Sukalyan Dash

Clouding behaviour in surfactant systems

A study on the phenomenon of clouding and the applications of cloud point technology has been thoroughly discussed. The phase behaviour of clouding and various methods adopted for the determination of cloud point of various surfactant systems have been elucidated. The systems containing anionic, cationic, nonionic surfactants as well as microemulsions have been reviewed with respect to their clouding phenomena and the effects of structural variation in the surfactant systems have been incorporated. Additives of various natures control the clouding of surfactants. Electrolytes, nonelectrolytes, organic substances as well as ionic surfactants, when present in the surfactant solutions, play a major role in the clouding phenomena. The review includes the morphological study of clouds and their applications in the extraction of trace inorganic, organic materials as well as pesticides and protein substrates from different sources.

Organically modified silica: synthesis and applications due to its surface interaction with organic molecules.

Silica gels can be chemically modified using organic precursors producing organically modified silica (ORMOSIL), a class of novel materials for hosting varieties of organic and inorganic substrates. Ormosil matrixed materials show an enhanced activity during catalysis, photochemical activities like absorption and emission, electrochemical sensitivities, sensing of gases, solvents, pH of solution and biomolecules, etc. Ormosil-based materials can be used as efficient protective coatings and can be utilized in designing wave guides that can carry out excellent photonic transmission of information. The synthetic and chemical modification of ormosil and some of the above applications have been discussed.

Sorption on eggshell waste--a review on ultrastructure, biomineralization and other applications.

The structure, adsorption behavior and applications of eggshell waste materials have been reviewed. The ultrastructure of eggshell particles has been discussed to understand the pore structure as well as the surface geometry of the materials leading to its multifarious applicability. Besides, the ultrastructure studies give full information regarding the chemical constituents of egghell particles as well as eggshell membranes. The process of biomineralization in living organisms, their consequent effect of controlling the formation of inorganic-organic composites propelling their application in biomimetic designing of advanced composites with optimized novel properties leading to advances in materials design have been discussed. Utilization of eggshell waste materials for the removal of organic dyes and heavy inorganic ions has been reviewed with suitable models for understanding their adsorption quality and capacity. The applications of these materials in various fields of research have been extensively discussed.

Preferential solvation of styrylpyridinium dyes in binary mixtures of alcohols with hexane, dioxane, and dichloromethane.

The absorption maxima of N-alkyl(methyl, hexyl, and hexadecyl)-4-[(4-N,N-dimethylamino)styryl]pyridinium halides in binary solvents were analyzed for probing preferential solvation by any one of the solvents. The probes have a donor-acceptor system and the corresponding absorption bands are found to be solvent-sensitive. In neat solvents, excluding a few, reversal in solvatochromism was observed, identifying a polarity scale for solvatochromic switch, which appears around 45-50 E(T)(30) scale. The change in apolarity due to change in alkyl chain in the probe could not sway the scale, as the solvatochromism in neat solution is due to the chromophoric group only. When one solvent is considered as the parent solvent (hexane, dichloromethane, and dioxane) and the other as cosolvent (10 different alcohols), the solvation phenomena of these probes have been investigated. Due to solvent-solvent interactions, in some cases, hypo- and hyperpolarity in the solvent cage were observed. The preferential solvations of the dyes by these solvents were analyzed by consideration of the interactions of solvents with hydrophilic and hydrophobic groups of the probes. Tentative orientations of the solvent molecules around the probes were proposed. Disorder of the solvents around the probes was also considered for preferential solvation phenomena.

Eggshell Particles (ESP) as Potential Adsorbent for Styryl Pyridinium Dyes—A Kinetic and Thermodynamic Study

Eggshell particles (ESP) of a definite mesh size have been prepared and characterized through infrared and scanning electron microscopy. Adsorption of some styryl pyridinium dyes (SP-1 and SP-2) has been studied on ESP surface from water-ESP interface and the effects of adsorbate concentration, adsorbent dosage, temperature, salts, and the contact time have been examined. A first time study of the effect of water-structure making salt (kosmotroph) such as NaCl and structure breaking salt (chaotroph) such as KCl and NH4SCN on the adsorption process on ESP has been reported. Both types of salts have opposing effects on the adsorption of SP-1 dye; however, in case of SP-2 dye both of them show similar effects. The adsorption process is found to follow a second order kinetics. Thermodynamic studies show the occurrence of a physical adsorption with exothermic energetic. The adsorption follows Langmuir isotherm model and the area of coverage has been calculated to show the impact of hydrogen bonding on the adsorption phenomenon.

Effect of temperature on pseudoternary system Tween-80–butanol–hexane–water

Phase diagrams of pseudoternary systems of Tween-80, butanol, hexane and water were constructed by a visual titration method. The cloud points (CPs) at various compositions were determined and the variations in the cloud points were analyzed on the basis of changes in the composition of the different components in the microemulsions. A quantitative model was established by using multiple regression analysis considering weight percent of emulsifier (surfactant+cosurfactant) and oil as independent variables. A lowering in the CP with increase in emulsifier content and decrease in oil content was observed. Addition of sodium chloride also depressed the CP significantly. Further, with the increase in temperature the turbid phase started separating to three different transparent zones. The upper layer was recognized as the oil-rich phase, middle layer was due to microemulsion and the lower layer was found to be a micellar system. Metal ions and colored organic substrates partitioned into these different phases, which provides scope for applications in metal ion preconcentration.

Adsorption of Some Tailor-Made Styrylpyridinium Dyes on Sodium Dodecylsulphate-Treated Eggshell Particles (SDS-ESP): Impact of Dye Chain-Length and Substituent

Eggshell particles (ESP), a solid bio-waste, treated with sodium dodecylsulfate (SDS) have been examined for the adsorption of some tailor-made cationic styrylpyridinium dyes. The adsorbent is characterized through Fourier transform infrared spectroscopy and scanning electron microscopy. The anionic headgroups of the surfactant bilayer on the SDS-treated ESP (SDS-ESP) provide avenue for binding with the dye molecules. Dependence of equilibrium adsorption capacity on various adsorption parameters and effects of substituent and hydrophobic tail of the adsorbate on adsorption are enumerated. Physical adsorption obeying pseudo-second order kinetics has been proposed. (Supplemental materials are available for this article. Go to the publishers online edition of Journal of Dispersion Science and Technology to view the free supplemental file.)

Tween-80–n-Butanol–Diesel–Water Microemulsion System—A Class of Alternative Diesel Fuel

Tween-80–n–butanol–diesel–water microemulsion systems with various surfactant:cosurfactant (S:C) ratio have been reported as a class of alternative diesel fuel from their phase behavior, clouding phenomena, conductivity, turbidity, and inflammation studies. Temperature induced clouding of microemulsion containing 2% brine at an S:C ratio of 1:1 from a suitable turbid zone has been examined to see the stability of the diesel–water microemulsion systems. Regression models have been proposed to understand the impact of various components of the microemulsion on their cloud point (CP) values. Conductivity of the microemulsions at various S:C ratio increases with the volume of brine having two cut points depicting the presence of three microheterogenous phases within the system, whereas turbidity shows a linear increase. Dye-probed investigation of water-rich and oil-rich zones of the microemulsions indicates the involvement of a dynamic mass transfer process within the various zones. The intensities of flames produced during burning of the microemulsions with various O:E:W weight percentages selected from the isotropic regions of the phase diagrams have been estimated using MATLAB image processing method and the impacts of various components on the fuel use of the microemulsions have been analyzed.

Alkylation of Ethanolamines: An Approach to a Novel Class of Functional Surfactants

Abstract Some monomeric and dimeric surfactants with functional head groups have been synthesized from di- and triethanolamine synthons. The treatment of alkyl bromide with triethanolamine resulted in simultaneous N-alkylation and O-alkylation products. However, with diethanolamine, N-alkylated products were obtained, which were further used to synthesize various double-tailed surfactants and gemini surfactants.

β-CD assisted dissolution of quaternary ammonium permanganates in aqueous medium

The non-polar internal cavity of β-cyclodextrin (β-CD) has been exploited for the entrapment of the hydrophobic tails of two water insoluble quaternary ammonium permanganates (QAPs): cetyltrimethylammonium permanganate (CTAP) and tetrabutylammonium permanganate (TBAP), for solubilization in aqueous medium. The solubilization and organizational behavior of the QAPs in aqueous β-CD solution have been determined from the comparison of their rates of self-oxidation in presence and in absence of β-CD. Effect of QAP concentration on their observed rate constants (k(obs)) at a fixed β-CD concentration, phase solubility analysis in varying β-CD concentration, impact of quaternary ammonium bromides (QABs) on the kobs values of CTAP and TBAP at fixed QAP and β-CD concentrations, and the temperature effect have been reported. A scheme to explain the solvation of QAPs in aqueous β-CD has been proposed based on dynamic light scattering (DLS) analysis of the samples.