Energetic and environmental optimizations and byproduct valorization of pyrolysis of textile dyeing sludge with FeCl3

Maximizing the circular economy of hazardous wastes is one of the imperatives not to overshoot the biogeochemical limits of Earth. This study aimed to characterize and valorize the textile dyeing sludge (TDS) pyrolysis in response to the addition of FeCl3 conditioner in the N2 and CO2 atmospheres. The increase fraction of FeCl3 decreased comprehensive pyrolysis index (CPI600) from 1.05 to 0.42 in the N2 atmosphere and from 0.71 to 0.41 in the CO2 atmosphere at 20 degrees C/min. The addition of FeCl3 diminished the pyrolysis performance, with a more pronounced inhibitory effect occurring in the N2 atmosphere than in the CO2 atmosphere. Regardless of the type of pyrolysis atmosphere, with or without FeCl3, all the TDS pyrolysis released CO, CO2, CH4, aromatics, NH3, and SO2. The main pyrolytic byproducts were nitrides and hydrocarbons, represented by ethanolamine (C2H7NO) and benzene (C6H6). Not only did 4 % FeCl3 addition facilitate the transformation of nitrides into hydrocarbons during the pyrolysis, but it also achieved the optimal energetic performance and emission reduction. Our findings provide novel and actionable insights into the byproduct valorization and pollution control during the TDS pyrolysis and the promotion of carbon capture, utilization, and storage.