Volume 50, Issue 6

The present study describes a screening approach in design of microemulsion preconcentrates (self-microemulsifying systems) comprising: PEG-8 caprylic/capric glycerides (Labrasol®) (surfactant), PEG-40 hydrogenated castor oil (Cremophor® RH40) (cosurfactant) (at surfactant-to-cosurfactant mass ratios 9:1, 7:3, 5:5, 3:7 and 1:9), and 10% w/w or 20% w/w of medium-chain triglycerides or olive oil (oil). The self-microemulsifying ability of the prepared surfactant/cosurfactant/oil mixtures in water and 0.1 M HCl (pH 1.2), was evaluated by droplet size and zeta potential analysis and cross-polarized light microscopy. The formation of microemulsions was observed only in the presence of medium-chain triglycerides at surfactant-to-cosurfactant ratios 7:3 and 5:5 (in the mixtures containing 10% w/w of the oil phase) and 3:7 and 1:9 (when 20% w/w of the same oil was used). The obtained results provide new implications for development of microemulsion preconcentrates suitable as delivery systems for food and pharmaceutical applications.

The adsorption of micro-organisms can be used in separation of valuable minerals from their gangue minerals. The coal is one of the important sources of energy. Most of the coal deposits are low rank coals that contain sulfur compounds and mineral matters which release harmful and toxic gases while burning of coal. In the current study, the interaction of Mycobacterium phlei ( M. phlei ) with coal was characterized with several techniques such as zeta potential, adsorption kinetics, adsorption isotherms and Fourier Transform InfraRed (FT-IR). In addition, the M. phlei was tested for sulfur and ash removal from coal. The results of surface characterization indicated that the optimum pH was 2–4 where the M. phlei is physically adsorbed to coal particles due to slight electrostatic interactions as well as the hydrophobic interaction. The M. phlei increases the coal separation selectivity from its associated impurities and reduces the total sulfur and ash to 0.9%and 2.1%, respectively.

The Gemini surfactant, N,N′-bis(sodium lauryl acyl proyl acid) ethylenediamine, was synthesized and symbolized as DLMC. The surface chemical properties and micellar behavior of DLMC with polyethylene oxide lauryl ether (C 12 E 6 ) in 0.1 mol · L −1 sodium bromide aqueous solution were investigated by surface tention measurements at 298 K. The critical micelle concentration (cmc) of DLMC is 1.01 × 10 −4 mol L −1 , and the cmc values of the binary surfactant system are all lower than those of pure constituent surfactants. The interaction parameter β of the binary surfactant system was calculated, which indicates the existence of synergism in surface tension reduction efficiency, mixed micelle formation and surface tension reduction ability.

Amphoteric surfactant, sodium N-lauroylglycine, was synthesized and symbolized as SLG. The surface chemical properties and micelle behaviors of SLG in 0–0.5 mol · L −1 aqueous solution of sodium chloride were investigated by surface tension measurements at 298–313 K. The critical micelle concentrations (cmc) of pure surfactant were determined in 0–0.5 mol · L −1 sodium chloride aqueous solution. Fluorescence and micelle aggregation number ( N agg ) measurements have been used to investigate the variations of micro-polarity and micellization behavior. The added NaCl has a tendency to increase the attractive interaction between the surfactant molecules in both the micellar phase and the adsorption layer. The Gibbs free energy of micellization (Δ G m 0 ) is negative for all investigated systems, and the thermodynamic parameters of SLG indicate that the micellization of SLG is entropy driven.

Two mixture solutions consisting of sulfo-betain zwitterionic surfactant and alcohol ether sulfate (AES) are designed and prepared; their surface tensions and critical micelle concentrations (cmc) with different mole ratio are determined by surface tensions scanning. With pseudo-regular solution theory, the interaction parameters in the micelle ( β m ) and at the surface ( β σ ) are evaluated. As the results reveal two different mixtures of sulfobetaine-(I)/AES and sulfobetaine-(II)/AES show good synergistic behaves in both surface tension reduction effectiveness/efficiency and mixed micelle formation at all mole fractions investigated.

A novel colorimetric method to measure the emulsifying ability of surfactants for crude oil has been proposed. The emulsifying ability of five surfactants for two kinds of crude oil was determined at different temperatures and salinities. The oil-water interfacial tension, particle size distribution of emulsion, emulsion stability and ability of reducing viscosity by emulsifying were investigated at the corresponding condition. The results show that there is no correlation between emulsifying ability and HLB value of surfactants. The property of crude oil has a certain impact on the emulsifying ability, and the interfacial activity is the main influencing factor on it. The emulsifying ability is affected obviously by temperature. At first it increases and then it decreases with rising temperature. Inorganic salts of low concentration are beneficial to enhance the emulsifying ability. The emulsifying ability has negative correlation with the particle size of emulsion, and positive correlation with the ability of reducing viscosity by emulsifying. There is no inevitable relation between emulsifying ability and emulsion stability.

Chromic acid oxidation of tartaric acid in aqueous acid media produces glycolaldehyde very sluggishly at room temperature. Suitable combination of promoter (2,2′-bipyridine and 1,10-phenanthroline) and micellar catalyst (sodium dodecyl sulphate, cetylpyridinium chloride, triton X-100) enhances the rate of reaction to almost 14-fold. Observation showed that anionic surfactant (SDS) and nonionic surfactant (TX-100) accelerates the process but cationic surfactant (CPC) retards the reaction. The efficient combination for the production of glycolaldehyde from tartaric acid is found to be 1,10-phenanthroline and SDS.

The purpose of this paper is to describe an efficient, easily separable and environmentally friendly glycerin oligomerization catalyst. We explored the catalytic effect of five different layered sodium silicate materials on the oligomerization reaction of glycerol and compared them with Na 2 CO 3 . High performance liquid chromatography (HPLC) was used to analyze the product composition. The following reactivity order was observed: δ-Na 2 Si 2 O 5 ≈β-Na 2 Si 2 O 5 ≈α-Na 2 Si 2 O 5 > Kanemite > Na-magadiite. δ-Na 2 Si 2 O 5 showed good selectivity for diglycerol and triglycerol. It was found that 2 wt.% δ-Na 2 Si 2 O 5 and 5 h at 260°C was the optimal set of reaction conditions. Under these conditions, 71.7% conversion of glycerol was achieved, with selectivity for diglycerol and triglycerol of 83.8%. The results reveal that δ-Na 2 Si 2 O 5 is an effective catalyst for controlling the degree of polymerization of glycerol.