Pyrolytic conversion of nylon-6 and red mud into N-doped carbon composite and its application into azo-dye degradation

Abstract

The continuous growth of the global population and industries has led to the mass generation of plastic and industrial waste, posing significant environmental challenges due to their incompatibility with conventional waste management practices. This study investigates the thermochemical conversion of plastic (nylon-6) and industrial waste (red mud) into value-added products, presenting a waste-to-resource conversion strategy. Nylon-6 and red mud were co-pyrolyzed, resulting in a metal-carbon composite characterized as porous N-doped graphitic carbon with embedded Fe0 particles. Application of the composite to an amaranth solution demonstrated its ability to activate persulfate, facilitating amaranth oxidation at a rate (kobs = 1.78 min−1) significantly higher than other Fe-based catalysts. Quenching experiments verified the generation of OH· and SO4·- radicals during activation, with the latter playing a dominant role in amaranth degradation. The composite exhibited robust reusability, maintaining an amaranth removal efficiency of >80 % after five reaction cycles. Additionally, red mud significantly enhanced syngas (H2 and CO) generation from nylon-6, suggesting a catalytic effect. In conclusion, the proposed thermochemical approach offers a viable method for converting waste materials into valuable products, including environmental catalysts and gas fuels.