Treating processes solvent extraction

Although silver is not treated by solvent extraction in any of the flow sheets, silver is recovered from aqueous solution in several other situations. For these processes, Cytec developed reagents with donor sulfur atoms to extract this soft element. For example, tri-isobutylphosphine sulfide (CYANEX 47IX) extracts silver from chloride, nitrate, or sulfate media selectively from copper, lead, and zinc [32]. The silver is recovered from the loaded organic phase by stripping with sodium thiosulfate, and the metal recovered by cementation or electrolysis. Silver can also be extracted from chloride solution by a dithiophosphinic acid (CYANEX 301) [33]. 

ENSR International Group soil cleaning process is an ex situ treatment for soils contaminated with petroleum hydrocarbons. The process uses a combination of soil washing and solvent extraction. Soil washing removes heavy metals and hydrocarbons from coarse soil particles, resulting in a reduced volume of material to be treated by solvent extraction. Solvent extraction uses a chemical additive that enhances the extraction of hydrocarbons from soil particles in an aqueous slurry. 

Oxide ores are generally treated by hydrometallurgical processes. After concentration they are leached with sulfuric acid. The copper-rich solutions are then treated by solvent extraction (SX) and copper is finally obtained by an electrolytic process (EW). The combined process is designated SX/EW. 

In the area of hydrocarbon rubber process oils, straight paraffinic grades are essentially innocuous and safe mineral oils. The aromatics content and molecular configuration of the naphthenic and aromatic oils have been examined extensively and severe hydro-treating and solvent extraction has upgraded most of the naphthenic product used in the rubber industry today while the highly aromatic extracts need to be labeled as carcinogenic. 

Synthetic Fuel. Solvent extraction has many appHcations in synthetic fuel technology such as the extraction of the Athabasca tar sands (qv) and Irish peat using / -pentane [109-66-0] (238) and a process for treating coal (qv) using a solvent under hydrogen (qv) (239). In the latter case, coal reacts with a minimum amount of hydrogen so that the solvent extracts valuable feedstock components before the soHd residue is burned. Solvent extraction is used in coal Hquefaction processes (240) and synthetic fuel refining (see Coal conversion processes Fuels, synthetic). 

The purified acid is recovered from the loaded organic stream by contacting with water in another countercurrent extraction step. In place of water, an aqueous alkafl can be used to recover a purified phosphate salt solution. A small portion of the purified acid is typically used in a backwashing operation to contact the loaded organic phase and to improve the purity of the extract phase prior to recovery of the purified acid. Depending on the miscibility of the solvent with the acid, the purified acid and the raffinate may be stripped of residual solvent which is recycled to the extraction loop. The purified acid can be treated for removal of residual organic impurities, stripped of fluoride to low (10 ppm) levels, and concentrated to the desired P2 s Many variations of this basic scheme have been developed to improve the extraction of phosphate and rejection of impurities to the raffinate stream, and numerous patents have been granted on solvent extraction processes. 

Codex has also defined the various types of cocoa butter ia commercial trade (10). Press cocoa butter is defined as fat obtained by pressure from cocoa nib or chocolate Hquor. In the United States, this is often referred to as prime pure cocoa butter. ExpeUer cocoa butter is defined as the fat prepared by the expeUer process. In this process, cocoa butter is obtained direcdy from whole beans by pressing ia a cage press. ExpeUer butter usuaUy has a stronger flavor and darker color than prime cocoa butter and is filtered with carbon or otherwise treated prior to use. Solvent extracted cocoa butter is cocoa butter obtained from beans, nibs, Hquor, cake, or fines by solvent extraction (qv), usuaUy with hexane. Refined cocoa butter is any of the above cocoa butters that has been treated to remove impurities or undesirable odors and flavors. 

Increasingly more copper is being produced by electrowinning because of economics and technical advances, such as in solvent extraction processes. Certain brands obtained by SX—EW are treated as cathode quahty and are used directly by wire-rod manufacturers. Whereas in 1984 100,180 t of copper was electrowon in SX—EW plants, in 1992, 439,043 t produced by SX—EQ was electrowon (7). 

ZENECA has developed a non-solvent based recovery process as an alternative to solvent extraction for the commercial production of poly(3HB) and poly(3HB-co-3V) by A. eutrophus [94,95], In this process the cells were first exposed to a temperature of 80 °C and subsequently treated with a cocktail of various hydrolytic enzymes consisting of lysozyme, phospholipase, lecithinase, the proteinase alcalase, and others. Most of the cellular components were hy-... 

Almost all solvent solutions used in solvent extraction processes require treatment, either before their initial use or after being stripped of the extracted species. After preparation of the solvent by mixing appropriate amounts of extractant, modifier, and diluent, the solution is treated by contacting with an appropriate aqueous solution before entering the extraction stage. Such pretreatment is generally referred to as equilibration of the solvent. 

The process flow sheet was first tested for direct leaching of steel mill flue dust and production of zinc metal by electrowinning. The tests were performed in a continuously operating pilot plant, producing 10-20 kg/day zinc metal. The same pilot plant was then used for treating copper/zinc-rich brass mill flue dust in a closed loop operation, recycling all the zinc solvent extraction raffinate to the copper circuit leach section. In the zinc circuit leach section, only the amount of zinc rich dust necessary for neutralization of the copper solvent extraction raffinate was used. The results obtained from the pilot plant tests indicated contamination problems within the solvent extraction loops. The estimation of economic data showed a weak return on the assets compared with the alkali route, and sensitivity toward the raw material price. 

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