Li Qian, Zhong Zhaoping, Du Haoran, Yang Yuxuan, Zheng Xiang, Zhang Bo, Jin Baosheng
Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, Southeast University, Nanjing 210096, China.
Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, Southeast University, Nanjing 210096, China.
Waste Manag. 2023 Oct 1;170:177-192. doi: 10.1016/j.wasman.2023.08.013. Epub 2023 Aug 16.
It is of great significance to reduce the secondary risk of heavy metals during the pyrolysis of paper sludge. This study used kaolin and alumina-silica-based xerogels to control heavy metals released during sludge pyrolysis. Pyrolyzing a mixture of sludge and 7% kaolin at 400 °C achieved high retention rates for Cu (95.85%), Zn (95.97%), Pb (97.15%), Cd (84.23%), and Cr (84.05%) when the pyrolysis tail gas was treated with 9 g of xerogel. The addition of kaolin facilitated the transformation of Cu, Zn, Pb, and Cr from the unstable fraction to the stable fraction in pyrolysis biochar, reducing their leachability. The xerogels also played a crucial role in adsorbing and stabilizing the heavy metals. The results of thermodynamic equilibrium calculations showed that Pb(g), PbS(g), PbCl(g), PbCl(g), Zn(g), ZnCl(g), and Cd(g) were the main gaseous products of Zn, Pb, and Cd during paper sludge pyrolysis. The Pb atoms in PbCl and PbS, and the Zn atoms in ZnCl bond with the oxygen atoms on the kaolin surface by covalent bonds, while the Cl atoms in PbCl and the Pb atoms of elemental lead form ionic bonds with H and O atoms on the kaolinite surface, respectively. These experimental and simulation results offer new ideas for controlling heavy metals during sludge pyrolysis.
在纸污泥热解过程中降低重金属的二次风险具有重要意义。本研究使用高岭土和基于氧化铝 - 二氧化硅的干凝胶来控制污泥热解过程中重金属的释放。当用9克干凝胶处理热解尾气时，在400℃下热解污泥与7%高岭土的混合物，对铜（95.85%）、锌（95.97%）、铅（97.15%）、镉（84.23%）和铬（84.05%）实现了高保留率。高岭土的添加促进了热解生物炭中铜、锌、铅和铬从不稳定组分向稳定组分的转化，降低了它们的浸出性。干凝胶在吸附和稳定重金属方面也发挥了关键作用。热力学平衡计算结果表明，Pb(g)、PbS(g)、PbCl(g)、Zn(g)、ZnCl(g)和Cd(g)是纸污泥热解过程中锌、铅和镉的主要气态产物。PbCl和PbS中的铅原子以及ZnCl中的锌原子通过共价键与高岭土表面的氧原子结合，而PbCl中的氯原子和单质铅中的铅原子分别与高岭石表面的氢和氧原子形成离子键。这些实验和模拟结果为污泥热解过程中控制重金属提供了新思路。
