Supercritical carbon dioxide and ionic liquids constitute some of possible environmentally friendly alternatives to the conventional organic solvents. Each of these solvents, nevertheless, presents its own disadvantages which comprise their widespread use and application. These shortcomings can probably be overcome by using combinations of these solvents at tuned process conditions.
Here we present preliminary results of recovery of antibiotics from aqueous solutions by using ionic liquids and supercritical carbon dioxide. All selected antibiotics are natural (produced by fermentation) and of industrial importance such as penicillin G, erythromycin, tetracycline and chloramphenicol. Preliminary results indicate possibility of recovering these antibiotics from aqueous media through three stages. First, selection of hydrophobic ionic liquids with good solvent power towards each selected antibiotic molecules has been achieved. As a second step, study of liquid – liquid extraction of an antibiotic from aqueous solution has been performed by an appropriate ionic liquid. As a final step, recovery of antibiotics from ionic liquid medium has been performed by using supercritical carbon dioxide at different pressures and temperatures. Thus, the process design includes coupling aqueous solution – ionic liquid extraction, with: (1) high-pressure carbon-dioxide extraction, followed by crystallization by rapid expansion, or in situ precipitation by a supercritical anti-solvent effect.