DIVERGENT ENVIRONMENTAL BEHAVIOUR OF IMIPENEM AND FLUOXETINE: STABILITY, INTERACTIONS, AND REMOVAL PROCESS

Abstract

The occurrence of pharmaceutical residues has long been recognized as a potential health concern; however, the fate of these pharmaceuticals has not been thoroughly investigated. In this regard, the present thesis aims to investigate the environmental behaviour of two model pharmaceuticals: Imipenem (IMP), an antibiotic, and Fluoxetine (FLX), an antidepressant, focusing on stability and metal interactions, and devising removal/degradation strategies where applicable.

The findings of the present dissertation indicate that the antibiotic IMP is photolabile and thermosensitive, undergoing rapid degradation under ambient light and temperature. The presence of dissolved organic matter (DOM) and Cu (II) further accelerate its degradation. The drug also exhibits potential to form Imipenem-metal complexes (IMP-Me), exhibiting increased antibacterial activity compared to IMP. Since the drug was observed to be labile, no degradation strategy was proposed.

In contrast to IMP, FLX resists natural attenuation, resulting in its persistence in aquatic environments and making its removal challenging. The present dissertation, thereby, investigates physically activated olive-stone-derived biochar for FLX removal. The optimized biochar demonstrated superior FLX adsorption, surpassing previously reported waste-derived biochar. To further improve practical implementation and achieve FLX degradation, an integration of biochar-based adsorption and UVC-based photocatalysis was employed. The proposed CuO-BC/UVC composite photocatalytic system achieved >95% FLX removal under 2 minutes of treatment. The synergistic CuO-BC/UVC system offers a practical, scalable, and safer alternative to more energy-intensive or chemically harsh oxidation processes.

Overall, the findings for both drugs represent the two extremes of emerging contaminants and highlight opposite ends of a decision framework. For IMP, intervention was not deemed necessary due to its chemically labile structure and natural attenuation; however, toxicity to bacteria persists both with and without transformation, indicating that risk is chemically dynamic and significant, despite rapid transformation. On the contrary, FLX is chemically stable, exhibits no metal complexation, remains bioavailable, and poses a risk for long-term exposure. This persistence, coupled with chronic effects, makes the invention essential. With these contrasting case studies of IMP and FLX, this dissertation aims to establish that the decision to intervene should be guided by stability, interaction dynamics, and toxicity of the contaminant.