In Situ Immobilization of Heavy Metals in Sewage Sludge by Microwave Irradiation

Rui MA, Yang ZHOU, Lin FANG, Xiao-Fang YUE, Xu-Xin ZHAO, Jiang-Long YAN, Na-Na YUAN


The immobilization effects and mechanism of heavy metals (Cr, Cu, Zn, Cd, Ni and Pb) in the process of original sludge pyrolysis by single-mode microwave have been investigated in the study, and immobilization effects and mechanism of heavy metals were compared by doping different additives such as Sic, graphite and sludge residues into sludge. The in situ immobilization effects of different microwave absorbing substances on the sludge were compared by Toxicity Characteristic Leaching Procedure (TCLP) and Synthetic Precipitation Leaching Procedure (SPLP) and the results showed that in-situ microwave-assisted pyrolysis can effectively immobilize Cr, Cu, Zn, Cd, Ni and Pb in the sludge, with leaching concentration reduced by 68.3% to 94.59%. Of them, the leaching concentration of sludge doped with pyrolysis residues reduced by 85.20%. The heavy metals speciation in the original sludge and the sludge with doping additives treated by microwave, were analyzed by sequential extraction procedure of Tessier, showing that the speciation of heavy metals treated by microwave turned into the most stable residue form.


Sludge, Microwave, Pyrolysis, Immobilization Mechanism of Heavy Metals, Leaching Law of Heavy Metals


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