Chemists Clean Up Money Laundering

Supercritical carbon dioxide, a fluid form of CO₂ created at the right combination of temperature and high pressure, is a solvent system that is popular for replacing organic solvents in applications such as decaffeinating coffee and dry cleaning. Scientists have now come up with another application: money laundering. The problem with money is that banknotes get coated with skin oils, sweat, materials such as motor oil, and bacteria that degrade the paper. Governments would like a low-cost way to clean banknotes and extend their lifetime to reduce the cost of producing new bills and disposing of the old ones—some 150 billion new banknotes are printed globally each year. Nabil M. Lawandy and Andrei Y. Smuk of Spectra Systems, a company based in Providence that develops and markets technology used to authenticate and process banknotes, created a supercritical CO₂ system (60 °C and up to 5,000 psi) for cleaning single bills and small packets of bills (Ind. Eng. Chem. Res. 2013, DOI: 10.1021/ie403307y). The process cleans soiled banknotes to near-pristine condition without disturbing security features such as threads, watermarks, and UV and magnetic inks. The next step for the team is scaling the process up to a 200-L reactor that can handle 100,000 banknotes at a time.