J. M. GOHIL, A. BHATTACHARYA and P. RAY*
Central Salt and Marine Chemicals Research Institute, G. B. Marg, Bhavnagar-364002, Gujarat.

Abstract — Present investigation aims at the studies on the variation of surface tension of a phase inversion medium for Polysulfone (PSf) membrane having polyvinyl alcohol (PVA) (Mw 14,000) as a surface-active additive in the gelling bath. Dimethyl formamide (DMF) and water are functioning as solvent and non-solvent for PSf. The entrapment of PVA during gelling of PSf results in a fall in the concentration of PVA in the bulk as well as at the surface which is reflected in the uprising surface tension of the system and the rate of enhancement is dependent upon both the concentration of PSf and PVA.

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Abstract — The aquation of tris-(1,10 Phenanthroline) iron (II) ([Fe (phen)₃]²⁺) has been reported to be immeasurably slow at pH equal to 6.97. But, the reaction is accelerated in the Triton X-100/hexanol/cyclohexane reverse micellar medium. The reaction obeys simple first order kinetics with no evidence of auto inhibition. The first order rate constant (k₁) has been determined at different values of W ([H₂O]/[Triton X-100]). The rate (k₁) decreases with increasing value of W. k₁ increases with increase in Triton X-100 concentration, at constant values of W showing that the reaction takes place at greater speed at the micellar interface. The kinetic results can be interpreted by the uni molecular pseudo phase model. The effect of W on rate (k₁) is more pronounced in the range, W = 1.7 to 4.2 but less pronounced at higher W. The reaction is further accelerated by Cl^– and SCN^– ions and the kinetic results provide an unambiguous evidence for the formation of ion pairs between the cation [Fe (phen)₃]²⁺ and both of these anions. The formation of such ion pairs has not been observed in aqueous medium but has been reported earlier in water alcohol mixtures. This result therefore provides evidence for the lower micro polarity of the solubilised water compared to ordinary water.
 

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Abstract — Indian coals are having high ash content, so it is necessary to wash them in washery. This paper examines the water pollution problems due to the discharge of coal washery effluents in the river Damodar and focuses on the characteristics of the solids in suspension and their dispersion behavior in the river system. Since most of the washeries are situated near the Damoder and discharge their effluents into the river, it looked black color. Apart from suspended solids, COD values were also found to be abnormally high. The approach for the selection of sampling locations, methodology adopted for sampling and analysis for the development of pollutnat dispersion models in the river is presented. The results of pollution load at different points of the river stream were found to be comparable with those of the experimental results. Treatability study for the effective removal of SS was conducted and the optimum area required for clarification of the effluent has been evaluated. A treatment scheme has been proposed for the abatement of surface water pollution in the area.
 

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Abstract — The effects of addition of polyvinyl pyrrolidones (PVP) of varying molar masses on the micellar properties of the mixed cationic micellar system of cetyltrimethyl ammonium and tetradecyl trimethyl ammonium bromides were investigated. The values of critical aggregation and critical micellar concentrations were determined employing conductivity technique. A regular solution approach was employed to determine the effects of the polymers on the values of the interaction parameter (β) and the composition of the mixed micelles. The excess Gibbs free energy of mixing was also calculated. The results have been explained on the basis of an increase in the incompatibility between the surfactant monomers in the mixed state due to interaction of the polymers with the surfactant monomers and the steric hindrance caused by the PVP adsorption at the micelle-solution interface.
 

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Abstract — The present investigation deals with pharmaceutically acceptable and stable water continuous microemulsion systems with and without incorporation of chitosan, a biodegradable polymer. Pseudoternary phase diagrams were constructed using Capmul-MCM (oil phase), Tween 20 (surfactant) and distilled water alone or 1% chitosan aqueous solution. The model microemulsions were characterized with regard to its eosin absorption, electrical conductivity behavior, interfacial tension and particle size measurement after dilution with water. The area of microemulsion zone was found to be greater for polymer incorporated microemulsion system as compared to that of an aqueous system. The results obtained from eosin absorption and electroconductivity studies were useful for prediction of structural changes of icroemulsions as a function of water content. The interfacial tension changes associated with polymer based microemulsion revealed ultralow values. Moreover the investigated particle size and polydispersity index after dilution with an excess of continuous phase proved homogeneous and thermodynamically stable nature of the system and ensured efficiency of microemulsion systems as a drug carrier.
 

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Abstract - The aqueous system, gelatin-sodium dehydrocholate (NaDHC) was studied by conductivity, ion-selective electrodes, pH, surface tension and dye solubilisation techniques. The interaction among gelatine and dehydrocholate (DHC^-) and sodium ions was analysed. The system behaviour was more complex than that of gelatin and sodium dodecyl sulphate: Na⁺ and DHC^- ions reacted with gelatin even at very low concentration, and formed different complexes. Similar to other anionic surfactant-gelatin systems, there was formation of gelatine-adsorbed NaDHC micelles at a concentration about one order of magnitude lower than the NaDHC critical micelle concentration (CMC). Superimposed to the interaction with the protein, NaDHC also formed some premicellar aggregates, which have been found in aqueous NaDHC solution, and formed micelles at its own CMC.
 

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KAJARI MAITI^a, MADHUMITA PRASAD, AMRITA CHATTERJEE^a, P. K. BHATTACHARYA^b and S. P. MOULIK^a+*
^aCenter for Surface Science, Department of Chemistry, Jadavpur University, Kolkata-700 032, India
^bIndian Institute of Chemical Biology, Kolkata-700032, India.
 

Abstract - Chiral compounds I, II, III and IV have been synthesized and characterized. Their interfacial (at air/solution interface) adsorption and self-association in aqueous medium have been studied by tensiometric, conductometric and spectrophotometric methods. The compounds have been found to form micelles in solution with low CMC values. The results have been analyzed and thermodynamics of the micellization of the chiral compounds and their adsorption at the air/solution interface have been evaluated and discussed.
 

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Abstract - Aqueous micellar solutions of nonionic n-dodecyloligo ethyleneoxide surfactants, dodeca and pentadeca oxyethylene n-dodecylether, C₁₂ and C₁₂E₁₅ [CH₃ (CH₂)₁₀ CH₂ (OCH₂ E₁₂CH₂)₁₂/₁₅ OH] have been investigated at different pH (acidic to alkaline) and in the presence of NaCl at different temperatures. The interfacial and micellization properties have been studied from surface tension measurements using du Nouy tensiometer. The cmc shows maximum value at neutral pH. With increase in the concentration of NaCl and also with the increase of temperature (35–50ºC), the cmc decreases. Apart from the thermodynamic quantities of micellization as well as adsorption at air/water interface, the heat capacity ( ∆C_p.m), transfer enthalpy ( ∆H_m.tr), transfer heat capacities ( ∆C_p.m.tr), and Traube (σ ) constant have been evaluated and discussed. Both micellization and adsorption processes have been found to be endothermic at all pH and in the presence of NaCl. An enthalpy-entropy compensation effect has been observed with an isostructural temperature from 299-315 K for both the micellization and interfacial adsorption processes. The CPs of C₁₂E₁₂ and C₁₂E₁₅ were significantly affected by the presence of NaCl but variation in pH does not have much C12effect. The micelle aggregation number (N_agg) has been measured by using steady state fluorescence quenching method at a total surfactant concentration ~ 10 mM at 30ºC. The micropolarity and the binding constant (K_sv) for C₁₂E₁₂ and C₁₂E₁₅ in the presence of increasing concentration of NaCl E12(0.1, 0.25, 0.5, 0.75 and 1.0M) were determined from the ratio of the intensities of the first and the third vibronic peaks (I₁/I₃) of pyrene fluorescence emission spectrum. The micellar interiors were found to be reasonably polar.
 

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Physicochemical Studies of Some Single and Mixed Microemulsion Systems. I : Phase Behaviour of Surfactant/Cosurfactant/Oil/Water Systems and the Effect of Temperature, Additives and Oil.

Abstract - Phase behaviours of pseudo-ternary systems containing surfactants (single and mixed)/ cosurfactant(s)/ oil(s)/water have been studied at 30ºC. The influence of charge types (cationic, anionic and nonionic) of surfactants along with their chain lengths, structure and mixing ratios, type of cosurfactants and oils (hydrocarbon, nonhydrocarbon, ester of myristic acid, plant/vegetable) on the extent of monophasic domain in the phase diagrams has been investigated. Role of cosurfactant of different lipophilicities vis-a-vis structures has been explained for microemulsions using hydrocarbon (iso-octane) and plant oil (eucalyptus). Development of microemulsions (both single and mixed surfactant types, nonionic-anionic, nonionic-cationic) with specific properties, namely, large monophasic domain using both hydrocarbon as well as plant/vegetable and biocompatible type of oils (clove, saffola, eucalyptus, isopropyl myristate) in single and mixed proportion, has been emphasized. In addition, some representative phase studies of single (CPC, CTAB, SDS and SDBS) and also mixed with nonionic surfactant (Brij-35) at different mass proportions using cosurfactants (1-butanol and 2-butanol) in four different types of oils (cyclohexane, heptane, isobutyl benzene and isopropyl myristate) have been carried out with a nonaqueous polar solvent (formamide) for comparison with water. The effect of temperature and additives (sodium chloride, urea and glucose) on the stability as well as on the extent of monophasic domain of single and mixed microemulsion systems has been explored. A data-base comprising large monophasic domain with high solubilization power and other characteristic features has been developed.
 

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Abstract - The extent of adsorption of long chain synthetic cationic and anionic surfactants on the surface of insoluble stearic acid (SA) powder has been studied at different physico-chemical conditions. The results have been presented in terms of adsorption isotherms and various thermodynamic parameters. Cationic surfactants like cetyltrimethylammonium bromide (CTAB) and myristyltrimethylammonium bromide (MTAB) can be adsorbed at the interface of insoluble stearic acid powder, where as in the case of anionic surfactant, sodium dodecyl sulphate (SDS), the excess positive hydration of stearic acid particle has taken place so that the adsorption of the surfactant becomes negative. All the isotherms for adsorption of cationic surfactants have similar features. Initially the extent of adsorption ( Г^m₂) increases with increase of surfactant concentration (C₂) in the bulk until it reaches the maximum value Г^m₂. At very high values of C₂, Г¹₂ again increases from value of Г^m₂ as a result of surface aggregation of adsorbates. Values of standard free enrgy change, ∆G° for adsorption of cationic surfactant per kg of stearic acid estimated on the basis of the integrated form of the Gibbs adsorption equation, are found to vary linearly with Г^m₂. Standard free energy change, ∆G^o_bfor transfer of one mole of CTAB from bulk to stearic acid surface estimated from the slope of ∆G° vs Г^m₂ plot is 32 kJ mol^–1. The adsorption process is found to be partly entropy and partly enthalpy controlled.