Wu Menglan, Liu Bo, Li Jun, Su Xintai, Liu Weizhen, Li Xiaoqin
School of Environment and Energy, Guangdong Provincial Key Laboratory of Solid Wastes Pollution Control and Recycling, South China University of Technology, Guangzhou, Guangdong, 510006, People's Republic of China.
The Key Laboratory of Pollution Control and Ecosystem Restoration in Industry Clusters of the Ministry of Education, South China University of Technology, Guangzhou, 510006, People's Republic of China.
Environ Sci Pollut Res Int. 2023 Jan;30(5):12608-12617. doi: 10.1007/s11356-022-22827-x. Epub 2022 Sep 16.
Pyrolysis of sludge to biochar can not only reduce the sludge volume, toxic organic compound, and pathogens, but also be applied as effective adsorbents. However, the immobilization of heavy metals in the sludge and the properties of the biochar greatly rely on the pyrolysis temperature. In this paper, municipal sludge biochar (SBC) was prepared from 400 to 1000 °C. Pyrolysis immobilized heavy metals in sludge and the potential ecological risk of heavy metals significantly decreased to low level at temperature above 500 °C. At 700 °C, the adsorption capacity of Cd(II) reached a maximum (120.24 mg·g). The Cd(II) adsorption fitted the Pseudo-second-order model, indicating the existence of chemical adsorption. The adsorption capacity increased along with the initial pH and slowed down after pH reached 5.5. The existence of coexisting cations (Ca and Na) and anions (SO and NO) displayed different degree of inhibitory action on Cd(II) adsorption. The SEM, XRD, FTIR, and XPS analysis of sludge biochar before and after adsorption revealed that there were CdCO, CdSO, CdSiO, Cd(PO), and Cd(PO) appearing on the surface of sludge biochar, suggesting that the adsorption of Cd(II) by SBC included co-precipitation, ion exchange, coordination with π electrons, and complexation. It was confirmed that different properties formed by pyrolysis temperature made a difference in adsorption mechanism of sludge biochar.
污泥热解制备生物炭不仅可以减少污泥体积、降低有毒有机化合物和病原体含量，还可作为有效的吸附剂。然而，污泥中重金属的固定以及生物炭的性质在很大程度上依赖于热解温度。本文在400至1000℃的温度范围内制备了城市污泥生物炭（SBC）。热解使污泥中的重金属得以固定，且在温度高于500℃时，重金属的潜在生态风险显著降低至低水平。在700℃时，Cd(II)的吸附容量达到最大值（120.24 mg·g）。Cd(II)的吸附符合准二级模型，表明存在化学吸附。吸附容量随初始pH值的升高而增加，在pH达到5.5后增速减缓。共存阳离子（Ca和Na）和阴离子（SO和NO）的存在对Cd(II)的吸附表现出不同程度的抑制作用。对吸附前后污泥生物炭的扫描电子显微镜（SEM）、X射线衍射（XRD）、傅里叶变换红外光谱（FTIR）和X射线光电子能谱（XPS）分析表明，污泥生物炭表面出现了CdCO、CdSO、CdSiO、Cd(PO)和Cd(PO)，这表明SBC对Cd(II)的吸附包括共沉淀、离子交换、与π电子配位和络合作用。证实了热解温度形成的不同性质对污泥生物炭的吸附机制产生了影响。
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