Kumar Ravinder, Dada Tewodros Kassa, Whelan Anna, Cannon Patrick, Sheehan Madoc, Reeves Louise, Antunes Elsa
College of Science & Engineering, James Cook University, Townsville, QLD 4811, Australia.
College of Science & Engineering, James Cook University, Townsville, QLD 4811, Australia; Townsville City Council, Wastewater Operations, Townsville, QLD 4810, Australia.
J Hazard Mater. 2023 Jun 15;452:131212. doi: 10.1016/j.jhazmat.2023.131212. Epub 2023 Mar 15.
Per- and polyfluoroalkyl substances (PFAS) are persistent organic chemicals detected in biosolids worldwide, which have become a significant concern for biosolids applications due to their increasing environmental risks. Hence, it is pivotal to understand the magnitude of PFAS contamination in biosolids and implement effective technologies to reduce their contamination and prevent hazardous aftermaths. Thermal techniques such as pyrolysis, incineration and gasification, and biodegradation have been regarded as impactful solutions to degrade PFAS and transform biosolids into value-added products like biochar. These techniques can mineralize PFAS compounds under specific operating parameters, which can lead to unique degradation mechanisms and pathways. Understanding PFAS degradation mechanisms can pave the way to design the technology and to optimize the process conditions. Therefore, in this review, we aim to review and compare PFAS degradation mechanisms in thermal treatment like pyrolysis, incineration, gasification, smouldering combustion, hydrothermal liquefaction (HTL), and biodegradation. For instance, in biodegradation of perfluorooctane sulfonic acid (PFOS), firstly C-S bond cleavage occurs which is followed by hydroxylation, decarboxylation and defluorination reactions to form perfluoroheptanoic acid. In HTL, PFOS degradation is carried through OHcatalyzed series of nucleophilic substitution and decarboxylation reactions. In contrast, thermal PFOS degradation involves a three-step random-chain scission pathway. The first step includes C-S bond cleavage, followed by defluorination of perfluoroalkyl radical, and radical chain propagation reactions. Finally, the termination of chain propagation reactions produces very short-fluorinated units. We also highlighted important policies and strategies employed worldwide to curb PFAS contamination in biosolids.
全氟和多氟烷基物质（PFAS）是在全球生物固体中检测到的持久性有机化学品，由于其日益增加的环境风险，已成为生物固体应用中的一个重大问题。因此，了解生物固体中PFAS污染的程度并实施有效的技术来减少其污染并防止有害后果至关重要。热解、焚烧和气化等热技术以及生物降解被认为是降解PFAS并将生物固体转化为生物炭等增值产品的有效解决方案。这些技术可以在特定的操作参数下使PFAS化合物矿化，这可能导致独特的降解机制和途径。了解PFAS降解机制可以为技术设计和工艺条件优化铺平道路。因此，在本综述中，我们旨在综述和比较热解、焚烧、气化、闷烧燃烧、水热液化（HTL）等热处理以及生物降解过程中PFAS的降解机制。例如，在全氟辛烷磺酸（PFOS）的生物降解中，首先发生C-S键断裂，随后是羟基化、脱羧和脱氟反应，形成全氟庚酸。在HTL中，PFOS的降解是通过OH催化的一系列亲核取代和脱羧反应进行的。相比之下，热PFOS降解涉及三步随机链断裂途径。第一步包括C-S键断裂，随后是全氟烷基自由基的脱氟，以及自由基链增长反应。最后，链增长反应的终止产生非常短的氟化单元。我们还强调了全球范围内为遏制生物固体中PFAS污染而采用的重要政策和策略。
