Syndets, removal

The solubihty characteristics of sodium acyl isethionates allow them to be used in synthetic detergent (syndet) bars. Complex blends of an isethionate and various soaps, free fatty acids, and small amounts of other surfactants reportedly are essentially nonirritant skin cleansers (66). As a rule, the more detersive surfactants, for example alkyl sulfates, a-olefin sulfonates, and alkylaryl sulfonates, are used in limited amounts in skin cleansers. Most skin cleansers are compounded to leave an emollient residue on the skin after rinsing with water. Free fatty acids, alkyl betaines, and some compatible cationic or quaternary compounds have been found to be especially useful. A mildly acidic environment on the skin helps control the growth of resident microbial species. Detergent-based skin cleansers can be formulated with abrasives to remove scaly or hard-to-remove materials from the skin. 

FIGURE 31.4 The amount of water soluble free amino acids (a) and cholesterol (b) removed from porcine skin after a single wash with a syndet bar versus a soap bar. Results show significantly higher removal from the soap washed site. 

Similar to water plasticizing the proteins, fluid lipids in the bilayer lipids are implicated in the elasticity of the corneum. Removal of fluid lipids can make the corneum brittle. For example, solvent treatment of the corneum to remove fluid lipids has been shown to make the SC brittle.29 It has been shown that soap treated corneum behaves somewhat similarly to the solvent treated corneum in the sense that both exhibit a brittle fracture under tension. In contrast, syndet bar treated corneum behaves more like water treated corneum exhibiting a more elastic and pliable structure. 

The increased use of synthetic detergents ( syndets ) can create problems of taste and foaming in the re-use of water. These syndets, measured as alkyl benzene sulfonate (ABS), are not removed by conventional sewage treatments and are not eliminated by water purification processes of coagulation, disinfection, and filtration. Based on an analysis of a number of streams, as of now the concentration of syndets in most streams is below levels that cause difficulties from foam or taste. With the increasing use of syndets, however, the situation could become significant, especially where many communities are located on a single stream with the consequent repeated re-use of the water. 

Activated carbon will remove syndets and two approaches are under study.54,55 In one, the effluent from a sewage plant is passed through granular carbon in a column or alternatively, the sewage effluent is treated in conjunction with alum. The other approach is to add powdered activated carbon in sufficient quantities in the water purification plant. 

Uses Foam booster/stabiiizerfor peariized detergent systems, opaque shampoos, conditioners, bath and shower gets, wrinkie removers, hand soaps, faciai masks, skin care, hair care, creams/iotions, soap and syndet bars Properties Paie cream powd. dean fresh odor pH 4-5.5 90% min. protein 3-7% moisture Use Level 1-3%... 

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