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1.
The effect of additives on the cloud point (CP) of nonionic surfactants has been studied for more than six decades. Ionic surfactants, however, generally do not show clouding. Recently, CP in ionic surfactant solutions have been reported in the presence of a few quaternary bromides. In this study, we report the effect of various additives (e.g., ureas, sugars, salts, organic solvents, acids) on the CP of sodium dodecyl sulfate (SDS) + tetra-n-butylammonium bromide (Bu4NBr) systems. An increase in CP of the system with urea concentration is explained by its water structure-breaking ability. An opposite effect of thiourea may be due to the direct interaction of the compound with the SDS-Bu4NBr mixed micelle. The CP-decreasing effect of sugars is due to their water structure-making ability. All the salts decrease the CP, owing to increased counterion binding. The organic solvents used here raise the CP, whereas the other organic additives decrease the CP. The overall criteria of CP variation seemingly depend upon the solubilities of the additive in the micellar interfacial region and the background solvent.  相似文献   

2.
Clomipramine hydrochloride (CLP), an antidepressant drug, is amphiphilic in nature and self-aggregates at 22 mM (25°C). The drug shows a critical demixing (liquid-liquid phase separation) when the temperature is raised. The critical point (CP; often referred to as the cloud point) is susceptible to the presence of additives. Herein, we report the clouding phenomenon occurring in CLP drug solutions in the presence of electrolytes. At a fixed drug concentration (50 mM) and fixed pH (6.25), CLP shows CP at 32°C, which can be tuned with the addition of salts. With NaX (X = F?, Cl?, Br?) and MBr (M = Li+, Na+, K+) salts, the CP increases due to adsorption and salting-in/salting-out phenomenon. Quaternary salts, tetramethylammonium bromide (TMAB), tetraethylammonium bromide (TEAB), tetrapropylammonium bromide (TPAB), and tetrabutylammonium bromide (TBAB) form mixed micelles and hence increase CP of the drug solution. Dye solubilization experiments on drug-electrolyte systems and energetic parameters evaluated for drug-NaF system also support the explanations forwarded for the process of clouding.  相似文献   

3.
The interaction between the amphiphilic drug amitriptyline hydrochloride (AMT) and the nonionic surfactants used in drug delivery has been investigated. Herein, we report the micellization behavior of AMT in presence of ethoxylated alkyl phenols in aqueous medium and the clouding phenomenon in the absence and presence of different nonionic surfactants in buffer solution. The values of critical micelle concentration (CMC) of AMT obtained using the conductivity method, decrease as nonionic surfactant concentration increases. With an increase in temperature, the CMC first increases and then decreases. At 303.15 K, the maximum CMC values were obtained with or without nonionic surfactant. The results obtained indicate attractive interactions (synergism) between the two mixing amphiphiles in solution. The experimentally obtained critical micelle concentration (CMC) values are always lower than ideal CMC values. Micellar mole fraction (X1) values, calculated by different proposed models, show the contribution of nonionic surfactant concentration. At a fixed drug concentration (50 mmol kg?1) and pH (=6.7) nonionic surfactants show continuous increase in cloud point (CP). Increase in drug concentration and pH, in the presence of fixed amounts of nonionic surfactant, increases and decreases the CP, respectively.  相似文献   

4.
Clouding is rarely observed with ionic surfactants. Herein we report the occurrence of clouding in sodium dodecyl sulfate (SDS, an anionic surfactant) solutions on addition of different symmetrical and unsymmetrical quaternary phosphonium bromides (tetra-n-butylphosphonium, tetraphenylphosphonium, and n-propyltriphenylphosphonium). Cloud point (CP) measurements were made with solutions having different SDS/salt combinations. The nature of the counterion had a crucial role in the occurrence of the phenomenon, whereas substitution of an alkyl chain by a phenyl ring made the salt more effective near ambient temperature. A linear relationship between the SDS and salt concentrations was obtained. It is proposed that both the electrostatic charge and the hydration state of the headgroup region are influenced by counterion addition and that the net charge or volume of the counterion has a key role to play in the overall phenomenon. The effect of the addition of some hydroxy compounds on CP variations in these SDS+salt systems was also studied, and the data were interpreted on the basis of incorporation of these compounds in the micellar headgroup region. The nature of the counterions influenced this incorporation.  相似文献   

5.
The present study investigates the effect of tetraethyl ammonium tetrafluoroborate [TEA(BF4)] ionic liquid (IL) on the cloud point (CP) of the following nonionic surfactants in aqueous solution: ter‐octylphenol ethoxylates with 9.5 and 4.5 ethylene oxide groups (abbreviated TOPEO9.5 and TOPEO4.5, respectively), cetyl alcohol ethoxylate with 10 ethylene oxide groups (C16EO10), and sorbitan monolaurate and monooleate both with 20 ethylene oxide groups (SMLEO20 and SMOEO20, respectively) in aqueous solutions. The thermodynamic parameters of these mixtures were calculated at different IL concentrations. The CP of most of the tested nonionic surfactants increased with the increment of IL concentrations with the exception of C16EO10 for which it decreased. The solubility of a nonionic surfactant containing polyoxyethylene (POE) hydrophilic chain was considered as maximum at the CP, hence the thermodynamic parameters were calculated at the same temperature. The results showed that the standard Gibbs free energy (?GCP0), the enthalpy (?HCP0) and the entropy (?SCP0) of the clouding phenomenon were found to be positive for ethoxylated octylphenol and sorbitan esters, whereas ?HCP0 and ?SCP0 were found to be negative for C16EO10. It was found that the overall clouding process is endothermic for ethoxylated octylphenol and sorbitan esters and exothermic for C16EO10. For all the studied systems, ?HCP0 > T?SCP0 indicated that the process of clouding is guided by both enthalpy and entropy. The positive value of standard Gibbs free energy (?GCP0) for the all mixed systems indicated that the process proceeds non‐spontaneously. The ?GCP0 decreased with increasing IL concentration for all the nonionic surfactants; however, it decreased with increasing surfactant concentration for TOPEO9.5, C16EO10, and SMOEO20, and increased with increasing surfactant concentration for TOPEO9.5 and SMLEO20.  相似文献   

6.
The effect of co‐solvent N‐methylacetamide (NMA) (0.035, 0.046, 0.127, and 0.258 mol kg?1) on the micellization behaviour of anionic surfactant sodium dodecylsulphate (SDS) (3.21–10.35 mmol kg?1) and cationic surfactant cetyltrimethylammonium bromide (CTAB) (0.19–3.72 mmol kg?1) in aqueous solution was explored by employing conductivity measurements at different temperatures (298.15–313.15 K). The critical micelle concentration (CMC) values for SDS and CTAB in aqueous solutions of NMA were determined from the conductivity versus surfactant concentration plots. The variations in the CMC values of SDS with NMA concentration are in striking contrast to those observed in the case of CTAB. The various relevant thermodynamic parameters of micellization, viz. standard enthalpy change, ΔHmo, standard entropy change, ΔSmo, and standard Gibbs free energy change, ΔGmo, were determined using the temperature variation of the CMC values and counterion binding. The results not only relate these thermodynamic parameters to the consequences of intermolecular interactions but are also able to differentiate between SDS–water–NMA and CTAB–water–NMA systems in terms of contributions from head groups as well as alkyl chains of surfactants.  相似文献   

7.
The work focuses on the clouding and dye solubilization phenomena in an amphiphilic drug, nortriptyline hydrochloride (NOT), which is a tricyclic antidepressant. A 30 mM drug solution prepared in 10 mM sodium phosphate buffer (pH: 7.07) showed CP at 45°C, which was found to decrease with the addition of long-chain alcohols and cyclohexanol but remained almost constant with short-chain alcohols. The behavior is explained on the basis of their nature: short-chain alcohols are water soluble and partition very little in micelles, whereas long-chain alcohols are hydrophobic and solubilize in drug aggregates. Diols decreased the CP. Addition of cationic surfactants increased the CP, whereas sugars caused a decrease. Dye solubilization results indicate micellar growth with fixed concentrations of surfactants.  相似文献   

8.
The dynamic noncovalent interaction between the anionic surfactant sodium dodecyl benzene sulfonate (SDBS) and 1,3-diphenylguanidine (DPG) was employed to control the interfacial activity of the surfactant. At high HCl concentration (1000 mg L−1), the SDBS/DPGn+ system could reduce the water/oil interfacial tension (IFT) to 10−4 mN m−1 order of magnitude, which was much lower than the IFT values in the SDBS/DPG+ system with a low HCl concentration (100 mg L−1) and the individual SDBS system by three and four orders of magnitude, respectively. The pH-switchable protonation of amido groups in DPG molecules determines the SDBS/DPG molecular interaction and the amplitude of IFT reduction, which was confirmed by control experiments using two other surfactants (sodium dodecyl sulfate [SDS] and dodecyl trimethylammonium bromide [DTAB]). Moreover, the investigation of the NaCl and temperature effects on the IFT indicated the intensity of mixed SDBS/DPGn+ adsorption layers at the water/oil interface.  相似文献   

9.
A series of rosin-based cationic gemini surfactants with different spacer length (n = 2, 3, 4) were synthesized and characterized. Surface activity and micellization parameters including the critical micelle concentration, the degree of counterion dissociation, and thermodynamic functions of micellization in aqueous solutions have been investigated. Free energy perturbation was performed to study the enthalpy-entropy compensation of the synthesized gemini surfactants in aqueous solutions. The experimental results showed that the micellization of rosin-based gemini surfactants in aqueous solutions is a spontaneous and entropy-driven process. The micellization process was found to follow the entropy–enthalpy compensation phenomenon.  相似文献   

10.
The phenol–formaldehyde condensation reaction to synthesize a gemini precursor was renewed by using high efficient and environmentally benign resin catalysts instead of protonic acids, and the conversion, yield and selectivity of the reaction were all upgraded from the 60 % by the traditional way to over 90 % by the new way. Three alkylaryl sulfonate gemini surfactants were derived from the above gemini precursor by O-methylation, sulfonation and neutralization, that is, sodium salt of sulfonated bis(2-hydroxy-5-nonylphenyl)methane (SBHNM), sodium salt of sulfonated bis(2-hydroxy-5-dodecylphenyl)methane (SBHDM) and sodium salt of sulfonated bis(2-methoxy-5-nonylphenyl)methane (SBMNM). And their performances in aqueous solution were further investigated. The results show that the three gemini surfactants exhibit higher effectiveness and efficiency in surface tension reduction than a monomeric reference surfactant sodium dodecylbenzene sulfonate (SDBS). Furthermore their critical micelle concentration values are at least one order of magnitude lower than that of SDBS. It is also shown that O-methylation of the hydroxyl group in the gemini precursor is effective at improving the surface activity of the gemini surfactants, such as efficiency in surface tension reduction, foam stability and calcium stability. It is suggested that the synthesized hydrophobic skeleton could be a multi-purpose gemini precursor from which various gemini surfactants could be derived by further hydrophobic or hydrophilic modification.  相似文献   

11.
A novel coating process of hydrous alumina on organic pigment particles through direct precipitation in aqueous solution was developed in this work. The aqueous suspensions of organic pigment particles were prepared using cetyltrimethylammonium bromide (CTAB) and sodium dodecylbenzene sulfonate (SDBS) as additives before the coating. The organic pigment particles were then coated with hydrous alumina using Al2(SO4)3 as precursor. The morphology and surface states of as-coated organic pigment particles were analyzed by high-resolution transmission electron microscopy (HRTEM) and zeta-potential. TEM images showed that a uniform hydrous alumina film could be formed on the organic pigment particle surface with anion surfactant SDBS. However, with cation surfactant CTAB, no alumina coating film was generated on the organic pigment particle surface.  相似文献   

12.
Interactions of a widely used commercial anionic surfactant, linear alkylbenzene sulfonate, with zein protein, a water insoluble protein, was studied to better understand the effects of the counterion on skin irritation of anionic surfactants. The neutralizing ions used were inorganics: Li+, Na+, K+, Mg2+, and NH4+ and organics: monoethanolamine, diethanolamine, and triethanolamine. According to the results obtained, the influence of counterions of anionic surfactants on zein solubilization is significant; with magnesium counterions showing lower zein solubilization. In aqueous solutions, zein solubilization by anionic surfactant is related to the effect of the counterion on the critical micelle concentration of the surfactant for the inorganic counter‐ions; for the organic counter‐ions, effects of tighter anionic binding in the micelle also contribute to zein solubilization trends.  相似文献   

13.
Aqueous biphasic systems based on nonionic surfactants have perspective applications in extraction processes, in particular, cloud point extraction of hazardous compounds or high valued products, especially biomolecules. Additives (e.g., ionic surfactants, salts) and variations in pH can significantly affect the surfactant-based separation processes, representing an additional degree of freedom for their optimization. However, there are few systematic studies of phase and partition behavior for these multicomponent surfactant systems.In this study we examined the clouding, phase compositions and partitioning equilibria for aqueous mixed surfactant systems of a nonionic surfactant (Triton X-114), ionic surfactants (cetyltrimethylammonium bromide or sodium dodecyl sulfate) and NaCl, in order to improve the extraction efficiency. Vanillin was used as a model substance at three different pH values, specifically in (partly) dissociated or non-dissociated states. The partition coefficients obtained in the batch experiments were compared to the predictions by the thermodynamic model COSMO-RS. Based on this knowledge a continuous multistep extraction process was carried out.To the best of our knowledge this is the first demonstration of using a mixed surfactant system for continuous countercurrent cloud point extraction.  相似文献   

14.
The interactions between sodium dodecylbenzene sulfonate (SDBS) and the components of an ethyl acrylate/methacrylic acid (EA/MAA) copolymer latex were examined and the influences of using D2O as the synthetic suspension medium were investigated. Whereas it is found that D2O has no detectable influence on the fully coalesced latex films, the film coalescence conditions are shown to significantly affect the nature of surfactant interactions within the film matrix. When films are prepared and stored under controllable low atmospheric water-vapor concentrations, hydrogen-bonding interactions between the surfactant SO3?Na+ groups and the copolymer acid functionality dominate. However, coalescence and storage of the films under higher relative humidity conditions results in a displacement of these interactions in favor of the hydrated form of the surfactant. It is also shown that the presence of an aromatic ring adjacent to the surfactant sulfonate group exerts an influence on the nature of the SO3? ··· HOOC interactions within the copolymer matrix. Relative to sodium dioctyl sulfosuccinate (SDOSS), the aromatic group near hydrophilic end of SDBS increases the strength of the S? O bond in the presence of acid interactions. © 1993 John Wiley & Sons, Inc.  相似文献   

15.
The micellization behavior of gemini surfactants i.e. alkanediyl-α,ω-bis(cetyldimethylammonium bromide) (C16-s-C16,2Br where s = 3, 4, 10) in 10% (v/v) ethylene glycol solution was investigated by surface tension and conductometric measurements at 300 K. The critical micelle concentration, degree of micellar ionization, surface excess concentration, minimum surface area per molecule of surfactant, surface pressure at the CMC and Gibbs energy of adsorption of the dimeric surfactants have also been determined in the presence of different salts (NaCl, NaBr and NaI). The critical micelle concentration and degree of micellar ionization values decrease significantly in the presence of sodium halides and follows the sequence NaCl < NaBr < NaI. The free energy, enthalpy and entropy of micellization of dimeric surfactants in 10% (v/v) ethylene glycol solution were determined using the temperature dependence of the critical micelle concentration. The standard free energy of micellization was found to be negative in all the cases.  相似文献   

16.
The micellization behavior of binary mixtures of sodium n‐dodecyl diamine sulfonate (C12AS) and octylphenol polyoxyethylene ether (10), OP‐10, in aqueous solutions at pH 3.5, 6.0, and 8.5 was investigated, and the values of mixed critical micelle concentration (CM) were determined by both UV–vis spectroscopy using pyrene as a probe and by tensiometry. Within the framework of the pseudophase separation model, four thermodynamic models were adopted to describe the micellization parameters including the interaction parameters (β12) between two surfactants, the components in real and ideal mixed micelles, the activity coefficients in mixed micelles, the thermodynamic parameters, and the thermodynamic stability. The experimental values of CM, inferior to the ideal values, show nonideal mixing; the negative values of β12 obtained from Rubingh's, Rodenas's, and Motomura's models mean the synergistic effect. Although there exist some divergences in the micellization parameters predicted by the three treatments, similar results were obtained, indicating the validity of these models in this investigation. Based on the calculation errors, Rubingh's model is best to describe the interacting behavior between the two surfactants in this investigation. Thermodynamic parameters predicted by the three treatments show a spontaneous process of micellization and an entropic contribution in the formation of mixed micelles. Different acidities of solutions result in different stabilities of micellization. The stability in feeble acidic solution is higher than in acidic or basic solution, and the stability in basic solution is slightly superior to that in acidic solution. All the above described phenomena can be explained rationally by the electrostatic effect of head groups of C12AS, the steric effect of head group for two surfactants, the molecular structures of surfactants, the influence of added counterion, and so on. © 2015 Society of Chemical Industry  相似文献   

17.
Due to the presence of non‐sulfonated residual alkyl ether (AE), sodium alkyl ether sulfonate (SAES) may exhibit clear point‐cloud point solubilization behavior in brine. Accordingly, the effect of temperature on the compatibility of iC17EOxS (x = 7 and 10), nC17EO10S, along with their analogous nonionic surfactants iC17EOxH (x = 7 and 10) and nC17EO10, in addition to iC9EO14 in brine has been investigated. Depending on their molecular structures, these surfactants exhibited concentration‐dependent clear point and cloud point solubilization behavior. The cloud point was associated with the AE component whereas the clear point was attributed to the sulfonated one. Interestingly, an increase in the cloud point of the nonionic component with respect to the corresponding nonionic AE (100 % active) was observed. Adding iC9EO14 (100 % active) to iC17EO7S (xan = 0.0–0.362) resulted in a significant decrease in the clear point of iC17EO7S from above 100 °C to below 22 °C with a concomitant increase in iC17EO7/iC9EO14 mixture cloud point from 68 °C. (xan = 0) to 72 °C (xan = 0.325). This relatively modest increase by 4 °C was attributed to the interrelationship of different competitive mechanisms, namely an increase in mixed micelle charge with increasing xan, the dehydration of OE groups via ion (SO3?)‐dipole (O → CH2) interactions, and possible shielding of SO3? groups by iC9EO14 nearby extended EO groups. To the best of our knowledge, this is the first instance where dual anionic‐nonionic solubilization behavior of SAES in brine characterized by high salinity and hardness is being reported.  相似文献   

18.
Polyacrylamide gel was synthesized to study interaction between surfactant and particle hydrogel. Surfactants used in this study include cationic surfactants, n-dodecylpyridinium chloride, (1-hexadecyl) pyridinium bromide; anionic surfactants, sodium salt of dodecylbenzene sulfonic acid, sodium 4-n-octyl benzene sulfonate and sodium branched alcohol propoxylate sulfate; and nonionic surfactants, Igepal® CO-530, Tergitol® NP-10 and Neodol® 25-12. It has been found that, after swelling of the dry particles, surfactant concentration shows a substantial increase. Meanwhile, dynamic modulus (G′ and G") of the gels shows a significant decrease in the surfactant solutions. Based on the experimental results, a mechanism has been proposed to elucidate the reduction of the gel dynamic modulus. Furthermore, this mechanism was discussed through surfactant critical packing parameters (CPP) at the interface of the hydrogel particle and surfactant aqueous solution, and confirmed by recovery of the gel dynamic modulus after removal of the surfactant from the hydrogels.  相似文献   

19.
《分离科学与技术》2012,47(12):2677-2691
Abstract

The aim of this work was the two‐aqueous phase extraction of neutral red and methylene blue from wastewater. This has been achieved on the basis of phase separation properties of non‐ionic surfactants above the so‐called cloud point curve and the solubilization phenomena of coacervate micelles (surfactant rich phase). Three commercial surfactants were used in this work; the Oxo‐C15E7 which is an ethoxylate fatty alcohol (Dehydol LT 7), Triton X‐114 (iso‐C8H17‐C6H4‐(OCH2CH2)7,5OH), and Triton X‐100 (iso‐C8H17‐C6H4‐(OCH2CH2)9,5OH) which are alkyl phenol ethoxylate surfactants. The phase diagrams of binary water/surfactants systems were drawn and the effect of sodium sulphate on water‐surfactant systems was therefore studied. Oxo‐C15E7 and Triton X‐114 were used for the cloud point extraction of neutral red and methylene blue from their aqueous solutions at 100 mg/L and 7 mg/L, respectively. The experimental extraction results were expressed by the following three responses: percentage of the extracted dye (E), residual concentrations of dye in the dilute phase (Xs,w), and the volume fraction of coacervate (φC) at the equilibrium. The results obtained for each parameter were also represented on three‐dimensional diagrams using an empirical smoothing method. The empirical modelling data were in agreement with the experimental ones. The main advantage was sought between E, which has reached 99% in the case of neutral red, whereas in the case of mehtylene blue 92% was obtained with respect to (φC), which should have a minimum value. At the optimal conditions, neutral red and methylene blue concentrations in the effluent were reduced to about 500 times and 7 times, respectively.  相似文献   

20.
Surface and micellization behavior of some cationic monomeric surfactants, viz., cetyldiethylethanolammonium bromide (CDEEAB), cetyldimethylethanolammonium bromide (CDMEAB), tetradecyldiethylethanolammonium bromide (TDEEAB) and dimeric surfactants, i.e., alkanediyl‐α, ω‐bis(dimethylhexadecylammonium bromide) (C16‐s‐C16, 2Br? where s = 4, 12), butanediyl‐1,4‐bis(dimethyldodecylammonium bromide (C12‐4‐C12, 2Br?) and 2‐butanol‐1,4‐bis(dimethyldodecylammonium bromide) (C12‐4(OH)‐C12, 2Br?), was studied in water‐organic solvents [10 and 20 % v/v ethylene glycol (EG) and diethylene glycol (DEG)] by conductivity, surface tension and steady‐state fluorescence methods at 300 K. The main focus of the present work is on the study of the effect of organic solvents on the critical micelle concentration (CMC), Gibbs free energy of micellization (ΔG°m), Gibbs free energy of transfer (ΔG°trans), Gibbs adsorption energy (ΔG°ads) and some interfacial parameters such as the surface excess concentration (Γmax), minimum area per surfactant molecule (Amin) and surface pressure (πCMC). The aggregation number (Nagg) and Stern‐Volmer quenching constant (KSV) were also determined by the steady‐state fluorescence method. It was observed that Nagg decreased with increasing volume percent of organic solvent. The results exhibited an increase in CMC in water‐organic solvents as compared to the respective surfactants in pure water. The negative values of ΔG°m and ΔG°ads indicate a spontaneous micellization process. The thermodynamics of micellization revealed that the micellization‐reducing efficiency of glycols increases with the concentration and the number of ethereal oxygens in the glycol.  相似文献   

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