Deconstruction and valorisation of a mixture of personal protective equipment using hydrothermal processing

Abstract

This study used non-catalytic hydrothermal deconstruction to examine the deconstruction of a mixture of numerous PPE items, including isolation gowns, gloves, goggles, face shields, surgical masks, and filtering-facepiece respirators. A mixture of PPE items was subjected to hydrothermal deconstruction at temperatures varying between 250 °C and 350 °C and reaction times of 90 min and 180 min, respectively. A reduction of up to 95 % was attained in the total suspended solids (TSS). The total chemical oxygen demand (tCOD) and soluble chemical oxygen demand (sCOD) decreased dramatically to 703 mg/L and 480 mg/L, respectively. Volatile fatty acids, mainly acetic acid and ammonia nitrogen (NH3-N) were the primary end products with a concentration of up to 15,625 mg/L and 38 mg/L after 180 min of deconstruction, respectively. Carbon dioxide and oxygen were found to be the primary gaseous product, with a concentration of up to 14 % (w/w) for CO2 and 76 % (w/w) for O2. Further experiments were conducted at 300 °C and 350 °C to reuse process water for five cycles to demonstrate the feasibility of process water recycling. The results propose that non-catalytic hydrothermal deconstruction may potentially reduce PPE waste by minimising solid waste and water usage.