Feedstock recycling of single-use garment simultaneously using CO₂ and MSW incinerator bottom ash

This study is aimed at proposing a feedstock recycling approach to make value-added monomer from single-use garment like stocking waste (SW) using incinerator bottom ash catalyst (IBAC). SW is made mainly of nylon 6 (>80 wt%) with minor components such as polyurethane. Thermochemical SW decomposition pathways are identified by evolved gas analysis and single-shot pyrolysis analysis, confirming that caprolactam (a value-added chemical re-used for manufacturing nylon 6) is the major product. IBAC is composed mainly of alkaline metal oxides (e.g., CaO). The use of IBAC in thermochemical SW conversion at 500 °C under CO₂ atmosphere increases the yield of caprolactam reaching 70.8 wt% (20 % higher than non-catalytic SW conversion (59.2 wt%)). Moreover, the caprolactam yield corrected to the nylon 6 content of SW is 86.8 wt%. The enhancement of caprolactam production by IBAC in CO₂ is most likely due to the synergistical effect of IBAC and CO₂ on promoting the molecular interaction of amide groups present on SW. It is hoped that this study brings the idea of new applications of concurrently reusing textile waste (e.g., SW) and municipal solid waste-treatment byproduct (e.g., IBAC).