Enhancement of catalytic detoxification of polycyclic aromatic hydrocarbons in fly ash from municipal solid waste incineration via magnetic hydroxyapatite-assisted hydrothermal treatment
Dezhi Shi, Jiayu Liu, Haihang Tong, Kun Fu, Muhammad Salam, Jie Huang, Shuo Xu, Xianyi Wen, Hui Xie, Pan Wang, Huayi Cai, Dan Luo
Abstract
The emission of carcinogenic, teratogenic, and mutagenic polycyclic aromatic hydrocarbons (PAHs) during municipal solid waste incineration (MSWI) of fly ash (FA) has attracted significant attention. Hydrothermal treatment (HT) has emerged as a practical approach for degrading PAHs during MSWI of FA by utilizing magnetite (Fe 3 O 4 ) as a catalyst and hydrogen peroxide (H 2 O 2 ) as an oxidizing agent. In this study, as an alternative to traditional hydroxyapatite (HAP), eggshell-derived magnetic hydroxyapatite (MHAP) was synthesized and applied in the hydrothermal catalytic degradation of PAHs in MSWI FA in an H 2 O 2 system for the first time. The degradation efficiency of the PAHs is influenced not only by H 2 O 2 but also by the choice of hydroxyapatite. Adding HAP or MHAP during hydrothermal treatment with H 2 O 2 substantially reduced the overall PAH concentration and toxicity equivalent quantity (TEQ), superior to that without H 2 O 2 . MHAP demonstrated superior catalytic activity compared to HAP in the presence of H 2 O 2 in the hydrothermal system . The hydrothermal detoxification of the PAHs increased with increasing MHAP dosage. By employing 0.5 mol/L H 2 O 2 as the oxidant and 15 wt% MHAP as the catalyst, a total PAH degradation rate of 88.9 % was achieved, with a remarkable TEQ degradation rate of 98.3 %. Notably, the level of 4–6-ring PAHs, particularly benzo(a) pyrene (BaP) and dibenz( a , h )anthracene (DahA), with a TEQ of 1.0, was significantly reduced (by 69.4 % and 46.0 %, respectively). MHAP remained stable during the hydrothermal catalytic process, whereas H 2 O 2 was effectively activated by MHAP and decomposed to produce strongly oxidizing hydroxyl (•OH) under hydrothermal conditions. •OH produced from the decomposition of H 2 O 2 and metals on the surface of MHAP act as catalytically active centers, efficiently converting high-ring PAHs to low-ring PAHs. These findings provide valuable insights and a technological foundation for PAH detoxification in MSWI FA via hydrothermal catalytic oxidation .