Surfactant cationic, additives

The setting of cationic emulsions can be accelerated or slowed down in the field by the use of additives. To accelerate the setting process, alkaline materials can be added to the emulsion to slow down the process, additional cationic surfactant (known as dope ) may be added. 

A reduction in the corrosive action of water is an extremely important property of surfactants. The mechanism of this phenomenon has been presented in a work by Somasundaran and Huang [89], The authors assume that the adsorbed film formed at the interface efficiently separates the water from the metal surface. Experiments confirming the anticorrosive action of surfactants have been presented in several works [90-94]. The following compounds were used in the experiments as additives cationic surfactants (cetyl pyridinium chloride and trimethyl ammonium bromide) [89], ethoxylated fatty acids [90], ethoxylated fatty alcohols [91], and ethoxylated sorbitan esters [92-94]. 

Figure 10.7 A diagrammatic representation of modes of binding of an anionic surfactant to a protein, after Dominguez [43]. Some modes of interaction, especially hydrophobic interactions with the amino acid hydrophobic residues would be equally appropriate for non-ionic and cationic surfactants. In addition, cationic surfactants could attach themselves electrostatically to the anionic sites. The hydrophobic interactions are supported by the results of Helenius and Simons [44] which demonstrated that lipophilic proteins bound up to about 70% of their weight of deoxycholate and Triton X-lOO but that hydrophilic proteins bound little surfactant.

Use of Surfa.cta.nts, Although the use of steam to improve dewatering is consistently beneficial, the effects of surfactants on residual moisture are highly inconsistent. Additions of anionic, nonionic, or sometimes cationic surfactants of a few hundredths weight percent of the slurry, 0.02—0.5 kg/1 of soHds (50), are as effective as viscosity reduction in removing water from a number of filter cakes, including froth-floated coal, metal sulfide concentrates, and fine iron ores (Table 2). A few studies have used both steam and a surfactant on coal and iron ore and found that the effects are additive, giving twice the moisture reduction of either treatment alone (44—46,49). 

The two-phase titration is based on the reaction of anionic surfactants with cations—normally large cationic surfactants—to form an ion pair. The preferred cationic is benzethonium chloride (Hyamine 1622, 1) because of the purity of the commercially available product. On neutralization of the ionic charges, the ion pair has nonpolar character and can be extracted continuously into the organic phase, e.g., chloroform, as it is formed. The reaction is monitored by addition of a water-soluble cationic dye, dimidium bromide (2), and a water-soluble anionic dye, disulfine blue (3). The cationic dye forms an extractable... 

The method developed by Epton [212,213] became the universally accepted method for the analysis of active matter of anionic and cationic surfactants. Epton s method, also known as the two-phase titration, is based on the titration of the anionic surfactant with cetylpyridinium bromide, a cationic surfactant, in the presence of methylene blue as indicator. A solution of the anionic surfactant is mixed with the indicator dissolved in dilute sulfuric acid, followed by further addition of chloroform, and then it is titrated with the cationic surfactant. Methylene blue forms a complex with the anionic salt that is soluble in chloroform, giving the layer a blue color. As the titration proceeds there is a slow transference of color to the water layer until the equivalence point. At the equivalence point colors of the chloroform and water layers are visually the same. On successive additions of titrant the chloroform layer lightens in shade and finally becomes colorless. 

Figure 14.1a shows aj vs. U curve in Cu + Sn + H2SO4 with (solid curve) and without (dashed curve) cationic surfactant. The addition of the surfactant causes a drastic change in they vs. U curve. Namely, an NDR appears in a narrow potential region of about 5 mV near —0.42 V, where the Cu-Sn alloy is electrodeposited. Another notable point in the surfactant-added solution is that a current oscillation appears when the Uis kept constant in (and near) the potential region of this NDR, as shown in Figure 14.1b. It was also revealed that both the NDR and current oscillation appeared only in the presence of cationic surfactant and not in the presence of anionic surfactant.

Gutfelt et al. (1997) have evaluated various ME formulations as reaction media for synthesis of decyl sulphonate from decylbromide and sodium sulphite. The reaction rate was fast both in water-in-oil and in bicontinuous ME based on non-ionic surfactants. A comparison was made with this reaction being conducted in a two-phase. system with quats as phase-transfer catalyst but was found to be much less efficient. However, when two other nucleophiles, NaCN and NaNOj, were used the PTC method was almost as efficient as the ME media. It seems that in the case of decyl sulphonate there is a strong ion pair formation between the product and the PTC. The rate in the ME media could be further increased by addition of a small amount of a cationic surfactant. 

CE has been used for the analysis of anionic surfactants [946,947] and can be considered as complementary to HPLC for the analysis of cationic surfactants with advantages of minimal solvent consumption, higher efficiency, easy cleaning and inexpensive replacement of columns and the ability of fast method development by changing the electrolyte composition. Also the separation of polystyrene sulfonates with polymeric additives by CE has been reported [948]. Moreover, CE has also been used for the analysis of polymeric water treatment additives, such as acrylic acid copolymer flocculants, phosphonates, low-MW acids and inorganic anions. The technique provides for analyst time-savings and has lower detection limits and improved quantification for determination of anionic polymers, compared to HPLC. 

Hydroaminomethylation of alkenes occurred to give both n- and /. so aliphatic amines catalyzed by [Rh(cod)Cl]2 and [Ir(cod)Cl]2 with TPPTS in aqueous NH3 with CO/H2 in an autoclave. The ratio of n-and /.soprimary amines ranged from 96 4 to 84 16.178 The catalytic hydroaminomethylation of long-chain alkenes with dimethylamine can be catalyzed by a water-soluble rhodium-phosphine complex, RhCl(CO) (Tppts)2 [TPPTS P(m-C6H4S03Na)3], in an aqueous-organic two-phase system in the presence of the cationic surfactant cetyltrimethy-lammonium bromide (CTAB) (Eq. 3.43). The addition of the cationic surfactant CTAB accelerated the reaction due to the micelle effect.179... 

Nearly all nonionic surfactants contain the same type of hydrophobes as do anionic and cationic surfactants, with solubilisation and surfactant properties arising from the addition of ethylene oxide to give a product having the general formula 9.40. Usually, depending on the... 

In recent years, there has been increased recognition that water is an attractive medium for organic reactions from the environmental point of view. The Michael addition of various nitroalkanes to conjugated enones can be performed in NaOH (0.025 M) and in the presence of cetyltrimethylammonium chloride (CTAC1) as cationic surfactant in the absence of organic solvents (Eq. 4.109).146 The Michael addition of nitromethane to methyl acrylate is carried out in water using NaOH as a base to give the mono adduct (Table 4.2).147... 

Direct determination of surfactants in complex matrices can also be carried out using ion-selective electrodes. Depending on the membranes and additives used, the detergent electrodes are optimized for the detection of anionic surfactants [81], cationic surfactants [82], and even nonionic surfactants [83]. The devices are sensitive to the respective group of surfactants but normally do not exhibit sufficient stability and reproducibility for their use in household appliances. With further optimization of membrane materials, plasticizers and measurement technology, surfactant-selective electrodes offer high potential for future applications. 

Most studies of micellar systems have been carried out on synthetic surfactants where the polar or ionic head group may be cationic, e.g. an ammonium or pyridinium ion, anionic, e.g. a carboxylate, sulfate or sulfonate ion, non-ionic, e.g. hydroxy-compound, or zwitterionic, e.g. an amine oxide or a carboxylate or sulfonate betaine. Surfactants are often given trivial or trade names, and abbreviations based on either trivial or systematic names are freely used (Fendler and Fendler, 1975). Many commercial surfactants are mixtures so that purity can be a major problem. In addition, some surfactants, e.g. monoalkyl sulfates, decompose slowly in aqueous solution. Some examples of surfactants are given in Table 1, together with values of the critical micelle concentration, cmc. This is the surfactant concentration at the onset of micellization (Mukerjee and Mysels, 1970) and can therefore be taken to be the maximum concentration of monomeric surfactant in a solution (Menger and Portnoy, 1967). Its value is related to the change of free energy on micellization (Fendler and Fendler, 1975 Lindman and Wennerstrom, 1980). 

The effect of mixtures of surfactants and polyelectrolytes on spontaneous, water-catalysed hydrolysis (Fadnavis and Engberts, 1982) was mentioned in Section 4, but mixtures of functionalized polyelectrolytes and cationic surfacants are effective deacylating agents (Visser et al., 1983). Polymerized isocyanides were functionalized with an imidazole group and the deacylation of 2,4-dinitrophenyl acetate in the polyelectrolyte was speeded by addition of single or twin chain quaternary ammonium ion surfactants, up to a plateau value. Anionic surfactants had essentially no effect. It is probable that the cationic surfactants accelerate the reaction by increasing the deprotonation of the imidazole groups. 

Isocyanide polymers functionalized with amino acid groups, typically di-or tripeptides containing histidine or serine, give enantioselective deacylation and rate enhancements. Their activity is increased by addition of cationic surfactants (Visser et al., 1985). 

Tb clarify the effect of addition of a cationic HC surfactant on phase separation behavior in the mixed monolayers of anionic HC and FC surfactants polyion complexed with cationic polymers, the mixed monolayers containing three amphiphilic components complexed with PVA were transferred on various substrate plates and studied by AFM, FFM, SSPM, and SIMS. As a cationic surfactant, ODTMAC was examined. 

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