The leaching behavior of hazardous element under different leaching procedure utilizing slag-fly ash-based agent: Chromium, antimony, and lead

Jia Li; Guoxiang Teng; Siqi Zhang; Pingfeng Fu; Jiajie Li; Chuanfu Wu; Wen Ni

doi:10.1016/j.scitotenv.2024.170782

The leaching behavior of hazardous element under different leaching procedure utilizing slag-fly ash-based agent: Chromium, antimony, and lead

Sci Total Environ. 2024 Apr 1:919:170782. doi: 10.1016/j.scitotenv.2024.170782. Epub 2024 Feb 9.

Authors

Jia Li¹, Guoxiang Teng², Siqi Zhang³, Pingfeng Fu⁴, Jiajie Li¹, Chuanfu Wu⁵, Wen Ni¹

Affiliations

¹ School of Civil and Resource Engineering, University of Science and Technology Beijing, Beijing 100083, China.
² CISRI Steel Industry Green and Intelligent Manufacturing Technology Center, China Iron and Steel Research Institute Group, Beijing 100081, China.
³ School of Civil and Resource Engineering, University of Science and Technology Beijing, Beijing 100083, China. Electronic address: zsq2017@ustb.edu.cn.
⁴ School of Civil and Resource Engineering, University of Science and Technology Beijing, Beijing 100083, China. Electronic address: pffu@ces.ustb.edu.cn.
⁵ School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, China.

PMID: 38342458
DOI: 10.1016/j.scitotenv.2024.170782

Abstract

Low-carbon cementitious materials based on blast furnace slag (BFS) and municipal solid waste incineration (MSWI) fly ash play a pivotal role in the construction industry by substituting cement clinker. This innovation significantly reduces CO₂ emissions and enables the extensive utilization of both industrial solid waste and hazardous urban waste on a large scale. However, the application of MSWI fly ash as a precursor for alkali-activated cementitious materials presents a significant leaching risk of heavy metal during the extended reaction process, posing a critical barrier to the efficient and widespread utilization of these solid waste. Three static leaching methods [horizontal vibration (HV), sulphuric acid & nitric acid (SN), and acetic acid buffer solution (AAB)], along with acid neutralization capacity (ANC) leaching tests, were applied in BFS-fly ash-based cementitious materials (BFCM) to assess the leaching behavior of high-risk elements-Cr, Sb, and Pb-within MSWI fly ash. The A4 matrix (BFS: MSWI fly ash:FGDG = 70:20:10) exhibits a compressive strength of 72.51 MPa at 180 day, with the leaching concentrations of target elements remaining below the standard limit under chemical attack (H⁺ and OH^-). The critical pH determined is 9.2 from the ANC leaching test results. Visual MINTEQ simulation illustrates the occurrence states of Cr, Sb, and Pb as (CrO₄)^2-, [Sb(OH)₆]^-, and Pb(OH)₃^- within the BFCM system, respectively. The "double salt effect", intended to enhance the dissociation degree of BFS, acts as the driving force behind the long-term hydration reaction. It also serves as an assurance in controlling the long-term leaching risk of object elements. The dissociation degree of BFS within A4 matrix increased by 38.71 %, with the relative content of the typical low-solubility double salt "Ettringite" reaching 29 % at 180 d. This study provides novel theoretical and data-driven evidence to investigate the leaching behavior associated with MSWI fly ash and the accomplishment of replacing cement clinker with low-carbon BFCM.

Keywords: Double salt effect; Leaching behavior; Long-term hydration; Low carbon; MSWI fly ash.