Surface contamination, with inorganic salts

MEG and some of its analogues are used for drying natural gas to prevent the formation of methane hydrate. MEG picks up water from the gas and is recycled through a simple continuous still of a few trays in which the MEG is dried. This operation can enable the desiccant to be used many times but it eventually is so contaminated by inorganic salt (mostly NaCl) that it must be evaporated. This can be done in a wiped surface evaporator under vacuum but this involves fairly expensive equipment and it can be done in a thick wall mild steel pot with an anchor stirrer provided high enough steam pressure or hot oil temperature is available. 

For removal of insoluble and/or water-immiscible inorganics by emulsification with detergent solutions For removal of ester and amide-based organics and inorganic salts by chemical hydrolysis with alkaline solutions For removal of metal ions from solutions and surfaces by chelation or complexation reactions For wetting and dispersion of soils with surfactants, suspension of soil residues in order to prevent resedimentation and recontamination on metal surface For removal of surface contaminations, rust scale, mill scale, and other bound moieties (including surface layers of metal itself) by chemical dissolution with acids or alkaline deoxidation with or without the application of an electric current... 

A large chemical company quartered on the East Coast spends about 400 million annually to remediate contaminated aquifiers and sites associated with past manufacturing operations. Much of this is spent on sites contaminated with lead from the manufacture of tetraethyl lead, lead-based paints, and lead cartridges. For example, the soil of a 25-acre site within a large plant located in New Jersey contains as much as 2,000 ppm of lead as inorganic salts to a depth of 2 feet. The distribution is as follows at the surface, 2,000 ppm 6 , 1,000 ppm 12 , 500 ppm 24 , 0 ppm. 

The cryogenic process uses pelletized carbon dioxide at -73°C as a fluidized abrasive cleaning agent for surface preparation and removal of corrosion and old coatings. Not only does this provide an abrasion mechanism, but certain inorganic salts and organic contaminants can be dissolved with supercritical carbon dioxide. 

Evidence for the formation of some type of Solid Permeable Interface (SPI) has been obtained in all cases smdied. It can be stated generally that the organic species formed on the different cathode electrodes are more or less the same varying more in degree than in their precise chemical nature layer thickness also vary from material to material they also tend to increase significantly with temperature. However, the inorganic species found are more dependent on electrode material type. Reactions with the lithium-salt anion used are also material dependent. It is especially important to reduce the impact of the PF anion and its related contaminants (HF and PF,) on electrode surface chemistry through the implementation of more stable salts. Such a development is currently underway. 

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