7 - A Survey on the Use of Supercritical Carbon Dioxide as a Cleaning Solvent

Abstract

This chapter presents a survey on the use of supercritical carbon dioxide (CO2) as a cleaning solvent. Because of the physiochemical properties of supercritical carbon dioxide it is ideally suited for removing commonly encountered contaminants found in the cleaning of a wide variety of components and assemblies. An overall survey was conducted using a small scale supercritical fluid extraction system to investigate removal efficiencies of a wide variety of compounds from an assortment of surfaces using supercritical CO2. Data are presented demonstrating the successful removal of numerous oils, fluids, adhesives, and chemical compounds from a wide variety of surfaces with supercritical C02. In total, the removal of 145 compounds from some 49 different substrates was investigated. It was found that to a first approximation, cleaning with supercritical C02 appears to be contaminant dependent while being surface independent, with an 85-99% removal rate for the wide variety of the compounds investigated. In addition, it was shown that supercritical CO2 is also capable of removing many compounds traditionally removed by aqueous cleaning, thus expanding the scope of cleaning applicability. Therefore, besides the effectiveness of cleaning with CO2, the economics of the entire cleaning process may direct the use of CO2 in cleaning applications where other replacement technologies are under consideration as well as processes other than precision cleaning. Finally, the use of supercritical CO2 as a cleaning solvent can reduce the overall use of organic solvents in manufacturing processes.