Nonionic Molecules Research Articles

Diffusion and Interaction Effects On Molecular Release Kinetics From Collapsed Microgels.

The efficient transport of small molecules through dense hydrogel networks is crucial for various applications, including drug delivery, biosensing, catalysis, nanofiltration, water purification, and desalination. In dense polymer matrices, such as collapsed microgels, molecular transport follows the solution-diffusion principle: Molecules dissolve in the polymeric matrix and subsequently diffuse due to a concentration gradient. Employing dynamical density functional theory (DDFT), we investigate the nonequilibrium release kinetics of nonionic subnanometer-sized molecules from a microgel particle, using parameters derived from prior molecular simulations of a thermoresponsive hydrogel. The kinetics is primarily governed by the microgel radius and two intensive parameters: the diffusion coefficient and solvation free energy of the molecule. Our results reveal two limiting regimes: a diffusion-limited regime for large, slowly diffusing, and poorly soluble molecules within the hydrogel; and a reaction-limited regime for small, rapidly diffusing, and highly soluble molecules. These principles allow us to derive an analytical equation for release time, demonstrating excellent quantitative agreement with the DDFT results-a valuable and straightforward tool for predicting release kinetics from microgels.

New QSPR molecular descriptors based on low-cost quantum chemistry computations using DFT/COSMO approach

This work presents a simple computational methodology to determine new theoretical molecular descriptor scales convenient for use in QSPR correlations and the analysis of solvation-related properties. On the basis of low-cost quantum chemical computations using DFT/COSMO approach, in particular that implemented in the ADF/COSMO-RS module of the Amsterdam Modeling Studio program package, optimized geometry and local screening charge density of a considered molecule are obtained and related to the proposed descriptors through an a priori simple reasoning. Values of four molecular descriptors, namely volume VCOSMO∗, hydrogen bond/Lewis acidity αCOSMO and basicity βCOSMO, and charge asymmetry of the nonpolar region of the molecule δCOSMO have been calculated and are presented for sets of 128 non-ionic organic molecules and 47 ions composing ionic liquids. Relation of the proposed scales to some others that are widely known or presented recently in the literature has been examined. Although the present methodology is completely independent of any experimental data, the theoretical descriptor scales proposed here have been found to correlate linearly quite well with the respective empirical scales (mostly R2 > 0.8, and for some R2 > 0.9). For non-ionic organics, just the direct proportionality provided adequate fits of the well-established prominent scales such as those of Abraham, Klamt, Kamlet-Taft, Catalan, Gutmann, and Laurence and showed only a few statistically justifiable outliers. For ions composing ILs, the linear fits of seven acidity or basicity scales presented previously with those proposed in this work were of similar quality. Examining the observed outliers, several descriptor values reported in the literature were identified as being in error. Good performance of the new descriptor scales has been demonstrated by employing them for LSER fitting of various solvation-related thermodynamic and kinetic properties such as standard vaporization enthalpy, standard hydration enthalpy, air–water partition coefficient, air-IL partition coefficient, and solvent effects on the activation Gibbs energy or rate constant of SN1 and SNAr reactions. The quality of these correlations appears to be comparable to that of the correlations currently available for these properties, regardless of the role, solute or solvent, the involved molecules played.

Analyzing the Accuracy of Critical Micelle Concentration Predictions Using Deep Learning.

This paper presents a novel approach to predicting critical micelle concentrations (CMCs) by using graph neural networks (GNNs) augmented with Gaussian processes (GPs). The proposed model uses learned latent space representations of molecules to predict CMCs and estimate uncertainties. The performance of the model on a data set containing nonionic, cationic, anionic, and zwitterionic molecules is compared against a linear model that works with extended connectivity fingerprints (ECFPs). The GNN-based model performs slightly better than the linear ECFP model when there is enough well-balanced training data and achieves predictive accuracy that is comparable to published models that were evaluated on a smaller range of surfactant chemistries. We illustrate the applicability domain of our model using a molecular cartogram to visualize the latent space, which helps to identify molecules for which predictions are likely to be erroneous. In addition to accurately predicting CMCs for some surfactant classes, the proposed approach can provide valuable insights into the molecular properties that influence CMCs.

Gustation-Inspired Dual-Responsive Hydrogels for Taste Sensing Enabled by Machine Learning.

Human gustatory system recognizes salty/sour or sweet tastants based on their different ionic or nonionic natures using two different signaling pathways. This suggests that evolution has selected this detection dualism favorably. Analogically, this work constructs herein bioinspired stimulus-responsive hydrogels to recognize model salty/sour or sweet tastes based on two different responses, that is, electrical and volumetric responsivities. Different compositions of zwitter-ionic sulfobetainic N-(3-sulfopropyl)-N-(methacryloxyethyl)-N,N-dimethylammonium betaine (DMAPS) and nonionic 2-hydroxyethyl methacrylate (HEMA) are co-polymerized to explore conditions for gelation. The hydrogel responses upon adding model tastant molecules are explored using electrical and visual de-swelling observations. Beyond challenging electrochemical impedance spectroscopy measurements, naive multimeter electrical characterizations are performed, toward facile applicability. Ionic model molecules, for example, sodium chloride and acetic acid, interact electrostatically with DMAPS groups, whereas nonionic molecules, for example,D(-)fructose, interact by hydrogen bonding with HEMA. The model tastants induce complex combinations of electrical and volumetric responses, which are then introduced as inputs for machine learning algorithms. The fidelity of such a trained dual response approach is tested for a more general taste identification. This work envisages that the facile dual electric/volumetric hydrogel responses combined with machine learning proposes a generic bioinspired avenue for future bionic designs of artificial taste recognition, amply needed in applications.

Development of Liposomal and Liquid Crystalline Lipidic Nanoparticles with Non-Ionic Surfactants for Quercetin Incorporation.

The aim of the present study is the development, physicochemical characterization, and in vitro cytotoxicity evaluation of both empty and quercetin-loaded HSPC (hydrogenated soy phosphatidylcholine) liposomes, GMO (glyceryl monooleate) liquid crystalline nanoparticles, and PHYT (phytantriol) liquid crystalline nanoparticles. Specifically, HSPC phospholipids were mixed with different non-ionic surfactant molecules (Tween 80 and/or Span 80) for liposomal formulations, whereas both GMO and PHYT lipids were mixed with Span 80 and Tween 80 as alternative stabilizers, as well as with Poloxamer P407 in different ratios for liquid crystalline formulations. Subsequently, their physicochemical properties, such as size, size distribution, and ζ-potential were assessed by the dynamic and electrophoretic light scattering (DLS/ELS) techniques in both aqueous and biological medium with serum proteins. The in vitro biological evaluation of the empty nanosystems was performed by using the MTT cell viability and proliferation assay. Finally, the entrapment efficiency of quercetin was calculated and the differences between the two different categories of lipidic nanoparticles were highlighted. According to the results, the incorporation of the non-ionic surfactants yields a successful stabilization and physicochemical stability of both liposomal and liquid crystalline nanoparticles. Moreover, in combination with an appropriate biosafety in vitro profile, increased encapsulation efficiency of quercetin was achieved. Overall, the addition of surfactants improved the nanosystem's stealth properties. In conclusion, the results indicate that the physicochemical properties were strictly affected by the formulation parameters, such as the type of surfactant.

Adsorption of poly(oxyethylene) and hydroxyl group-containing nonionic surfactants on silica particles in NH4OH solution and its effect on the interaction force with Si surface

In the semiconductor manufacturing processes, surface cleaning is one of the most critical steps because particle contamination directly affects device yield. In addition, surface etching and oxidation should be minimized during the particle removal process. In this study, the dissolved oxygen concentration (DOC) in an NH4OH solution was reduced to suppress oxidation of Si. Additionally, nonionic surfactants were added to the solution to suppress the Si surface roughening and improve the particle removal efficiency in the NH4OH solution. Nonionic surfactant molecules were adsorbed on the Si surface, preventing the Si surface from attack by OH-. In addition, they were also adsorbed on the silica particle surfaces, producing repulsive hydration and osmotic forces between the adsorbed surfaces of the Si and silica particles while reducing the adhesion force between them. As a result, more than 95 % of particle removal efficiency and less than 0.6 nm of surface roughness were obtained when the particle-contaminated Si surface was treated with a low-DOC NH4OH solution containing a nonionic surfactant.

Structure Identification of Adsorbed Anionic–Nonionic Binary Surfactant Layers Based on Interfacial Shear Rheology Studies and Surface Tension Isotherms

Mixtures of anionic sodium oleate (NaOl) and nonionic ethoxylated or alkoxylated surfactants improve the selective separation of magnesite particles from mineral ores during the process of flotation. Apart from triggering the hydrophobicity of magnesite particles, these surfactant molecules adsorb to the air-liquid interface of flotation bubbles, changing the interfacial properties and thus affecting the flotation efficiency. The structure of adsorbed surfactants layers at the air-liquid interface depends on the adsorption kinetics of each surfactant and the reformation of intermolecular forces upon mixing. Up to now, researchers use surface tension measurements to understand the nature of intermolecular interactions in such binary surfactant mixtures. Aiming to adapt better to the dynamic character of flotation, the present work explores the interfacial rheology of NaOl mixtures with different nonionic surfactants to study the interfacial arrangement and viscoelastic properties of adsorbed surfactants under the application of shear forces. Interfacial shear viscosity results reveal the tendency on nonionic molecules to displace NaOl molecules from the interface. The critical nonionic surfactant concentration needed to complete NaOl displacement at the interface depends on the length of its hydrophilic part and on the geometry of its hydrophobic chain. The above indications are supported by surface tension isotherms.

Protic ionic liquids based on fatty acids: A mixture of ionic and non-ionic molecules

Fatty acids are long chain carboxylic acids naturally and abundantly found in oils and fats; therefore, they are interesting candidates for protic ionic liquids (PILs) synthesis. Mixtures of carboxylic acids and amines should lead to intermediate proton transfer from the acid to the amine to form PILs, with both ionic molecules (PIL) and non-ionic molecules observed in these mixtures, depending on the nature of the amine. This work studied the physicochemical properties of mixtures between fatty acids and amines, with phase transitions, thermal stability, viscosity, solvation (Kamlet-Taft parameters) and proton transfer evaluated. Our results show that like other carboxylic acids the proton transfer is highly dependent on the structure of the amine, being much higher for primary amines than for tertiary amines. Also, hydroxyl groups on tertiary amines increase the proton transfer. The extent of the proton transfer strongly influences the physicochemical properties of the mixtures, where a larger proton transfer leads to a higher melting point and higher viscosity. Also, mixtures based on highly volatile amines decomposed at low temperatures even when a high degree of proton transfer was observed. Surprisingly, mixtures based on butylamine or triethylamine exhibited high hydrogen bond acceptor capacity and low dipolarity-polarizability which is an unusual characteristics of ionic liquids, potentially opening new solvent application space for ionic liquids.

A framework for understanding the bioconcentration of surfactants in fish.

Surfactants are a class of chemicals released in large quantities to water, and therefore bioconcentration in fish is an important component of their safety assessment. Their structural diversity, which encompasses nonionic, anionic, cationic and zwitterionic molecules with a broad range of lipophilicity, makes their evaluation challenging. A strong influence of environmental pH adds a further layer of complexity to their bioconcentration assessment. Here we present a framework that penetrates this complexity. Using simple equations derived from current understanding of the relevant underlying processes, we plot the key bioconcentration parameters (uptake rate constant, elimination rate constant and bioconcentration factor) as a function of its membrane lipid/water distribution ratio and the neutral fraction of the chemical in water at pH 8.1 and at pH 6.1. On this chemical space plot, we indicate boundaries at which four resistance terms (perfusion with water, transcellular, paracellular, and perfusion with blood) limit transport of surfactants across the gills. We then show that the bioconcentration parameters predicted by this framework align well with in vivo measurements of anionic, cationic and nonionic surfactants in fish. In doing so, we demonstrate how the framework can be used to explore expected differences in bioconcentration behavior within a given sub-class of surfactants, to assess how pH will influence bioconcentration, to identify the underlying processes governing bioconcentration of a particular surfactant, and to discover knowledge gaps that require further research. This framework for amphiphilic chemicals may function as a template for improved understanding of the accumulation potential of other ionizable chemicals of environmental concern, such as pharmaceuticals or dyes.

Study on the adsorption of cement particles on surfactant and its effect on the characteristics of inorganic curing foam for prevention of coal spontaneous combustion in a goaf

In this paper, the adsorption pattern of cement particles to different surfactants was investigated by Zeta potential method, and the adsorption amounts of cement particles on different surfactants were analyzed by Fourier Infrared Spectrometer. Additionally, the expansion ratio, compressive strength, stacking capabilities, and capacity to avert coal spontaneous combustion of inorganic curing foam (ICF) manufactured by various surfactants were tested to analyze the effects of various adsorption behaviors on the performance of ICF. The findings demonstrated that different surfactants affected cement particle Zeta potential in various ways, which was connected to the mode of adsorption of cement particles to various surfactants. After the addition of surfactant, alterations in the zeta potential of the cement particles led to changes in the zero-shear viscosity of the fresh cement slurry. Furthermore, compared to zwitterionic, nonionic, and cationic surfactant molecules, anionic surfactant molecules were absorbed by cement particles in the greatest amounts. The peak areas of CH2/CH3 of the two anionic surfactants in the IR spectra were 19.5 L/g and 9.82 L/g, respectively, while the peak areas of CH2/CH3 of the other surfactants were below 4 L/g. According to the study on the characteristics of ICF, ICF made using a surfactant that had a lot of adsorption had higher compressive strength, a lower expansion ratio, and worse stacking characteristics. The ICF made with various surfactants all had a cooling effect on the coal fire, and after covering the coal, the temperature of the coal was quickly lowered from 300℃ to 100℃. Meanwhile, the surface temperature of ICF prepared with different surfactants was recorded when extinguishing coal fire, and it was found that the thermal insulation property of ICF was better due to the higher expansion ratio of ICF. The purpose of the study in this paper is to provide a new process for the preparation of ICF to prevent coal spontaneous combustion in a goaf and a theoretical guide for the screening of ICF-blowing agents.

Exploring Solvent and Substituent Effects on the Excited State Dynamics and Symmetry Breaking of Quadrupolar Triarylamine End-Capped Benzothiazole Chromophores by Femtosecond Spectroscopy.

We investigate herein the excited state dynamics and symmetry breaking processes in three benzothiazole-derived two-photon absorbing chromophores by femtosecond fluorescence and transient absorption (fs-TA) spectroscopies in solvents of various polarity. The chromophores feature a quasi-quadrupolar D-π-A-π-D architecture comprised of an electron-withdrawing benzothiazole core and lateral triphenylamine donors (Qbtz-H), while the acceptor strength of the central unit is enforced by attached cyano groups (Qbtz-CN) and the electron-donating strength of the arylamine moieties by introduction of peripheral methoxy groups (Qbtz'-CN). Steady state spectroscopy reveals positive solvatochromism, which is mostly pronounced for Qbtz'-CN. Femtosecond spectroscopy of Qbtz-H reveals the coexistence of the Franck-Condon (FC) state and states populated after symmetry breaking (SB) in low-polarity solvents such as toluene and tetrahydrofuran, while the SB state becomes favorable in polar acetonitrile. For the other two molecules possessing a stronger electron-accepting unit and thus more polar excited state, SB takes place even in low-polarity solvents, as shown by fs-TA spectroscopy. Global fitting of the fs-TA spectra together with investigation of the evolution associated spectra (EAS) reveals the existence of an initial FC state in Qbtz-H, in all studied solvents, which relaxes toward Intermediate Charge Transfer (I-CT) and SB states. On the other hand, for Qbtz-CN and Qbtz'-CN in more polar solvents, the FC state undergoes ultrafast relaxation toward symmetry-broken charge transfer (SB-CT) states which in turn show very fast recombination to the ground state. Our measurements confirm that the extent of symmetry breaking is larger for D-π-A-π-D systems with the stronger acceptor core and increases further by increasing electron-donating strength of triarylamine moieties, giving rise to symmetry breaking in these nonionic quadrupolar molecules with ethynylene (triple bond) π-spacers also in less polar solvents.

Interaction of protoporphyrinix (PPIX) and 5-amino levulinic acid (ALA) in nanoemulsion

Nanoemulsion is an interesting and unique fluid system in that it is used to solubilize both ionic and non-ionic molecules. Because of its uniqueness it has been used as a medium for drug delivery. It is therefore used in this work to study the interaction of Protoporphyrin (PPIX) and 5-Amino levulinic acid (ALA). While ALA is a distant precursor of PPIX, PPIX itself is not only a precursor of Heme but also a photosensitizer in the modality of Photodynamic Therapy (PDT). Both compounds are used use in PDT regimen. A steady-state fluorescence technique is used for the study of the interaction of these very important biological compounds. It is found that ALA quenches the fluorescence of PP IX in nanoemulsion. This observed quenching is diffusion controlled. The bimolecular quenching constant, kq, was determined as 2.86x 1010/M-s with an interaction constant, Ka, of 4.48 x 105 with the free energy of interaction, ΔGa of -32.234kJ/mole.

The fluorescence study of the quenching of nanoemulsion by protoporphyrin IX (PPIX)

Nanoemulsion is a unique and versatile fluid that solubilizes both ionic and non-ionic molecules. It has been used extensively for drug delivery. Nanoemulsion, prepared with water-oil-surfactant and co-surfactant, is fluorescent at or the near IR region of electromagnetic spectrum. However, when protoporphyrin (PPIX), a useful photosensitizer in PDT modality, and a poorly water-soluble compound, is introduced into the nanoemulsion medium, the observed fluorescence of the nanoemulsion is quenched. We have used the steady-state fluorescence technique to study the mechanism of this quenching. It is observed that the interaction between nanoemulsion and PPIX is 1:1 and the interaction constant, Ka, is about 2.37 x 105/mol and the Free energy of interactions, Ga, is -30.66 kJ/mol.

Non-ionic polar small molecules induced transition from elastic hydrogel via viscoelastic wormlike micelles to spherical micelles in zwitterionic surfactant systems

• A C18-tailed zwitterionic surfactant supramolecular hydrogel is constructed with OHSB and NaSal. • The non-ionic polar small molecules, TPA1, could control the microstructure and viscoelasticity of zwitterionic hydrogel. • Rheological measurement shows transition from Elastic Hydrogel via Viscoelastic Wormlike Micelles to Spherical micelles. • The microstructure of the system was analyzed by cryo-TEM and cryo-SEM. • The construction and transition mechanism were proposed, stating the detailed controlling process clearly. Supramolecular assembly determines the formation and transformation of soft materials. So far, the construction and transformation of conventional (<C20) zwitterionic surfactant elastic hydrogel have been a challenging and vital issue. In this work, a C18-tailed zwitterionic surfactant supramolecular hydrogel is constructed with N -octadecyl- N , N -dimethyl-3-ammonio-2-hydroxy-1-propane-sulfonate (OHSB) and sodium salicylate (NaSal). The N , N ,2,2-tetramethyl-1, 3-propanediamine (TPA1), as the non-ionic polar small molecules, were chosen to control the microstructure and macro-viscoelasticity of zwitterionic surfactant supramolecular hydrogel. With the addition of TPA1, the rheological properties and microstructural images of the OHSB/NaSal system show that the microstructure has changed from elastic hydrogels via viscoelastic wormlike micelles (WLMs) to spherical micelles. With the N , N , N’ , N’ -tetramethyl-1,3-propanediamine (TPA2), the isomer of TPA1, is added into OHSB/NaSal system in the same concentration, the difference in rheology and microstructure indirectly indicates the influence of hydrogen bonding on self-assembly. By systematically varying components, insight into the intermolecular interaction between OHSB, NaSal, and TPA1 and its effect on the microstructure during aggregation and transition are gained by the complementary use of 1 H NMR, rheological property, cryo-SEM, cryo-TEM, and DLS. We expect it to be a good model for conventional zwitterionic surfactant supramolecular hydrogel and a new method for controlling the internal nanostructure of micelles, which is helpful to understand the construction and finely tune of conventional zwitterionic surfactant supramolecular hydrogel and widen their applications.

Saponins Form Nonionic Lipid Nanodiscs for Protein Structural Studies by Nuclear Magnetic Resonance Spectroscopy.

Structural studies of membrane proteins in native-like environments require the development of diverse membrane mimetics. Currently there is a need for nanodiscs formed with nonionic belt molecules to avoid nonphysiological electrostatic interactions between the membrane system and protein of interest. Here, we describe the formation of lipid nanodiscs from the phospholipid DMPC and a class of nonionic glycoside natural products called saponins. The morphology, surface characteristics, and magnetic alignment properties of the saponin nanodiscs were characterized by light scattering and solid-state NMR experiments. We determined that preparing nanodiscs with high saponin/lipid ratios reduced their size, diminished their ability to spontaneously align in a magnetic field, and favored insertion of individual saponin molecules in the lipid bilayer surface. Further, purification of saponin nanodiscs allowed flipping of the orientation of aligned nanodiscs by 90°. Finally, we found that aligned saponin nanodiscs provide a sufficient alignment medium to allow the measurement of residual dipolar couplings (RDCs) in aqueous cytochrome c.

Overview of Polyethylene Glycol-based Materials with a Special Focus on Core-Shell Particles for Drug Delivery Application.

Polyethylene glycols (PEG) are water-soluble non-ionic polymeric molecules. PEG and PEG-based materials are used for various important applications, such as solvents, adhesives, adsorbents, drug delivery agents, tissue engineering scaffolds, etc. The coating of nanoparticles with PEG forms core-shell nanoparticles. The PEG-based core-shell nanoparticles are synthesized for the development of high-quality drug delivery systems. In the present review, we first explained the basics and various applications of PEGs and PEG-based composites materials and then concentrated on the PEG-based core-shell nanoparticles for biomedical applications, specifically their use in drug delivery.

Effect of Surfactant Concentration and Hydrophobicity on the Ordering of Water at a Silica Surface.

The performance of nonionic surfactants is mediated by the interfacial interactions at the solid-liquid interface. Here we applied sum frequency generation (SFG) vibrational spectroscopy to probe the molecular structure of the silica-nonionic surfactant solution interface in situ, supplemented by quartz crystal microbalance with dissipation monitoring (QCM-D) and molecular dynamics (MD) simulations. The combined studies elucidated the effects of nonionic surfactant solution concentration, surfactant composition, and rinsing on the silica-surfactant solution interfacial structure. The nonionic surfactants studied include ethylene-oxide (EO) and butylene oxide (BO) components with different ratios. It was found that the CH groups of the surfactants at the silica-surfactant solution interfaces are disordered, but the interfacial water molecules are ordered, generating strong SFG OH signals. Solutions with higher concentrations of surfactant lead to a slightly higher amount of adsorbed surfactant at the silica interface, resulting in more water molecules being ordered at the interface, or a higher ordering of water molecules at the interface, or both. MD simulation results indicated that the nonionic surface molecules preferentially adsorb onto silanol sites on silica. A surfactant with a higher EO/BO ratio leads to more water molecules being ordered and a higher degree of ordering of water molecules at the silica-surfactant solution interface, exhibiting stronger SFG OH signal, although less material is adsorbed according to the QCM-D data. A thin layer of surfactants remained on the silica surface after multiple water rinses. To the best of our knowledge, this is the first time the combined approaches of SFG, QCM-D and MD simulation techniques have been applied to study nonionic surfactants at the silica-solution interface, which enhances our understanding on the interfacial interactions between nonionic surfactants, water and silica. The knowledge obtained from this study can be helpful to design the optimal surfactant concentration and composition for future applications.

The facile synthesis of an amphiphilic macrocycle and its “turn-on” dual targets sensing of both Zn2+ and lysosome triggered by supramolecular disassembly

Engineering supramolecular disassembly for “turn-on” chemosensing receives increasingly interests in recent years, but remains less investigated. So far, there is no disassembly triggered bis-targets fluorescent sensors available. Toward this end, we design and synthesize a nonionic amphiphilic macrocyclic molecule (CTB). Two synthetic routes for CTB have been attempted and a facile one is found. At physiological pH, CTB could be able to specifically detect Zn2+ with “turned-on” fluorescence as Zn2+ disassembles its well-dispersed nanoparticle. CTB could stain the living L02 cell and specifically localize at its lysosome organelle, which indicates CTB a promising bis-targets' sensor for further applications.

Molecular investigation on the desorption process of alkane contaminant from fused silica surface in nonionic surfactant solution

In this article, the molecular level investigation on the detachment process of the alkane contaminant from the fused silica surface in nonionic surfactant solution is performed by using molecular dynamics simulation. Three important cleaning parameters including surfactant molecule structure, temperature and surfactant concentration are discussed. We found that the hydrophilic tail of the nonionic surfactant molecule plays a leading role in the desorption process of the oil droplet. The activated chemical activity in surfactant solution with the increasing temperature of solution facilitates the desorption of alkane contaminant. The critical surfactant concentration is vital for cleaning in a real situation. High surfactant concentration can facilitate the desorption of oil droplet in a static solution. The efficiency of water flooding decrease, when the concentration of surfactant is high. Our study can help to understand the cleaning mechanism in surfactant solution and is important for its application in industrial cleaning.

ADSORPTION BEHAVIOUR OF IONIC AND NON-IONIC SURFACTANTS ONTO TALC A NATURALLY HYDROPHOBIC MINERAL-A COMPARATIVE STUDY

In present study, the adsorption behaviour of surfactants which are cationic (hexadecyltrimethylammonium bromide, HTAB), anionic (sodium dodecyl sulphate, SDS) and non-ionic (Triton X-100, TX-100) onto naturally hydrophobic talc were investigated. In this scope, a series of batch adsorption tests at natural pH were performed to determine adsorption isotherms and zeta potential (ZP) measurements of the ionic and non-ionic surfactants onto talc surfaces were measured using electrophoresis technique. To understand the mechanism of the adsorption process, the adsorption of ionic and non-ionic surfactants was studied as a function equilibrium concentration (mol/L). The amount of maximum adsorption of the surfactants onto talc are ordered as in the following: TX-100 (9.0x10-5 mol/m2)&gt;HTAB (8.5x10-5 mol/m2) &gt; SDS (5.32x10-5 mol/m2). Even though both the SDS and talc have negative surface charge, SDS can adsorb onto talc. Moreover, a good correlation was seen between the adsorption isotherms and the zeta potential curves. Considering their adsorption isotherms, the ionic surfactants were showed different adsorption behaviour concerning the non-ionic surfactant molecules. The adsorption isotherms of TX-100 and SDS increase rapidly in a narrow concentration range until the plateau region, while such a sharp increase does not appear for HTAB. The maximum adsorption amount of TX-100 and HTAB is greater than SDS. The results indicate that hydrophobic interaction and hydrogen bonding play a decisive role on the adsorption of non-ionic and anionic surfactants onto talc a naturally hydrophobic mineral, whereas electrostatic interaction becomes more important in the adsorption of cationic surfactant.