Adsorption Capacity Of Surfactants Research Articles

Synergistic improvement of the fine size coal dewatering performance by using binary surfactant mixtures

In this study, gemini surfactants and binary surfactant mixtures were used in order to enhance the dewatering performance of fine size coal particles. Compared to three single gemini surfactants, binary surfactant mixtures presented a better dewatering performance of fine size coal particles, especially the binary surfactant mixture composed of Gemini − 1 surfactant and sodium dodecyl benzene sulfonate (SDBS). Meanwhile, the binary surfactant mixture composed of Gemini − 1 surfactant and sodium dodecyl sulfonate (SDS) was further used in the experimental test as a comparison and showed better dewatering performance than that of the binary surfactant mixture composed of Gemini − 1 surfactant and SDBS. The lowest cake moisture content (20.72 %) was gained when the dosage of Gemini − 1 surfactant and SDS was 400 g/t at the molar ratio of 6 to 7. Surface functional groups of the prepared coal samples were characterized by a Fourier transform infrared spectroscopy (FTIR). Wetting heat values of coal samples before and after adsorbing surfactants were measured by a microcalorimeter. The adsorption capacity of surfactant on coal surface was investigated for studying the difference between three single surfactants and the binary surfactant mixture. Intermolecular interaction calculation and thermodynamics of micellization for the judgment of synergistic effect indicated that the synergistic interaction was formed in the binary surfactant mixture and the binary surfactant mixture of Gemini − 1 surfactant and SDS showed a stronger synergistic interaction. A possible hydrophobic mechanism was supposed that the water molecules were displaced by the binary surfactant mixture for the improvement of hydrophobicity of coal particle surface.

Study on the Behavior of Saturated Cardanol-Based Surfactants at the Crude Oil/Water Interface through Molecular Dynamics Simulations.

Cardanol is a green biosurfactant with broad application prospects, which is expected to be used to enhance oil recovery (EOR). This paper designed two types of surfactants (extended and nonextended), including six kinds of nonionic and anion-nonionic surfactants. The position changes of PO and EO chains and the effects of different hydrophilic groups on the interface properties were studied with molecular dynamics simulations by constructing a model of crude oil (containing four components) and water molecules. The results of interfacial tension and solvent-accessible surface area showed that the interfacial properties of sulfate were better than those of sulfonates and nonionic surfactants. Meanwhile, the interface properties of nonextended surfactants were better than those of extended surfactants. The gyration radius (Rg) and tilt angle data demonstrated that when EO chains were located between hydrophobic groups and PO chains (nonextended surfactants), the adsorption capacity of surfactants at crude oil and water interfaces could be effectively improved. The radial distribution function of the hydrophilic group and hydrophobic group of surfactants with water molecules and four components of the crude oil molecule, respectively, explained that surfactants (8EO8POSO4) had better emulsification performance when the intermolecular interactions between crude oil and water two phases were relatively balanced. This study provides a theoretical reference for the design of oil-displacement surfactants and the mechanism analysis of emulsification properties.

Exploring the surfactant structure efficacy in controlling growth and stability of HgS nanoparticles in aqueous medium

Surfactants exhibit many inherent properties, one of the properties is their favorable capacity to absorb at the interface or surface in which surfactant molecules are transferred from bulk phase of solution to the interface. With the evolution in the synthesis routes of nanoparticles (NPs) via colloidal chemistry approaches, now the adsorption capacity of surfactants is being exploited concerning the stabilization of the NPs. In present research work, colloidal mercuric sulfide nanoparticles (HgS NPs) have been synthesized with effective sizes below 15 nm in aqueous solutions of various surfactants through facile chemical precipitation technique. Different head groups and hydrophobic chain length moieties have been tested for various cationic and anionic surfactants. These surfactants have been demonstrated to produce dispersed spherical configured HgS NPs, in which the composition of surfactant has controlled growth assessment. Although, the NPs in the pulverized form exhibit β-HgS form except of the surfactant opted. Surfactant adsorption at the surface of NP has been shown due to change in inter-particle potential and prevents the self-aggregation of NPs. Additionally, it has been demonstrated that the surfactants (stabilizers) have some favorable chemical moiety which promotes the binding at NP surface, generates an adequate size of particles and eventually inhibits their unlimited growth. The kinetics of nucleation and growth of surfactant stabilized HgS NPs follows the first-order rate law in all the surfactants. However, the first order rate constant has shown prominent surfactant dependence.

Effect of nanobubbles on adsorption of sodium oleate on calcite surface

The aim of the study is to explore the effect of nanobubbles on the adsorption capacity of surfactants on mineral surfaces. Firstly, nanobubbles were imaged under the condition that the solution had a dissolved oxygen difference (DOD) by atomic force microscope (AFM). Subsequently, the calcite particles with 37–74 μm and sodium oleate (NaOL) were mixed and stirred under different mixing times and different pressure control (nanobubbles can be produced under the condition of decompression) through a self-made pressurization and decompression device. After nature sedimentation, the supernatant was extracted, and the change of the adsorption capacity of NaOL on the surface of calcite was detected by high performance liquid chromatography (HPLC). Finally, in order to study the direct influence of nanobubbles on the adsorption of NaOL on the surface of calcite, the NaOL on the surface of calcite were imaged under different pressure conditions by AFM. The experimental results showed that many nanobubbles were found on the calcite surface by AFM under the dissolved oxygen difference (DOD) condition of −4 mg/L. Furthermore, the order of adsorption of sodium oleate on the surface of calcite under different pressure conditions was as follows: constant low pressure (0.3 atm) > inflating (0.3 atm to 1 atm) > constant normal pressure (1 atm) > pumping gas (1 atm to 0.3 atm). More interestingly, compared with the constant pressure condition, the coverage of NaOL on the calcite surface was reduced under decompression pressure, about 30% lower at natural pH and about 20% lower at pH = 10, and this decrease was obvious. However, the change in adsorption height was considered by the author to be difficult to judge by AFM.The study concludes that nanobubbles can be generated under the condition that the DOD is less than 0. Moreover, nanobubbles not only promote the formation of floc, but also directly inhibit the adsorption of NaOL on the calcite surface, both reasons can inhibit the adsorption capacity of NaOL on the calcite surface.It provides a better idea and method for understanding of nanobubble, flotation, dissolved air flotation (DAF), and the interaction between surfactant and particles or particles and particles. These findings are benefit for these fields, such as mineral processing, biomedicine, etc.

Effect of mineralogy on the adsorption characteristics of surfactant—Reservoir rock system

Emphasizing upon the effect of rock mineralogy, aqueous media salinity and temperature, this work addresses the adsorption characteristics of surfactant on real reservoir rocks. The experimental methodology involves mineralogy and morphology analysis of reservoir rock and thermal aging based surfactant stability studies. Surfactants were screened based on the interfacial tension reduction with reservoir crude oil. Among alternate models, Langmuir isotherm model and pseudo-second order kinetics fit well to represent pertinent surfactant adsorption characteristics. An important inference from the carried out research indicates that adsorption capacity of surfactant is strongly dependent on the mineral content of the rock in the order of illite>feldspar>montmorillonite>kaolinite. These findings provide newer insights into real time surfactant adsorption characteristics, which are often ignored in conventional approaches and methodologies.

Impact of surfactant in fracturing fluid on the adsorption–desorption processes of coalbed methane

The effect of three surfactants in the fracturing fluid on the adsorption–desorption processes of coalbed methane (CBM) was studied by conducting an isothermal adsorption–desorption experiment. The adsorption capacity of surfactants and the wettability of the coal surface were also systematically investigated to illustrate the impact of surfactants. The experimental results showed that compared with the anionic surfactant sodium dodecyl sulfate (SDS) and the cationic surfactant octadecyl trimethyl ammonium chloride (OTAC), the nonionic surfactant N-(2-hydroxypropyl) perfluorooctane amide (FCS) exhibits lower Langmuir pressure during the entire CBM desorption process, which promotes the desorption of CBM. The adsorption capacity and contact angle results demonstrated that the nonionic surfactant FCS has the weakest adsorption capacity on the coal surface and can increase contact angle slightly, which enhances the hydrophobicity and inhibits water from entering the deep and fine pores of coal. This phenomenon results in reduced damage of the fracturing fluid for CBM desorption. This study is significant with regard to the selection of a fracturing fluid system with high surface activity, high desorption efficiency of CBM, and low damage to the coal reservoir.

Adsorption of surfactants from water onto raw and HCl-activated clays in fixed beds

The removal of surfactants from water by adsorption onto raw and HCl-activated montmorillonite in fixed beds was studied. Three surfactants hexadecylpyridinium chloride (cationic), sodium dodecyl sulfate (anionic), and Triton X-102 (non-ionic) were selected in the concentration ranges lower than their critical micelle concentrations in fixed bed experiments. It was shown that the adsorption of anionic surfactant onto Ca-montmorillonite (SAz-1) decreased with increasing pH but that of cationic surfactant increased. The adsorption capacity of non-ionic surfactant was maximized at pH 7.0. For given clay, the adsorption capacities of surfactants were strongly pH-dependent. The adsorption capacity and adsorption rate of non-ionic surfactant onto SAz-1 could be largely improved after acid activation of the clay. Such an improvement was due to the fact that the dissolution of Al 3+ or Fe 2+ of montmorillonite occurs in acid solution. The calculated breakthrough curves in fixed bed agreed with the measured ones (standard deviation < 6%). The 50% C/C 0 breakthrough time ( τ ) decreased with increasing liquid flow rate. The effects of flow rate on the adsorption constant and adsorption capacity were also discussed.

Influence of clay mineral structure and surfactant nature on the adsorption capacity of surfactants by clays

Adsorption of three surfactants of different nature, Triton X-100 (TX100) (non-ionic), sodium dodecylsulphate (SDS) (anionic) and octadecyltrimethylammonium bromide (ODTMA) (cationic) by four layered (montmorillonite, illite, muscovite and kaolinite) and two non-layered (sepiolite and palygorskite) clay minerals was studied. The objective was to improve the understanding of surfactant behaviour in soils for the possible use of these compounds in remediation technologies of contaminated soils by toxic organic compounds. Adsorption isotherms were obtained using surfactant concentrations higher and lower than the critical micelle concentration (cmc). These isotherms showed different adsorption stages of the surfactants by the clay minerals, and were classified in different subgroups of the L-, S- or H-types. An increase in the adsorption of SDS and ODTMA by all clay minerals is observed up to the cmc of the surfactant in the equilibrium solution is reached. However, there was further TX100 adsorption when the equilibrium concentration was well above the cmc. Adsorption constants from Langmuir and Freundlich equations (TX100 and ODTMA) or Freundlich equation (SDS) were used to compare adsorption of different surfactants by clay minerals studied. These constants indicated the surfactant adsorption by clay minerals followed this order ODTMA > TX100 ≫ SDS. The adsorption of TX100 and ODTMA was higher by montmorillonite and illite, and the adsorption of SDS was found to be higher by kaolinite and sepiolite. Results obtained show the influence of clay mineral structure and surfactant nature on the adsorption capacity of surfactants by clays, and they indicate the interest to consider the soil mineralogical composition when one surfactant have to be selected in order to establish more efficient strategies for the remediation of soils and water contaminated by toxic organic pollutants.