Wang Zhipu, Tian Qingmei, Guo Jing, Wu Ruiqi, Zhu Henan, Zhang Hongzhen
State Key Laboratory of Heavy Oil Processing, China University of Petroleum-Beijing at Karamay, Karamay 834000, China.
School of Chemical and Environmental Engineering, China University of Mining & Technology (Beijing), Beijing 10083, China.
Waste Manag. 2021 Nov;135:199-207. doi: 10.1016/j.wasman.2021.08.042. Epub 2021 Sep 11.
The co-pyrolysis of sewage sludge and biomass is considered a promising technique for reducing the volume of sewage sludge, adding value, and decreasing the risk associated with this waste. In this study, sewage sludge and cotton stalks were pyrolyzed together with different amounts of KCO to evaluate the potential of chemical activation using KCO for improving the porosity of the biochar formed and immobilizing the heavy metals present in it. It was found that KCO activation effectively improved the pore structure and increased the aromaticity of the biochar. Moreover, KCO activation transformed the heavy metals (Cu, Zn, Pb, Ni, Cr, and Cd) into more stable forms (oxidizable and residual fractions). The activation effect became more pronounced with increasing amount of added KCO, eventually resulting in a significant reduction in the mobility and bioavailability of the heavy metals in the biochar. Further analysis revealed that, during the co-pyrolysis process, KCO activation resulted in a reductive atmosphere, increased the alkalinity of the biochar, and led to the formation CaO, CaCO, and aluminosilicates, which aided the immobilization of the heavy metals. KCO activation also effectively reduced the leachability, and thus, the environmental risks of the heavy metals. Thus, KCO activation can improve the porosity of the biochar derived from sewage sludge/cotton stalks and aid the immobilization of the heavy metals in it.
污水污泥与生物质的共热解被认为是一种很有前景的技术，可用于减少污水污泥的体积、增加附加值并降低与此类废物相关的风险。在本研究中，将污水污泥和棉秆与不同量的碳酸钾（KCO）一起进行热解，以评估使用碳酸钾进行化学活化对于改善所形成生物炭的孔隙率以及固定其中存在的重金属的潜力。研究发现，碳酸钾活化有效地改善了生物炭的孔隙结构并增加了其芳香性。此外，碳酸钾活化将重金属（铜、锌、铅、镍、铬和镉）转化为更稳定的形态（可氧化态和残渣态）。随着碳酸钾添加量的增加，活化效果变得更加显著，最终导致生物炭中重金属的迁移性和生物可利用性显著降低。进一步分析表明，在共热解过程中，碳酸钾活化导致形成还原性气氛，增加了生物炭的碱度，并促使氧化钙、碳酸钙和铝硅酸盐的形成，这有助于固定重金属。碳酸钾活化还有效地降低了重金属的浸出性，从而降低了其环境风险。因此，碳酸钾活化可以改善源自污水污泥/棉秆的生物炭的孔隙率，并有助于固定其中的重金属。
