Synergistic anionic/zwitterionic mixed surfactant system with high emulsification efficiency for enhanced oil recovery in low permeability reservoirs

Emulsification is one of the important mechanisms of surfactant flooding. To improve oil recovery for low permeability reservoirs, a highly efficient emulsification oil flooding system consisting of anionic surfactant sodium alkyl glucosyl hydroxypropyl sulfonate(APGSHS) and zwitterionic surfactant octadecyl betaine(BS-18) is proposed. The performance of APGSHS/BS-18 mixed surfactant system was evaluated in terms of interfacial tension, emulsification capability, emulsion size and distribution, wettability alteration, temperature-resistance and salt-resistance. The emulsification speed was used to evaluate the emulsification ability of surfactant systems, and the results show that mixed surfactant systems can completely emulsify the crude oil into emulsions droplets even under low energy conditions. Meanwhile,the system exhibits good temperature and salt resistance. Finally, the best oil recovery of 25.45% is achieved for low permeability core by the mixed surfactant system with a total concentration of 0.3 wt%while the molar ratio of APGSHS:BS-18 is 4:6. The current study indicates that the anionic/zwitterionic mixed surfactant system can improve the oil flooding efficiency and is potential candidate for application in low permeability reservoirs.

Effect of solvent on the initiation mechanism of living anionic polymerization of styrene:A computational study

For living anionic polymerization(LAP),solvent has a great influence on both reaction mechanism and kinetics.In this work,by using the classical butyl lithium-styrene polymerization as a model system,the effect of solvent on the mechanism and kinetics of LAP was revealed through a strategy combining density functional theory(DFT)calculations and kinetic modeling.In terms of mechanism,it is found that the stronger the solvent polarity,the more electrons transfer from initiator to solvent through detailed energy decomposition analysis of electrostatic interactions between initiator and solvent molecules.Furthermore,we also found that the stronger the solvent polarity,the higher the monomer initiation energy barrier and the smaller the initiation rate coefficient.Counterintuitively,initiation is more favorable at lower temperatures based on the calculated results ofΔG_(TS).Finally,the kinetic characteristics in different solvents were further examined by kinetic modeling.It is found that in benzene and n-pentane,the polymerization rate exhibits first-order kinetics.While,slow initiation and fast propagation were observed in tetrahydrofuran(THF)due to the slow free ion formation rate,leading to a deviation from first-order kinetics.

Interactions of Anionic and Neutral Serine with Pure and Metal-doped Graphene Studied by Density Functional Theory

We present a theoretical study of interactions of anionic and neutral serine （Ser） on pure or metal-doped graphene surfaces using density functional theory calculations. Interactions of both types of Ser with the pure graphene surface show weak non-covalent interactions due to the formation of-COOH…π, -COO^-…π, and -OH…π interactions. On metal- doped graphene, covalent interactions to the surface dominate, due to the formation of strong metal-O and O-metal-O interactions. Furthermore, the doped Fe, Cr, Mn, A1, or Ti enhances the ability of graphene to attract both types of Ser by a combination of the adsorption energy, the density of states, the Mulliken atomic charges, and differences of electron density. At the same time, the interaction strengths of anionic Ser on various graphene surfaces are stronger than those of neutral Ser. These results provide useful insights for the rational design and development of graphene-based sensors for the two forms of Ser by introducing appropriate doped atoms. Ti and Fe are suggested to be the best choices among all doped atoms for the anionic Ser and neutral Ser, respectively.

Preparation and utilization of wheat straw anionic sorbent for the removal of nitrate from aqueous solution

In order to reduce the impact of eutrophication caused by agricultural residues （i.e., excess nitrate） in aqueous solution, economic and effective anionic sorbents are required. In this article, we prepared anionic sorbent using wheat straw. Its structural characteristics and adsorption properties for nitrate removal from aqueous solution were investigated. The results indicate that the yield of the prepared anionic sorbent, the total exchange capacity, and the maximum adsorption capacity were 350%, 2.57 mEq/g, and 2.08 mmol/g, respectively. The Freundlich isotherm mode is more suitable than the Langmuir mode and the adsorption process accords with the first order reaction kinetic rate equation. When multiple anions （SO4^2-, H2PO4^-, NO3^-, and NO2^-） were present, the isotherm mode of prepared anionic sorbent for nitrate was consistent with Freundlich mode; however, the capacity of nitrate adsorption was reduced by 50%. In alkaline solutions, about 90% of adsorbed nitrate ions could be desorbed from prepared anionic sorbent. The results of this study confirmed that the wheat straw anionic sorbent can be used as an excellent nitrate sorbent that removes nitrate from aqueous solutions.

Effect of an Anionic Surfactant on Hydraulic Conductivities of Sodium- and Calcium-Saturated Soils

The effect of sodium dodecylbenzenesulfonate (SDBS), an anionic surfactant used widely in household products and industrial processes, on saturated hydraulic conductivities (Ksat) of an Anthrosol saturated with sodium (Na-soil) or calcium (Ca-soil) was analyzed in a laboratory experiment using the constant head method, and adsorption and dispersion experiments were also conducted to infer the possible mechanisms of Ksat fluctuations. The results showed that SDBS was more intensely adsorbed in the Ca-soil than in the Na-soil. With an increase in the SDBS concentration, the stability of the Na-soil suspensions decreased when the SDBS concentration was less than 1.2 mmol L-1 and then above this concentration, increased markedly, while the stability of the Ca-soil suspensions increased gradually at all SDBS concentrations studied. With an increase in the SDBS concentration, the Ksat of the Na-soil increased, which resulted mainly from the increase of water channels in the soil because of the coagulation of the soil particles, while the Ksat of Ca-soil decreased mainly on account of the clogging of partial water channels by precipitated Ca(DBS)2 and the fine soil particles generated.

THE RELATIONSHIP BETWEEN THE STRUCTURAL TYPE OF ANIONIC GROUP AND SHG EFFECT IN BORON-OXYGEN COMPOUNDS

The relationship between the Structural type of anionic group and SHG effect in oxide compounds has been reviewed.

Preparation of a Novel Acid Doped Polyaniline Adsorbent for Removal of Anionic Pollutant from Wastewater

Polyaniline(PANI) was one of the most extensively studied adsorbents due to its low cost and good environmental stability. The objective of the current study was to improve the selective capabilities of PANI for anionic dyes. We found that the acid doped PANI prepared with hydrochloric acid and p-toluenesulfonic acid(PTSA) could selectively adsorb anionic dyes. It exhibited very good selectivity for OG dye, the mechanism was proposed based on the chemical interaction of PANI with the sulfonate group of the dyes. The effects of solution p H, initial dye concentration, and different HCl/PTSA mole ratios on the adsorption capacity of OG have been investigated. Kinetic simulations indicated that the adsorption process could be well represented by pseudo-second-order kinetic plots. The isothermal adsorption curve fitting also showed that the adsorption process could be well described by the Langmuir isothermal equation. The results showed that acid doped PANI could be employed as a promising adsorbent for anion removal from dye wastewater.

Fundamental Understanding and Effect of Anionic Chemistry in Zinc Batteries

With the merit of high capacity,high safety,and low cost,zinc-ion batteries(ZIBs)possess huge application potential in the domain of large-scale energy storage.However,due to the relatively narrow voltage window and large lattice distortion of cationic redox reaction,ZIBs tend to present low energy density,poor kinetics,and unstable cyclic performance.Anion chemistry seems to provide a novel strategy to solve these issues from different aspects,such as enhanced operating voltage,extra capacity contribution,and boosted reaction kinetics.Considering the significance of this theory and the lack of relevant literatures,herein,in-depth comprehension of anionic chemistry and its positive effects on zinc storage performance have been emphasized and summarized.This review aims to present a full scope of anionic chemistry and furnish systematic cognition for rational design of advanced ZIBs with high energy density.Furthermore,insightful analysis and perspectives based on the current research status also have been proposed,which may point out some scientific suggestions and directions for the future research.

Coupling of anionic wetting agents to dust of sulfide ores by dropping liquid method

By using the experimental approach of dropping liquid, the coupling of three anionic wetting agents with ten dust samples of sulfide ores was studied, and particularly the wetting effects of the wetting agents on the sulfide dust influenced by factors of agent concentration and sulfate additive in the wetting agent solutions were investigated. The results show that when the solution temperature is about 20 ℃, all the selected wetting agents are effective to most dust samples, but the effect is different. Wetting agents are more effective to the dust which is difficult to be wetted. Wetting agent solution with sodium sulfate can improve the wetting ability of sulfide dust. For sodium dodecyl benzene sulfonate, the suitable concentration of sodium sulfate is 12 mmol/L. The cost of wetting agents can be reduced because the sodium sulfate is much cheaper than many surfactants. Since the dust of sulfide ores is composed of various minerals and elements, the whole effect of depressing dust should be considered while innovating a wetting agent.

Synthesis,Structure and Biological Activities of a Novel Anionic Organotin(Ⅳ)Complex{[(pClC6H4CH2)Sn(H2O)(Cl)2OCOCH(O)CH(O)CO2Sn(H2O)(Cl)2(p-ClC6H4CH2)]·2(HNEt3)}

A novel anionic organotin(Ⅳ) complex {[(pClCHCH)Sn(HO)(Cl)OCOCH(O)CH(O)COSn(HO)(Cl)(p-ClCHCH)]·2(HNEt)}(1) was synthesized by the reaction of di(p-chlorobenzy)tin dichloride with the D-tartaric acid in 2:1 molar in the presence of an organic base triethylamine. The structure was characterized by elemental analysis, IR, TG, XRD and single-crystal X-ray diffraction. It crystallizes in triclinic, P1 space group, with a = 0.7067(1), b = 1.9762(3), c = 2.2383(3) nm, α = 91.544(2)°, β = 90.075(2)°, γ = 90.110(2)°, V = 3.1247(7) nm~3, Z = 3, Dc = 1.621 g/cm~3, m(Mo Kα) = 16.29 cm–1, F(000) = 1530, R = 0.0394, wR = 0.1092,(Δρ)max = 1224 and(Δρ)min = –840 e/nm~3. The stabilities, orbital energies and composition characteristics of some frontier molecular orbitals of 1 have been carefully investigated with quantum chemistry calculation. In addition, the in vitro antitumor activity suggested that 1 had stronger inhibitory activity on H460, MCF7 than on A549.

Phase Separation and Microstructure of Mixed Surfactants Solution Containing Cationic Geminis and Traditional Anionic Surfactant

The properties of aqueous two-phase system (ATPS) of mixed solution containing gemini cationic surfactant trimethylene-1,3-bis(dodecyldimethyl ammonium) bromide (12-3-12, 2Br-) and traditional anionic surfactant sodium dodecyl sulfate (SDS) with or without added salt have been studied. An ATPS is formed in a narrow region of the ternary phase diagram different from that of traditional aqueous cationic-anionic surfactant systems. In ATPS region, the lowest total concentration of surfactants varies with the mixing ratio of geminis to SDS. Photographs obtained from freeze-etching, negative-staining and transmission electron microscopy show that the microstructures of two phases are different from each other. Micelles and vesicles can coexist in a single phase. The addition of salts can change the phase diagram of ATPS. Furthermore, the added salts promote the aggregation of rod-like micelles to form coarse network structure that increase the viscosity of solutions. The negative ions of the added salts are the determining factor.

Enhanced electrode kinetics and properties via anionic regulation in polyanionic Na_(3+x)V_(2)(PO_(4))_(3-x)(P_(2)O_(7))_(x) cathode material

Mixing polyanion cathode materials are promising candidates for the development of next-generation batteries, owing to their structural robustness and low-volume changes, yet low conductivity of polyanion hinders their practical capacity. Herein, the anion-site regulation is proposed to elevate the electrode kinetics and properties of polyanionic cathode. Multivalent anion P_(2)O_(7)^(4-) is selected to substitute the PO_(4)^(3-) in Na_(3)V_(2)(PO_(4))_(3) (NVP) lattice and regulate the ratio of polyanion groups to prepare Na_(3+x)V_(2)(PO_(4))_(3-x)(P_(2)O_(7))_(x)(NVPP_(x), 0 ≤ x ≤ 0.15) materials.The optimal Na_(3.1)V_(2)(PO_(4))_(2.9)(P_(2)O_(7))_(0.1) (NVPP_(0.1)) material can deliver remarkably elevated specific capacity(104 mAh g^(-1) at 0.1 C, 60 mAh g^(-1) at 20 C, respectively), which is higher than those of NVP. Moreover, NVPP_(0.1) exhibits outstanding cyclic stability(91% capacity retention after 300 cycles at 1 C). Experimental analyses reveal that the regulation of anions improves the structure stability, increases the active Na occupancy in the lattice and accelerates the Na+migration kinetics. The strategy of anion-site regulation provides the researchers a reference for the design of new high-performance polyanionic materials.

Evaluation of chitosaneanionic polymers based tablets for extended-release of highly watersoluble drugs

The objective of this study is to develop chitosaneanionic polymers based extendedrelease tablets and test the feasibility of using this system for the sustained release of highly water-soluble drugs with high drug loading.Here,the combination of sodium valproate(VPS)and valproic acid(VPA)were chosen as the model drugs.Anionic polymers studied include xanthan gum(XG),carrageenan(CG),sodium carboxymethyl cellulose(CMC-Na)and sodium alginate(SA).The tablets were prepared by wet granulation method.In vitro drug release was carried out under simulated gastrointestinal condition.Drug release mechanism was studied.Compared with single polymers,chitosaneanionic polymers based system caused a further slowdown of drug release rate.Among them,CS exanthan gum matrix system exhibited the best extended-release behavior and could extend drug release for up to 24 h.Differential scanning calorimetry(DSC)and Fourier transform infrared spectroscopy(FTIR)studies demonstrated that polyelectrolyte complexes(PECs)were formed on the tablet surface,which played an important role on retarding erosion and swelling of the matrix in the later stage.In conclusion,this study demonstrated that it is possible to develop highly water-soluble drugs loaded extendedrelease tablets using chitosaneanionic polymers based system.

Synthesis and Characterization of Zirconia Nanocrystallites by Cationic Surfactant and Anionic Surfactant

Study on nanomaterials has attracted great interests in recent years. In this article, zirconia nanocrystallites of different structures have been successfully synthesized via hydrothermal methods with cationic surfactant （CTAB） and anionic surfactant （SDS）, respectively. Differential Scanning Calorimeter （DSC-TG）, X-ray Diffractometer （XRD）, Transmission Electron Microscope （TEM）, Ultraviolet-Visible （UV-vis） and N2 adsorption-desorption analyses are used for their structure characteristics. The results show that the cationic surfactant has a distinctive direction effect on the formation of zirconia nanocrystallites, while the anionic surfactant has a self-assembly synergistic effect on them. The sample synthesized with the cationic surfactant presents good dispersion with the main phase of tetragonal zirconia, and the average nanocrystal size is around 15 nm after calcination at 500 ℃. While the sample synthesized with the anionic surfactant exhibits a worm-like mesoporous structure with pure tetragonal phase after calcination at 500 ℃ and with good thermal stability.

Tuning anionic redox activity to boost high-performance sodium-storage in low-cost Na_(0.67)Fe_(0.5)Mn_(0.5)O_(2) cathode

Na-based layered iron-manganese oxide Na_(0.67)Fe_(0.5)Mn_(0.5)O_(2) containing only low-cost elements is a promising cathode for Na-ion batteries used in large-scale energy storage systems.However,the poor cycle stability restricts its practical application.The capacity decay of Na_(0.67)Fe_(0.6)Mn_(0.5)O_(2) mainly originates from the irreversible anionic redox reaction charge compensation due to the high-level hybridization between oxygen and iron.Herein,we rationally design a surface Ti doping strategy to tune the anionic redox reaction activity of Na_(0.67)Fe_(0.5)Mn_(0.5)O_(2) and improve its Na-storage properties.The doped Ti ions not only enlarge the Na migration spacing layer but also improve the structure stability thanks to the strong Ti-O bond.More importantly,the d0-shell electronic structure of Ti^(4+) can suppress the charge transfer from the oxidized anions to cations,thus reducing the anionic redox reaction activity and enhancing the reversibility of charge compensation.The modified Na_(0.67)Fe_(0.5)Mn_(0.5)O_(2) cathode shows a reversible capacity of 198 mA h g^(-1) and an increased capacity retention from 15% to 73% after about1 month of cycling.Meanwhile,a superior Na-ion diffusion kinetics and rate capability are also observed.This work advances the commercialization process of Na-based layered iron-manganese oxide cathodes;on the other hand,the proposed modification strategy paves the way for the design of high-performance electrode materials relying on anionic redox reactions.

Influences of anionic and cationic dopants on the morphology and optical properties of PbS nanostructures

Selenium and zinc are used as anionic and cationic dopant elements to dope PbS nanostructures. The undoped and doped PbS nanostructures are grown using a thermal evaporation method. Scanning electron microscopy （SEM） results show similar morphologies for the undoped and doped PbS nanostructures. X-ray diffraction （XRD） patterns of three sets of the nanostructures indicate that these nanostructures each have a PbS structure with a cubic phase. Evidence of dopant incorporation is demonstrated by X-ray photoelectron spectroscopy （XPS）. Raman spectra of the synthesized samples con- firm the XRD results and indicate five Raman active modes, which relate to the PbS cubic phase for all the nanostructures. Room temperature photoluminescence （PL） and UV-Vis spectrometers are used to study optical properties of the undoped and doped PbS nanostructures. Optical characterization shows that emission and absorption peaks are in the infrared （IR） region of the electromagnetic spectrum for all PbS nanostructures. In addition, the optical studies of the doped PbS nanos- tructures reveal that the band gap of the Se-doped PbS is smaller, and the band gap of the Zn-doped PbS is bigger than the band gap of the undoped PbS nanostructures.

Crystalline Morphology and Crystallization Characteristics of In-situ Blends of Anionic Polyamide 6 with Noncrystallizable Semiaromatic Polyamide Copolymer

A noncrystallizable semiaromatic polyamide copolymer（NSAP） was dissolved in molten caprolactam, and PA6/ NSAP blends were produced in-situ via the anionic ring-opening polymerization of caprolactam. The presence of a single loss tangent（tanS） peak measured by means of dynamic mechanical analysis（DMA） proves the miscibility between PA6 and NSAP in the blends. It was found that there existed drastic changes in the crystallographic form and crystallization kinetics for the in-situ blends, e.g. , when 20% NSAP was added, nearly all crystallites existed in the ,y form and the crystallization could hardly occur upon cooling even at a rate of 2.5 ℃/min. Moreover, cold crystallization appears during the subsequent heating, and its melting point is 40 ℃ lower than that of the virgin system. On the other hand, the size of the spherulites only decreases modestly. It is suggested that the introduction of irregular stiff segments originated from NSAP into PA6 macromolecule chain, which resulted from transamidation during the polymerization play a dominant role in the drastic change of crystallization kinetics and the resultant morphology of the in-situ blends.

Removal of anionic ions from single material solution by bauxite tailings modified with FeCl_3·6H_2O

The adsorbabilities of the unmodified and modified bauxite tailings for Cr（Ⅵ）, As（Ⅴ） and F（Ⅰ） ions were investigated. Batch experiments were carried out to determine the removal rate as a function of adsorbent dosage, solution pH value and shaking time. The results show that the maximum removal rates of Cr（Ⅵ）, As（Ⅴ） and F（Ⅰ ） are respectively 99%, 99% and 90% by using the modified bauxite tailings. The isoelectric point of the unmodified bauxite tailings is 3.6, and that of the modified bauxite tailings is 5.0, which shifts to lower pH values in Cr（Ⅵ） solution. This indicates a specific adsorption of the anionic species on the modified bauxite railings. A new band of Cr2O72 appears in the FTIR, showing that Cr（Ⅵ） is adsorbed on the modified bauxite railings in the form of chemistry adsorption. The adsorption data of Cr（Ⅵ） on the modified bauxite tailings are well described by Freundlich model. The investigations of kinetic models show that pseudo-second-order kinetic model provides the best correlation for the experimental data.

Single-atom catalysts with anionic metal centers: Promising electrocatalysts for the oxygen reduction reaction and beyond

Ongoing efforts to develop single-atom catalysts(SACs) for the oxygen reduction reaction(ORR) typically focus on SACs with cationic metal centers,while SACs with anionic metal centers(anionic SACs) have been generally neglected.However,anionic SACs may offer excellent active sites for ORR,since anionic metal centers could facilitate the activation of O_(2) by back donating electrons to the antibonding orbitals of O_(2).In this work,we propose a simple guideline for designing anionic SACs:the metal centers should have larger electronegativity than the surrounding atoms in the substrate on which the metal atoms are supported.By means of density functional theory(DFT) simulations,we identified 13 anionic metal centers(Co,Ni,Cu,Ru,Rh,Pd,Ag,Re,Os,Ir,Pt,Au,and Hg) dispersed on pristine or defective antimonene substrates as new anionic SACs,among which anionic Au and Co metal centers exhibit limiting potentials comparable to,or even better than,conventional Pt-based catalysts towards ORR.We also found that anionic Os and Re metal centers on the defective antimonene can electrochemically catalyze the nitrogen reduction reaction(NRR) with a limiting potential close to that of stepped Ru(0001).Overall,our work shows promise towards the rational design of anionic SACs and their utility for applications as electrocatalysts for ORR and other important electrochemical reactions.

A comparison of anionic and cationic flotation of a siliceous phosphate rock in a column flotation cell

Flotation performance of a de-slimed（-150＋53μm）Jordanian siliceous phosphate was evaluated in a batch laboratory flotation column 100 cm high and 5 cm inside diameter.The collector used during anionic flotation was sodium oleate while an amine acetate（AEROMINE 3100C）was used for cationic flotation.Flotation comparison at different collector dosage,superficial gas velocity,and frother concentration showed that the maximum difference in performance between cationic and anionic flotation was obtained with these flotation parameters：30×10^（-6）（mg/L）frother concentration,250 g/t collector concentration,and 3.4 cm/s superficial gas velocity.At these operating conditions amine （cationic）flotation gave 7%higher flotation recovery,a 6%cleaner concentrate grade,and was 6%more efficient at removing silica.