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.     

Hydrotropic effect and thermodynamic analysis on the solubility and mass transfer coefficient enhancement of ethylbenzene

Concentrated aqueous solutions of a large number of hydrotropic agents, urea, nicotinamide, and sodium salicylate, have been employed to enhance the aqueous solubilities of poorly water soluble organic compounds. The influence of a wide range of hydrotrope concentrations (0–3.0mol·L^?1) and different system temperatures (303–333 K) on the solubility of ethylbenzene has been studied. The solubility of ethylbenzene increases with increase in hydrotrope concentration and also with system temperature. Consequent to the increase in the solubility of ethylbenzene, the mass transfer coefficient was also found to increase with increase in hydrotrope concentration at 303 K. The enhancement factor, which is the ratio of the value in the presence and absence of a hydrotrope, is reported for both solubility and mass transfer coefficient of ethylbenzene. The Setschenow constant, K _s , a measure of the effectiveness of a hydrotrope, was determined for each case. To ascertain the hydrotropic aggregation behavior of ethylbenzene, thermodynamic parameters such as Gibb’s free energy, enthalpy, and entropy of ethylbenzene were determined.     

Equilibria,Kinetics, and Modeling of Extraction of Citric Acid from Aqueous Solutions with Alamine 336 in 1-Octanol

Experimental equilibrium and kinetic data on the extraction of citric acid from aqueous solutions using Alamine 336 in 1-octanol have been determined. The distribution coefficient has increased from 0.029 to 71.727 with increase of Alamine 336 concentration from 0 to 30% (v/v). The chemical equilibria was interpreted as a result of consecutive formation of acid-amine species with 1:1 stoichiometry and the equilibrium complexation constant, K _E1 , has been estimated as 20.186 m³ kmol^?1. The mass-transfer coefficients of citric acid, Alamine 336, and 1:1 acid-alamine complex in 1-octanol were calculated from acetic acid mass-transfer coefficient, which was determined by measuring its fluxes of simple diffusion from kerosene to water. Based on the Hatta number and the criterion given by Doraiswamy and Sharma, the reaction regime has been found to be instantaneous reaction regime occurring at the interface on the organic phase side. An extraction model comprising 1:1 equilibrium complextion constant, K _E1 , and complex mass-transfer coefficient, k _BA (3.79 × 10^?6 m s^?1), has been developed, and it explained the present system satisfactorily.     

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.     

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.     

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.     

Hydrotropic properties of some short-chain alkylbenzene- and alkylnaphthalene sulfonates

Alkylbenzene sulfonates based on toluene, xylene and cumene, and alkylnaphthalene sulfonates act as hydrotropes in surfactant systems. One measure of hydrotropicity is the amount of hydrotrope required to clear a cloudy detergent formulation; some hydrotropes are more effective than others, depending on the surfactant formulation. Another measure is the modification of the viscosity of surfactant formulations; the change in the viscosity depends on the amount and type of hydrotrope used and on the specific formulation involved. Additionally, alkylnaphthalene sulfonate hydrotropes change the solubility of nonionic surfactants in water, and both types of hydrotrope raise the cloud point of nonionic surfactant solutions; however, the naphthalene-based hydrotropes are more efficient. Ross-Miles foam test data are used to compare the foam characteristics of different alkylnaphthalene sulfonates. A critical micelle concentration (CMC) was determined for the alkylnaphthalene sulfonates, but although alkylbenzene sulfonates do show some surface activity, a CMC could not be found for these materials. Presented as a poster session at the AOCS Annual Meeting & Expo, May 1997, Seattle, Washington, and at Soaps, Detergents, and Oleochemicals: An AOCS International Conference, October 1997, Fort Lauderdale, Florida.     

Hydrotropic properties of a novel alkylnaphthalene sulfonate

Alkylbenzenesulfonates based on toluene, xylene, as well as cumene, and alkylnaphthalenesulfonates, act as hydrotropes in surfactant systems. A novel sodium diisopropyl-naphthalene sulfonate (SDIPNS) has been devepoped that contains about 92% diisopropylnaphthalene sulfonate, compared to other diisopropylnaphthalene sulfonate preparations that contain less than 50% diisopropylnaphthalene sulfonate. This material is both a hydrotrope and a surfactant. The color of a 35% solution is light yellow, Gardner 3, significantly lighter than comparable materials. Draves wetting time for a 0.5% solution is about 30 s. The Ross-Miles foam test (1% solution) indicates a significant level of initial foam, but the foam is unstable. The solubilites of toluene and limonene in SDIPNS are much higher than in other hydrotropes tested. Hydrotropes raise the cloud point of nonionic surfactants; SDIPNS is the most efficient hydrotrope found for this application. Another measure of hydrotropicity is the amount of hydrotrope required to clear a cloudy detergent formulation; this hydrotrope is quite effective. Another measure is the modification of surfactant formulation viscosity; SDIPNS is quite effective. Additionally, SDIPNS changes the solubility of nonionic surfactants in water. SDIPNS is a surfactant as well as a hydrotrope, demonstrating a critical micelle concentration at about 1%. Presented as a poster session at the American Oil Chemists' Society Annual Meeting & Expo, May 11–13, 1998, Chicago, IL.     

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.     

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.     

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.     

Partitioning of o/p-Nitrophenols in the Presence of Hydrotropes in Aqueous Solutions

Abstract

Partitioning of o/p-nitrophenols between organic solvents and water in the presence of hydrotropes such as sodium toluene sulfonate, sodium xylene sulfonate, and sodium cumene sulfonate, has been experimentally investigated and modelled in terms of co-aggregation of the hydrotrope and nitrophenols in aqueous solutions. The phenol-hydrotrope and hydrotrope-hydrotrope interactions are characterized by an aggregation model. The experimental data for a series of hydrotropes are further used to predict the partitioning behavior of p-nitrophenol in the presence of sodium butyl benzene sulfonate (Na-NBBS). The aggregation number of NaNBBS, (～30) obtained from the partitioning data, matches well with that obtained by small angle neutron scattering.     

Comparative Study on Reactive Extraction of Picolinic Acid with Six Different Extractants (Phosphoric and Aminic) in Two Different Diluents (Benzene and Decan-1-ol)

The equilibrium study on reactive extraction of picolinic acid by six different extractants (phosphoric and aminic) dissolved in two different diluents (benzene and decane-1-ol) is carried out to evaluate the performance of extractants and diluents. The extraction ability in terms of the distribution coefficient (K _D) is found to be in the order of tri-n-octylamine (TOA) ≥ tri-n-dodecylamine (TDDA) > di-2-ehylhexyl phosphoric acid (D2EHPA) > tri-n-butyl phosphate (TBP) > tri-octyl methyl ammonium chloride (Aliquat 336) > tri-n-octyl phosphine oxide (TOPO) with both diluents. Decan-1-ol is found to be the better solvating medium for the acid-extractant complexes. A mathematical model based on mass action law is employed to estimate the values of partition coefficient (P) and dimerization constant (D) in physical extraction, and equilibrium extraction constants (K _E) in chemical extraction. The values of loading ratios (Z) less than 0.5 imply the formation of (1:1) acid:extractant solvates in the organic phase. Decan-1-ol with TOA is the most effective solvation medium with K _{D, max} = 9 at 0.01 kmol · m^?3 of picolinic acid and K _E = 19.448 m³ · kmol^?1.     

酸性助水溶剂脱除木质素机理分析

系统探讨了酸性助水溶剂对甲苯磺酸(p-toluenesulfonic acid,TSA)和马来酸(maleic acid,MA)分离桉木各组分的工艺过程,并对其中木质素脱除机理进行了研究。通过分析对比两种优化后的工艺发现：(1)两种酸性助水溶剂都可以高效脱除木质素,TSA木质素脱除率为67.94%,MA为65.14%;(2)在相同质量分数下,TSA的木质素脱除率比MA更高;(3)在温和条件下,TSA木质素的β-芳醚键含量比MA的高,随着反应条件的加剧,TSA和MA处理后木质素产品中β-芳醚键含量逐渐减少;(4)两种酸性助水溶剂处理后,纤维素保留率都较高,可保持90%以上;但是半纤维素的降解程度随着反应条件的加剧而增加;(5)酸性助水溶剂质量分数越高,在疏水表面的接触角越小,对木质素的助溶作用越明显,脱除木质素效率越高,溶液中木质素聚集体的粒径越小。综上所述,酸性助水溶剂对木质素的脱除基于润湿溶解、木质素芳醚键断裂、半纤维素降解等的综合作用。相关研究可为后续实现温和条件脱木质素工艺优化及机理提供参考。     

REACTIVE EXTRACTION OF LEVULINIC ACID FROM AQUEOUS SOLUTIONS WITH TRI-n-OCTYLAMINE (TOA) IN 1-OCTANOL: EQUILIBRIA,KINETICS, AND MODEL DEVELOPMENT

Levulinic acid, a carboxylic acid containing a ketone structure, can be used as an acidulant in foods and beverages. Reactive extraction is a promising alternative for the recovery of carboxylic acids from aqueous streams. The design of an amine extraction process requires kinetic data for the acid-amine + solvent system used. In this study, equilibrium and kinetic data on the extraction of levulinic acid from aqueous solutions using tri-n-octylamine (TOA) in 1-octanol have been determined. The mass transfer coefficients of levulinic acid, TOA, and 2:1 levulinic acid-amine complex in 1-octanol were calculated from the acetic acid mass transfer coefficient, which was determined by measuring its fluxes of simple diffusion from kerosene to water. Based on the Hatta number and the criterion given by Doraiswamy and Sharma, the reaction regime has been found to be instantaneous reaction regime occurring at the interface on the organic phase side. An extraction model comprising equilibrium complexation constant w.r.t 2:1 levulinic acid-TOA complex formation, K_E2i (14.794 (m³ kmol^?1)²), and complex mass transfer coefficient, k_B2A (2.193 × 10^?6 m s^?1), has been developed.     

Reactive Extraction of Pyridine Carboxylic Acids with N,N-Dioctyloctan-1-Amine: Experimental and Theoretical Studies

The paper represents the equilibrium study on reactive extraction of pyridine-3-carboxylic acid (NA) and pyridine-4-carboxylic (iNA) acid from aqueous solution by N, N-dioctyloctan-1-amine (TOA) dissolved in five different diluents [dodecane, methyl benzene, decan-1-ol, 4-methylpentan-2-one (MIBK), and chloroform] at constant temperature of 298 ± 1 K. According to an experimental study, the extraction ability of diluents with TOA is found to be in the order of chloroform > decan-1-ol > MIBK > methyl benzene > dodecane for both acids. The highest extraction efficiency in terms of the distribution coefficient (K _D) is found to be 45.15 and 25.79 for NA (0.12 mol · dm^?3) and iNA (0.03 mol · dm^?3), respectively. The values of loading ratio, Z (between 0.194 and 0.512) for both acids indicate the formation of 1:1 acid-TOA complexes in the organic phase. The values of the equilibrium constants (K ₁₁) are determined from the experimental data using mass action law. These estimated values of K ₁₁ are compared with the predicted values of K ₁₁ from relative basicity and linear solvation energy relationship (LSER) models. The LSER model predicts the K ₁₁ with an error limit of ±3% for NA and ±2% for iNA.     

Employing Luminescence to Determine Eu-DTPA Complex Formation Rate Constants in Lactate and Citrate Media: Experiment and Aggregate-Species Kinetic Modelling

The formation kinetics for DTPA binding to europium ions in aqueous media were determined using the change in photoluminescence. The influence of lactic acid and citric acid on these kinetics were also investigated. The total formation rate constant of DTPA complexation with europium ions was strongly dependent upon the pH and DTPA speciation, with values ranging from 5 × 10³ M^–1s^–1 to >1 × 10⁶ M^–1s^–1 over the pH range 1.5 to 2.3. The ligand-metal binding in the presence of lactate and citrate ions showed an inverse kinetic behavior, with strongly decreasing reaction rates at higher buffer concentrations and pH.     

Study of Solubility Efficiency of Polycyclic Aromatic Hydrocarbons in Single Surfactant Systems

Water solubility enhancements of two polycyclic aromatic hydrocarbons i.e., naphthalene (Naph) and anthracene (Anth) in single surfactants system have been measured by UV–VIS-Spectrophotometer. The relationships between solubilizing capacity and their solubilization efficiency towards polycyclic aromatic hydrocarbons (PAH) have been quantified and discussed in terms of the molar solubilization ratio (MSR), the micelle-water partition coefficient (K _m) and standard free energy of solubilization (ΔG°_s). The micellar and surface properties of some cationic and anionic surfactants have been investigated by conductivity, surface tension and fluorescence measurements at 300 K. Above the CMC, maximum solubilization occurs in cationic surfactants where as the solubilization is least in the presence of anionic surfactants. The negative value of ΔG°_s shows spontaneity of the solubilization process. The MSR values are larger in naphthalene than anthracene (Naph > Anth). The present studies provide valuable information for the selection of surfactants for solubilizing water-insoluble compounds.     

Extraction of Piperine from Piper Nigrum (Black Pepper) by Aqueous Solutions of Surfactant and Surfactant + Hydrotrope Mixtures

Abstract

The effect of combining butyl benzene sulfonate as hydrotrope with a surfactant in aqueous solutions is investigated for isolation of piperine, an alkaloid, from black pepper. The standard free energy change associated with piperine solubilization in the aqueous solutions of surfactant and hydrotrope individually and in their mixtures is determined from the solubility of piperine in these solutions. A combination of sodium dodecyl sulfate (SDS) and the hydrotrope gives increased percentage extraction of piperine as compared to the hydrotrope alone. The piperine purity recovered from aqueous solutions was higher as compared to the purity of piperine recovered using organic solvents. The piperine crystallized from aqueous solutions of surfactants and hydrotrope also showed cleaner surfaces and uniform structures with sharp edges, unlike the particles crystallized from organic solvents.     

Interactions of Some Hofmeister Cations with Sodium Dodecyl Sulfate in Aqueous Solution

In this work, we have investigated the influence of some alkali metal ions on the Krafft temperature (T_K) and critical micelle concentration (CMC) of a classical ionic surfactant, sodium dodecyl sulfate (SDS), over a wide range of temperature. The alkali metal cations such as Li⁺, Na⁺, Cs⁺, and K⁺ are found to affect the solubility and hence the T_K of the surfactant. It was observed that kosmotropic Li⁺ lowers the T_K of the surfactant. Due to the common ion effect, the solubility of SDS decreases in the presence of Na⁺, resulting in an increase in the T_K. On the other hand, chaotropic K⁺ and Cs⁺, capable of forming contact ion pairs with the chaotropic dodecyl sulfate ion, lower the solubility and hence elevate the T_K. In terms of decreasing the T_K, the ions follow the trend: Li⁺ > Na⁺ > Cs⁺ > K⁺ except for 0.0025 M CsCl. The added cations screen the charge of the micelle surface and facilitate closer packing of the surfactant with a consequent decrease in the CMC. In terms of the effectiveness in lowering the CMC, the ions follow the order: Cs⁺ > K⁺ > Na⁺ > Li⁺. In the presence of added electrolytes, the γ_CMC values are found to be lower than the corresponding values in pure water. The thermodynamic parameters (Gibbs free energy, enthalpy, and entropy changes) of micellization were calculated to gain insights into the mechanism of the process.