CONTINUUM ELECTROSTATICS INVESTIGATION OF IONIC MICELLES USING ATOMISTIC MODELS

The key parameter related to the structure of the electric double layer of ionic surfactant micelles – electrostatic potential – is considered. A brief overview of experimental methods and theoretical models for estimating electrostatic potential- is given. The calculating method for the electrostatic potential based on a numerical solution of the Poisson-Boltzmann equation using an atomistic model of anionic surfactant micelle - is proposed. The parameters necessary for the construction of atomistic models - are obtained from molecular dynamic modeling. The electrostatic potentials for the micelles of sodium dodecyl sulfate and cetyltrimethylammonium bromide at different ionic strengths - were calculated by this method. The results are discussed in comparison with the values calculated in the simplified model, the Ohshima – Healy – White equation.

Micellar-Enhanced Ultrafiltration Using a Plant-Derived Surfactant for Dye Separation in Wastewater Treatment

Micellar-enhanced ultrafiltration (MEUF) is one of several membrane methods used for the removal of trace organic pollutants from aqueous streams. In this process, a surfactant is added to a polluted aqueous solution at a concentration higher than its critical micelle concentration (CMC). Unlike synthetic surfactants, natural surfactants, from plants such as the saponin, while ecologically adaptable as surfactants in MEUF systems, are also biodegradable, renewable, and environmentally safe. This study applied Sapindus rarak extract as the natural surfactant in MEUF for Remazol dye separation. It was found that the presence of Sapindus rarak extract increased separation of Remazol red and blue dyes by up to 97.02% and 99.42%, respectively. However, the addition of surfactant decreased permeate fluxes due to membrane fouling and concentration polarization. In addition, loading micelle (Lm), representing the performance of the surfactant micelle for dye separation, as well as the blocking mechanism, was investigated. Lm was found to be in the range of 0.002–0.068 mM dyes/mM saponin. Ultrafiltration blocking mechanisms, as confirmed by the Hermia model, were: standard blocking, for cases without the addition of surfactant; cake formation, for cases with surfactant below the CMC; and complete blocking, for cases with surfactant above the CMC.

A BRIEF REVIEW OF MICELLAR ENHANCED ULTRAFILTRATION (MEUF) TECHNIQUES FOR TREATMENT OF WASTEWATER IN INDIA

In this paper, we have reviewed the application and efficiency of Miceller Enhanced Ultrafiltration (MEUF) method which is used to remove Heavy Metals, Dyes, Polyaromatic Hydrocarbons (PAH), Novel Compounds, Chromium, Phosphorous and Phenolic Compounds. It uses various surfactants like Hexadecylpyridinium chloride (CPC), Sodium Dodecyl Sulphate (SDS), Hexadecyltrimethyl Ammonium Bromide (CTAB), Oxyethylated Methyl Dodecanoate (OMD) and Alkylpolyglucoside (APG). These surfactants are retained after the process to be reused. Bisorption, Coagulation, polyelectrolyte enhanced ultrafiltration, Reserve Osmosis, Nanofitration are some of the methods that are used for the treatment of wastewater. Available research focused on the removal of metals, phenol, organic & inorganic materials, aromatic hydrocarbons by MEUF mainly on the type of surfactant used, surfactant concentration, applied pressure, operating time and pH. Formation of surfactant micelle and mechanisms for the attraction between micelle and metal ions are ignored during the research study on MEUF. It has been reported that MEUF combines the efficacy and simplicity of the conventional options with the operational flexibility of membrane-based separation. MEUF could be used for removal of wastewater provided the pollutants have low molecular weight. Higher reagent and electrical costs are reported in conventional MEUF method as compared to the hybrid process with MEUF. The hybrid process requires fewer surfactants. MEUF is considered a better alternative to the typically available membrane separation processes. The advantages of this method over other methods are high removal efficiency, low energy consumption, and easy operation. The selection of surfactant for the removal purpose is based on the target pollutants.

Preparation of Mesoporous Silica by Nonionic Surfactant Micelle–Templated Gelation of Na2SiO3 and H2SiF6 and Application as a Catalyst Carrier for the Partial Oxidation of CH4

Mesoporous silica (MSPN12) was prepared by nonionic surfactant micelle–templated gelation of sodium silicate (Na2SiO3) and fluorosilicic acid (H2SiF6) in aqueous solution, characterized by a range of instrumental techniques, and tested as a support for Ni and Rh catalysts in the partial oxidation of methane (POM). Calcined and sintered MSPN12 exhibited well-defined d00l-spacings (3.5–4.39 nm), narrow pore distributions (2.4–3.1 nm), and large specific surface areas (552–1,246 m2 g−1), and was found to be highly thermally stable. Microscopic imaging revealed that MSPN12 comprised spherical particles with a uniform diameter of ~0.7 µm, with each particle featuring firm and regular honeycomb-type pores. MSPN12-loaded Ni and Rh maintained stable POM activity at 700 °C during almost 100 h on stream, which were comparable to those for the commercial Rh(5)/Al2O3 catalyst in terms of methane conversion and H2 formation selectivity. Thus, the combination of structural stability and favorable physicochemical properties resulted in good POM performance.

Mononuclear Binary Complex Formation Equilibria of L-Ornithine with Biologically Essential Metals in TBAB Micellar Media

Investigation of mononuclear complex of L-ornithine in tetrabutylammonium bromide (TBAB, a cationinc surfactant) micelle media has been made pH metrically at constant temperature and ionic strength in different percentage of micellar solutions (0.0-2.5 %). Stability constants and best fit model for metal complexes were obtained by MINIQUAD75 computer program on the basis of the analysis of residues and other statistical parameters. Accordingly, ML, ML2, MLH and ML2H for both Co(II) and Cu(II) and ML2 and ML2H for Ni(II) mononuclear chemical models were obtained. The stabilization/destabilization equilibria of the binary system for the model species with percentage composition of micelles at constant ionic strength and temperature could be attributed to dielectric constant and other intrinsic interaction properties of tetrabutylammonium bromide micelle with ligands and metal ions. The plot of percentage of species against pH values has been generated from SIM refined data using origin85 software.