Valorization of hazardous COVID-19 mask waste while minimizing hazardous byproducts using catalytic gasification

Abstract

This study proposes a method to valorize hazardous waste such as used COVID-19 face mask via catalytic gasification over Ni-loaded ZSM-5 type zeolites. The 25% Ni was found as an optimal loading on ZSM-5 in terms of H2 production. Among different zeolites (ZSM-5(30), ZSM-5(80), ZSM-5(280), mesoporous (m)-ZSM-5(30), and HY(30)), 25% Ni/m-ZSM-5(30) led to the highest H2 selectivity (45.04 vol%), most likely because of the highest Ni dispersion on the m-ZSM-5(30) surface, high porosity, and acid site density of the m-ZSM-5(30). The content of N-containing species (e.g., caprolactum and nitriles) in the gasification product was also reduced, when steam was used as gasifying agent, which is the source of potentially hazardous air pollutants (e.g., NOx). The increase in the SiO2/Al2O3 ratio resulted in lower tar conversion and lower H2 generation. At comparable conditions, steam gasification of the mask led to ~15 vol% higher H2 selectivity than air gasification. Overall, the Ni-loaded zeolite catalyst can not only suppress the formation of hazardous substances but also enhance the production of hydrogen from the hazardous waste material such as COVID-19 mask waste.