Characteristics of changes in hazardous elements and heavy metals during pyrolysis treatment of oily sludge

ABSTRACT

Oily sludge is a hazardous solid waste, hazardous ingredients (hazardous elements and heavy metals) in pyrolysis products have the potential for secondary pollution. The distribution of hazardous elements (N/S/Cl) during the pyrolysis of oily sludge was determined at different pyrolysis temperatures (350–750°C), and the potential ecological risk of heavy metals (Zn/Cu/Cd/Cr/Pb) in the solid residue was evaluated. The results showed that N-pollutants in oily sludge were mainly distributed at higher pyrolysis temperatures (550°C), S and Cl-pollutants were mainly distributed at 450°C. The leaching concentration of Zn metal in oily sludge was 119.73 mg/L, which has exceeded the concentration limit (100 mg/L) stipulated by GB 16,889–2008. The pyrolysis treatment could reduce the leaching rate of Zn metal to 18.39 mg/L Moreover, the risk assessment code (RAC) values for Zn showed a very high risk environmental risk level. Pyrolysis treatment could reduce the RAC value of Zn and change the environmental risk level of Zn to low risk. The results of this study provide a theoretical basis for the pyrolysis treatment of oily sludge and the control of harmful ingredients.

KEYWORDS:

• Oily sludge
• hazardous elements
• heavy metals
• risk assessment
• pyrolysis treatment

Acknowledgements

The authors appreciate the financial support from the Applied Basic Research Project of Science and Technology Department of Sichuan Province (No. 2021YJ0344), the Open Project Program of State Key Laboratory of Petroleum Pollution Control, CNPC Research Institute of Safety and Environmental Technology (No. PPC2020003), the Student Innovation Fund Project of Southwest University of Science and Technology (No. JZ22-025), the Research project of State Key Laboratory of Environment-friendly Energy Materials (No. 22fksy12).

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article [and/or] its supplementary materials.

Additional information

Funding

The work was supported by the Student Innovation Fund Project of Southwest University of Science and Technology [JZ22-025]; The Research project of State Key Laboratory of Environment-friendly Energy Materials [22fksy12]; Open Project Program of State Key Laboratory of Petroleum Pollution Control [PPC2020003]; Applied Basic Research Project of Science and Technology Department of Sichuan Province [2021YJ0344].