglomeration of rhodochrosite fines in aqueous suspensions with sodium oleate has been investigated through wettability measurement, optical microscopy observation, laser-based particle size detection, micro-flotation test, zeta potential measurement in this work. The experimental results indicated that the hydrophobicity of rhodochrosite was a dominant factor for the hydrophobic agglomeration. And a higher sodium oleate concentration could contribute to bigger agglomeration particle size and more regular agglomerates. The increased apparent particle size of minerals through hydrophobic agglomeration interaction was conducive to the micro-flotation recovery improvement of rhodochrosite fines in spite of a simultaneous increase in the negative zeta potential of rhodochrosite, meaning that the chemical adsorption was the primary reason between sodium oleate and rhodochrosite. Furtherly, the data calculated from extended DLVO theory was also convinced that hydrophobic interaction between the particles increased much more strongly than electrostatic repulsion from the adsorption of sodium oleate.

Preparation of Fe2O3-coated vermiculite composite by hydrophobic agglomeration and its application in As/Cd co-contaminated soil

ABSTRACT Exploring an economic and efficient method for simultaneous passivation of As and Cd in soils is of great current significance. In this study, a low-cost composite material, Fe2O3-vermiculite (Fe-V), for effectively passivating As/Cd was synthesized successfully based on hydrophobic aggregation method. The reaction products were characterized by XRD, SEM, EDS and FTIR, results showed that Fe2O3 was successfully loaded onto the surface of vermiculite by the connection with sodium stearate and employed this composite material to passivate the co-contaminated soil with As/Cd. All the percentage of toxicity reduction (Pd value) was higher than the control group, which indicated the passivation was effective. In soil A (As 45 mg/kg and Cd 6 mg/kg), the Pd of As were higher than 90%, the Pd of Cd were 80–100%. And in soil B (As 80 mg/kg and Cd 10 mg/kg), the Pd of As were more than 84.68%, the Pds of Cd were about 99%. In the meantime, the application of Fe-V could apparently increase the residual fraction of As and Cd in soil A and soil B. Moreover, the passivation of As and Cd in soils by Fe-V composite materials was a combined physical and chemical action system. This research shows that Fe-V could play a good role in the passivation of As/Cd in different pollution levels of soils.

Synergistic enhancement of fine-kaolinite-particle hydrophobic agglomeration by combining dodecylamine with octanoic acid

Because it is difficult to hydrophobically agglomerate fine kaolinite particles to obtain stronger, larger flocs using only dodecylamine (DDA) as a flocculant, octanoic acid (OA) was used as a synergistic flocculant to improve DDA-induced fine-kaolinite particle agglomeration. Particle settlement tests were conducted to study flocculation and synergistic flocculation behaviours of fine kaolinite particles for different DDA and/or OA concentrations. Results showed that OA strengthened DDA-induced particle agglomeration. Aggregate sedimentation rates and Stokes’ equivalent diameters exceeded 21.7 m/h and 84.4 µm, respectively. A clearer kaolinite suspension was obtained and a more compact aggregate layer accumulated within 3 min. Contact angles and Fourier-transform infrared (FTIR) spectroscopy were used to investigate kaolinite hydrophobicity before and after hydrophobisation and mechanisms of DDA and/or OA interactions with the kaolinite surface. Results suggested that faster sedimentation and larger equivalent-diameter aggregates were both related to significantly increased kaolinite-surface hydrophobicity. FTIR data confirmed that enhanced kaolinite surface hydrophobicity was owed to DDA and OA physisorption. The kaolinite micro-particle aggregation mechanism was analysed by SEM images. Kaolinite particle self-aggregation changed after OA was adsorbed on the kaolinite Si–O basal plane. Owing to DDA/OA synergistic effects, kaolinite particles hydrophobically agglomerated by actions of Al–O/Al–O and Al–O/Si–O faces, thereby promoting fine-kaolinite particle agglomeration and sedimentation. Study findings could lead to development of enhanced water-purification methods.

Hydrophobic agglomeration of montmorillonite fines in aqueous solutions induced by dodecyl trimethyl ammonium bromides

Dodecyl trimethyl ammonium bromides (DTAB) was used to adsorb on the isomorphous substitutions of montmorillonite (MMT) for masking hydrophilic sites. The adsorbed DTAB tails together with siloxane sites of MMT surfaces would greatly increase hydrophobicity of MMT, leading to stronger hydrophobic agglomeration of MMT fines in water. The experimental results showed that DTAB was adsorbed on the isomorphous substitution sites of MMT due to electrostatic interaction, and thus rendered MMT surfaces more hydrophobic. The aggregation of MMT fines in water was greatly enhanced by the addition of DTAB because of the formation of hydrophobic agglomeration at an appropriate shear field.

Hydrophobic agglomeration behaviors of clay minerals as affected by siloxane structure

Due to the very hydrophobic characteristic, silica tetrahedron (siloxane) structure on clay minerals surfaces was believed to affect many surface property of clay minerals, such as surface wettability, dispersion and agglomeration property. In this work, kaolinite and talc, with different number of siloxane surfaces, were chosen for studying how the siloxane structure affected hydrophobic agglomeration behaviors in aqueous solution. In-situ turbidity measurement of flocs suspension in the settlement progress had been applied to characterize the agglomeration behaviors of clay minerals. Through molecular dynamics simulation (MDs) results, it was found that the hydroxyl surface of kaolinite was very hydrophilic, while the siloxane surface of kaolinite (on the Si-tetrahedral side) and talc (both basal surfaces) showed a strong hydrophobicity due to the highly symmetrical siloxane structure. As a result, the talc and kaolinite showed vast differences on hydrophobic agglomeration behaviors. Because of the much more exposed siloxane structures on talc surface, the hydrophobic agglomeration degrees are far stronger than that of kaolinite due to the both hydrophobic basal surfaces. Besides, the sizes of talc flocs are also far larger than that of kaolinite due to the formation of layer by layer floc structure. Therefore, the siloxane structure on clay minerals surface has a significant influence on the agglomeration behaviors, including the agglomeration degree and the size of resulted flocs. It is the first time that the hydrophobic agglomeration behaviors were correlated to the siloxane structure on clay mineral surfaces, which has profound guiding significance on the study of dispersion stability of colloidal clay minerals.