<p>This study explores the chemical speciation, leaching characteristics, and environmental risk associated with heavy metals (HMs) (Mn, Cr, Zn, Ni, Cu, and Pb) in biochar and bio-oil derived from the pyrolysis of wet sewage sludge across a temperature range of 400℃ to 800℃. Our findings unveil a pH elevation in biochar alongside a reduction in the H/C and O/C ratios, culminating in heightened aromaticity. Despite the augmentation of exchangeable HMs in bio-oil with rising pyrolysis temperatures, the predominant form of HMs in bio-oil remains non-exchangeable. Post-pyrolysis, a substantial portion of HMs exists in oxidizable and residual forms, particularly evident at 700℃, resulting in a significant decrease in bioavailability and consequently, a low environmental risk associated with biochar. This investigation underscores the promise of wet sewage sludge pyrolysis as a method for HMs immobilization in biochar, emphasizing the potential to mitigate the adverse impacts of biochar by controlling pyrolysis temperature.</p> Graphical Abstract <p></p>