Nonaqueous Cleaning Solutions

Although aqueous systems constitute the major portion of surfactant applications in detergency, nonaqueous or dry cleaning processes also constitute an important economic factor. Included in such processes are the familiar dry cleaning processes as applied to fine fabrics and articles that are adversely affected by water, as well as processes for the cleaning of various metal and ceramic parts that cannot tolerate significant exposure to moisture. 

In such applications, solubility of the surfactant in the nonaqueous solvent is obviously the primary requirement. A wide variety of structures have been found useful in such applications, including nonionic materials such as POE alkylphenols, amides, and phosphate esters, sodium dialkyIsulfosuccinates, alkyl-aryl sulfonates, and petroleum sulfonates. Although extensive experimental data are not available, it appears that the polar head group of the surfactant in such uses is of primary importance, given a hydrophobic tail sufficient to ensure the proper overall solubility. 

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Activated tertiary amines such as triethanolamine (TEA) and methyl diethanolamine (MDEA) have gained wide acceptance for CO2 removal. These materials require very low regeneration energy because of weak CO2 amine adduct formation, and do not form carbamates or other corrosive compounds (53). Hybrid CO2 removal systems, such as MDEA —sulfolane—water and DIPA—sulfolane—water, where DIPA is diisopropylamine, are aqueous alkaline solutions in a nonaqueous solvent, and are normally used in tandem with other systems for residual clean-up. Extensive data on the solubiUty of acid gases in amine solutions are available (55,56). 

What is mass (or chemical) transport It is the transport of a solute (the dissolved chemical) in a solvent (everything else). The solute is the dissolvee and the solvent is the dissolver. There are liquids that are generally classified as solvents because they typically play that role in industry. Some examples would be degreasing and dry cleaning solvents, such as trichloroethylene. In environmental applications, these solvents are the solutes, and water or air is usually the solvent. In fact, when neither water nor air is the solvent, the general term nonaqueous phase liquid is applied. A nonaqueous phase liquid is defined as a liquid that is not water, which could be composed of any number of compounds. 

Beverages and seawater are examples of aqueous solutions, solutions in which the solvent is water. Aqueous solutions are very common in everyday life and in chemical laboratories for that reason, most of the solutions mentioned in this text will be aqueous. Nonaqueous solutions are solutions in which the solvent is not water. Although they are less common than aqueous solutions, they have important uses. In dry cleaning, the grease and dirt on fabrics are dissolved in tetrachloro-ethene, C2C14, a compound of carbon and chlorine. There are also solid... 

In nonaqueous solutions the formation of oxide on the surface of silicon requires the presence of water. In solvents such as acetonitrile, nitromethane, and dimethyl sulfoxide, the HF-cleaned silicon surface gradually evolves from a H-terminated passive surface to a silicon oxide-covered surface due to the residual water (-lOpprn) present... 

Formation of the first layers of oxide (i.e., native oxide) on the surface of silicon, according to Ozanam and Chazalviel, " appears to also require the presence of water even in nonaqueous solutions. On immersion into the solution the silicon surface is gradually evolving from a Fi-terminated surface (after FiF cleaning) to a silicon oxide-covered surface due to the residual water present in the nonaqueous electrolyte (10 ppm). Initially the water is molecularly adsorbed at the silicon surface, then slowly oxidizes the surface silicon atoms to form oxide islands. The oxide islands are about 0.6 nm thick and cover about 60% of the surface area after 1 week of immersion in various nonaqueous electrolytes. 

Degreasing or solvent metal cleaning employs nonaqueous solvents to remove soils from the surface of metal articles that are to be electroplated, painted, repaired, inspected, assembled, or further machined. Metal work pieces are cleaned with organic solvents because water or detergent solutions exhibit a slow drying rate, electrical conductivity, high surface tension, a tendency to cause rusting, and a... 

Normal-phase sorbents such as silica and Florisil are used to isolate low to moderate polarity species from nonaqueous solutions. Examples of applications include lipid classification, plant pigment separations, and separations of fat-soluble vitamins from lipid extracts, as well as the clean-up of organic solvent concentrates obtained from a previous SPE method or liquid-liquid extraction. Alumina is used to remove polar species from nonaqueous solutions. Examples include vitamins in feeds and food and antibiotics and other additives from feed. Normal-phase chromatography has been used for a number of years, and most applications for normal-phase column chromatography may be easily transferred over to normal-phase SPE. 

When a water solution in which the nonaqueous component is the more volatile is fractionated, so that the water is removed as the residue product, the heat required can be provided by admission of steam directly to the bottom of the tower. The reboiler is then dispensed with. For a given reflux ratio and distillate composition, more trays will usually be required in the tower, but they are usually cheaper than the replaced reboiler and its cleaning costs. 

Abstract FUV or DUV absorption spectrum has very strong absorptivity with a steep absorption edge. Since the spectral changes in the intensity, position, and bandwidth of the band are observed sensitively even at the portion of the tail band, these spectra can be applied for a powerful method in industrial analytical applications. The potential of FUV and DUV spectroscopy is revealed as a highly sensitive analytical method for aqueous solutions such as mineral water, springwater, and variety of industrial cleaning water. In addition, it is proposed that FUV spectroscopy is useful for not only analysis of aqueous solutions and nonaqueous solvents but also for non-solvent substances such as polymer films. 

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