Hydrothermal deconstruction of single-use personal protective equipment during the COVID-19 pandemic.

To minimise the transmission of the SARS-CoV-2 virus, there has been a substantial increase in the production and usage of synthetic personal protective equipment (PPE) globally. Consequently, single-use PPE have been widely adopted without appropriate regulations for their disposal, leading to extensive environmental contamination worldwide. This study investigates the non-catalytic hydrothermal deconstruction of different PPE items, including isolation gowns, gloves, goggles, face shields, surgical masks, and filtering-facepiece respirators. The selected PPE items were subjected to hydrothermal deconstruction for 90 min in the presence of 30-bar initial oxygen pressure, at temperatures ranging between 250 °C and 350 °C. The solid content in form of total suspended solids (TSS) was reduced up to 97.6%. The total chemical oxygen demand (tCOD) and soluble chemical oxygen demand (sCOD) decreased with increasing deconstruction temperature, and at 350 °C the lowest tCOD and sCOD content of 546.6 mg/L and 470 mg/L, respectively, was achieved. Short-chained volatile fatty acids were produced after 90 min of deconstruction, predominantly acetic acid at concentrations up to 8974 mg/L. Ammonia nitrogen content (NH3-N) of up to 542.6 mg/L was also detected. Carbon dioxide (CO2) and unreacted oxygen (O2) were the main gaseous by-products at up to 15.6% (w/w) and 88.7% (w/w), respectively. The findings suggest that non-catalytic hydrothermal deconstruction is a viable option to process and manage PPE waste.

Deconstruction and Valorisation of a Mixture of Personal Protective Equipment using Hydrothermal Processing

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.

Hydrothermal deconstruction of single-use personal protective equipment: process design and economic performance.

Increased demand for single-use personal protective equipment (PPE) during the COVID-19 pandemic has resulted in a marked increase in the amount of PPE waste and associated environmental pollution. Developing efficient and environmentally safe technologies to manage and dispose of this PPE waste stream is imperative. We designed and evaluated a hydrothermal deconstruction technology to reduce PPE waste by up to 99% in weight. Hydrothermal deconstruction of single-use PPE waste was modelled using experimental data in Aspen Plus. Techno-economic and sensitivity analyses were conducted, and the results showed that plant scale, plant lifetime, discount rate, and labour costs were the key factors affecting overall processing costs. For a 200 kg/batch plant under optimal conditions, the cost of processing PPE waste was found to be 10 NZD/kg (6 USD/kg), which is comparable to the conventional practice of autoclaving followed by landfilling. The potential environmental impacts of this process were found to be negligible; meanwhile, this practice significantly reduced the use of limited landfill space.