Co-pyrolysis of sludge and kaolin/zeolite in a rotary kiln:Analysis of stabilizing heavy metals  

作　　者：Qian Li Zhaoping Zhong Haoran Du Xiang Zheng Bo Zhang Baosheng Jin 

机构地区：[1]Southeast University,Key Laboratory of Energy Thermal Conversion and Control(Ministry of Education),Nanjing,210096,China

出　　处：《Frontiers of Environmental Science & Engineering》2022年第7期21-33,共13页环境科学与工程前沿（英文）

基　　金：funded by National Key Research and Development Program of China(No.2018YFC1901202).

摘　　要：Pyrolysis is a promising technique used for treating of sewage sludge.However,the application of pyrolysis products is limited due to the presence of heavy metals.In this study,sewage sludge mixed with kaolin/zeolite was pyrolyzed in a rotary kiln,aiming to improve the immobilization of heavy metals in pyrolytic carbon.The total concentrations,speciation distributions,leaching toxicities,and potential ecological risk indices of heavy metals in pyrolysis biochar were explored to examine the effects of kaolin/zeolite and pyrolytic temperature on immobilizing heavy metals.Further,mineral composition and surface morphology of biochar were characterized by X-ray diffraction and scanning electron microscopy to reveal the potential mechanism of immobilizing heavy metals.Increasing pyrolysis temperature facilitated the stabilization of heavy metals in pyrolysis biochar.The proportions of stable heavy metals in biochar obtained at 650℃ were 54.50%(Cu),29.73%(Zn),79.29%(Cd),68.17%(Pb)and 86.70%(Cr).Compared to sewage sludge,the potential contamination risk index of pyrolysis biochar obtained at 650℃ was reduced to 17.01,indicating a low ecological risk.The addition of 7%kaolin/zeolite further reduced the risk index of co-pyrolysis biochar prepared at 650℃ to 10.86/15.28.The characterization of biochar revealed that increase in the pyrolysis temperature and incorporation of additives are conducive to the formation of stable heavy metal-inorganics.This study demonstrates that the formation of stable mineral compounds containing heavy metals is the key to stabilizing heavy metals in pyrolysis biochar.

关 键 词：CO-PYROLYSIS Sewage sludge Heavy metals Rotary kiln Immobilization mechanism 

分 类 号：X703[环境科学与工程—环境工程]