Iron-biochar production from oily sludge pyrolysis and its application for organic dyes removal

In this study, a single-step pyrolysis approach was developed to directly convert oily sludge (OS) with high iron content into a magnetic iron-char catalyst for organic dyes removal. Magnetic iron-char catalysts were employed to degrade crystal violet (CV), methylene blue (MB), and sunset yellow (SY). The OC800 iron-char catalyst prepared from OS was not only rich in iron (mainly stable Fe3O4), but also showed favorable pore structures. Effects of operation parameters like temperature, H2O2 dosage, and pH on dye removal based on Fenton degradation were examined. In OC800 Fenton system (0.5 mL H2O2, 500 mg/L dye concentration, and pH = 2 in 50 mL solution), the maximum dye removal capacities of SY, CV, and MB were 83.61, 639.19, and 414.25 mg/g, respectively. In dyes degradation experiments, the prepared catalyst could be reused (more than 3 successive cycles) due to higher stability and less leaching of iron. One-step pyrolysis of OS with high iron content thereby represents a promising approach to transform sludge waste to functional biochar that removes hazardous dyes.

Automated summary

A single-step pyrolysis approach was developed to convert oily sludge with high iron content into a magnetic iron-char catalyst for organic dyes removal. The prepared catalyst showed favorable pore structures and high stability, allowing for effective and reusable degradation of dyes. This one-step pyrolysis method represents a promising approach to transform sludge waste into functional biochar that removes hazardous dyes.