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

doi:10.1016/j.scitotenv.2024.170467

Enhancement of catalytic detoxification of polycyclic aromatic hydrocarbons in fly ash from municipal solid waste incineration via magnetic hydroxyapatite-assisted hydrothermal treatment

Sci Total Environ. 2024 Mar 25:918:170467. doi: 10.1016/j.scitotenv.2024.170467. Epub 2024 Jan 28.

Authors

Dezhi Shi¹, Jiayu Liu², Haihang Tong³, Kun Fu², Muhammad Salam², Jie Huang², Shuo Xu², Xianyi Wen², Hui Xie², Pan Wang⁴, Huayi Cai², Dan Luo²

Affiliations

¹ Key Laboratory of Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, College of Environment and Ecology, Chongqing University, Chongqing 400044, PR China. Electronic address: shidezhi@cqu.edu.cn.
² Key Laboratory of Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, College of Environment and Ecology, Chongqing University, Chongqing 400044, PR China.
³ School of Energy and Environment, City University of Hong Kong, Kowloon Tong, 999077, Hong Kong.
⁴ Chongqing Water Resources and Electric Engineering College, Chongqing 402160, PR China. Electronic address: wangpan@cqsdzy.com.

PMID: 38290685
DOI: 10.1016/j.scitotenv.2024.170467

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 (Fe₃O₄) as a catalyst and hydrogen peroxide (H₂O₂) 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 H₂O₂ system for the first time. The degradation efficiency of the PAHs is influenced not only by H₂O₂ but also by the choice of hydroxyapatite. Adding HAP or MHAP during hydrothermal treatment with H₂O₂ substantially reduced the overall PAH concentration and toxicity equivalent quantity (TEQ), superior to that without H₂O₂. MHAP demonstrated superior catalytic activity compared to HAP in the presence of H₂O₂ in the hydrothermal system. The hydrothermal detoxification of the PAHs increased with increasing MHAP dosage. By employing 0.5 mol/L H₂O₂ 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 H₂O₂ was effectively activated by MHAP and decomposed to produce strongly oxidizing hydroxyl (•OH) under hydrothermal conditions. •OH produced from the decomposition of H₂O₂ 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.

Keywords: Catalytic oxidant; Hydrothermal detoxification; Magnetic hydroxyapatite; Municipal solid waste incineration fly ash; Polycyclic aromatic hydrocarbons.