Alternative Solvents for Separation Processes

The development of a successful crystalhzation process for purification and isolation of an organic compound requires the selection of a suitable solvent or solvent mixture to date, no logical method has been established for determining the best solvent com- 

The characteristics of supercritical fluids make them ideal for the recovery of natural products (Molero et al., 1996). As a result, the food industry was among the first to implement supercritical fluid extraction (SFE) widely using CO2. Not only is this process environmentally benign, it is also nontoxic, a primary concern when manufacturing edible products. 

SFE has also replaced many regulated solvents in analytical chemistry applications in recent years, primarily because it provides a more reliable measure of the concentrations of environmental contaminants and can play an important role in pollution assessment, abatement, and control. Advantages have been shown for using SFE compared to the conventional Soxhlet extraction with toluene for determining the presence of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in ashes from a municipal incinerator (Dolezal et al., 1995). SFE allows the complete extraction of the analytes from the sample, whereas conventional extraction results in an incomplete, and hence, inferior extraction. 

Removal of organic or heavy metal ion contaminants from aqueous streams can be achieved using a variety of different separation strategies, one of which is solvent extraction. Potential counter-contamination of the streams being treated with the ex- 

Solvent-coated magnetic particles dispersed within the feed phase can be used to process metal waste solutions (Kaminski et al., 1997 Nunez et al., 1996). Once the desired solutes have been removed by extraction, these particles can be recovered conveniently using magnetic filtration. 

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