Long-chain surfactant

The proposed mechanism of effect of surfactant and ultrasound is reported in Fig. 7.5. The long chain surfactant molecules attach to surface of nanoparticles due to physical adsorption. Only thin layer is adsorbed onto the CaC03 nanoparticles. Due to presence of ultrasound and use of surfactant will control the nucleation. Surfactant keeps the particles away from each other by preventing flocculation due to change in surface tension of reaction mass. The concentration of additives was changed from 0.2 to 1.0 g/L. Addition of 0.2 g/L tripolyphosphate shows the increase in the rate of precipitation which is determined from the Ca(OH)2 consumption. Polyacrylic acid shows the least rate of precipitation (0.115 mol/1), which... 

N. E. Baryla, J. E. Melanson, M. T. McDermott, and C. A. Lucy, Characterization of Surfactant Coatings in Capillary Electrophoresis by Atomic Force Microscopy, Anal. Chem. 2001, 73, 4558 M. M. Yassine and C. A. Lucy, Enhanced Stability Self-Assembled Coatings for Protein Separations by Capillary Zone Electrophoresis Through the Use of Long-Chained Surfactants, Anal. Chem. 2005, 77, 62. 

The strong cooperativity of amphiphile association into micelles is well established and for long-chain surfactants it is often a good approximation to consider micelle formation as analogous to a phase separation. Even if the concentration dependence of many physico-chemical properties, within experimental accuracy, is in concor-... 

Fuerstenau") was the first who used the Stern-Grahame model of EDL to describe the adsorption of long-chain surfactants for the equilibrium in heterogeneous systems. The adsorption density in the Stem plane is given by the equation... 

Fig. 9. Adsorbed long chain surfactant on negatively charged solid (A) without lateral interaction (C < Cmono,ayer) (fl) with lateral interaction between hydrocarbon chains at higher concentrations...

Roy and Fuerstenau153 and Mellgren154) determined the adsorption heat of long-chain surfactants on oxides with PDI H+ and OH" and with surfactants adsorbing as counterions in the EDL. The former authors153 studied the immersion heat of a-Al2C>3 in... 

Recent developments in the preparation and use of nanoparticulate oxide materials, more specifically isolated nanoparticles of simple and compound oxides, are reviewed. While oxide nanoparticles have been known and studied for many decades, it is only in recent years that methods for their preparation have achieved the level of sophistication which permits monodisperse nanoparticles to be produced in quantity. In addition, it is only in recent years that the notion of capping of oxide nanoparticle surfaces by long-chain surfactants, with the corollary that they become soluble, has taken firm hold. The emphasis is on new routes for the preparation of oxide nanoparticles, and how these could be distinct from those used for metals or chalcogenides. Properties of oxide nanopartides are discussed with special reference to how they are distinct from the bulk material. Present and possible applications are discussed in context. 

Unfortunately, information about the activity of hydrotrope molecules in the concentration range of interest is not available. The only determination in existence, to our knowledge, is concerned with a more complex associated system [55], This is in contrast to the case for traditional long-chain surfactants, which have been thoroughly investigated [56-59], the results of which justified the approach to use concentrations instead of activities in the common plot of surface tension to determine critical micellization concentrations. The closest to hydrotrope molecules should be bile salts, which have been investigated [60],... 

In the case of long chain surfactants used as collectors, a signiflcant correlation between their adsorption in the form of aggregates and flotation of minerals with them was established in the 1960 s by Somasundaran et al. (1964). Somasundaran et al. (1976, 1985) developed the relevant dissociation and aggregation equilibria for flotation reagents in the solution as well as at the mineral-solution interface. Importantly, the ion-molecule complexes phenomenon was proposed later by Somasundaran (1976), Hanna and Somasundaran (1976) to account for the flotation maximum exhibited at certain pH values by hydrolyzable surfactants. 

Most of the theories on interactions of surfactants with minerals are closely related to their solution chemistry. For example, the ion-exchange adsorption theory proposed by Gaudin (1932, 1934) and Wark (1938) and the molecular adsorption theory proposed by Cook and Nixon (1950) are based on the dissociation equilibria and states of the collectors in water. More recently, Somasundaran (1976) observed that ion-molecule complexes of long-chain surfactants in flotation systems can have high surface activity depending upon the association equilibria of the surfactants in solutions (Ananthapadmanabhan et al., 1979 Kulkarni and Somasundaran, 1980). Also the cationic flotation behavior of salt type minerals is closely related to the formation of alkyl amine salt (Hu and Wang, 1990). In this chapter, solution equilibria of reagents relevant to selected flotation systems are examined. 

STRONG ASSOCIATION AND MICELLIZATION EQUILIBRIA OF LONG-CHAIN SURFACTANTS... 

Strong association and micellization equilibria of long-chain surfactants... 

Solubility of long-chain surfactants has been reported to have a linear relationship with the number of carbon atoms in hydrocarbon chain with a slope of —0/2.303As shown in Fig. 2.21 (Lin and Somasundaran, 1971), 0 values obtained for fatty acids, amines and alkyl sulfonates are — A5RT, —. 5 >RT and —1.01 RT, respectively. 

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