Removal of Common Organic Solvents from Aqueous Waste Streams via Supercritical CO₂ Extraction: A Potential Green Approach to Sustainable Waste Management in the Pharmaceutical Industry

Abstract

Supercritical CO2 extraction of aqueous streams is a convenient and effective method to remove commonly used solvents of varying polarities from aqueous waste streams. The resulting aqueous layers can potentially be sewered; whereas the organic layer can be recovered for potential reuse. Supercritical fluid extraction (SFE) is a technology that is increasingly being used in commercial processes (1). Supercritical fluids are well suited for extraction of a variety of media, including solids, natural products, and liquid products. Many supercritical fluids have low critical temperatures, allowing for extractions to be done at modestly low temperatures, thus avoiding any potential thermal decomposition of the solutes under study (2). Furthermore, the CO2 solvent strength is easily tuned by adjusting the density of the supercritical fluid (The density is proportional to the pressure of the extraction process). Since many supercritical fluids are gases at ambient temperature, the extract can be concentrated by simply venting the reaction mixture to a cyclone collection vessel, using appropriate safety protocols.

Future Trends for Green Chemistry in the Pharmaceutical Industry

“…This medium is also used as an extraction solvent and in API isolation, although its use at any scale 6) www.bioniqs.com for this application is limited at present, and the driver for its use is more particle engineering than Green Chemistry. An interesting use of SC -CO 2 to remove solvents from waste water streams has recently been published by Merck [51] . Metalcatalyzed Heck, Suzuki, and diaryl ether formation reactions [52] and hydrogenation in SC -CO 2 [53] are probably the most studied applications in the synthesis of pharmaceutical intermediates (Figure 16.5 ), but are still a long way from being adopted at large scale.…”

A Versatile Lab to Pilot Scale Continuous Reaction System for Supercritical Fluid Processing

“…Compressible gases as near- or supercritical fluids (SCFs) are highly attractive media for many applications including chromatography, material syntheses, polymer processing, , extractions, solvent recovery, formulation, synthesis, and catalysis − on both laboratory and industrial scale . Exploiting the beneficial properties of compressible gases requires highly accurate control of temperature, pressure, and composition due to the nonlinear response to parameter variations and complex phase behavior with solutes .…”