Natural surfactants

THE INFLUENCE OF SURFACTANTS NATURE AND CONCENTRATION ON THE ANALYTICAL SIGNAL IN THE ATOMIC ABSORPTION DETERMINATION OF LEAD, CADMIUM AND CHROMIUM... 

Surfactants (Fig. 23) represent one of the major and most versatile groups of organic compounds produced around the world [314]. Their main uses are industrial, 54% (cleaning products, food, and industrial processing), household, 29% (laundry, dishwashing, etc.) and personal care, 17% (soaps, shampoos, cosmetics). The worldwide production in 1988 [315] was 2.8 million tons. Surfactants, natural [316,317] or synthetic, change the solubility and physicochemical state of other environmental micro-constituents [318, 319] and influence their accumulation and spreading at phase boundaries [320]. 

A. 1. Cooper, et al.. Extraction of a hydrophilic compound from water into liquid CO2 using dendritic surfactants. Nature 389,368-371 (1997). 

As discussed before (4) it is perhaps convenient to classify these theories into three main categories interfacial or mixed film theories, solubilisation theories and thermodynamic theories. Below a brief description of each of these classes will be given with particular emphasis on the role of surfactant nature and structure. 

M.P. Aronson and H.M. Princen Contact Angles in OU-in-Water Emulsions Stabilized by Ionic Surfactants. Nature 286, 370 (1980). 

The various types of compounds which have been purified with peroxygens and which will be discussed here are petroleum products, miscellaneous organic chemicals, surfactants, natural oils, waxes and gums, natural sugars and starches, synthetic polymers, inorganic acids and salts, clays, talc and minerals. 

Kabalnov described water-based inkjet ink compositions that are miniemulsions, i.e., an aqueous vehicle having emulsified oil particles with dissolved dye molecules, where the oil droplets have a diameter of less than 1 m. In his patent, Kabalnov mentioned the advantages of miniemulsions in comparison to microemulsions, namely the surfactant nature and concentration which allow better penetration control to the printed papers, and the dye load in miniemulsions can also be increased compared to microemulsions at acceptable viscosity limits. According to this invention, the aqueous inkjet ink composition is comprised of an oil-soluble dye, a solvent, and an aqueous vehicle wherein particles of the oil-soluble dye are dissolved in low-polarity oil particles having a particle size of less than 1 m, the particles forming miniemulsions in water. 

Surfactant replacement therapy (SRT) is widely accepted as the most clinically acceptable and cost-effective approach to the treatment of RDS. Clinical trials have been carried out worldwide using an array of artificial, modified natural, and natural surfactants. Natural surfactants are either processed extracts of minced lungs or extracts of lavaged surfactant, which affects the surfactant protein makeup of the preparation. The differences in preparations can be discerned from key components and dosing strategies, which are summarized in Table 28-6. 

The surface excess F2 can be calculated from the Hnear portion of the Y log C2 curves before the cmc. Such y-log C curves are illustrated in Figure 5.2 for the air/water (A/W) and O/W interfaces (Cj ) denotes the concentration of surface active agent in bulk solution. It can be seen that, for the A/W interface, y decreases from the value for water (72 mN m at 20°C) and reaches about 25-30 mN m near the cmc this is clearly schematic as the actual values depend on the surfactant nature. For the O/W case, y decreases from a value of about 50 mN m (for a pure... 

Similar differences in the surfactant nature of soluble and insoluble species can be found in studies of foam stability. Broadly speaking, insoluble or solid-type surfactants do not efficiently stabilise foams (Garrett, 1967b). On the other hand, water-soluble surfactants such as the alkyl sulphonates, phosphates and tri-alkyl ammonium salts, all common detergents, form prolific foams. Wilson (1959) noted the accumulation of albuminoid-N compoimds in coastal sea foams, while Southward (1953), who found a variety of planktonic and benthic oi anisms in such foams, concluded that proteins were probably responsible for the foam stability. Wilson and Collier (1972) have observed the production of such foam-stabilising events in appreciable quantities by various marine organisms such as diatoms. 

Many investigators have offered explanations for QAC mechanisms of antimicrobial action. Most theories center on the interactions between QACs and the membranes of their target cells. The surfactant nature of these agents suggests that they act as other membrane-active agents, perturbing homeostasis. However,... 

The reaction of entry of a surfactant in a micelle is controlled for conventional surfactants with an alkyl chain containing up to 14 carbon atoms.This means that the rate of entry is essentially determined by the number of collisions between micelles and free surfactants. The values of the entry rate constant k are all around 10 M . irrespective of the surfactant nature and length of... 

Unlike commercial surfactants, natural surfactants represent a class of components rather that a pure substance. Natural surfactants have different compositions and properties from one crude to an other. The nature of the asphaltenes is probably as important as the concentration of these surface-active agent when it comes to hydrate transportability, and oflier factors such as resins, waxes, aromatics, water quality, etc., have to be assessed in order to have a complete understanding of the transportability. An enhanced hydrate transportability of a crude as a result of increasing the amount of natural surfactants was demonstrated for several systems. In all cases it seems likely that the hydrate-slurry transportability is limited to 30% water cut. 

Figure 13.10 Effect of the surfactant nature on the electropherograms of a complex antitussive preparation containing 14 solutes (analgesic, antitussive, antipyretic principles, conservatives and excipients). Buffer 0.02 M phosphate-borate, pH 9. Capillary 50 pm, 65 cm fused silica. Detection UV 210 nm. Adapted from [47].

An extensive variety of chemical demulsifiers are available to enhance resolution of the water-in-od emulsion that is produced at the wellhead These demulsifiers are simply surfactants that are used to counteract the effect of surfactants naturally present in the wellhead or process emulsions, and which stabilize the water in the oil phase. In the petroleum industry, emulsions of oU in water are known as reverse emulsions. Demulsifiers are also used to destabilize these oil-in-water emulsions. The wide variety of oU types and produced water chemistries in petroleum industry emulsions necessitates an even wider variety of chemical demulsifiers. In addition, production and processing variables require demulsification chemicals tailored to particular process needs. 

Surfactants can be classified by the charge of the hydrophilic group as cationic, anionic, neutral, and zwitterionic (includes positive and negative charges in the same molecule). The use of surfactants for the removal of COC by electrokinetics has been demonstrated in literature [17]. Several surfactants have been used such as Brij 35, TritonX-100, Sodium dodecyl sulfate, Tween 80, and Igepal CA-720, but COC removal results largely depend on surfactant nature and dosage, characteristics of the soil and contaminant, and operation conditions. Therefore, it is necessary to test the surfactant for each application [8]. 

Entry Surfactant Nature Solvent StarchnanopaitiGtes lnoorporated(%)... 

Furthermore, differences in the obtained K., values were also attributable to the micellar structure of IL-based surfactants. These results aimed to employ IL-based surfactant in efficient and selective extraction methods by adequate selection of the IL-based surfactant nature and/or the group of compounds to be determined. 

The main problem of measurement for surfactant solutions is that the accumulation of surfactant molecules takes some time. At high concentrations, the equilibrium is established in less than a second, but it may take hours for low concentrations, depending on the surfactant nature. 

Surfactants can reach the environment via different paths, either directly, e.g., in connection with pesticides, or indirectly adsorbed in sewage sludge applied as fertilizer in agriculture. Surfactants are also encountered in rivers and lakes. Apart from synthetic surfactants, nature also produces surface-active substances by biodegradation, and even the human organism daily produces approx. 20 g of surfactants in the form of bile acids. 

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