These agents are often defined according to their behavior in aqueous 

 solutions. These solutions will usually wet surfaces readily, remove dirt, 

 penetrate porous materials, disperse solid particles, emulsify oil and grease, 

 and produce foam when shaken. These properties are interrelated; that is, 

 no surface-active agent possesses only one of them to the exclusion of the 

 rest. 



Surfactants can be divided into two broad classes, depending on the 

 character of their colloidal solutions in water: ionic and nonionic. Ionic 

 surfactants form ions in solution, and, like the soaps, are typical colloidal 

 electrolytes. Nonionic surfactants do not ionize, but owe their solubility 

 to the combined effect of a number of weak solubilizing groups such as ether 

 linkages or hydroxy groups in the molecule. A more detailed discussion of 

 SAA is given by Poliakoff (1969). 



Commonly used SAA in oil-spill dispersants include soaps, sulfonated 

 organics, phosphated esters, carboxylic acid esters of polyhydroxy compounds, 

 ethoxylated alkyl phenols and alcohols (APE, LAE), block polymers, and 

 alkanolamides. 



SOLVENTS 



Since many of the surface-active agents applicable to oil-spill dispers- 

 ant compounding are viscous or solid materials, some form of solvent is often 

 necessary in order to reduce viscosity for ease of handling. In addition, 

 the solvent may act to dilute the compound for economic reasons, to depress 

 the freezing point for low temperature usage, to enable more rapid solubility 

 in oil, and to achieve optimum concentration of surface-active agents for 

 performance reasons. The presence of a suitable solvent also serves to thin 

 the oil to be dispersed, reducing viscosity and making it more easily emulsi- 

 fiable. The solvent usually comprises the bulk of the dispersant product. 



The three general classes of solvents used in oil spill dispersants are 

 petroleum hydrocarbons, alcohols or other hydroxy compounds, and water. 



Petroleum Hydrocarbons 



Petroleum fractions with boiling points above 149 C (300 F) are usually 

 used, and these may produce finished dispersants with flash points as low 

 as 43 C (110 F). The proportion of aromaticity is of concern, since this affects 

 solubility and emulsification properties, as well as toxicity. Wardley Smith, 

 Warren Spring Lab, UK, in describing the Torrey Canyon incident, reported 

 that the aromatic solvents used were 10 times as toxic to marine life as 

 were the surface-active agents. Some typical fractions of applicable petro- 

 leum solvents include mineral spirits, kerosene, No. 2 fuel oil, and heavy aro- 

 matic naphthas which contain significant quantities of higher alkylated benzenes. 



Alcoholic or Hydroxy Group of Solvents 



This group includes alcohols, glycols, and glycol ethers. These solvents 

 also lower the viscosity as well as the freezing points of finished dispers- 

 ants. In addition, they furnish a cosolvent effect, often needed to dissolve 

 the various ingredients in a dispersant for stability of the compound in 

 storage. This group of solvents may be used in conjunction with petroleum 



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