Extraction of pharmaceuticals from hospital wastewater with eutectic solvents and terpenoids: computational, experimental, and simulation studies

Abstract

The presence of pharmaceuticals in wastewater, mainly in hospital wastewater, is a serious environmental concern, as they are not removed by conventional processes in wastewater treatment plants and are discharged into the natural environment. This work proposes extracting drugs from hospital wastewater using natural, renewable, and non-toxic solvents such as terpenes and eutectic solvents. First, molecular simulation has been used with the COSMO-RS method performing a massive screening of 43 terpenes, 11 eutectic solvents, and 5 conventional solvents with 31 common pharmaceuticals. The most promising solvents in the screening have been chosen to extract 11 pharmaceuticals simultaneously. Experimental tests with ultrapure water and real hospital wastewater matrices showed a strong influence of pH and matrix on extraction. Under the optimal conditions, global pharmaceutical extraction yields with carvacrol of 94.16 % and the eutectic solvent thymol+dodecanoic acid of 96.86 % were obtained. The regeneration and reuse of both solvents were studied in 5 consecutive stages, showing the carvacrol's high stability and regenerability. Using carvacrol, countercurrent extraction tests showed a fast mass transfer of pharmaceuticals and high extraction yields using low solvent-to-feed (S/F) ratios. The predictions obtained with COSMO-RS were similar to the experimental results, confirming the reliability of this method for selecting alternative solvents for the extraction of pharmaceuticals. Finally, the drug removal process was simulated in a countercurrent extraction. The complete removal of pharmaceuticals from hospital wastewater could be achieved using carvacrol with an S/F of 2.00 at pH 4.00 in an extractor with six equilibrium stages.