School of Environmental Science and Engineering, Huazhong University of Science and Technology (HUST), Wuhan 430074, PR China; Hubei Provincial Engineering Laboratory of Solid Waste Treatment, Disposal and Recycling, Wuhan 430074, PR China.
State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology (HUST), Wuhan 430074, PR China.
Water Res. 2024 May 1;254:121376. doi: 10.1016/j.watres.2024.121376. Epub 2024 Feb 29.
The present study provided an innovative insight into the formation mechanism of persistent free radicals (PFRs) during the pyrolysis of Fenton-conditioned sludge. Fenton conditioners simultaneously improve the dewatering performance of sewage sludge and catalyze the pyrolysis of sewage sludge for the formation of PFRs. In this process, PFRs with a total number of spins of 9.533×10 spins/g DS could be generated by pyrolysis of Fenton-conditioned sludge at 400°C. The direct thermal decomposition of natural organic matter (NOM) fractions contributed to the formation of carbon-centered radicals, while the Maillard reaction produced phenols precursors. Additionally, the reaction between aromatic proteins and iron played a crucial role in the formation of phenoxyl or semiquinone-type radicals. Kinetics analysis using discrete distributed activation energy model (DAEM) demonstrated that the average activation energy for pyrolysis was reduced from 178.28 kJ/mol for raw sludge to 164.53 KJ/mol for Fenton conditioned sludge. The reaction factor (f) indicated that the primary reaction in Fenton-conditioned sludge comprised of 27 parallel first-order reactions, resulting from pyrolysis cleavage of the NOM fractions, the Maillard reaction, and iron catalysis. These findings are significant for understanding the formation process of PFRs from NOM in Fenton-conditioned sludge and provide valuable insight for controlling PFRs formation in practical applications.
本研究为芬顿调理污泥热解过程中持久性自由基（PFRs）的形成机制提供了新的见解。芬顿调理剂同时提高了污水污泥的脱水性能，并催化了污水污泥的热解，从而形成了 PFRs。在这个过程中，通过在 400°C 下热解芬顿调理污泥，可以产生总自旋数为 9.533×10 自旋/g DS 的 PFRs。天然有机物（NOM）分数的直接热分解有助于形成碳中心自由基，而美拉德反应则产生了酚类前体。此外，芳香族蛋白质和铁之间的反应在酚氧或半醌型自由基的形成中起着关键作用。使用离散分布活化能模型（DAEM）的动力学分析表明，热解的平均活化能从原始污泥的 178.28 kJ/mol 降低到芬顿调理污泥的 164.53 kJ/mol。反应因子（f）表明，芬顿调理污泥中的主要反应由 27 个平行的一级反应组成，这些反应源自 NOM 分数的热解裂解、美拉德反应和铁催化作用。这些发现对于理解芬顿调理污泥中 NOM 形成 PFRs 的过程具有重要意义，并为实际应用中控制 PFRs 形成提供了有价值的见解。
