Abstract:The pyrolysis of phytoremediated giant reed (Arundo donax) biomass could cause secondary pollution of heavy metals. The stabilization of heavy metals in the pyrolysis process with external materials such as Al₂O₃, CaCO₃, FeCl₃ and NaOH, was studied. The results showed that 37% As and 97% Cd in biochar were stabilized when giant reed powder was pyrolyzed at 250 °C with 5% Al₂O₃ for 2 h. Furthermore, 59% Pb in biochar was stabilized at 400 °C with 5% CaCO₃ for 1 h. Under biochar produced in optimized pyrolysis conditions, Cd mainly existed in a residual fraction, while Pb and As mainly existed in oxidizable fraction in BCR analysis. In XRD analysis, As was only found in Ca₂As₂O₇; Cd in biochar mainly existed in Cd (AlCl₄)₂, CdPbO₃ or CdSO₃; and Pb mainly existed as Pb₃O₂SO₄.

Key words: phytoremediated giant reed; pyrolysis; biochar; heavy metal; stabilization