Synergistic effects, gaseous products, and evolutions of NOx precursors during (co-)pyrolysis of textile dyeing sludge and bamboo residues

Highlights: • 50% bamboo residues (BR) with textile dyeing sludge (TDS) had the greatest synergy. • Adding BR increased CO₂, CO, CH₄, CO and CO emissions from co-pyrolysis. • Adding 50% BR significantly reduced NH₃ and HCN emissions from co-pyrolysis. • Co-pyrolysis enhanced the formations of more N-5 and N-Q structures in biochar. • Co-pyrolysis inhibited the hydrogenation and ring-opening reactions at N-sites. This study aimed to investigate the synergistic influences of the textile dyeing sludge (TDS) and bamboo residues (BR) co-pyrolysis, and its effects on the formation mechanisms of NH₃ and HCN. The mass loss rate was lower for TDS than BR, with the co-pyrolysis with 50% BR exerting the strongest synergistic effect. The pyrolysis stages 1 (2, CO, CH₄, CO, and CO and reduced the aromatic compounds. The thermal stability of N-A structure was lower in TDS than BR. The co-pyrolysis with 50% BR significantly inhibited the formations of NH₃ and HCN and improved the aromaticity of biochar. This may due to the weakened hydrogenation reaction at N sites, the enhanced conversion of NH₃, the inhibition of the ring cleavage in the char-secondary cracking, and the formation of more quaternary-N. Our results provide insights into the co-treatment of TDS and BR, and controls over NO_x precursors for a cleaner energy production.