Recent advances on the speciation distribution of heavy metals in sludge pyrolysis residue

The amount of urban and industrial sewage generated in China has reached 7.34×1010 t/a, and the number of sludge produced by its treatment has reached 7.29×107 t/a. The main utilization methods of sludge are land application, incineration for power generation and for building materials. Heavy metals, especially Cr, Cu, Zn, Ni etc., have a great impact on these reuse processes. The sludge treatment mainly adopts pyrolysis technology. Heavy metals are concentrated in the pyrolysis residue during the pyrolysis process. Explaining the speciation distribution of heavy metals in the pyrolysis residue is of great significance to the reuse process. Based on the modified European Community Bureu of Reference (BCR) sequential extraction method, the speciation distribution of heavy metals in the sludge pyrolysis residue is summarized, the effect of pyrolysis conditions (pyrolysis temperature, residence time and catalyst), co-pyrolysis and pretreatment on the speciation distribution of heavy metals in the pyrolysis residue is described, and the future research trends of heavy metals in sludge pyrolysis residues are discussed. © 2022, Editorial Board of CIESC Journal. All right reserved.