In this study

biochars produced from three different particle sizes of sewage sludge (d≤0.15 mm

0.15 mm <d ≤0.27 mm

and d>0.27 mm) using the fixed bed reactor at a temperature of 500℃. Pyrolysis characteristics of sludge and the heavy metals distributions in sludge and its biochar were investigated

respectively. Moreover

the leaching toxicity of heavy metals in sludge and its biochar were assessed applying toxicity characteristics leaching procedure (TCLP) method. The experimental results showed that with the increase of sludge particle size

the biochar and gas yield obtained from pyrolysis process decreased

while tar yield was an opposite trend. During the pyrolysis process of sludge

the most heavy metals in the sludge were accumulated in biochar except As and their relative enrichment factors were all higher than 90%. The contents of Cu

Zn

and Ni in the sludge increased and decreased for the contents of Cr and Pb with augmenting of particle size. Although the leaching pattern of the heavy metals was different between biochars obtained from the different particle sizes of sewage sludge

the pyrolysis technology significantly suppressed the heavy metals leaching from biochars. The TCLP-leaching rates of most heavy metals except As and Zn from biochar were all lower than 3.0%.