Exploration of the potential capacity of fly ash and bottom ash derived from wood pellet-based thermal power plant for heavy metal removal

Jong-Hwan Park; Ju-Hyun Eom; Su-Lim Lee; Se-Wook Hwang; Seong-Heon Kim; Se-Won Kang; Jin-Ju Yun; Ju-Sik Cho; Young-Han Lee; Dong-Cheol Seo

doi:10.1016/j.scitotenv.2020.140205

Exploration of the potential capacity of fly ash and bottom ash derived from wood pellet-based thermal power plant for heavy metal removal

Sci Total Environ. 2020 Oct 20:740:140205. doi: 10.1016/j.scitotenv.2020.140205. Epub 2020 Jun 15.

Authors

Affiliations

¹ Division of Applied Life Science (BK21 Plus), Institute of Agriculture and Life Science, Gyeongsang National University, Jinju 52828, South Korea.
² Soil and Fertilizer Division, National Institute of Agricultural Sciences, Wanju 55365, South Korea.
³ Department of Bio-Environmental Sciences, Sunchon National University, Suncheon 57922, South Korea.
⁴ Division of Plant Environmental Research, Gyeongsangnam-do Agricultural Research and Extension Service, Jinju 660-360, Republic of Korea.
⁵ Division of Applied Life Science (BK21 Plus), Institute of Agriculture and Life Science, Gyeongsang National University, Jinju 52828, South Korea. Electronic address: dcseo@gnu.ac.kr.

PMID: 32569919
DOI: 10.1016/j.scitotenv.2020.140205

Abstract

This study was conducted to explore the potential capacity for the removal of heavy metals from the fly ash (FA) and bottom ash (BA) emitted by wood pellet thermal power plants. Fly ash consists of inorganic compounds such as CaSiO₃, P₂O₅, and K₂O, whereas BA shows properties very similar to the biochar derived from organic biomass. The adsorption properties of both FA and BA for Cd were described well by the Langmuir and pseudo-second-order models, and the maximum adsorption capacity of FA for Cd was 4.2 times higher than that of BA. The results indicate that FA can be applied to the treatment of wastewater that contains heavy metals over pH range from 2-6; however, BA is considered to be most effective for application with wastewater that contains heavy metals at a pH of 5-6. Study of the mechanism concluded that the adsorption of Cd by FA is dominated by the formation of Cd₂SiO₄ complexes by chemical reactions between CaSiO₃ and Cd ions as well as via the precipitation of Cd(OH)₂ in the neutral and alkaline solutions that is caused by the dissolution of K. It was found that the adsorption of Cd by BA was influenced by the binding of functional groups (CC and COH), coupled CaCO₃ dissolution-CdCO₃ precipitation reaction and ion exchange between some minerals with Si and Cd ions in weakly acidic conditions. Results indicate that the FA and BA emitted from wood pellet thermal power plants have high potential for heavy metal removal, and their practical use in the purification and restoration of heavy metals could be an effective way to reduce the waste produced by power plants and clean the environment.

Keywords: Biochar; Bottom ash; Fly ash; Heavy metal; Thermal power plant; Wood pellet.