Impact of ethanol on the flotation efficiency of imidazolium ionic liquids as collectors:Insights from dynamic surface tension and solvation analysis

To conduct extensive research on the application of ionic liquids as collectors in mineral flotation,ethanol(EtOH)was used as a solvent to dissolve hydrophobic ionic liquids(ILs)to simplify the reagent regime.Interesting phenomena were observed in which EtOH exerted different effects on the flotation efficiency of two ILs with similar structures.When EtOH was used to dissolve 1-dodecyl-3-methylimidazolium chloride(C12[mim]Cl)and as a collector for pure quartz flotation tests at a concentration of 1×10^(−5)mol·L^(−1),quartz recovery increased from 23.77%to 77.91%compared with ILs dissolved in water.However,quartz recovery of 1-dodecyl-3-methylim-idazolium hexafluorophosphate(C12[mim]PF6)decreased from 60.45%to 24.52%under the same conditions.The conditional experi-ments under 1×10^(−5)mol·L^(−1)ILs for EtOH concentration and under 2vol%EtOH for ILs concentration confirmed this difference.After being affected by EtOH,the mixed ore flotation tests of quartz and hematite showed a decrease in the hematite concentrate grade and re-covery for the C12[mim]Cl collector,whereas the hematite concentrate grade and recovery for the C12[mim]PF6 collector increased.On the basis of these differences and observations of flotation foam,two-phase bubble observation tests were carried out.The EtOH promoted the foam height of two ILs during aeration.It accelerated static froth defoaming after aeration stopped,and the foam of C12[mim]PF6 de-foaming especially quickly.In the discussion of flotation tests and foam observation,an attempt was made to explain the reasons and mechanisms behind the diverse phenomena using the dynamic surface tension effect and solvation effect results from EtOH.The solva-tion effect was verified through Fourier transform infrared(FT-IR),X-ray photoelectron spectroscopy(XPS),and Zeta potential tests.Al-though EtOH affects the adsorption of ILs on the ore surface during flotation negatively,it holds an positive value of inhibiting foam mer-ging during flotation aeration and accelerating the defoaming of static foam.And induce more robust secondary enrichment in the mixed ore flotation of the C12[mim]PF6 collector,facilitating effective mixed ore separation even under inhibitor-free conditions.

Densities and surface tensions of ionic liquids/sulfuric acid binary mixtures

The densities and surface tensions of [Bmim][TFO]/H2SO4, [Hmim][TFO]/H2SO4 and [Omim][TFO]/H2SO4 binary mixtures were measured by pycnometer and Wilhelmy plate method respectively. The results show that densities and surface tensions of the mixtures decreased monotonously with increasing temperatures and increasing ionic liquid （IL） molar fraction. IL with longer alkyl side-chain length brings a lower density and a smaller surface tension to the ILs/H2SO4 binary mixtures. The densities and surface tensions of the mixtures are fitted well by Jouyban-Acree （JAM） model and LWW model respectively. Redlich-Kister （R-K）equation and modified Redlich-Kister （R-K） equation describe the excess molar volumes and excess surface tensions of the mixtures well respectively. Adding a small amount of ILs （XIL 〈 0.1 ） into sulfuric acid brings an obvious decrease to the density and the surface tension. The results imply that the densities and surface tensions of IL5/H2SO4 binary mixtures can be modulated by changing the IL dosage or tailoring the IL structure.

Study on the Surface Property of Surfactant Ionic Liquids Solutions

The surfactant TX-100 can be dissolved in ionic liquid bmimPF6 and decrease the surface tension of 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6) solutions. Here, we confirmed that in this new system, the pure solvents need rearrangement at the air-water interface at the initial stage. The dynamic surface tension (DST) study shows that at the initial adsorption stage, the adsorption model of surfactant accords with the diffusion-controlled adsorption mechanism, and the dilute ionic liquids solutions is further close to the diffusion-controlled adsorption.

Investigation of Different Ionic Liquids in Improving Oil Recovery Factor

In order to improve oil recovery, Enhanced Oil Recovery (EOR) techniques have been applied to several light and medium oil reservoirs. This research was directed towards the development of chemical flooding methods for such reservoirs. The main objective of this experimental work was to investigate the efficiency of introducing various types of Ionic Liquids (ILs), 1-Ethyl-3-methylimidazolium Chloride [EMIM][Cl], 1-Benzyl-3-methylimidazolium Chloride [BenzMIM][Cl], and Trihexyltetradecylphosphonium Chloride [THTDPh][Cl] on the Recovery Factor (RF) of medium oil (Weyburn oil, 30.25 API°) at room temperature. The series of flooding experiments were carried out by introducing a slug of IL mixtures. Results demonstrated that maximum oil recovery factor was obtained when [EMIM][Cl] was added in the displacing fluid. Further investigations have been conducted to examine the effect of ILs concentrations on the recovery mechanisms by measuring Surface Tension (SFT), pH, and viscosity of the displacing phases. Finally, the effect of theses ILs in wettability alteration was examined.

Effect of Aromatic Ring, Cation, and Anion Types of Ionic Liquids on Heavy Oil Recovery

Surfactant/alkali flooding is one of the best chemical flooding methods to enhance the oil Recovery Factor(RF).In this research,Ionic Liquid/Alkali(ILA)mixtures were chosen to represent a form of chemical flooding experiments.The selected Ionic Liquids(ILs),{[EMIM][Cl],[THTDPH][Cl],[EMIM][Ac],[BzMIM][Cl],[DMIM][Cl],[BzMIM][TOS],[dMIM][TOS]and[MPyr][TOS]},were introduced to investigate their efficiency in improving heavy oil(14o API)RF from the sand packs.Besides,the use of mixtures of the same ionic liquids and brine(3.37 wt.% salts)with an alkali(Sodium Bicarbonate[NaHCO3])were also investigated.In this experimental study,the flooding process started with injecting about 3.2 Pore Volumes(PVs)of only brine,followed by one PV of the chemical composites,and flushed with two PVs of formation brine.The study discussed the influence of cation type,anion type,the structure of the ILs,and the effect of combining ILs/alkali on the RF.The results revealed that the proposed chemical mixtures are effective in enhancing the recovery factor.ILs with shorter alkyl chain and more aromatic rings are noticeably more efficient in enhancing the RF.Finding the optimum composition of([DMIM][Cl]+NaHCO3)the chemical slug increased the additional RF up to 31.55(%OOIP).Also,increasing the slug size to two PVs improved the RF to 42.13(%OOIP).The recovery factor mechanism was explained and supported by measuring the effect of IL types on the viscosity,Surface Tension(SFT),and Zeta Potential(ZP)of the mixture.

Effect of Sodium Halide on Dynamic Surface Tension of a Cationic Surfactant

The equilibrium and dynamic surface tension （DST） of the novel cationic surfactant, 3-（p-nonylphenoxy）-2-hydroxylpropyl trimethyl ammonium bromide, abbreviated as RTAB, were studied. The effect of sodium halide such as NaCl, NaBr and NaI on the DST behavior of the RTAB solution below its CMC was studied in detail. Due to the preferential adsorption, the effect of hydration and salting out, the ability to reduce the DST values at the same concentration was in the order of NaI〉NaBr〉NaCl. Attributed to its high surface activity, the equilibrium time of the DST of the surfactant solution was insensitive to the ionic strength.

Study on Surface Tension and Displacemem efficiency of Ionic Liquid Surfactants Containing Amine Functional Groups

Description is given to preparation of three ionic liquid surfactants containing amine functional groups, characterization of their functional groups using the infrared spectrometer, determination of their surface tension and the oil displacement test in this paper to investigate the effect of alkane branch chains with different carbon numbers on the surface tension and the displacement efficiency. The result shows that, the surfactants exhibit the structural characteristic of the ionic liquid as the characteristic absorption peaks occur on C-N and C-H of the imidazole rings at the wave numbers of 1338cm-1, 1234em-1, 1465crn-1 and 3142cm-1, respectively. The surface tension isothermal curves and the oil displacem ent test proved that the ionic liquid imidazole surfactants with shorter-chain groups are more active on surface, with the minimal surface tension up to 32.5 mN/m, and led to higher displacement efficiency, increasing by 3.3% at the concentration of 1000mg/L compared with the water flooding.

Theoretical and experimental study on surface tension and dynamic surface tension of aqueous lithium bromide and water with additive

The surface tensions of water and aqueous lithium bromide (LiBr) with 2-ethyl-1-hexa- nol (2EH) and 1-octanol were measured using Wilhelmy plate method, and the oscillation of sur-face tension under the open condition for LiBr solution was observed. The dynamic surface ten-sions of water and LiBr solution in the presence of the 2EH and 1-octanol vapor were measured in this paper. The results showed that the additives vapor could obviously affect surface tension. For water, the dynamic surface tension was also affected by the mass of the tested liquid; however, for LiBr solution, the dynamic surface tension was not related to the mass of the tested solution. Ac-cording to the experimental results, the hypothesis that surface tension varies linearly with the surface excess concentration is advanced, which could overcome the limit of Gibbs equation. The equations of surface absorption and desorption are modified, the units of the adsorption coefficient and desorption coefficient are unified; the effects of the liquid and vapor of additive on the surface tension are unified; the theoretical relations of the static surface tension and dynamic surface ten-sion with the relative contents of the liquid and vapor of additive are obtained under the combined actions of them; the theoretical equations are validated by the experiments results.

Interactions of ferro-nanoparticles(hematite and magnetite) with reservoir sandstone: implications for surface adsorption and interfacial tension reduction

There are a few studies on the use of ferro-nanofluids for enhanced oil recovery,despite their magnetic properties;hence,it is needed to study the adsorption of iron oxide(Fe2 O3 and Fe3 O4) nanoparticles(NPs) on rock surfaces.This is important as the colloidal transport of NPs through the reservoir is subject to particle adsorption on the rock surface.Molecular dynamics simulation was used to determine the interfacial energy(strength) and adsorption of Fe2 O3 and Fe3 O4 nanofluids infused in reservoir sandstones.Fourier transform infrared spectroscopy and X-ray photon spectroscopy(XPS) were used to monitor interaction of silicate species with Fe2 O3 and Fe3 O4.The spectral changes show the variation of dominating silicate anions in the solution.Also,the XPS peaks for Si,C and Fe at 190,285 and 700 eV,respectively,are less distinct in the spectra of sandstone aged in the Fe3 O4 nanofluid,suggesting the intense adsorption of the Fe3 O4 with the crude oil.The measured IFT for brine/oil,Fe2 O3/oil and Fe3 O4/oil are 40,36.17 and 31 mN/m,respectively.Fe3 O4 infused with reservoir sandstone exhibits a higher silicate sorption capacity than Fe2 O3,due to their larger number of active surface sites and saturation magnetization,which accounts for the effectiveness of Fe3 O4 in reducing IFT.

Prediction of the thermodynamic properties of 1-alkyl-3-methylimidazolium lactate ionic liquids [C_nmim][Lact](n=2,3,4,5,and 6) by parachor

An ionic liquid (IL) based on lactate,1-butyl-3-methylimidazolium lactate ([C4mim][Lact]),has been prepared and characterized by 1H nuclear magnetic resonance (NMR) spectroscopy and differential scanning calorimetry (DSC).Since the IL can form strong hydrogen bonds with water,trace water is a problematic impurity in the IL.Using the standard addition method (SAM),the density,refractive index and surface tension of [C4mim][Lact] were measured in the temperature range (308.15 to 343.15 ± 0.05) K.On the basis of the experimental data,the parachor and molar volume for [C4mim][Lact],and the molecular volume V m,surface tension γ,molar enthalpy of vaporization △lgHm 0,refractive index n D,and the thermal expansion coefficients,for the homologues [Cnmim][Lact] (n=2,3,4,5,and 6) were estimated using semi-empirical methods.The estimated values are in good agreement with the experimental data.

AN APPROACH TO CALCULATE THE SURFACE TENSION OF THE LIQUID NITROGEN FILM ON SOLIDS FROM AN ADSORPTION ISOTHERM

The equations, used in this paper to calculate the surface tension of the liquid nitrogen film formed by the physical adsorption on many different model solids (e.g. spherical partiele, plane particle and spherical cavity pores or cylindrical pores at the openings of both ends in solid bodies), have been derived on the thermodynamie principle. The calculated results have shown that the surface tension (γ) of the adsorbed liquid nitrogen film on most of non-porous solid surfaces diminishes with the rise of the nitrogen gas pressure (p) or of the adsorbed layers (n) at 77.3K; when p reaches the vapour pressure (p_s) of the bulk liquid nitrogen, y turns into the surface tension (γ_o) of the bulk liquid nitrogen; whgn p /p, 【0.98, there is an obvious difference between γ and γ_O.

Diffusion-controlled Adsorption Kinetics at Air/Solution Surface Studied by Maximum Bubble Pressure Method

In studying the diffusion-controlled adsorption kinetics of aqueous surfactant solutions at the air/solution surface by means of the maximal bubble pressure method, Fick's diffusion equation for a sphere should be used. In this paper the equation was solved by means of Laplace transformation under different initial and boundary conditions. The dynamic surface adsorption F(t) for a surfactant solution, which was used to describe the diffusion-controlled adsorption kinetics at the solution surface, was derived. Different from the planar surface adsorption, the dynamic surface adsorption F(t) for the short time consists of two terms: one is the same as Ward-Tordai equation and the other reflects the geometric effect caused by the spherical bubble surface. This effect should not be neglected for the very small radius of the capillary. The equilibrium surface tension γeq and the dynamic surface tension γ(t) of aqueous C10E6 [CH3(CH2)9(OCH2CH2)6OH] solution at temperature 25℃ were measuredby means of Wilhelmy plate method and maximal bubble pressure method respectively. As t→ 0, the theoreticalanalysis is in good agreement with experimental results and the dependence of γ(t) on is linear.

Modeling of Surface Tension and Viscosity for Non-electrolyte Systems by Means of the Equation of State for Square-well Chain Fluids with Variable Interaction Range

The equation of state(EOS)for square-well chain fluid with variable range(SWCF-VR) developed in our previous work based on statistical mechanical theory for chemical association is employed for the correlations of surface tension and viscosity of common fluids and ionic liquids(ILs).A model of surface tension for multi-component mixtures is presented by combining the SWCF-VR EOS and the scaled particle theory and used to produce the surface tension of binary and ternary mixtures.The predicted surface tensions are in excellent agreement with the experimental data with an overall average absolute relative deviation(AAD)of 0.36%.A method for the calculation of dynamic viscosity of common fluids and ILs at high pressure is presented by combining Eyring’s rate theory of viscosity and the SWCF-VR EOS.The calculated viscosities are in good agreement with the experimental data with the overall AAD of 1.44% for 14 fluids in 84 cases.The salient feature is that the molecular parameters used in these models are self-consistent and can be applied to calculate different thermodynamic properties such as pVT,vapor-liquid equilibrium,caloric properties,surface tension,and viscosity.

Highly efficient [C8mim][Cl] ionic liquid accompanied with magnetite nanoparticles and different salts for interfacial tension reduction

The 1-octyl-3-methylimidazolium chloride, [C8 mim][Cl] ionic liquid(IL) was used as a novel surfactant in n-heptane/water system. The interfacial tensions(IFT) were measured and corresponding variations were investigated. An IFT reduction of 80.8% was appropriate under the IL CMC of about 0.1 mol·L^-1 and stronger effects were achieved when magnetite nanoparticles and salts were present profoundly under alkaline p Hs.The equilibrium IFT data were accurately simulated with the Frumkin adsorption model. Hereafter, the saturated surface concentration, equilibrium constant and interaction parameter were obtained and their variations were demonstrated. Further, emulsion stability and contact angle of oil/water interface over quartz surface were studied. The oil/water emulsion stability was hardly changed with nanoparticles;however, the stability of oil/water + IL emulsions was significantly improved. It was also revealed that the presence of sodium and calcium chloride electrolytes fortifies the IL impact, whereas sodium sulfate weakens. From dynamic IFT data and fitting with kinetic models, it was found that the IL migration toward interface follows the mixed diffusion–kinetic control model. Consequently, the IL diffusion coefficient and the appropriate activation energy were determined.

离子液体改性碳材料及其应用的研究进展

阐述了离子液体改性碳材料的几种主要方法,包括物理改性、化学改性等。论述了不同改性方法的特点和优缺点,以及不同改性方法制备的离子液体改性碳材料的主要用途。综述了目前离子液体改性碳材料的主要应用,展望了离子液体改性碳材料的应用前景。

离子液体1-乙基-3-甲基咪唑亚磷酸甲酯盐与1-乙基-3-甲基咪唑亚磷酸乙酯盐的热物性

合成了1-乙基-3-甲基咪唑亚磷酸甲酯盐([Emim][OMP])和1-乙基-3-甲基咪唑亚磷酸乙酯盐([Emim][OEP])两种烷基咪唑亚磷酸酯离子液体,并使用核磁共振波谱仪和元素分析仪对产物进行了表征,在常压下测定了其热稳定性、相行为、密度和黏度(293.15~353.15K)、电导率和表面张力(293.15~343.15K)。采用自然对数方程关联离子液体的密度,根据实验值计算得到离子液体体积性质,包括热膨胀系数、分子体积、标准熵和晶格能。采用VFT方程关联离子液体黏度和电导率。采用线性方程关联表面张力,并根据实验值计算得到离子液体的表面熵和表面焓。实验结果表明,两种离子液体的分解温度(T_(onset))分别为271.0℃和259.2℃,玻璃化温度(T_(g))分别为-84.87℃和-85.00℃,离子液体的密度、黏度和表面张力随温度的升高而减小,而电导率随温度的升高而增大。Walden规则分析表明,两种烷基咪唑亚磷酸酯离子液体均符合Walden规则,且均被归类为“good ionic liquids”。

Diffusion-controlled Adsorption Kinetics of Surfactant at Air/Solution Interface

For the diffusion-controlled adsorption, the expression of dynamic surface adsorption P（t） was ob- tained by solving the diffusion equation. Two cases, i.e. the short and long time limits, were mainly discussed in this paper. From the measured dynamic surface tension of aqueous surfactant sodium dodecyl sulfate （SDS） solutions at 25 ℃, the adsorption kinetics of SDS at air/solution interface was studied. It was proved that for both of the short and long time limits, the adsorption process of SDS was controlled by diffusion.

Adsorption Kinetics of Alkyl Polyglucoside at the Air-Solution Interface

The air-solution equilibrium tension ge and dynamic surface tension gt, of nonionic surfactant alkyl polyglucoside have been studied. ge was measured by the Wilhelmy method with Krüss K12 tensiometer. The CMC and the surface excesses Γwere determined from the surface tension vs. concentration curve. The gt decays were measured in the range 0.2～20 s using a maximum bubble pressure instrument and analyzed with the Ward and Tordai equation.

Diffusion-Controlled Adsorption Kinetics of Triton X-100 at Air/Solution Interface

In this paper, the equilibrium surface tension and the dynamic surface tension of aqueous Triton X-100 solution at temperature 25 ℃ were measured by means of Wilhelmy plate method and maximal bubble pressure method respectively. The determined critical micellar concentration（cmc） of Triton X-100 at 25 ℃ is (2.2×10-4) mol/dm3. The adsorption mechanics of Triton X-100 at air/solution was determined. For the submicellar concentrations it is diffusion-controlled. The diffusion coefficient was calculated from the experimental data in the range of short limit. In the range of long time adsorption, the subsurface concentration is fitted from the measured dynamic surface tensions.

Apparent Active Adsorption Force at a Solid-Liquid Interface with Active Adsorption

The paper presents a new relationship between the three surface tensions on the solid-liquid-vapor interface, γ_(sl)-γ_(sv)+γ_(lv)cosθ=βin order to understand the wetting on the liquid-solid interface in the case of active adsorption.The authors suggest a new force“apparent active adsorption force”βto take part in the balance at the three interface lines of contact in the solid-liquid-vapor phases,its dimen- sion isβ=Σα_iRT(Γ_i^(sl)-Γ_i^(sv)+Γ_i^(lv)cosθ),and its direction is dependent on the sign of β,whenβis a positive, the direction is agree with surface tension of the sol- id-vapor interface γ and vice versa.