Supercritical water oxidation of recalcitrant acetaminophen with methanol, ethanol, n-propanol, isopropanol and glycerol as co-fuels

Abstract

Pharmaceuticals are recalcitrant molecules that demand advanced treatment techniques for their complete elimination in wastewater streams. Supercritical water oxidation has been proved as an effective technology to remove the recalcitrant molecules from wastewater streams. Supercritical water oxidation of acetaminophen was performed in the presence of various co-fuels such as methanol, ethanol, n-propanol, isopropanol, and glycerol. The key operating parameters such as temperature (400–500 °C) and oxidation coefficient (OC: 1–3) have been varied to note total organic carbon (TOC) removal efficiency at different conditions. Temperature and OC showed a positive impact on the removal efficiency for all the co-fuels implemented. The addition of co-fuels has increased the free radicals that act on the organics and thereby enhanced TOC removal efficiency. Near-complete removal efficiencies (99.7%) were attained with ethanol and n-propanol at an operating temperature of 500 °C with an oxidation coefficient of 3. The gas composition analysis reflects the highest H2 volume fraction for ethanol followed by glycerol and n-propanol at the lowest supercritical temperature 400 °C and OC 1. However, with the rise in temperature (500 °C) and OC 3, the CO2 mole fraction increased confirming the acceleration of oxidation reactions.

Keywords

• Pharmaceutics
• Acetaminophen
• Supercritical water
• Total organic carbon
• Oxidant coefficient
• Free radicals