Sodium alkyl sulphates

Research work carried out at the Mechanobre Institute in Russia involved the evaluation of cationic and anionic collectors [8], The anionic collectors examined included sodium oleate and sodium alkyl sulphate. The results obtained indicated that with the use of sodium oleate, both zircon and pyrochlore can be floated with good recoveries (Figure 22.3). 

Flotation of pyrochlore using sodium alkyl sulphate is dependent on flotation pH. At a pH above 5.5, no pyrochlore flotation is achieved. At this pH, microcline, limonite and aegirine were floated. It appears that the use of alkyl sulphate at slightly acidic to alkaline pH number of gangue minerals can be selectively floated from pyrochlore. At a pH between 1.5 and 3.0, alkyl sulphate floats pyrochlore and zircon, whereas floatability of limonite, microline and aegirine is greatly reduced (Figure 22.4). 

Figure 22.4 Effect of sodium alkyl sulphate on flotation of minerals from pegmatite ores at a pH of 1.4.

For flotation of barite, sodium silicate was used as a depressant and barium chlorite as a barite activator. Barite collector SR82 was composed of petroleum sulphonate, sodium alkyl sulphate and succinamate mixture. The collector was selective towards both fluorite and bastnaesite. Over 96% of the barite was recovered in a relatively high-grade concentrate. 

The data from Figure 25.1 indicate that ilmenite can be recovered at a wide pH range. There is, however, a difference in the floatability of ilmenite from different ore types. Ilmenite can be successfully floated using fatty acid tall oil collectors at alkaline pH or with sodium alkyl sulphate (Ci6H330S03Na) at acidic pH. Figure 25.2 shows the effect of pH on ilmenite flotation from a sand deposit using alkyl sulphate collector. 

Table 10.4 Krafft point temperatures8 for sodium alkyl sulphates in water...

The value of TK is best determined by warming a dilute solution of surfactant, and noting the temperature at which it becomes clear. Table 10.4 lists the Krafft points for a series of colloidal systems based on aqueous solutions of sodium alkyl sulphate (cf. structure III). 

The author quotes the following figures which illustrate the effect of the addition of sodium alkyl sulphate on the induction period of a mixture of furfural with 98% nitric acid ... 

Addition of 0.5% sodium alkyl sulphate to furfuryl alcohol 14.4 millisec... 

Epton, S.R. 1948. New method for the rapid titration analysis of sodium alkyl sulphates and related compounds. Trans. Faraday Soc. 44 226-230. 

J. Clifford and B.A. Pethica, Properties of micellar solutions, Part 2, N.m.r. chemical shift of water protons in solutions of sodium alkyl sulphates, Trans. Faraday doc. 60 (1964) 1483-1490. 

Table 4.3 Critical micelle concentrations for a homologous series of sodium alkyl sulphates in water at 40°C"...

This combination is comparably milder combination than that of caustic soda and hence ideally suitable for more delicate cloths and colour woven goods compensating for the slower action of the milder alkali by the addition of a detergent. Anionic products like sodium alkyl sulphates and alkyl aromatic sulphonates and non-ionics like polyethoxylated compounds are used as detergent. Sometimes mixtures of anionic and non-ionic products are used. It is possible to obtain a synergistic effect between a detergent and alkali, so that the two agents when combined increase their total activities rather than inhibit each other. Fig. 4-2 shows the syn-... 

Low concentrations of sodium chloride, in fact, reduce detergent power but any increase above 2 g/1 produces a rapid improvement. This effect is apparent with the non-ionic surface-active compounds as well as with the sodium alkyl sulphates. 

The most common emulsions used in dermatological therapy are creams. These are two-phase preparations in which one phase (the dispersed or internal phase) is finely dispersed in the other (the continuous or external phase). The dispersed phase can be either hydrophobic based (oil-in-water creams, O/W) or aqueous based (water-in-oil creams, W/O). Whether a cream is O/W or W/O is dependent on the properties of the system used to stabilize the interface between the phases. Given the fact that there are two incompatible phases in close conjunction, the physical stability of creams is always tenuous, but may be maximised by the judicious selection of an appropriate emulsion stabilizing system. In most pharmaceutical emulsions, stabilizing systems are comprised of either surfactants (ionic and/or non-ionic), polymers (non-ionic polymers, polyelectrolytes or biopolymers) or mixtures of these. The most commonly used surfactant systems are sodium alkyl sulphates (anionic), alkylammonium halides... 

The purity of the prepared solutions can be checked by the criteria discussed above. For special surfactants, a specific analysis of impurities by very sensitive methods is possible. Czichocki et al. (1981) and Vollhardt Czichocki (1990) have shown the strong impurity effect of isomeric alcohols on the adsorption properties of sodium alkyl sulphates. The purity of the solutions could be analysed in this case by a highly sensitive HPLC method, which carmot simply be transferred to other surfactant systems. 

Rate-retarding effects of ca 105 were observed in hydrolyses of sodium alkyl sulphates in basic solution60, where Z is the strongly electron-donating substituent O-. Primary substrates showed second-order kinetics, but first-order rate constants were obtained for secondary alkyl substrates e.g. for i-propyl at 100 °C, the (interpolated) rate constant is 3.0 x 10 6 s-1 for the sulphate salt, whereas for hydrolysis of i-propyl tosylate the (extrapolated) rate constant is 0.7633. 

As expected, the CMCs of individual surfactants, such as sodium alkyl sulphates (compiled in Table 1.10), are highly dependent on the alkyl chain length according to the following equation [91, 141-146, 203,212] ... 

The lower homologues of sodium alkyl sulphates were studied in [67] only. Essential differences exist between the data presented in [67, 70, 75] for C,4S04Na. Therefore, to... 

The presence of EO groups in the oxyethylated sodium alkyl sulphate molecule (CnEOmS04Na), similarly to other ionic surfactants, affects significantly the adsorption behaviour at the water/air interface [76]. The experimental data for n, = 8, 10 and 12, and m = 1,2, 3 obtained in [69, 76] are presented in Fig. 3.49. For comparison the isotherms for sodium alkyl sulphates with the same hydrocarbon chain length are shown. One can see that the... 

The addition of one, two and three EO groups results in an approximately six, nine and eleven times increase of the constant b for the corresponding sodium alkyl sulphate, respectively. In Figure 3.50 the dependencies lg(b) vs nc are compared for CnE02S04Na with the data for non-oxyethylated C S04Na homologues. 

Fig, 6,3 Concentration relationships of the collapse rate of bubble foam (O) and high-expansion foam ( ) surface tension of the aqueous solution of C]o-Cn sodium alkyl sulphates ( ) and the relative residual concentration in die dispersion medium of a high-expansion foam in wt% ( ) foaming rate 0.83 cm /s (O), 13.5cmVs( ) ... 

The study of electrolyte effects on the surfactant behaviour in aqueous solutions has shown that even for industrial surfactants which are mixtures of homologues the electrolyte effect on c and CMC is significant. At a sodium chloride concentration of 100 g/1 the CMC of sodium alkyl sulphates decreases by more than one order of magnitude. Relatively small electrolyte additives (up to 10 g/1) increase the stability of foams, i.e. an increase of Wp° is observed at lower bulk surfactant concentrations. However, a subsequent increase in electrolyte concentration produces practically no influence on Wp . As noted above, an appreciable volume of bubble foam is produced not only at Wp = 0, but also in the entire interval 0 < Wp <100. Throughout the whole concentration range, the addition of electrolyte lowers the Wp value by 20—30 %. For example, while there is practically no foaming (Wp = 95 %) at 0.0045 wt% of Cio—Ci3 sodium alkylsulphates in distilled water, the Wp value falls to 60 % with the addition of sodium chloride up to the concentration of 10 g/1 and the formation of an appreciable amount of foam is observed in the experiment. 

Fig. 6.4 Effect of NaCl on the formation of high-expansion foams from 0.3% sodium alkyl sulphate solution of foaming rate Wo=12.8 cmVs, CNaci 0 ( ), 10 ( )> 30 (o), 50 (A), 120 ( ) g/l...

Soap (or fatty acid) Unsulphonated fatty ester Low-MW sodium alkyl sulphate (R = methyl to butyl)... 

These are esters of sulphuric acid - the most commonly used compound is sodium lauryl sulphate, which is a mixture of sodium alkyl sulphates. The main component is sodium dodecyl sulphate, Ci2H25-0-S0 Na+. It is used pharmaceutically as a preoperative skin cleanser having bacteriostatic action against Gram positive bacteria. It is also used in medicated shampoos and tooth paste (as foam producer). 

---