Extraction of antibiotics identified in the EU Watch List 2020 from hospital wastewater using hydrophobic eutectic solvents and terpenoids

The increasing consumption of pharmaceuticals, along with the ineffectiveness of conventional wastewater treatment, has resulted in an increased presence of these pollutants in both drinking water supplies and aquatic environments. The potential adverse health effects and environmental impact of these chemicals are drawing the attention of several bodies around the world. For instance, some antibiotics such as ciprofloxacin, trimethoprim, and sulfamethoxazole have been included in the most recent European Surface Water Watch List under the EU Water Framework Directive (Decision 2020/1161). The present work proposes the use of terpenoids and eutectic solvents, as effective and green solvents with low toxicity, for multicomponent liquid-liquid extraction of ciprofloxacin, trimethoprim, and sulfamethoxazole from ultrapure water and hospital wastewater. The COSMO-RS method was used for a predictive initial solvent screening. Thymol, carvacrol, eutectic solvents (thymol + fatty acids), and conventional solvents (methyl isobutyl ketone and ethyl acetate) were selected to be used in the experiments. The influence of the volumetric S/F ratio, aqueous matrix, and pH was analysed. Conventional solvents show significantly lower overall extraction yields than those observed for eutectic solvents and terpenoids at any pH and matrix. Carvacrol presented the most favourable conditions, reaching overall extraction yields above 98.0% (98.9% for trimethoprim, 99.5% for ciprofloxacin, and 97.0% for sulfamethoxazole) with hospital wastewater at pH 5.0 and S/F ratio of 1.00. Carvacrol showed a feasible operation in a continuous extraction column at room temperature, providing effective reuse and regeneration processes in this study.

Automated summary

The increasing consumption of pharmaceuticals has led to higher levels of drug pollution in water environments, attracting global attention. Research on the use of terpenoids and eutectic solvents for efficient drug extraction in hospital wastewater has shown that carvacrol is the most effective solvent for this purpose.