The HLD-NAC Model for Mixtures of Ionic and Nonionic Surfactants

The HLD-NAC model has been used as an “equation of state” to predict the properties of microemulsion (μE) systems formulated with either anionic or nonionic surfactants. The model uses the concept of the hydrophilic-lipophilic difference (HLD) to calculate the chemical potential difference of transferring a surfactant from the oil to the aqueous phase; as a function of formulation variables such as type of surfactant, oil, temperature, electrolyte concentration. The value of HLD is used as a scaling parameter to calculate the net and average curvatures (NAC) of the surfactant at the water/oil interface. These curvatures determine the phase volumes, phase transitions, and solubilization capacity of μEs. In this work, the HLD-NAC model is extended to nonideal surfactant mixtures of anionic and nonionic surfactants. The phase behavior of limonene μEs formulated with binary mixtures of sodium dihexyl sulfosuccinate with nonionic nonylphenol ethoxylates and alcohol ethoxylates was used to determine the deviations of the HLD from the ideal mixing behavior. The deviations were fitted using a 2-parameters Margules equation. The results suggests that the deviations in anionic-rich systems are due to the charge shielding effect of nonionic surfactants, and in nonionic-rich systems, the deviations seem to be explained by the increase in hydration of the surfactant headgroups due to the presence of anionic surfactants. When these corrections were used to predict the curvature of dioctyl sulfosuccinate-dodecyl pentaethylene glycol-heptane μEs, the HLD-NAC model corrected for the nonidealities reproduced not only the trends but also the actual range of values reported in the literature.

Degradation of Pesticides Wastewater by Silyl Based Cationic Surfactants

New stable silayl cationic surfactants have been studied for the destruction of toxic organophosphorus pesticides. Hexadecyl, dodecyl trimethyl silane ammonium chloride or iodide surfactants were synthesized and evaluated in the degradation of pesticides such as Diazinon, Malathion or Chlorpyrifos. The hydrolytic efficiency of each surfactant was tested by measuring the kinetics of model substrates cleavage under a pseudo-first order reaction. The iodo silayl based surfactants showed more destructive power than the chloro derivatives. Meanwhile, the hexadecyl moiety showed more effective pesticide degradation than the corresponding dodecyl moiety.

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Effect of Selected Nonionic Surfactants on the Activated Sludge Morphology and Activity in a Batch System

In this study, two nonionic surfactants, one alcohol ethoxylate (AE) and one alkylphenol ethoxylate (APE) were investigated with regard to their influence on the morphology of activated sludge flocs, microbial activity and wastewater treatment efficiency in a laboratory batch system. The experiments were carried out for a range of nonionic surfactants concentrations in wastewater from 5 to 500 mg L⁻¹. Additionally, these results were compared to the data obtained in previous experiments on anionics and performed under the same conditions. Both nonionics tested caused a decrease in the size of activated sludge flocs but they did not affect the shape of the flocs. The circularity index and convexity of flocs remained similar to the control run, containing no surfactant. The presence of nonionic surfactants within the tested concentrations range caused a decrease in biomass activity. In spite of morphological changes of activated sludge flocs and a decrease in microbial activity, only higher concentrations of nonionics in wastewater starting with the level of 50 mg L⁻¹ can induce pinpoint flocs and decrease wastewater treatment efficiency. APE showed a stronger impact on the decrease in floc size and microbial activity than alcohol ethoxylate did. APE was also more difficult to biodegrade than AE. Comparing the efficiency of wastewater treatment (in terms of COD removal) in the presence of nonionic and anionic surfactants at the same concentration of 50 mg L⁻¹, the degree of organic pollutant removal was found to be higher by about 10% for anionics than for nonionics.

Synthesis of Unsymmetrical Bolaform Surfactants with a Sulfonate Group and a Carboxyl Group

Three unsymmetrical bolaform surfactants with different aromatic rings and a ω-carboxyalkyl chain were synthesized and their molecular structures were characterized by ESI–MS and ¹H NMR. The percentages of conversion of alkylation were judged by the iodine value measurements and the effect of reaction temperature on sulfonate content of synthesized products has also been discussed.

Comparison of Surface-Active Properties of (Alkyloxycarbonylmethyl)trimethylammonium Chlorides and Alkyltrimethylammonium Chlorides

Surface-active properties of cleavable surfactants with a betaine ester group—(n-alkyloxycarbonylmethyl)trimethylammonium chlorides, used as separation reagents—were investigated. Critical micelle concentrations, dispersing powers, and foaming powers were comparable to those of alkyltrimethylammonium chlorides with the same total number of carbon atoms. On the other hand, the solubilities of the four hydrophobic dyes N,N-dimethyl-3-nitroaniline, naphthalene, pyrene, and oil orange SS in the former surfactant solutions were equal to or slightly smaller than those in the solutions of the latter surfactants with the same alkyl chain length. The alkali hydrolysis yields of the formers approached 100% in aqueous buffer solution at pH 10 and 25 °C within 10 min, and the yield at pH 9 was dependent on the alkyl chain length. This type of surfactant was also found to be as an efficient separation reagent which disperses carbon black and solubilizes the above dyes into aqueous neutral solution and then separates them instantaneously and almost perfectly as precipitates when a small excess of NaOH is added.

Comparison of QSAR and QSPR Based Aquatic Toxicity for Mixed Surfactants

In the present study, quantitative structure-activity relationship (QSAR) equations were derived using the logarithm of the octanol/water partition co-efficient for the prediction of acute aquatic toxicity of mixed surfactant systems. Further mixed surfactant systems of an anionic surfactant (sodium lauryl sulfate) and several nonionic surfactants (alkyl polyglucoside) of different hydrophobic chain lengths were taken together to calculate the parameter pEC50. Quantitative structure-properties relationship (QSPR) equations based on pC20, and A _min were developed from the surface tension data to predict pEC50 values and compared with QSAR derived pEC50 values to understand the probable mechanisms of action of the mixed surfactants blends for aquatic toxicity. The established QSAR and QSPR equations for mixed surfactants indicate that given blends of surfactants act as a polar narcotic.

Preparation and Application of Fluorinated Cationic Surfactants

Four fluorinated cationic surfactants were prepared by condensing 2,2,3,3, tetrafluoro-1-propyl chloroacetate with stoichiometric amounts of pyridine, 2-hydroxypyridine, 8-hydroxyquinoline and 8-hydroxyquinaldine to produce four quaternary ammonium salts. The surface and biocidal properties of these surfactants were investigated. Surface properties of their solutions including surface tension, critical micelle concentration (CMC), effectiveness (Π_cmc), maximum surface excess (Γ_max) and minimum surface area (A _min) were investigated with respect to different concentrations at 25 °C. Standard free energies of micellization and adsorption of the prepared surfactants in the aqueous solution were studied. The biocidal activity was determined via the inhibition zone diameter of prepared compounds which tested against six strains as a representative group of microorganisms.

Synthesis,Surface Properties and Antimicrobial Activity of Bolaamphiphile/Oppositely Charged Conventional Surfactant Mixed Systems

Four ionic bolaamphiphiles were synthesized from four bolasingle systems and the surface properties of bolasingle systems and bola\oppositely charged conventional mixed surfactant systems were studied. Variations in the structure of the hydrophobic chain of bolaamphiphiles has a great influence on their antimicrobial activities. The bolaform surfactants prepared have significant antimicrobial and antifungal activities relative to their conventional analogues. The Г_∞ (saturated adsorption amount) and A _min (minimum average area per surfactant molecule) of these bolaamphiphiles in both water and 0.1 M NaCl solutions were calculated and CMC of the mixed systems with oppositely charged conventional surfactants in both water and 0.1 M NaCl solutions were determined.

Synergistic Behavior of a Triblock Copolymer with Anionic and Cationic Surfactants in Aqueous Solution

The synergistic behavior of poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO–PPO–PEO) triblock copolymer in aqueous solution with the synthesized anionic surfactants [decyl sulfonate (A10), myristyl sulfonate (A14) and cetyl sulfonate (A16)] and cationic surfactants [decyl pyridinium bromide (C10), myristyl peridinium bromide (C14) and cetyl pyridinium bromide (C16)] was investigated using a surface tension technique at 25 °C. The results show that the CMC values of binary mixtures for anionic and cationic surfactants with the triblock copolymer are lower than that of single surfactants. The synergistic interaction between surfactant molecules and copolymer molecules in binary mixed solution enhance the adsorption of surfactant molecules at the interface. The micellar mole fractions (X _m) and the interaction parameter (β) of these surfactants in mixed micelles were determined.

Optimization of an Alkylpolyglucoside-Based Dishwashing Detergent Formulation

The aim of this work was to formulate and optimize the washing performance of an alkylpolyglucoside-based dishwashing detergent. The liquid detergent was formulated with five ingredients of commercial origin: anionic (linear sodium alkylbenzenesulfonate and sodium laurylethersulfate), nonionic (C₁₂–C₁₄ alkylpolyglucoside) and zwitterionic (a fatty acid amide derivative with a betaine structure) surfactants, and NaCl for viscosity control. In addition to the plate test, other properties were investigated including “cloud point”, viscosity, and emulsion stability. Statistical analysis software was used to generate a central composite experimental design. Then, a second order design and analysis of experiments approach, known as the Response Surface Methodology, was set up to investigate the effects of the five components of the formulation on the studied properties in the region covering plausible component ranges. The method proved to be efficient for locating the domains of concentrations where the desired properties were met.

Synthesis of Ethoxylated Alkyl Sulfosuccinate Surfactants and the Investigation of Mixed Solutions

A series of ethoxylated sodium monoalkyl sulfosuccinate (ESMASS) ester surfactants were prepared by reacting polyethylene glycol (molecular weight 600) with sodium monoalkyl sulfosuccinate (SMASS). The esters were prepared by reacting octyl, lauryl, or cetyl alcohol with sodium sulfosuccinate (SSS) to prepare E(14)SMOSS, E(14)SMLSS, and E(14)SMCSS. The chemical structures of the prepared surfactants were confirmed by Fourier transform infrared (FTIR) and ¹H-NMR spectroscopy. The surface tension of the synthesized surfactants was measured at 25 °C individually or mixing at different molar fractions with sodium dioctyl sulfosuccinate. The surface active properties were calculated and the micellization process of the mixture was investigated. The molar ratio of anionic (SDOSS) and anionic–nonionic surfactant moieties [E(14)SMOSS, E(14)SMLSS, and E(14)SMCSS] in the mixed aggregates were deduced using the regular solution approximation equations. Depending on the critical micelle concentration values measured for each surfactant individually, and as well as the mixed systems, the minimum surface tension was exhibited at a ratio of 0.6 SDOSS:0.4 E(14)SMCSS. The micellar composition of the mixed aggregates were explained and discussed based on the effect of their chemical structures. The activity coefficient (f ₁, f ₂), interaction parameter (β), and ideality of anionic–nonionic mixed aggregates were evaluated.

Synthesis and Biological Activity of 8-Hydroxyquinoline and 2-Hydroxypyridine Quaternary Ammonium Salts

Two series of quaternary cationic surfactant were synthesized by reaction of 8-hydroxyquinoline and 2-hydroxypyridine with long chain alkyl halides (dodecyl, tetradecyl- and hexadecyl-bromide). Surface tension was measured in aqueous solution for different concentrations at 25 °C. Various surface properties of the synthesized surfactants were evaluated, particularly critical micelle concentration (CMC), efficiency (Π_CMC) as well as maximum surface excess (Γ_max) and minimum surface area (A _min). Micellization and adsorption in liquid/air interfaces thermodynamics were investigated. The synthesized cationic surfactants were evaluated for their biocidal activity. All compounds prepared showed good antibacterial and antifungal activities.

The Characteristic Curvature of Ionic Surfactants

Characterizing the hydrophilic-lipophilic nature of a surfactant molecule has been a challenge for colloid scientists and technologists. The hydrophilic-lipophilic balance (HLB), the packing factor, the phase inversion temperature (PIT) and the natural curvature of the surfactant are all terms that seek to address this issue. In this article we build on the hydrophilic–lipophilic difference concept (HLD) (Salager et al. Langmuir, 16, 5534–5539, 2000) to develop a methodology to determine a characteristic curvature (Cc) for ionic surfactants based on the phase behavior of mixed ionic surfactant microemulsions. In essence, the method consists of evaluating the shift in optimal electrolyte concentration as a function of the mole fraction of the test surfactant in a mixture with a reference surfactant, sodium dihexyl sulfosuccinate (SDHS) and applying the appropriate HLD equation for ionic surfactant mixtures to determine Cc. The values of Cc were determined for a range of surfactants, including sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS), sodium naphthenate, and others. The method was also extrapolated to nonionic additives and hydrophilic linkers. It was observed that the calculated values of Cc were similar to those predicted by group contribution models, however the proposed method can be used even for complex surfactant mixtures. Finally, when Cc values were compared to apparent packing factor and HLB values, it was found that Cc is correlated with the apparent packing factor of ionic surfactants, and that Cc correlates with the HLB value for nonionic amphiphiles. The physical interpretation of Cc, and its potential application in the Net-Average Curvature equation of state for oil-surfactant-water systems is discussed.

Characterization and Surfactant-Enhanced Washing Treatability of Drilling Fluids Stored for More than 20 Years

Drilling fluids represent a significant environmental hazard owing to the fact that they are frequently stored in open vessels without any treatment. The drilling fluids studied in this work have been stored for 20–30 years in open cesspits in the state of Tabasco (Mexico). The aim of this work was to characterize the drilling fluids produced in this region and to determine their treatability by means of surfactant-enhanced washing. Two anionic and two non-ionic surfactants (sodium lauryl ethersulfate SLES and sodium dodecylsulfate SDS, ethoxylated nonylphenol ENP and an unknown composition ethoxylated nonionic Surfynol 440 respectively) were employed for surfactant-enhanced washing assessments in the presence of a commercial dispersant. Drilling fluids were contaminated with 135,400 mg of total petroleum hydrocarbons (TPH)/kg soil, including seven polycyclic aromatic hydrocarbons (PAHs) from 1.18 to 57.28 mg/kg. TPH removal efficiencies as high as 55.7% were reached when washing drilling fluids with SDS (4%), followed by ENP 906 (1%), which showed a TPH removal of 52.2%, and ENP itself at a lower dose (0.1%). SLES and S440 gave removal of around 10–15% with the assessed doses.

Pure N-Alkylaminopropionic Acid and N-Alkylaminodipropionic Acid Sodium Salts: Synthesis, Characterization, and Physicochemical Properties

Fourteen pure β-aminopropionic acid amphoteric surfactants were synthesized from methyl acrylate using primary amines. The synthesis was done in two steps. First, Michael addition of a primary amine to methyl acrylate gave two separable addition products. Second, because the resulting esters gave, by the classical saponification procedure, undesired retro-Michael products, they were treated with sodium trimethylsilanolate to give the corresponding pure anhydrous acid salt under mild non-aqueous reaction conditions. Two types of amphoteric surfactants were obtained: the monocarboxylate and the dicarboxylate series. The pure surfactants were characterized by IR, ¹H NMR, and ¹³C NMR spectroscopy. The surfactant critical micelle concentrations were evaluated. From these the Gibbs free energy of micellizations [∆G(–CH₂–)_mic] were calculated. These are related to the methylene units that contribute an average of −1.0 (±0.3) kJ mol⁻¹ for both the monocarboxylate and the dicarboxylate series.

Preparation,Surface-Active Properties and Antimicrobial Activities of Bis(Ester Quaternary Ammonium) Salts

New cationic surfactants, bis-quaternary ammonium salts, were prepared from N,N-dimethylaminoalkyl esters of saturated fatty acids and products of the reactions of epichlorohydrin with primary amines: pentyl-, hexyl- and octylamine. The bis (ester–ammonium) salts obtained were examined in respect to their surface-active properties: critical micelle concentration (CMC), effectiveness of surface tension reduction (γ_CMC), and adsorption efficiency (pC₂₀). All these surfactants showed good water solubility and low critical micelle concentrations of more than two orders of magnitude lower than these of corresponding mono-alkylammonium salts. They also showed good wetting capability, but worse foaming properties. All the surfactants tested were nontoxic to gram-negative bacteria, but some of them inhibited the growth of gram-positive bacteria and yeast.

Synthesis of Cleavable Aryl Sulfonate Anionic Surfactants and a Study of their Surface Activity

A series of cleavable aryl sulfonate anionic surfactants were synthesized from cyanuric chloride, aliphatic amine and H-acid mono sodium salt. Their structures were identified by ¹H NMR, Infrared Spectrum (IR) and Elementary Analysis (EA). Their critical micelle concentrations (CMC) in aqueous solutions at 25 °C were determined by a steady-state fluorescence probe method and a surface-tension method. With the increasing length of the carbon chain, the value of their CMCs and surface tensions under CMC (γ _CMC) initially decreased and then reached a minimum (respectively 2.63 × 10⁻⁵ mol L⁻¹ and 28.29 mN m⁻¹) when the carbon number was 10. The CMC and γ _CMC then increased when the carbon number was increased to 12. The results showed that, compared with sodium dodecyl benzene sulfonate (SDBS), such kinds of surfactants have much lower surface adsorption amounts and greater molecular areas on the aqueous surface.

Syntheses and Characterization of Some Cationic Surfactants

A series of novel cationic surfactants were synthesized from the quaternization of triethyl amine and various long chain alkyl halide. The chemical structure of the prepared compounds was confirmed using elemental analysis, FTIR and ¹H-NMR spectra. The physical properties of the synthesized surfactants including, electrical conductivity, critical micelle concentration, (CMC) and the degree of ionization of the micelle, (β) were studied. The thermodynamic parameters of micelle formation, standard free energy ΔG _m°, enthalpy ΔH _m°, and entropy ΔS _m° were calculated. The results of the surface parameter determination were correlated with their chemical structures. It was found that the hydrocarbon chain length is the main factor which has an effect on the value of the thermodynamic parameters.

Adsorption of Anionic–Cationic Surfactant Mixtures on Metal oxide Surfaces

This research evaluates the adsorption of anionic and cationic surfactant mixtures on charged metal oxide surfaces (i.e., alumina and silica). For an anionic-rich surfactant mixture below the CMC, the adsorption of anionic surfactant was found to substantially increase with the addition of low mole fractions of cationic surfactant. Two anionic surfactants (sodium dodecyl sulfate and sodium dihexyl sulfosuccinate) and two cationic surfactants (dodecyl pyridinium chloride and benzethonium chloride) were studied to evaluate the effect of surfactant tail branching. While cationic surfactants were observed to co-adsorb with anionic surfactants onto positively charged surfaces, the plateau level of anionic surfactant adsorption (i.e., at or above the CMC) did not change significantly for anionic–cationic surfactant mixtures. At the same time, the adsorption of anionic surfactants onto alumina was dramatically reduced when present in cationic-rich micelles and the adsorption of cationic surfactants on silica was substantially reduced in the presence of anionic-rich micelles. This demonstrates that mixed micelle formation can effectively reduce the activity of the highly adsorbing surfactant and thus inhibit the adsorption of the surfactant, especially when the highly adsorbing surfactant is present at a low mole fraction in the mixed surfactant system. Thus surfactant adsorption can be either enhanced or inhibited using mixed anionic–cationic surfactant systems by varying the concentration and composition.

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Environmentally Friendly Vegetable Oil Microemulsions Using Extended Surfactants and Linkers

Microemulsion formation of triglyceride oils at ambient conditions (temperature and pressure) and without the addition of co-oil and/or alcohols is challenging at best. Undesirable phases, such as macroemulsions, liquid crystals and sponge phases, are often encountered when formulating triglyceride microemulsions. The purpose of this study is to investigate the use of extended surfactants, lipophilic linkers, and hydrophilic linkers in enhancing triglyceride solubilization and interfacial tension reduction. We have studied two classes of extended surfactants, linear alkyl polypropoxylated sulfate (LAPS) surfactants and linear alkyl polypropoxylated ethoxylated sulfate (LAPES) surfactants. Linkers evaluated were oleyl alcohol (lipophilic linker), sodium mono and dimethyl naphthalene sulfonate (SMDNS), and polyglucoside (hydrophilic linkers). Oils studied include olive, peanut, soybean, canola and sunflower oils. The effect of electrolyte concentration on microemulsion phase behavior was studied. The microemulsion “fish” diagram was obtained by plotting the total surfactant and linker concentrations versus the electrolyte concentration. We were able to form Winsor Type I, II, III and IV microemulsions at ambient conditions and without co-oil or short and medium chain length alcohol addition. Winsor Type III and IV triglyceride microemulsions are particularly useful in numerous applications such as cosmetics, vegetable oil extraction and soil remediation.