Combining mechanisms of black carbon and magnetic minerals in power plant fly ash

Meng Yao Li; Zhou Xin Peng; You Ying Chen; Shi Yun Xiao; Bo Wen Zhang; Yi Xin Shen; Sheng Kang Wang; Xue Song Wang; Zhao Xiang Han

doi:10.1016/j.scitotenv.2023.162059

Combining mechanisms of black carbon and magnetic minerals in power plant fly ash

Sci Total Environ. 2023 May 10:872:162059. doi: 10.1016/j.scitotenv.2023.162059. Epub 2023 Feb 11.

Authors

Meng Yao Li¹, Zhou Xin Peng¹, You Ying Chen¹, Shi Yun Xiao¹, Bo Wen Zhang¹, Yi Xin Shen¹, Sheng Kang Wang², Xue Song Wang³, Zhao Xiang Han⁴

Affiliations

¹ School of Environmental and Chemical Engineering, Jiangsu Ocean University, Lianyungang, Jiangsu 222005, China.
² School of Environmental and Chemical Engineering, Jiangsu Ocean University, Lianyungang, Jiangsu 222005, China. Electronic address: wangshengkang@jou.edu.cn.
³ School of Environmental and Chemical Engineering, Jiangsu Ocean University, Lianyungang, Jiangsu 222005, China. Electronic address: snowpine1969@126.com.
⁴ School of Environmental and Chemical Engineering, Jiangsu Ocean University, Lianyungang, Jiangsu 222005, China. Electronic address: 895561709@qq.com.

PMID: 36775142
DOI: 10.1016/j.scitotenv.2023.162059

Abstract

Black carbon (BC), one of the pollutants emitted from fossil fuel combustion, is closely associated with minerals and other hazardous substances. To date, little is known about the mechanisms between BC and magnetic minerals. Accordingly, further investigating the association between magnetic minerals and BC is necessary. In this work, the extraction of BC from fly ash and the magnetic fraction from BC was achieved by flotation and magnetic separation, respectively. The morphology, mineralogical composition, and magnetic properties of BC and magnetic fraction were characterized by FTIR, XRD, SEM-EDS, and vibrating sample magnetometer (VSM). The results show that BC and magnetic minerals have similar mineral compositions, rich in quartz, mullite, magnetite, and hematite. The magnetic minerals have prominent spherical characteristics and are distributed on the surface and inside the pores of BC with irregular honeycomb features. The VSM and XRD analyses show that Fe₃O₄ is the primary magnetic material. Moreover, large amounts of C, O, and Fe around and on the surface of magnetic spheres were detected by EDS, indicating that the spherical particles may be the structure of BC-coated Fe₃O₄. Pyrolysis experiments showed that the yield of the magnetic fraction in the pyrolysis product reached 60 %, far exceeding the theoretical yield of 12 % based on 5 % of doped Fe. This further proves that Fe₃O₄ was combined with a large number of organics during its formation, which may be due to coating and chemical adsorption. Quantum chemical calculations also confirmed this chemical adsorption between Fe₃O₄ with BC based on density flooding theory, in which adsorption energies ranged from -213.374 KJ/mol to -827.741 KJ/mol.

Keywords: Black carbon; Chemisorption; Density functional theory; Fe(3)O(4); Magnetic fractions.