Abstract:
Pharmaceutical waste represents a highly toxic waste stream. With the ever-growing population and advancements in the pharmaceutical industry, and no standardised protocol for their disposal, pharmaceuticals contribute to land and water contamination. Conventional treatment practices include autoclaving and discarding at landfill sites, leading to formation of toxic leachate. High-temperature incineration is another alternative used commercially. However, incineration is prohibited in various countries as it contributes to the release of poisonous emissions such as dioxins, nitrous oxides, persistent organic pollutants, and heavy metals.
Hydrothermal deconstruction of pharmaceutical wastes is a viable waste management technique, non-toxic, environmentally benign and economically feasible. This study focuses on investigating the non-catalytic hydrothermal deconstruction of commonly used local anaesthetics (bupivacaine and lignocaine), antibiotics (amoxicillin and metronidazole), hormones (adrenaline and progesterone). The drugs were subjected to 60 min hydrothermal deconstruction at temperatures varying between 200 and 350 °C. Treated samples were analysed for chemical oxygen demand (COD), ammonia-nitrogen (NH3) content. High-performance liquid chromatography was carried out to confirm the deconstruction of the drugs. Furthermore, gas chromatography equipped with a flame ionisation detector (GC-FID) was performed to measure the quantity of volatile fatty acids (VFAs) produced during the treatment reaction. Additionally, a reactive force field (ReaxFF) molecular dynamic simulation was executed to validate the formation of VFAs.
Results suggest that hydrothermal deconstruction can efficiently destroy pharmaceutical waste. A reduction in COD of up to 91.3 % for anaesthetics, 94.8 % for antibiotics and 85.1
% was achieved for hormones deconstruction. Short-chain volatile fatty acids, predominantly acetic acid was produced during the treatment process. Complete degradation of local anaesthetics achieved at 250 °C after 10 min, up to 99.4% degradation of antibiotics at 350 °C after 60 min and 100 % degradation of hormones at 300 °C after 30 min. Ammonia nitrogen content (NH3-N) of up 60 mg/L was traced for local anaesthetics, 29.8 mg/L for antibiotics and 6.41 mg/L for hormones. The reactive force field (ReaxFF) molecular dynamic simulation suggested that the hydroxyl radicals were responsible for the degradation of the drugs.