Syngas production from textile dyeing sludge via carbon dioxide-assisted pyrolysis

Abstract

The textile dyeing process utilizing synthetic dyes generates by-products known as textile dyeing sludge (TDS), which comprises various harmful chemicals. However, disposal of TDS through conventional methods of waste present significant environmental hazards, leading to the dissemination of hazardous chemicals into the ecosystem. Therefore, this study introduces thermo-chemical platform for the disposal of TDS. Specifically, this study employs CO₂ as a reactive feedstock to maximize the production of syngas and minimize formation of toxic chemicals. Prior to pyrolysis, the hazardous potential of TDS was qualitatively evaluated. The pyrolysis of TDS under CO₂ environments demonstrated gas-phase reactions between volatile substances and CO₂. These reactions led to increased CO production while simultaneously reducing the formation of toxic compounds such as benzene derivatives and polycyclic aromatic hydrocarbons (PAHs) within pyrogenic oil. The reduction in benzene derivatives and PAHs was quantified as −10.31 % under single-step pyrolysis and −25.16 % under multi-step pyrolysis. To expedite kinetics of gas-phase reactions, Ni-based catalyst was employed for catalytic pyrolysis of TDS. Compared to non-catalytic pyrolysis, the Ni catalyst enhanced CO production by expediting gas-phase reactions. Compared to multi-step pyrolysis under the CO₂ condition (3.81 mol%), the CO formation from catalytic pyrolysis under CO₂ condition exhibited significant enhancement (15.35 mol%). Consequently, all experimental results highlight potential of pyrolysis with CO₂ as a promising method for the disposal of TDS, while converting it into valuable energy resources.