Effect of hydrotropes on the aqueous solution behavior of surfactants

Aqueous solutions of surfactants—cationic: tetradecyltrimethylammonium bromide (C₁₄TABr); anionic: sodium dodecyl sulfate (SDS); and nonionic: polyoxyethylene t-octylphenol (trade name Triton X-102, also called OPE-8)— in the presence of three hydrotropes, viz., sodium xylene sulfonate, sodium p-toluene sulfonate, and sodium chlorobenzene sulfonate, were examined by measuring surface tension, viscosity, and cloud points for the nonionic surfactant. The results show a marked decrease in the critical micelle concentration with increase in hydrotrope concentration for C₁₄TABr, a marginal decrease for SDS, and very little change for OPE-8 up to 0.1 M hydrotrope. The viscosity of cationic surfactant solutions showed a remarkable increase in the presence of trace amounts of hydrotropes (up to 15 mM). In contrast, the SDS solution showed only a slight increase in viscosity at high hydrotrope concentration (150 mM), and the viscosity of the OPE-8 solution remained constant. The cloud point of OPE-8 increased in the presence of hydrotropes, unlike its behavior with the simple salt NaCl. The strong dependence of the solution behavior of cationic surfactants on the presence of hydrotropes is discussed in terms of electrostatic interaction.     

Selective Extraction of Embelin from Embelia ribes by Hydrotropes

Abstract

The research work proposes an alternate strategy of the extraction of embelin (2,5‐dihydroxy‐3‐undecyl‐p‐benzoquinone) from Embelia ribes. The aromatic hydrotropes such as sodium n butyl benzene sulfonate (NaNBBS), and sodium cumene sulfonate (NaCS) were found to be effective for the selective extraction of embelin with a recovery of 95% embelin from the aqueous solution of hydrotropes with high purity. The process was further optimized with respect to concentration of hydrotropes and temperature of extraction.     

Effect of hydrotropes on solubility and mass transfer coefficient of lauric acid

A comprehensive investigation on the solubility and mass transfer coefficient enhancement of lauric acid through hydrotropy has been undertaken. The solubility and mass transfer studies were carried out using hydrotropes such as sodium cumene sulfonate, sodium p-xylene sulfonate and sodium p-toluene sulfonate under a wide range of hydrotrope concentrations (0 to 3.0 mol/L) and different system temperatures (303 to 333 K). The effectiveness of hydrotropes was measured in terms of Setschnew constant K _s and reported for all hydrotropes used in this study. The solubility data are also fitted in a polynomial equation as the function of hydrotrope concentration.     

Hydrotrope-Induced Enhancement of Room Temperature Surface Activity for High Krafft Point Fluorinated Surfactants

Potassium perfluorooctane sulfonate (KPFOS) and sodium perfluorooctane sulfonate (NaPFOS) exhibit poor surface activities in aqueous solution at room temperature because of their high Krafft points. In this work, we attempted to increase the solubility of KPFOS and NaPFOS and consequently improve their surface activities at room temperature with sodium p‐methylbenzene sulfonate (BS) and urea, which are typical hydrotropes in industrial applications. The effects of BS and urea on the surface tension of the aqueous solutions of KPFOS and NaPFOS were investigated at 25 °C. When the hydrotropes were added, the effectiveness of KPFOS and NaPFOS in surface tension reduction was greatly enhanced and KPFOS showed higher efficiency in surface tension reduction than NaPFOS. On the other hand, BS had much stronger ability than urea to reduce the surface tension of KPFOS and NaPFOS in water. In particular, with the assistance of BS the minimum surface tension of KPFOS approached 19 mN/m at 25 °C. It was worth noting that in the presence of BS, the surface tension of an apparently “saturated” solution (i.e., with coexisting surfactant solid) continuously decreased with increasing surfactant concentration. This behavior was ascribed to enrichment of branched PFOS isomers in aqueous phase with the assistance of BS, as evidenced by high‐resolution ¹⁹F NMR. Hydrotropes were able to recover the inherent character of KPFOS and NaPFOS as highly surface‐active fluorinated surfactants by increasing the solubility of branched isomers. This is an easy way to enhance the effectiveness in surface tension reduction at room temperature for fluorinated surfactants with high Krafft points.     

Aqueous Hydrotropic Solution as an Efficient Solubilizing Agent for Andrographolide from Andrographis paniculata Leaves

Abstract

An aqueous solution based extraction process for andrographolide from Andrographis paniculata leaves has been developed using alkyl benzene sulfonates and carboxylates as hydrotropes. The plant cells are permeabilized by the hydrotrope solutions followed by solubilization of andrographolide into the solutions. The extraction and solubilization of andrographolide is affected by structure and concentration of hydrotrope, temperature and particle size. Sodium cumene sulfonate (Na‐CS) shows the most efficient solubilization of andrographolide amongst the hydrotropes studied. The solubility of andrographolide increased by two orders of magnitude in Na‐CS aqueous solutions and ～96% andrographolide extraction was achieved in just 20 min.     

Hydrotropic Extraction of Reserpine from Rauwolfia vomitoria Roots

Aqueous solutions of sodium cumene sulfonate give quantitative and faster extraction of reserpine from Rauwolfia vomitoria as compared to the extraction using methanol. The extraction rate is influenced by intraparticle diffusion and increases with increasing temperature and hydrotrope concentration. The dynamic extraction data were fitted in a mass transfer model to evaluate diffusion coefficient of reserpine in the solid plant matrix. Amongst all hydrotropes, sodium cumene sulfonate, gave the best extraction and extraction rates of reserpine. The reserpine crystals recovered from aqueous hydrotrope solutions were much smaller in size and showed different morphology than those from methanol.     

EXTRACTIVE DISTILLATION WITH AQUEOUS SOLUTIONS OF HYDROTROPES

The effect of hydrotropes on vapor-liquid equilibrium of a mixture provides a potential technique of extractive distillation for systems which are difficult or impossible to separate by normal rectification. Various hydrotropes, such as sodium toluate, sodium toluence sulfonate, sodium cymcnc sulfonate, sodium mesitylene sulfonate and sodium salicylate, in aqueous solutions have been tested for the separation of close-boiling point mixtures, such as p-cresol/2,6-xylenol, isopropanol/ fm-butanol, and wc-butanol/rert-butanol. The changes in the relative volatility increase with the concentration of hydrotrope and with the hydrotrope to solute ratio.     

ENHANCEMENT OF SOLUBILITY AND MASS-TRANSFER COEFFICIENT OF 1,2-DIHYDROXY-9,10-ANTHRAQUINONE (ALIZARIN) THROUGH HYDROTROPY

The effect of hydrotropes potassium p-toluene sulfonate (KPTS), citric acid, and nicotinamide on the solubility and mass-transfer coefficient of 1,2-dihydroxy-9,10-anthraquinone (alizarin) was studied. Solubility studies were carried out under a wide range of hydrotrope concentrations (0 to 3.0 mol·L^?1) and different system temperatures (303 to 333 K). It was observed that the solubility and mass-transfer coefficient of alizarin increases with an increase in hydrotrope concentration and system temperature. The maximum enhancement factor, the ratio of the value of solubility in the presence and absence of a hydrotrope, was determined for all experiments under study. The effectivity of hydrotropes was measured by the determination of the Setschenow constant, K_s. The order of effectiveness of various hydrotropes based on K_s values is potassium p-toluene sulfonate > citric acid > nicotinamide.     

Intensification of heterogeneous reactions through hydrotropy: Alkaline hydrolysis of esters and oximation of cyclododecanone

Hydrotropic substances are capable of increasing the solubility of sparingly soluble organic compounds in aqueous solutions and can thus enhance the rates of two-phase reactions substantially. The increase in the solubility of sparingly soluble organic substances due to hydrotropes has been found to be an exponential function of the hydrotrope concentration over a wide range. A study of the rates of solid—liquid and liquid—liquid alkaline hydrolysis of esters and solid—liquid oximation of cyclododecanone, in the presence of different hydrotropes, was carried out. The potassium salts of different hydrotropes, such as, butyl monoglycol sulfate, p-cumyl phenol, cumene sulphonic acid were found to be more effective than the corresponding sodium salts. In some cases intensification factors as high as 1000 were observed.     

Performance of New Biodegradable Di‐Sulfonate Surfactants as Hydrotropes in High‐Temperature and Salinity Environments

Propyl alkyl ether sulfonate (PAES) surfactants, recently developed by The Dow Chemical Company, show excellent electrolyte, hard water and caustic solubility, with attractive ECOTOX profile and biodegradability. Due to their unique structure and properties, they are good candidates for use as hydrotropes in formulations containing nonionic surfactants. The goal of these studies was to evaluate hydrotropic efficiency of PAES materials via cloud point analysis. The effects of PAES alkyl tail length, concentration, and mono‐ and di‐sulfonate components on the cloud point of TERGITOL? 15‐S‐9 in solutions of varying electrolyte strength were investigated. In the presence of high electrolyte levels, PAES 12C had the highest hydrotropic efficiency of all materials tested, including commonly used commercial hydrotropes. Di‐sulfonate components of the PAES materials were found to be more efficient hydrotropes than mono‐sulfonate in high electrolyte environments for all tail lengths tested. The di/mono ratio and tail length were found to be critical parameters.     

Hydrotropic and surfactant properties of novel diisopropyl naphthalene sulfonates

A novel surfactant and hydrotrope, sodium diisopropylnaphthalene sulfonate (SDIPNS) has been developed. It contains about 92% diisopropylnaphthalene sulfonate, compared to other materials which are less than 50% diisopropylnaphthalene sulfonate. Aqueous solutions of 34–36% active SDIPNS have dual functionality. They have excellent surface properties and are compatible with conventional anionic, nonionic, and amphoteric surfactants. They demonstrate good laundering detergency in combination with sodium lauryl ethoxy sulfate, with or without builder. They maintain surface activity in 150 ppm hard water (Ca²⁺/Mg²⁺=2∶1), 5% NaCl, pH 2, and pH 12. They are effective hydrotropes. They enhance surfactant solubility, raise the cloud point of nonionic surfactants, and modify the viscosity of surfactant formulations. They are light in color and are low-foaming. Presented as a Poster Session at the American Oil Chemists' Society Annual Meeting, May 9–12, 1999, Orlando, Florida.     

Anionic hydrotropes for industrial and institutional rinse aids

The effectiveness of eight commercial hydrotropes having differing structures (sodium xylenesulfonate, sodium-2-ethyl hexysulfate, phosphate ester of oxyethylated phenol, amine alkylaryl sulfonate, linear alkyl naphthalene sulfonate, TEA salt of DDBS, sodium dihexyl sulfosuccinate, and sodium dodecylbenzene sulfonate) was evaluated with seven commercial rinse aid surfactants of the following structural types: block copolymers and alcohol oxyalkylates with high and low levels of ethylene oxide. Two hydrotrope levels (3 and 6 wt %) were evaluated at two surfactant levels (20 and 40 wt %). Dispersibility, compatibility index, and blender foam heights were measured; the test methods are described.     

Purification of Glucose Oxidase and β‐Galactosidase by Partitioning in a PEG‐Salt Aqueous Two‐Phase System in the Presence of PEG‐Derivatives

Abstract

Purification of glucose oxidase from Aspergillus niger and that of β‐galactosidase from Kluyveromyces lactis have been attempted using poly(ethylene glycol) (PEG)‐sodium sulfate aqueous two phase system (ATPS) in the presence of PEG‐derivatives, i.e. PEG‐Coomassie brilliant blue G‐250 and PEG‐benzoate, PEG‐palmitate and PEG‐TMA, respectively. The enzymes showed poor partitioning towards the PEG phase in comparison with other proteins in ATPS containing no ligands. Selective partitioning of other proteins was observed towards the PEG phase in the presence of PEG‐benzoate and PEG‐palmitate enriching β‐galactosidase in the salt phase whereas in the case of glucose oxidase, PEG‐Coomassie brilliant blue G‐250 derivative worked as a better affinity ligand for other proteins. A 19‐fold purification was obtained with the PEG dye derivative after 5 stage cross extractions with 80% recovery of glucose oxidase and an enrichment factor upto ～7 for β‐galactosidase with the PEG‐TMA derivative. The interaction of PEG‐benzoate and PEG‐TMA ligands with the active site of β‐galactosidase has been evaluated by molecular modeling. The effect of the molecular weight of glucose oxidase on its partitioning was confirmed as the molecular simulation shows strong affinity interaction of PEG‐glucoside with the enzyme.     

Preparation and performance of a transparent poly(3,4‐ethylene dioxythiophene)–poly(p‐styrene sulfonate‐co‐acrylic acid sodium) film with a high stability and water resistance

Poly(p‐styrene sulfonate‐co‐acrylic acid sodium) (PSA) from the copolymerization of acrylic acid sodium and p‐styrene sulfonate monomers were used to dope poly(3,4‐ethylene dioxythiophene) (PEDOT) to generate PEDOT–PSA antistatic dispersions. Compared to those of the PEDOT–poly(p‐styrene sulfonate sodium) (PSS), the physical and electrical properties of the PEDOT–PSA conductive liquids were much better. The PEDOT–PSA films possessed a better water resistance without a decrease in the conductivity. The sheet resistance of the PEDOT–PSA–poly(ethylene terephthalate) (PET) films was about 1.5 × 10⁴ Ω/sq with a 100 nm thickness, the same as the PEDOT–PSS–PET films. The transmittance of the PEDOT–PSA–PET films exceeded 88%. Furthermore, the environmental dispersity of the PEDOT–PSA antistatic dispersion was apparently improved by the dopant PSA so that the stability was extraordinarily promoted. Meanwhile, the water resistances of the PEDOT–PSA–PET and PEDOT–PSA films were also enhanced. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45163.     

Block copolymers of n-propyl p-styrene sulfonate with isoprene and styrene: Synthesis,characterization, and phase separation behavior

A series of ABA block copolymers based on n-propyl p-styrene sulfonate (A block) and isoprene or styrene (B block) were synthesized and characterized. The synthesis was based on methods developed previously for the anionic polymerization of n-propyl p-styrene sulfonate [S. J. Whicher and J. L. Brash, J. Polym. Sci., Polym. Chem. Ed., 19 , 1995 (1981)], and consisted of forming a polyisopryl dianion by initiation with sodium naphthalene in THF at 0°C. n-Propyl p-styrene sulfonate was then added and propagated at ?94°C. As was the case for n-propyl p-styrene sulfonate alone, it was found that only limited chain growth of this monomer initiated by living polyisoprene was possible, resulting in maximum A block molecular weights of about 10,000. The phase separation behavior of copolymers having a range of composition, as well as that of a blend of polyisoprene and poly(n-propyl p-styrene sulfonate) was investigated by examining thin films in the electron microscope. In the copolymers, phase separation was observed with transmission EM when THF was used as the solvent for film casting. Domain morphology was as expected for the various copolymer compositions. When films were cast from chloroform, phase separation was minimal, although it could be improved by annealing. Annealing produced relatively diffuse intermixed domains which occasionally formed unusual triangular patterns. Phase separation of the blend of homopolymers gave domains that were large enough to be mapped with SEM using both secondary electron and EDXA detectors.     

Synthesis of Sodium (+)-(12S,13R)-Epoxy-cis-9-octadecenyl Sulfonate from Vernonia Oil

A water-soluble, foaming epoxyalkene sulfonate, sodium (+)-(12S,13R)-epoxy-cis-9-octadecenyl sulfonate, was synthesized from vernonia oil (VO) by a series of simple reactions that include transesterification, metal hydride reduction, tosylation, and S_N2 reactions. Conversion of VO into vernonia oil methyl esters (VOME) using sodium methoxide was quantitative. Subsequent reduction of VOME with lithium aluminum hydride yielded (+)-(12S,13R)-epoxy-cis-9-octadecenol (94%), along with minor amounts of hexadecenol, octadecenol, cis-9-octadecenol, and cis-9,12-octadecandienol. The (+)-(12S,13R)-epoxy-cis-9-octadecenol, was tosylated with p-toluenesulfonyl chloride to give (+)-(12S,13R)-epoxy-cis-9-octadecenyl tosylate at 96% yield. Iodination of the tosylate with sodium iodide and subsequent S_N2 reaction with sodium sulfite afforded (+)-(12S,13R)-epoxy-cis-9-octadecenyl sulfonate (63% yield). This study demonstrates the ability to produce an epoxyalkenyl sulfonate, belonging to a class of anionic surfactants, from VO without destroying the epoxy functionality in the (+)-(12S,13R)-epoxy-cis-9-octadecenyl moiety of VO. The critical micelle concentration of the synthesized sulfonate was also determined.     

Competitive interaction of polyanions and anionic dye with bovine serum albumin

The binding of anionic dye, p-(2-amino-6-sulfonyl-8-naphthylazo)benzene sulfonic acid disodium salt (ASANA) to bovine serum albumin (BSA) at pH 7.5 has been studied by spectrophotometric techniques. The values of the dissociation constants were obtained with the use of the Benesi-Hildebrand equation for ASANA. Competitive binding of polyanions, sodium poly(styrene sulfonate) (PSSNa), potassium poly(vinyl sulfonate) (PVSK), poly(acrylic acid) (PAA), and poly(methacrylic acid) (PMAA) and anionic dye to BSA was evaluated through the variations in the different spectra of BSA-dye-polymer systems.     

Adsorption of Anionic Surfactant Mixtures by Polymeric Resins

Abstract

Results concerning the single-solute adsorption of two anionic surfactants were presented in a previous paper; this paper deals with their mixtures. Equilibrium adsorption isotherms of mixtures of sodium lauryl sulfate and sodium dodecylbenzene sulfonate in aqueous solution by Amberlite XAD-4 and XAD-7 polymeric resins at 10 and 30°C have been obtained and are compared to the predictions given by several multicomponent adsorption models that make use of the single solute adsorption data already available. Reasonable agreement has been achieved in some cases, especially when predicting total surfactant adsorption.     

Effective Separation of Petro Products through Hydrotropy

This paper presents a comprehensive study on the effect of hydrotropes such as sodium salicylate, sodium benzoate, and nicotinamide on the separation of a near boiling mixture, o‐/p‐xylene. The influence of a wide range of hydrotrope concentrations (0 to 3.0 mol/L) and different system temperatures (303 to 333 K) on the separation of o‐/p‐xylene were studied. All hydrotropes used in this work showed an enhancement in the percentage extraction of p‐xylene to different degrees. The percentage extraction of p‐xylene from the o‐/p‐xylene mixture increases with an increase in hydrotrope concentration and also with system temperature. A minimum hydrotrope concentration (MHC) was found essential to initiate significant extraction of p‐xylene from the o‐/p‐xylene mixture. The maximum enhancement factor, which is the ratio of the value in the presence and absence of a hydrotrope, was determined for both cases. The Setschenow constant, k_s, a measure of the effectiveness of a hydrotrope, was determined for each case.     

Extractive Distillation of p-Cresol/2,6-Xylenol Mixtures in the Presence of Alkanolamines

Abstract

The separation of p-cresol/2,6-xylenol mixtures has been investigated by extractive distillation in the presence of alkanolamines. The interaction parameters of liquid phase models, such as Wilson, NRTL, and UNIQUAC, have been estimated from binary vapor-liquid equilibrium data. The predicted relative volatility values for the p-cresol/2,6-xylenol mixtures in the presence of the alkanolamines were compared with experimental data.