Anionic Sodium Lauryl Sulfate Research Articles

Pillarization of Sumatera Bentonite by Sodium-assisted As Effective Adsorbent of Anionic Surfactants Sodium Lauryl Sulphate (SLS) Waste

In this work, the Sumatera bentonite was sodium-pillarized in a new low-temperature and restricted time preparation route and then applied in anionic surfactant sodium lauryl sulphate removal. Structure characterization used Fourier Transform Infra Red (FT-IR), Scanning Electron Microscope - Energy Dispersive X-ray (SEM-EDX), X-ray Diffraction (XRD), and Brunauer–Emmett–Teller (BET) analysis. A strong peak at 22° and 35.66° in XRD analysis was detected as Sodium-pillar that increased crystallinity, then the functional changes of dehydration in lattice structure were detected in 1013 cm−1 by FTIR analysis. The morphology and compositional transformation were analyzed by SEM-EDX and BET analysis, denoted by increasing particle shape and sodium intercalant composition homogeneity. Moreover, the surface area increased from 61.791 to 66.086 m2/g. The sodium lauryl sulphate adsorption by bentonite-Na reached maximum capacity at 8.403 mg/g, which is higher than the pristine bentonite (5.747 mg/g) under the optimum condition. The adsorption mechanism is feasible, endothermic, and conformed to the pseudo-second-order and Freundlich adsorption model. The new route proposed for sodium intercalation effectively improves the Sumatera bentonite adsorption ability to remove sodium lauryl sulphate waste. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Toxicity of Different Types of Surfactants via Cellular and Enzymatic Assay Systems.

Surfactants have a widespread occurrence, not only as household detergents, but also in their application in industry and medicine. There are numerous bioassays for assessing surfactant toxicity, but investigations of their impact on biological systems at the molecular level are still needed. In this paper, luminous marine bacteria and their coupled NAD(P)H:FMN-oxidoreductase + luciferase (Red + Luc) enzyme system was applied to examine the effects of different types of surfactants, including cationic cetyltrimethylammonium bromide (CTAB), non-ionic polyoxyethylene 20 sorbitan monooleate (Tween 80) and anionic sodium lauryl sulfate (SLS), and to assess whether the Red + Luc enzyme system can be used as a more sensitive indicator of toxicity. It was shown that the greatest inhibitory effect of the surfactants on the activity of luminous bacteria and the Red + Luc enzyme system was in the presence of SLS samples. The calculated IC50 and EC50 values of SLS were 10-5 M and 10-2 M for the enzymatic and cellular assay systems, respectively. The results highlight the benefits of using the enzymatic assay system in ecotoxicology as a tool for revealing surfactant effects on intracellular proteins if the cellular membrane is damaged under a long-term exposure period in the presence of the surfactants. For this purpose, the bioluminescent enzyme-inhibition-based assay could be used as an advanced research tool for the evaluation of surfactant toxicity at the molecular level of living organisms due to its technical simplicity and rapid response time.

Hydroquinone loaded solid lipid nanoparticles comprised of stearic acid and ionic emulsifiers: Physicochemical characterization and in vitro release study

Solid lipid nanoparticles (SLNs) were successfully prepared using stearic acid and cationic/anionic emulsifiers by ultrasonication method. The model drug hydroquinone (HQ) which is used for the treatment of hyperpigmentation was loaded into SLNs. HQ loaded SLNs help to overcome drawbacks of hydroquinone including instability due to its rapid oxidation and its severe side effects on the skin. Six free SLN formulations (without HQ) and six HQ loaded SLN formulations were prepared using stearic acid and various concentrations (5 %, 10 % and 15 %) of cationic emulsifier cetyltrimethylammonium bromide (CTAB) and anionic emulsifier sodium lauryl sulphate (SLS). The detailed physicochemical characterization of SLNs was performed using a combination of light scattering, microscopic, calorimetric and spectroscopic techniques. All the prepared SLNs were in nanometer range (150–275 nm) and contain stearic acid in stable polymorphic form. The drug in vitro release behaviour from SLNs was studied using novel electrochemical method based on differential pulse voltammetry (DPV). HQ entrapment increases with increase in emulsifier concentration. CTAB stabilized SLNs displayed continuous prolonged release of HQ whereas, SLS stabilized SLN at higher concentration (15 %) gives burst release of HQ. The burst release can be correlated with smallest particle size of HQ-SLNs, lowest crystallinity and partitioning of drug into aqueous emulsifier phase at higher SLS concentration. Thus validated electrochemical DPV method proved to be highly applicable for quantification of HQ in SLN and release behaviour of HQ from SLNs.

Investigation of surfactant effect during synthesis of magnesium oxide nanoparticles from bittern using ultrasonic destruction process

Magnesium oxide (MgO) nanoparticles have been widely used in a variety of applications because of their good surface reactivity. Magnesium oxide from bittern has a larger surface area compared to magnesium oxide from calcined magnesite and magnesium ions precipitation from bittern using sodium hydroxide has higher purity than using calcium hydroxide or ammonium hydroxide. In this research, sodium hydroxide was added to a bittern solution obtaining magnesium hydroxide precipitate, followed by the calcination process to produce magnesium oxide. Nano magnesium oxide was synthesized by the ultrasonic destruction process using ethanol and 2-propanol as media. In this study, sonication time and particle concentration effect on the ultrasonic destruction process were investigated. During the process, the sonication time was varied between 8, 16, 32, 64, and 128 minutes while the magnesium oxide concentration was varied between 1 %, 2 %, and 3 %. Increasing sonication time and particle concentration will decrease the particle size. The previous study shows that particles with very small sizes tend to have an agglomeration effect. The aim of this work is to optimize nano magnesium oxide production from bittern. Surfactant addition was also studied to prevent agglomeration between particles. Four types of surfactant namely anionic (sodium lauryl sulfate), cationic (cetyl tri-methyl-ammonium bromide), amphoteric (fatty acid amido alkyl betaine), and non-ionic (nonylphenol 10 ethoxylated) with a concentration of 1 % and a volume of 0.125 ml were added during the second ultrasonic destruction process. All types of surfactants have a positive effect to prevent agglomeration during the ultrasonic destruction process, with the amphoteric surfactant having the highest performance

О влиянии ПАВ на байкальскую олигохету Mesenchytraeus bungei Michaelsen

Pollution of natural objects with surfactants is relevant, including for the lake Baikal. Here, until the near future, there was a constant increase in the tourist flow and, as a result, the ingress of these pollutants into the reservoir. First of all, the inhabitants of the littoral zone come into contact with the incoming pollutants. In this regard, the work evaluated the effect of surfactants on the survival rate of the Baikal endemic oligochaetes Mesenchytraeus bungei Michaelsen, 1901. These enchitreids are a common species. They are widespread throughout the lake from the water's edge to the deepest depths. Therefore, M. bungei is recommended as an indicator object for ecological monitoring of the lake Baikal. The tested compounds are representatives of different types of surfactants: anionic – sodium lauryl sulfate, cationic –cetyltrimethylammonium bromide and nonionic – tween-80. Baikal oligochaetes M. bungei Michaelsen, 1901 were collected in July – August 2020 in the splash zone of Lake Baikal in settlement Bolshiye Koty (South Baikal). Enchitreid about 1.8-2.0 cm long was used in the experiments. After adaptation to laboratory conditions (2 days with water aeration using a microcompressor), further incubation was carried out in glass or plastic cages with nonsterile Baikal water at a temperature of 8–10 °C and an illumination of 250-300 lux. River sand was placed at the bottom, the layer thickness of which was 0.8-1.5 cm. Baikal oligochaetes M. bungei Michaelsen, 1901 turned out to be sensitive to the anionic surfactant sodium lauryl sulfate and cationic cetyltrimethylammonium bromide at a content of 0.005-0.006 mM. So, with the addition of 0.006 mM sodium lauryl sulfate for 3 days of the experiment, the proportion of dead individuals of the test object was 40%, at 0.0125 mM – 60%, at 0.025 mM – 90%, and at 0.05 mM complete death of all enchitreid individuals was observed. Adding CTAB at a concentration of 0.005 mM increased the proportion of dead oligochaetes to 40%. TAB twice – up to 0.01 mM – led to the death of all worms. The nonionic surfactant tween-80 did not have a negative effect on the Baikal oligochaetes in the concentration range from 1 to 60 mM. The tested surfactants to reduce the degree of their effect on the survival of oligochaetes can be arranged in the following row: cetyltrimethylammonium bromide (LC100 = 0.01 mM)> sodium lauryl sulfate (LC100 = 0.05 mM)> tween-80 (harmless up to 60 mM inclusive).

The Influence of Ionic and Nonionic Surfactants on the Colloidal Stability and Removal of CuO Nanoparticles from Water by Chemical Coagulation.

The widespread use of copper oxide nanoparticles (CuO NPs) and surfactants in various consumer products makes it likely that they coexist in aqueous environments, making it important to study the effects of surfactants on the fate and transport behavior of CuO NPs. The present study aims to investigate the influence of anionic sodium lauryl sulfate (SLS) and nonionic nonylphenol ethoxylate (NPEO, Tergitol NP-9), on CuO NPs adsorption, aggregation, and removal from water by the coagulation process. The result of the sorption study indicates that both surfactants could be adsorbed on the surface of CuO NPs, and that SLS remarkably decreases the ζ potential as well as the hydrodynamic diameter (HDD) of CuO as compared to NP-9. The kinetic aggregation study showed that both SLS and NP-9 reduced the HDD of CuO NPs and retarded the settling rates at surfactant concentrations above 0.015% (w:v) over a 24 h-period. Moreover, enhanced aggregation of CuO NPs was observed in two environmental waters as compared to pure water, which could be related to their high ionic strength. The addition of surfactants in natural waters has been shown to reduce the aggregation and sedimentation of CuO; however, the reductive effect of SLS was more pronounced than that of NP-9. Finally, the coagulation results showed that the removal efficiencies of CuO, Cu2+, and the surfactant in all tested waters at optimum ferric chloride dosage reached around 98, 95, and 85%, respectively. Furthermore, the coagulation mechanism revealed that the combination of charge neutralization and adsorptive micellar flocculation (AMF) might be involved in the removal of both pollutants. The results of the present study provide new insight into the environmental behavior of coexisting NPs and surfactants in wastewater treatment processes.

Facile synthesis of phase pure ZnAl2O4 nanoparticles for effective photocatalytic degradation of organic dyes

The present work focuses on the surfactant mediated synthesis of ZnAl2O4 nanoparticles (1−3) using sol–gel method. 1 has been synthesized without any surfactant and during the synthesis of 2 and 3 cationic (cetyltrimethylammonium bromide) and anionic (sodium lauryl sulfate) surfactant, respectively, have been added. 1–3 have been characterized by P-XRD, FT-IR, SEM, SAED, TEM and BET techniques which suggest that surfactant reduces the particle size of ZnAl2O4 nanoparticles to half (12 nm in 1, 6 nm in 2 and 3). Zeta (ζ) potential measurements have been performed to determine the surface charges of all the samples. Moreover, the photocatalytic activities of these ZnAl2O4 nanoparticles have also been investigated. 2 exhibits better adsorption (28–41%) and degradation (97–99%) efficiency for anionic dyes due to high surface area (129.62 m2 g−1) and positively charged surface (ζ potential 30.06 mV). Radical trapping experiments suggest O2− and OH to be the major reactive species for the degradation of dyes.

Concentration, salt and temperature dependence of strain hardening of step shear in CTAB/NaSal surfactant solutions

By measuring stress relaxation following a step strain, we find that strain hardening is prevalent over a temperature range of 15–25 °C for a solution of cetyl trimethylammonium bromide (CTAB) with the added hydrotrope sodium salicylate (NaSal) at hydrotrope-to-surfactant concentration ratios (CS/CD) between 0.5 and 3.0. The extent of strain hardening upon nonlinear deformation varies nonmonotonically as a function of salt-to-surfactant ratio for different temperatures. As the strain amplitude is progressively increased, a transition from strain hardening to softening or linear response is observed at strains that are dependent on temperature and concentration. Strain hardening was also found in CTAB when using sodium 3-Hydroxy-2-naphthoate as a hydrotrope with CTAB, but solutions of anionic sodium lauryl sulfate surfactants in salt with no hydrotrope showed no strain hardening, indicating that the hydrotrope is critical to obtaining strain hardening in step strains. The results indicate a stress relaxation mechanism that is more complex than that of simple disentanglement and micelle breakage and rejoining, possibly involving strain-induced associations between micelles facilitated by hydrotropes that may act as linkers.

Preparation of an Injectable Macroporous α-TCP Cement

One of the most important characteristics of calcium phosphate cements is their resorbability when implanted in the body. However, the in vivo resorption rate is slow due to the lack of intrinsic open porosity. In this study, macroporous structures were obtained by mixing alpha-tricalcium phosphate (α-TCP) cement with a foamed liquid phase containing different concentrations of sodium hydrogen phosphate and non-ionic (Lutensol) or anionic (Sodium Lauryl Sulfate) surfactant. The cement paste was prepared by hand mixing in a system of two syringes connected by a polyvinyl chloride (PVC) valve, an environmentally friendly method. Solutions with Lutensol (L110) showed greater foamability than solutions with Sodium Lauryl Sulfate (SLS). Scanning Electron Microscopy characterization helped verify that the prepared samples showed a macroporous interconnected structure, and X-ray diffraction analysis evidenced the transformation of α-TCP into calcium deficient hydroxyapatite (CDHA). This study suggests that the calcium phosphate cement samples foamed with Lutensol may be further evaluated as suitable materials for bone filling.

Fast and efficient cesium removal from simulated radioactive liquid waste by an isotope dilution–precipitate flotation process

The performance of an isotope dilution–precipitate flotation process for Cs-137 removal from low-level liquid radioactive waste is evaluated in this study using sodium tetraphenylborate (NaTPB) as the precipitating agent. In absence of Fe(III), neither the anionic sodium lauryl sulfate (SLS) nor the cationic cetylpyridinium chloride (CPC) could float the CsTPB precipitate over the studied pH range of 2.5–11.9. It is proposed that iron oxide coated CsTPB particles are formed upon addition of Fe(III) solution and their floatability is greatly dependent on the solution pH and the Fe(III) content. At the optimum conditions, remaining Cs-137 activity values <1.3nCi/L (SLS, pH ∼6.8) and <2.3nCi/L (CPC, pH ∼10.2) are achieved from radioactive wastewater within half a minute which are below its discharge limits. The mechanism of flotation is proposed and cesium removal is suggested to proceed via flotation of iron oxide coated CsTPB. Flotation technique is compared to other conventional solid–liquid separation processes (decantation, centrifugation and filtration) for separation of the iron oxide coated CsTPB particles. The results showed that the best separation was attained by flotation process. The data obtained by the present combined process, precipitation followed by flotation, for Cs-137 from radioactive wastewater are also compared to those reported by other treatment methods. Based on the data obtained, the combined process has great potential as a radioactive wastewater treatment technology.

Interfacial Composition, Solubility, and Solubilization Capacity of Microemulsions Containing Cationic Gemini and Anionic Surfactants

Synergistic effects of cationic gemini 1,4-bis(3-dodecylimidazolium-1-yl) butane bromide (C12–4–C12)Br2 and anionic sodium lauryl sulfate (SLS) on the interfacial composition, solubility, and solubilization capacity of the microemulsions were investigated. When the mole fractions of (C12–4–C12)Br2 in a (C12–4–C12)Br2 and SLS mixture (X(C12–4–C12)Br2) is in the ranges of 0.7 to 1 and 0 to 0.1, the three-phase microemulsion region appears. The solubilization capacity (SP*) of the microemulsions containing both (C12−4−C12)Br2 and SLS surfactants become much greater in contrast to the microemulsions that are either (C12–4–C12)Br2-based or SLS-based. The solubilization capacity (SP*) reaches a peak value at X(C12–4–C12)Br2 = 0.7. The effects of oils, NaCl contents, and temperatures, on the oil +(C12–4–C12)Br2 + SLS + butan-1-ol + aqueous NaCl microemulsion system’s e–β phase diagrams were also discussed.

Surfactant-Mediated Dissolution of Metformin Hydrochloride Tablets: Wetting Effects Versus Ion Pairs Diffusivity

The aqueous solubility of metformin (pKa: 2.8 and 11.5) in the pH range of 1.2-6.8 is 300 mg/mL. Thus, the dissolution of metformin hydrochloride tablets should be pH independent. However, 850 mg metformin hydrochloride tablets dissolved more slowly in pH 1.2 and 4.5 dissolution media than in pH 6.8 medium. It is hypothesized that the additional protonation of metformin at the acidic pH results in higher solvation and a larger hydrodynamic radius, leading to slower diffusion and dissolution. This hypothesis was supported by the observation that cationic metformin and anionic sodium lauryl sulfate (SLS), 0.1% (w/v), formed an insoluble salt (1:2 molar ratio) at pH 1.2 and 4.5, but not at pH 6.8. SLS at 0.01% (w/v) in all three media enhanced metformin dissolution. The slower metformin dissolution at pH 1.2 and 4.5 media with SLS can be attributed to the formation of metformin-lauryl sulfate (Met-LS) (1:2 and 1:1) ion pairs, which are more hydrophobic than Met-LS (1:1) ion pairs at pH 6.8. Slower metformin diffusivity in pH 4.5 with 0.05% (w/v) SLS was observed by diffusion-ordered spectroscopy nuclear magnetic resonance. Improved metformin wetting by SLS outweighed the lower diffusivity of metformin-LS ion pairs because similar enhancement in dissolution was noted with 0.5% (w/v) nonionic polysorbate 80.

Soy-Based Surface Active Copolymers As a Safer Replacement for Low Molecular Weight Surfactants

Environmentally friendly soybean-based polymeric surfactants (SBPS) were synthesized using cationic polymerization of a vinyl ether monomer derived from soybean and tri(ethylene glycol) ethyl vinyl ether. The ability of SBPS to form micelles that solubilize hydrophobic molecules has been shown. Micellar “capacity” (size of micellar interior) increased with increasing polymeric surfactant concentration and temperature. The obtained results provide evidence for potential use of SBPS as a safer replacement for low molecular weight surfactants in the solubilization of poorly soluble ingredients in cosmetics. The macromolecules developed can be used as both a surface active agent and an additive that enhances the surface activity of low molecular weight surfactants (for example, anionic sodium lauryl sulfate) in personal-care products.

Interaction of Natural Dye (Allium cepa) with Ionic Surfactants

Allium cepais a natural dye that has been extracted from onion skin with the help of soxhlet apparatus. The pigment in the dye pelargonidin was found to be 2.25%. The interaction of the dye with ionic surfactants, namely, cationic surfactant (cetyltrimethylammonium bromide) and anionic (sodium lauryl sulphate) has been studied by spectrophotometrically, conductivity, and surface tension measurements. The thermodynamic and surface parameters have been evaluated for the interaction process. The results indicate{surfactant-dye}complex formation and domination of adsorption in comparison to micellization.

Experimental Study of CMC Evaluation in Single and Mixed Surfactant Systems, Using the UV–Vis Spectroscopic Method

AbstractIn this study, the critical micellar concentration (CMC) of anionic, cationic and nonionic surfactants was determined using the UV–Vis spectroscopic method. Sodium lauryl sulfate (SDS) as anionic, hexadecyl‐trimethyl‐ammonium bromide as cationic, tert‐octylphenol ethoxylates TOPEON (with N = 9.5, 7.5 and 35) and lauryl alcohol ethoxylate (23EO) as nonionic surfactants have been used. Concentration of surfactants varies both from below and above the CMC value in the pyrene solution. In addition, the amount of the CMC was determined using the values from the data obtained from the graph of absorbance versus concentration of surfactants. A comparative study was conducted between the results of the present study and the literature which shows a good agreement, in particular for TOPEO9.5 and LAEO23. Furthermore, the CMC value of SDS (as an ionic surfactant) in the presence of nonionic surfactants was also examined. The result reveals that with addition of small amount of nonionic surfactant to the anionic SDS surfactant, a decline in the CMC value of the anionic–nonionic system relative to the CMC of pure anionic surfactant was observed. In addition and for the first time, the effect of UV irradiation on the size of the micelle formations was studied. It was found that UV irradiation causes the formation of smaller micelles which is of prime concern in membrane technology.

Formulation, in vitro, and in vivo evaluation of matrix-type transdermal patches containing olanzapine

Transdermal patches of olanzapine were aimed to be prepared to overcome the side effects by oral application. The strategy was formulation of eudragit-based polymeric films to prepare transdermal patches by using nonionic (span-20), anionic (sodium lauryl sulfate), cationic surfactant (benzalkonium chloride), and vegetable oil (olive oil) as permeation enhancers. The patches were subjected to physicochemical, in vitro release and ex vivo permeation studies. On the basis of in vitro release performance, ERL 100:ERS 100 in the ratio of 3:2 was selected for incorporation of permeation enhancers. The permeation studies showed that formulation containing 10% span 20 (OD3) exhibited greatest cumulative amount of drug permeated (19.02 ± 0.21 mg) in 72 h, so OD3 was concluded as optimized formulation and assessed for pharmacokinetic, pharmacodynamic, and skin irritation potential. In vivo studies of optimized olanzapine patch in rabbit model revealed prolongation of action with Frel 116.09% during 72-h study period. Neuroleptic efficacy of transdermal patch was comparable to oral formulation during rotarod and grip test in Wistar albino rats with no skin irritation. Thus, developed formulation of olanzapine is expected to improve the patient compliance, form better dosage regimen, and provide maintenance therapy to psychotic patients.

Fluorescence quenching of 1- and 2-naphthols by Cu 2+ in anionic micelle

The fluorescence quenching behaviour of naphthols by copper ion has been studied in different concentration of anionic sodium lauryl sulphate micelle. Various quenching processes have been analyzed to explain the quenching efficiency. The quenching behaviour of naphthols and naphtholates explained by a biphasic model consisting of two phases i.e.(a) quenching spheres containing the excited fluorophores and the quenchers resulting in transient component (for ROH*) and (b) the bulk phase where quenching is dynamic or diffusional (for RO¯*). The probable number of quenchers present in the quenching sphere of action has been calculated.

A Study on the Vinyl Acetate‐co‐Butyl Acrylate Latexes in the Presence of N‐Methylol Acrylamide and Mixed Type Emulsifiers

AbstractSummary: The properties of copolymer latexes depend on the copolymer composition, polymer morphology, initiator, polymerization medium and colloidal characteristics of copolymer particles. Poly(vinyl acetate‐co‐butyl acrylate) latexes with N‐metylol acrylamide were prepared by applying semicontinuous emulsion polymerization. The systems studied were (a) the mixture of anionic sodium lauryl sulfate ether (SELES) with nonionic 30 moles ethoxylated nonyl phenol (NP 30) (50:50), (b) the mixture of anionic sodium lauryl sulfate ether (SELES) with nonionic 30 moles ethoxylated nonyl phenol (NP 30) (70:30), and (c) anionic sodium lauryl sulfate ether (SELES) (100%). The effects of the emulsifier and emulsifier composition on the physicochemical properties of obtained vinyl acetate‐co‐butyl acrylate latex properties in the presence of N‐methylol acrylamide initiated by ammonium persulfate were investigated.

Kinetics of the acid hydrolysis of isoproturon in the absence and presence of sodium lauryl sulfate micelles

Kinetics of the hydrolysis of isoproturon by hydrochloric acid has been studied spectrophotometrically in the absence and the presence of anionic sodium lauryl sulfate (NaLS) micelles. The anionic micelle was found to increase the rate of reaction. The reaction followed first-order kinetics with respect to isoproturon and was linearly dependent upon [HCl]. In both aqueous and micellar pseudophases, the reaction was started with the protonation of the amino group of isoproturon followed by attack of water to yield phenylcarbamic acid and the corresponding amine, thus obeying the addition–elimination mechanism. The surfactant decreased the activation entropy. The binding constant in consistence with the rate constants was evaluated on the basis of pseudophase ion-exchange model. The added salts (NaCl and KCl) decreased the rate of reaction due to the exclusion of H+ from micellar surfaces.

Effect of micellar aggregates on the kinetics of oxidation of α-aminoacids by chloramine-T in perchloric acid medium

The kinetics of oxidation of some α-aminoacids viz. alanine, phenylalanine and valine by chloramine-T in HClO 4 medium have been investigated in absence and in presence of three types of surfactants, viz. an anionic (sodium lauryl sulphate), a cationic (cetyltrimethylammonium bromide) and a non-ionic (polyoxyethylene (23) lauryl ether, commonly known as Brij 35) surfactant. In absence of surfactant, the rate of oxidation may be represented as, d [ chloramine-T ] d t = k [ chloramine-T ] [ aminoacid ] 1 + K [ H + ] where k and K are the constants. The presence of a small amount of any surfactant well below its critical micelle concentration strongly enhanced the rate of reaction suggesting a premicellar aggregation. The kinetic data have been analysed in terms of earlier reported models for micellar catalysis. The binding constants between the reactants and the surfactant evaluated from the two models proposed by Piszkiewicz and Raghvan and Srinivasan are in good agreement.