Cetylpyridinium Chloride Micelles Research Articles

Antibiotic entrapment in antibacterial micelles as a novel strategy for the delivery of challenging antibiotics from silica nanoparticles

Silica materials are popular in biomedical applications as composites and drug delivery platforms due to their low toxicity and biocompatibility. Mesoporous silica nanoparticles are attractive drug delivery systems based on their porous silica framework with high surface area. In the preparation of mesoporous silica frameworks, most commonly, MCM-41, the efficient removal of the template responsible for introducing porous networks, cetyltrimethyl ammonium bromide (CTAB), is a critical step due to the template's high toxicity in the environment and human health. In this work, we present a new one-pot approach of introducing challenging antibiotics within a silica framework without the need of toxic templates, but instead using micelle formation by an antibacterial agent. We demonstrate that micelles formed by cetylpyridinium chloride (CPC), a known antibacterial agent, entrap antibiotics such as rifampicin and ciprofloxacin. Extensive NMR studies elucidate the precise localisation of the antibiotic within the CPC micelle. Ciprofloxacin is placed between the outer and palisade region while rifampicin is located further into the hydrophobic CPC micelle core. In both cases, the formation of the silica framework can be built around the CPC-antibiotic loaded micelles. The resulting silica nanoparticles show loading of both CPC and antibiotic agents, porosity and dual antibacterial release upon disruption of the micelle within the silica framework. The design not only provides a strategy of a therapeutic design to form porous frameworks but also highlights the potential of precise antibiotic dose and release in nanoparticle systems.

Fabrication of a novel composite gel bead to reclaim methyl orange from a binary dye mixture: An active role of adsolubilization phenomenon

The present work demonstrates a novel protocol in accordance with the reduce, reuse, and recycle principle of waste management rules for dye wastewater treatment as well as selective extraction of desired dye. Here two model dyes viz., methyl orange (MO) (an anionic dye) and methylene blue (MB) (a cationic dye) have been considered as the components of dye wastewater, and alginate-xanthan (Alg-Xan) biopolymer composite hydrogel beads modified with a cationic surfactant such as cetylpyridinium chloride (CPC), as the sorbent material. CPC bilayers on Alg-Xan composite surface showed excellent MO uptake performance (>85-90%) via adsolubilization when the MO is present alone or in a binary mixture with MB. On the other hand, MB got partially transferred (~30-50%) to the solid surface through diffusion phenomenon both in the presence (~50%) and absence (~30%) of MO. After the accumulation of the dye molecules, MO can be easily reclaimed (>90%) using 1-butanol as the extracting solvent; however, no detachment of MB from the solid surface takes place. The stability and suitability of the hydrogel beads were investigated under different operating conditions. Furthermore, Alg-Xan-CPC composite beads have been characterized using FTIR, SEM analysis, and particle size distribution. The newly developed Alg-Xan-CPC composite beads show good reusability up to four cycles and they perform well in real wastewater (~95% recovery of MO). The novelty of the current research includes the synthesis of a CPC micelle anchored biopolymer adsorbent, which is capable of attracting both the cationic and anionic dyes from water bodies, followed by extractive reclamation of the anionic dye only. The application of biopolymers for wastewater treatment and resource recovery from the waste stream is undoubtedly a sustainable environmental remediation option. Hence, this research work is expected to present a novel application of biopolymers for dye wastewater mitigation as well as reclamation of desired useful dye.

Interaction of metanil yellow dye with cationic surfactants: Conductometric and spectroscopic studies

Conductometric and spectroscopic methods were used to examine the interactions among the cationic surfactants, tetradecyltrimethylammonium bromide (TTAB) and cetylpyridinium chloride (CPC), and the anionic azo dye metanil yellow (MY) in an aqueous solution. The standard Gibb’s energy (ΔGm0), enthalpy (ΔHm0), and entropy (ΔSm0) of micellization were determined with the help of the equilibrium model. With temperature rise, the critical micelle concentration (cmc) increases because of the interruption of the organized water (WR) molecules enclosing the surfactant’s hydrophobic groups. As the total carbon atoms of the hydrophobic group are more in CPC than TTAB, a considerable fall in cmc value was observed. The presence of MY caused a higher degree of ionization (α) of micelles of TTAB and CPC. The negative values of ΔGm0 and ΔHm0 for both the surfactants in WR and aqueous MY solution (WR-MY) show that the micellization process is spontaneous and exothermic. As indicated by the -TΔSm0 values, which were found to be greater than ΔHm0 values, the entropy gain is typically what regulates the micellization process and the micellization was found to have a negative heat capacity (ΔCp,m0). UV–Visible spectra show that CPC has a higher binding constant (Kb) value as compared to TTAB implying that CPC has a comparatively greater binding affinity with MY dye in aqueous media (WR). The decreasing value of ΔGb for CPC indicates that the chance for the MY–CPC complex formation is more than that of the MY–TTAB complex. As shown by the rise in absorbance values as surfactant concentrations increase, a large number of the MY molecules are attracted to TTAB and CPC micelles.

Inhibition of Staphylococcus aureus and Pseudomonas aeruginosa biofilms by quatsomes in low concentrations.

Staphylococcus aureus and Pseudomonas aeruginosa are primary pathogens in chronic rhinosinusitis (CRS), and the presence of S. aureus and P. aeruginosa biofilms has been associated with negative outcomes after surgery. This study investigated the inhibition effect of cetylpyridinium chloride (CPC)-quatsomes at low concentrations on both S. aureus and P. aeruginosa biofilms in vitro, as well as their toxicities towards cultured human airway epithelial (NuLi-1) cells. S. aureus ATCC 25923 and P. aeruginosa ATCC 15692 were used to establish biofilms. CPC-quatsome and CPC micelle solutions at concentrations of 0.01%, 0.025%, and 0.05% were prepared. AlamarBlue was used to test the viability of both planktonic S. aureus and P. aeruginosa and their biofilms after treatment for 5 min and 2 h, respectively. Confocal laser scanning microscopy (CLSM) was used to investigate the interactions between CPC-quatsomes and S. aureus and P. aeruginosa biofilms. A lactate dehydrogenase (LDH) assay was used to determine the toxicity of CPC-quatsomes on NuLi-1 cells. CPC-quatsome and CPC micelle solutions had significant inhibition effects at all tested concentrations on planktonic S. aureus and P. aeruginosa and their biofilms after 5-min exposure ( P < 0.05). In the CLSM study, different interactions between CPC-quatsomes and S. aureus or P. aeruginosa biofilms were observed. After 2-h treatment, the size of S. aureus biofilms decreased, while the number of dead bacteria increased in P. aeruginosa biofilms. Neither CPC-quatsomes nor CPC micelle solutions showed significant toxicity on NuLi-1 cell at all tested CPC concentrations ( P < 0.05). CPC-quatsomes at low concentrations inhibited S. aureus and P. aeruginosa in both planktonic form and biofilms. No adverse effects on NuLi-1 cells were observed, indicating their promising potential in the treatment of CRS. Impact statement Staphylococcus aureus and Pseudomonas aeruginosa biofilms are significant contributors to chronic rhinosinusitis (CRS), and are associated with poor prognosis. The killing effect of CPC-quatsomes on S. aureus biofilm at or above the CPC concentration of 0.5% (5 mg/mL) has been reported previously. This is the first study that showed the significant inhibition effect of CPC-quatsomes at low concentrations on both S. aureus and P. aeruginosa biofilms in vitro, and no adverse effects towards cultured human airway epithelial (NuLi-1) cells. In our study, CPC-quatsomes at concentrations of 0.01%, 0.025%, and 0.05% had significant inhibition effects on both planktonic and biofilms of S. aureus and P. aeruginosa. The result of this study indicates the promising potential of CPC-quatsome in the treatment of CRS.

Binding ability of sodium valproate with cationic surfactants and effect on micellization: calorimetric, surface tension, light scattering and spectroscopic approach

The interactions of surfactant molecules with biologically active pharmaceutical ingredients remain an important area of research due to the necessity to improve drug delivery and solubilization systems. In the present study, the various interactions present between a hydrophilic drug sodium valproate (SV) and cationic surfactants, viz. dodecyltrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB), hexadecyltrimethylammonium bromide (HTAB) and cetylpyridinium chloride (CPC), in aqueous media have been explored by using various techniques. The partitioning of SV in the micelles of respective surfactants has been studied by using isothermal titration calorimeter (ITC), and various parameters like binding/partitioning constant (K), enthalpy, entropy, free energy and stoichiometry of binding have been determined in post-micellar regions. The outcomes reveal that CPC binds strongly to the SV as it provides more hydrophobic interactions, and the positive values of enthalpy (ΔrH) are overcome by higher positive value of entropy (ΔrS) which makes the overall process thermodynamically favorable. The binding parameters obtained for TTAB, HTAB and CPC are further compared with the double-tailed surfactants, i.e., didodecyldimethylammonium bromide (DDAB) and dihexadecyldimethylammonium bromide (DHDAB). In addition, the effect of SV on the micellization behavior of TTAB, HTAB and CPC was also studied using ITC and surface tension measurements, and various thermodynamic and interfacial parameters have been derived. Dynamic light scattering and proton (1H) NMR studies have been performed to determine the locus of SV molecules within micelles of HTAB, TTAB and CPC.

The Droplet-Size Effect Of Squalene@cetylpyridinium Chloride Nanoemulsions On Antimicrobial Potency Against Planktonic And Biofilm MRSA.

BackgroundIt is important to explore the interaction between antibacterial nanoparticles and microbes for understanding bactericidal activity and developing novel applications. It is possible that the nanoparticulate size can govern the antibacterial potency.PurposeThe purpose of this study was to evaluate the antimicrobial and antibiofilm properties of cetylpyridinium chloride (CPC)–decorated nanoemulsions against methicillin-resistant Staphylococcus aureus (MRSA).MethodsThe droplet size could be adjusted by varying the percentage of squalene, the main ingredient of the oily core.ResultsWe fabricated cationic nanoemulsions of three different sizes, 55, 165, and 245 nm. The nanoemulsions showed greater storage stability than the self-assembled CPC micelles. The tested nanoemulsions exhibited more antimicrobial activity against Gram-positive bacteria than Gram-negative bacteria and fungi. The killing of MRSA was mainly induced by direct cell-membrane damage. This rupture led to the leakage of cytoplasmic DNA and proteins. The nanoemulsions might also degrade the DNA helix and disturb protein synthesis. The proteomic analysis indicated the significant downregulation of DNA-directed RNA polymerase (RNAP) subunits β and β’. The antibacterial effect of nanoemulsions increased with decreasing droplet size in the biofilm MRSA but not planktonic MRSA. The small-sized nanoemulsions had potent antibiofilm activity that showed a colony-forming unit (CFU) reduction of 10-fold compared with the control. The loss of total DNA concentration also negatively correlated with the nanoemulsion size.ConclusionThe present report established a foundation for the development of squalene@CPC nanosystems against drug-resistant S. aureus.

Simultaneous removal of arsenate and nitrate from aqueous solutions using micellar-enhanced ultrafiltration process

Arsenate (As(V)) and nitrate (NO3– removal from aqueous solutions was investigated via micellar-enhanced ultrafiltration (MEUF) using a prepared polyacrylonitrile (PAN) membrane and cetylpyridinium chloride (CPC) as the cationic surfactant. The PAN ultrafiltration (UF) membrane was produced using the phase inversion method and used in a dead-end cell system. The morphology and physiochemical properties of the prepared membrane were characterized using SEM, EDX, XRD, FTIR, and AFM. Parameters, including surfactant concentration, solution pH, and transmembrane pressure (TMP) were examined to determine their effects on the permeate flux and removal efficiency of As(V) and NO3–, besides CPC rejection. Increasing CPC concentration from 0.1 to 5 mM, removal of As(V) and NO3– increased from 49.3% to 96.9% and from 0.3% to 90.5%, and the permeate flux reduced from 36.6 to 10.2 L/m2/h and from 54.2 to 33.3 L/m2/h, respectively. In addition, simultaneous removal of As(V) and NO3– via MEUF was studied, which showed that removal of NO3– was majorly prevented by As(V) because of competitive binding of CPC micelles between NO3– and As(V); however, As(V) removal was only slightly inhibited by NO3–. It was shown that the prepared PAN membrane could remove more than 90% of As(V) and NO3– under optimal conditions (CPC concentration = 5 mM, pH = 7–8, and TMP = 1 bar), using the MEUF process.

Role of Surfactants Cetyl Pyridinium Chloride (CPC) and Cetyltrimethyl Ammonium Bromide (CTAB) in the Reverse Micellar Extraction of Ternary Mixture of Acid Dyes from Textile Effluent

AbstractTextile industry produces colored effluent which is the major cause of water pollution. Removal of color from effluent is very important before discharging. Extraction of ternary mixture of anionic dyes, namely, Acid Orange 7 (AO-7), Acid Blue 1(AB-1) and Acid Yellow 17 (AY-17) was carried out from aqueous solutions using reverse micelles of Cetyl Pyridinium Chloride (CPC) and Cetyltrimethyl ammonium bromide (CTAB) in isoamyl alcohol. Extraction efficiency of CPC and CTAB was studied under various experimental conditions, such as pH of feed solution, concentration of surfactant, extraction time, temperature and initial dye concentration. Under the optimized experimental conditions, 93–98 % of dyes were extracted. It was observed that CTAB is more efficient than CPC for extraction of dyes from aqueous medium.

Micellar catalyzed hydrolysis of mono-2,3-dichloroaniline phosphate

ABSTRACTThe kinetics of micellar catalyzed hydrolysis of mono-2,3-dichloroaniline phosphate in the presence of different surfactants has been studied at 303 K. The rate of reaction has been found to be first order with respect to both [substrate] and [HCl]. The cationic micelles of cetylpyridinium chloride (CPC), anionic micelles of di-octyl sodium sulphosuccinate (AOT), and non-ionic micelles of polyoxyethylene sorbitan monooleate (Tween 80) enhanced the rate of reaction to a maximum value and after that the increase in concentration of surfactant decreased the reaction rate. The applicability of different kinetic models has been tested to explain the observed micellar effects. The various thermodynamic activation parameters (Ea, ΔH≠, ΔS≠, ΔG≠) have been evaluated. The added salts viz. KCl, KNO3, K2SO4 enhanced the rate of reaction in the presence of CPC, AOT, and Tween 80 micelles. The kinetic parameters were determined from the rate (surfactant) profile and a suitable mechanism consistent with the experimental finding has been proposed.

Unusual nanosized associates of carboxy-calix[4]resorcinarene and cetylpyridinium chloride: the macrocycle as a glue for surfactant micelles.

The association of cetylpyridinium chloride (CPC) micelles in the presence of octaacetated tetraphenyleneoxymethylcalix[4]resorcinarene (CR) leads to the formation of unusual spherical supramolecular nanoparticles (SNPs). Within the range of CR/CPC molar ratios from 10/1 to 1/10 (except for 1/8), CR, acting as a counterion, decreases the critical micelle concentration of CPC by one order of magnitude and leads to the formation of SNPs with an average hydrodynamic radius of 164 nm and an average zeta potential of -60 mV. The formation of SNPs was studied by NMR FT-PGSE and 2D NOESY, DLS, TEM, fluorimetry, and UV-Vis methods. The stability of SNPs at different temperatures and pH values and in the presence of electrolytes was investigated. The specificity of the interactions of the SNPs with substrates that were preferentially bound by a macrocycle or CPC micelle was studied. The enhancement of cation dye binding in the presence of SNPs is shown. The presented supramolecular system may serve as a nanocapsule for water-soluble and water-insoluble compounds.

Interactions between non-phospholipid liposomes containing cetylpyridinium chloride and biofilms of Streptococcus mutans: modulation of the adhesion and of the biodistribution

Cetylpyridinium chloride (CPC) is a surfactant that binds strongly to bacteria and bacterial biofilms. In this study, fluorescence-based techniques were used to determine the penetration and adhesion of CPC when it was introduced in liposomes. In spite of a reduced adhesion as compared to pure CPC micelles, CPC-containing liposomes adhered significantly to the biofilms of Streptococcus mutans. In contrast, no binding was observed for liposomes that were composed of phosphatidylcholine-cholesterol. The influence of the charge of the liposome on its adhesion to biofilms was studied using cholesterol (Chol) and cholesterol sulfate (Schol). In spite of similar binding to the biofilms, positively charged CPC/Chol liposomes were located mainly in the core of the biofilm microcolonies, whereas the negatively charged CPC/Schol liposomes were mainly concentrated at their periphery. This effect may be attributed to the different availability of the CPC head group. In summary, this work demonstrates the high potential for tailoring drug nanovectors by modulating sterol selection in order to selectively target and bind biofilms.

Effects of co-solutes on Cr(VI) removal by micellar enhanced ultrafiltration (MEUF) process

Abstract The effect of electrolyte (NaCl salt) during chromate (Cr2O3 −2) ion separation from effluent by Micellar enhanced ultrafiltartion (MEUF) and leakage of cationic surfactant Cetyl Pyridinium Chloride (CPC) in permeate stream has been studied. It is revealed that though electrolyte (NaCl) reduces the critical micelles concentration of surfactant, but with increase of NaCl concentration in feed, decreases the chromium separation efficiency and increases surfactant, CPC concentration in permeate. The increase of ionic strength of the aqueous medium decreases the adsorption (chemisorption) of negatively charged chromate ions on positively charged CPC micelles, resulting in decrease of Cr(VI) separation by ultrafiltration. Effect of electrolyte on chromium separation at different pH, surfactant concentration is investigated. More than 95% hexavalent chromium is retained at 10 mM electrolyte concentration.

A cationic surfactant-concentration dependent binding of a guest molecule with the nanotubes of β-cyclodextrin and its release from the nanotubular cavities

The effect of concentration of a cationic surfactant, cetylpyridinium chloride (CPyCl), on the inclusion complex between β-cyclodextrin (β-CD) and a guest molecule, trans-2-[4-(dimethylamino)styryl]benzothiazole (DMASBT), has been studied by exploiting the twisted intramolecular charge transfer (TICT) fluorescence properties of the latter. The steady-state fluorescence, fluorescence anisotropy, time-resolved fluorescence of DMASBT and dynamic light scattering (DLS) methods have been used to monitor the different phases of binding of CPyCl with the β-CD–DMASBT system. At the chosen concentration of β-CD (8.0 mM), the β-CD molecules in the presence of 5.0 μM of DMASBT exist as extended nanotubes forming rod-like suprastructures along with simple adducts and single nanotubes. At a very low concentration of CPyCl (<0.7 mM), it partially binds with all the forms of β-CD–DMASBT inclusion complexes. Above 0.7 mM, CPyCl effectively binds with the β-CD–DMASBT system forming a β-CD–DMASBT–CPyCl complex. The premicellar aggregation starts at ∼10.0 mM of CPyCl, while micellization occurs at ∼20.0 mM, which is suggested to be the apparent critical micellar concentration (CMC*) of CPyCl. Above CMC*, the CPyCl molecules replace almost all DMASBT molecules from the cavities of nanotubes and the released DMASBT molecules then get solubilized in the micelles of CPyCl. This phenomenon suggests that the present system can be explored for the development of a drug-delivery system. The hydrodynamic radii of various components in the solution have been determined by the DLS method.

Structural evolution in catanionic mixtures of cetylpyridinium chloride and sodium deoxycholate

Sodium deoxycholate (NaDC) is a water soluble bile salt commonly used in applications ranging from cell lysis, liposome preparation and isolation of membrane proteins. We present the microstructural evolution in aqueous mixtures of biocompatible cationic surfactant cetylpyridinium chloride (CPC) and bile salt NaDC using dynamic light scattering (DLS), small angle neutron scattering (SANS) and small angle X-ray scattering (SAXS). When the total concentration of the mixture (CT) is less than 370 mM, associative phase separation occurs, near the equimolar ratio, which vanishes at high concentrations (>370 mM). The associative phase separation observed at low CT has been explained on the basis of competition between electrostatic attraction and entropy of mixing of the components. Pure CPC micelles undergo shape transition from prolate to oblate, as the concentration increases from 50 mM to 400 mM. Small addition of NaDC to 400 mM of CPC leads to marginal size change in the oblate micelles. On the other hand, pure NaDC micelles are prolate ellipsoids for which the micellar size increases by incorporation of CPC. The observed structural transition is explained in terms of the electrostatic binding of bile salts to cationic surfactants and the incorporation of the steroidal skeleton in the bile salt at the micelle core-head group interface. Microstructure evolution in catanionic mixtures comprising biocompatible surfactants offers potential pharmaceutical applications.

Ultrafast Electron Transfer Dynamics in Micellar Media Using Surfactant as the Intrinsic Electron Acceptor

Ultrafast photoinduced intermolecular electron transfer (ET) dynamics involving 7-aminocoumarin derivatives as electron donor and pyridinium moiety of surfactant molecules in cetylpyridinium chloride (CPC) micelle as electron acceptor has been investigated to understand the role of separation and orientation of reactants on micellar ET reactions. Unlike in noninteracting micelles (like Triton-X-100, sodium dodecyl sulfate, dodecyltrimethylammonium bromide, etc.), where surfactant-separated donor-acceptor pairs are understood to give the ultrafast ET component with the shortest time constant in the range of approximately 4 ps, in CPC micelles with pyridinium moiety as the intrinsic acceptor the ultrafast ET component is found to be in the subpicosecond time scale (of around 240 fs). This time scale is very similar to the values reported in the cases of ultrafast ET reactions involving coumarin dyes in electron-donating solvents. The ultrafast ET times in CPC micelles are significantly faster than the diffusive solvation dynamics in the micellar media. Correlation of the observed ET rates in the present cases with the free-energy changes of the reactions shows the inverse-bell-shaped correlation, predicted by Marcus ET theory. Interestingly, the onset of the Marcus inversion appears at a relatively lower exergonicity, which is attributed to the nonequilibrium solvent configuration during the ultrafast ET reaction, as envisaged from two-dimensional ET (2DET) model. Along with the ultrafast ET component, there are also slower ET components in these systems, which are attributed to those close-contact donor-acceptor populations in the micelles that have relatively weaker electronic coupling due to improper orientation of the interacting donor-acceptor pairs. The present results suggest that, along with the shifting of Marcus inversion at lower exergonicity, the ET rates can also be maximized in a micellar media by using surfactant molecule as an intrinsic reactant.

Aggregation and adsorption behavior of cetylpyridinium chloride in aqueous sodium salicylate and sodium benzoate solutions

The critical micelle concentration (cmc) values of cetylpyridinium chloride (CPC) were determined in the presence of salicylate and benzoate ions in the less explored concentration region where viscosity is Newtonian. The cmc of CPC decreased from 9 × 10 −4 to 7 × 10 −7 and 3 × 10 −6 mol kg −1 by adding about 0.3 mol kg −1 of salicylate and benzoate, respectively. The ortho hydroxyl group in salicylate thus has a remarkable influence on the micellization of CPC and the extent of this favorable effect is found to be about 3.5 kJ mol −1. The Corrin–Harkins equation was modified to explain the variation of cmc with electrolyte concentration in the presence of mixed counterions. The slope of the equation does not provide the value of the total counterion binding constant ( β), but gives us information about the lower limit to the value of β, which is found to be 0.66. Addition of salicylate and benzoate increases the counterion binding to CPC micelles compared to that in the presence of chloride alone. An adsorption isotherm was derived to estimate the surface excess of CPC in the presence of mixed counterions.

Diphenyl-4-nitrophenylphosphinate(DPNPIN)의 탈인산화반응에 미치는 Alkylbenzimidazole의 친핵적 및 Cetylpyridinium chloride(CPyCl) 미셀 촉매효과

Abstract This study is mainly focused on micellar effect of cetylpyridinium chloride(CPyCl) solution including alkyl- benzimidazole(R-BI) on dephosphorylation of diphenyl-4-nitrophenylphosphinate(DPNPIN) in carbonate buffer(pH 10.7). The reactions of DPNPIN with R-BI ⊖ are strongly catalyzed by the micelles of CPyCl. Dephosphorylation of DPNPIN is accelerated by BI ⊖ ion in 10 -2 M carbonate buffer(pH 10.7) of 4×10 -3 M CPyCl solution up to 100 times as compared with the reaction in carbonate buffer by no BI solution of 4×10 -3 M CPyCl. The value of pseudo first order rate constant(k mBI ) of the reaction in CPyCl solution reached a maximum rate constant increasing micelle concentration. Such rate maxima are typical of micellar catalyzed bimolecular reactions. The reaction mediated by R-BI ⊖ in micellar solutions are obviously slower than those by BI ⊖ , and the reaction rate were decreased with increase of lengths of alkyl groups. It seems due to steric effect of alkyl groups of R-BI

Investigation of interaction between phenol and cetylpyridinium chloride micelle in the absence and in the presence of electrolyte by 1H NMR spectroscopy

In recent years, the micellar enhanced ultrafiltration (MEUF) of phenol in wastewater using cetylpyridinium chloride (CPC) as surfactant has gained many attentions. However, so far no research has focused on the interaction between phenol and CPC micelle. In this study, the interaction between phenol and CPC micelle with and without electrolyte was investigated by using 1H NMR spectroscopy. In the absence of electrolyte, at low phenol concentrations (0.5 mM and 1 mM) phenol was solubilized at the micelle–water interface by the ion interaction between C 6H 6O − and C 5H 5N +, and in the hydrophilic head group region of CPC micelle by the polar interaction between phenol and CPC micelle. When phenol concentration range was from 1 mM to 8 mM, the micelle–water interface and the hydrophilic head group region of CPC micelle saturated with C 6H 5O − and phenol, then phenol penetrated into the palisade layer deeper but was still close to the hydrophilic head group of CPC micelle. The presence of NaCl and Na 2SO 4 had almost no influence on the solubilization of phenol in CPC micelle, however, the presence of Na 2CO 3 promoted the solubilization of phenol in CPC micelle significantly. In the presence of Na 2CO 3, more C 6H 5O − ions were solubilized at the water–micelle interface by the ion interaction between C 6H 6O − and C 5H 5N +. At low Na 2CO 3 concentration the micelle–water interface of CPC micelle saturated with C 6H 5O −, and benzene ring penetrated into the palisade layer of CPC micelle, but deeper penetration was not observed with the increase of Na 2CO 3 concentration. Excessive CO 3 2− could make some C 6H 5O − transfer from CPC micelle to water, resulting in the decrease of the solubilization extent of phenol in CPC micelle.

Physicochemical studies on the micellization behavior of cetylpyridinium chloride and triton X-100 binary mixtures in aqueous medium

Physicochemistry of micellization of binary mixtures of cetylpyridinium chloride (CPC) and Triton X-100 (TX-100) have been investigated and the data collected have been analyzed and correlated. Tensiometric, conductometric, spectrophotometric, calorimetric and polarographic methods have been employed in the study. Parameters like critical micellar concentration (CMC), counter-ion binding, energetics of micellization, interfacial surfactant adsorption and minimum area of amphiphile head groups at CMC have been determined. The diffusion coefficients of pure and mixed micelles in solution have been determined by the polarographic method. The regular solution theory of Rubingh has been considered to get information on the micellar composition and their mutual interaction (synergistic for the studied system) in solution. The packing of the monomer in micelle has been estimated to witness spherical geometry for CPC and its mixtures with TX-100, whereas the later has been found to be spheroidal. Polarographic measurements have evidenced comparable diffusion coefficients of CPC and TX-100 micelles whereas their mixed micelles have shown lower values with a minimum, at equimolar composition.

Surface-Enhanced Raman Spectroscopy Studies of Surfactant Adsorption to a Hydrophobic Interface

Surface-enhanced Raman spectroscopy is used to investigate the kinetics of adsorption of the cationic surfactant cetylpyridinium chloride (CPC) to hydrophobic surfaces from water. A hydrophobic surface, with stable and reproducible SERS activity, is produced by binding gold colloids to an amine-terminated glass slide and then modifying this surface with octadecyltrimethoxysilane. In situ SERS-detected adsorption of CPC from aqueous solution is found to follow a Frumkin isotherm. Interactions between the charged head groups could be detected in frequency shifts in the symmetric ring breathing mode, consistent with an interfacial surfactant environment similar to a CPC micelle. Rates of surfactant adsorption were determined by time-resolved SERS measurements and were found to be much slower than the diffusion-controlled limit, indicating a significant kinetic barrier to adsorption. Desorption kinetics were heterogeneous, consistent with the spectroscopic results. Alkylsilane-modified gold colloids were shown to be useful substrates for investigating amphiphile adsorption from aqueous solutions to hydrophobic surfaces, where the adsorption kinetics could also be used to determine analyte concentrations in solution.