Insights into solidification mechanism of Cr(III) and Cr(VI) in chromite ore processing residue via composite geopolymers synthesized from calcined red mud and granulated blast furnace slag

Yan Ke; Sha Liang; Huabo Duan; Junda Quan; Xingwu Li; Huijie Hou; Jingping Hu; Yin Yang; Xing Liu; Yibing Zuo; Jiakuan Yang

doi:10.1016/j.jhazmat.2025.139185

Insights into solidification mechanism of Cr(III) and Cr(VI) in chromite ore processing residue via composite geopolymers synthesized from calcined red mud and granulated blast furnace slag

J Hazard Mater. 2025 Jul 8:496:139185. doi: 10.1016/j.jhazmat.2025.139185. Online ahead of print.

Authors

Yan Ke¹, Sha Liang², Huabo Duan³, Junda Quan¹, Xingwu Li¹, Huijie Hou¹, Jingping Hu¹, Yin Yang⁴, Xing Liu¹, Yibing Zuo⁵, Jiakuan Yang⁶

Affiliations

¹ Hubei Key Laboratory of Multi-media Pollution Cooperative Control in Yangtze Basin, School of Environmental Science & Engineering, Huazhong University of Science and Technology (HUST), 1037 Luoyu Road, Wuhan, Hubei 430074, China.
² Hubei Key Laboratory of Multi-media Pollution Cooperative Control in Yangtze Basin, School of Environmental Science & Engineering, Huazhong University of Science and Technology (HUST), 1037 Luoyu Road, Wuhan, Hubei 430074, China. Electronic address: liangsha@mail.hust.edu.cn.
³ Hubei Key Laboratory of Multi-media Pollution Cooperative Control in Yangtze Basin, School of Environmental Science & Engineering, Huazhong University of Science and Technology (HUST), 1037 Luoyu Road, Wuhan, Hubei 430074, China. Electronic address: huabo@hust.edu.cn.
⁴ Energy Development Research Institute, China Southern Power Grid, 11 Kexiang Road, Guangzhou 510663, China; Smith School of Enterprise and the Environment, School of Geography and the Environment, University of Oxford, OUCE, South Parks Road, Oxford OX1 3QY, United Kingdom.
⁵ School of Civil and Hydraulic Engineering, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China.
⁶ Hubei Key Laboratory of Multi-media Pollution Cooperative Control in Yangtze Basin, School of Environmental Science & Engineering, Huazhong University of Science and Technology (HUST), 1037 Luoyu Road, Wuhan, Hubei 430074, China; Hubei Provincial Engineering Laboratory of Solid Waste Treatment, Disposal and Recycling, 1037 Luoyu Road, Wuhan, Hubei 430074, China.

PMID: 40639228
DOI: 10.1016/j.jhazmat.2025.139185

Abstract

Chromite ore processing residue (COPR), which contains soluble toxic Cr(Ⅵ), is a hazardous waste from chromium salts production process. The pre-reduced COPR was solidified using composite geopolymers synthesized from the calcined red mud (RM) and the granulated blast furnace slag (GBFS). Results indicated that higher Na₂S doses reduced the compressive strength of cured specimens but significantly enhanced chromium immobilization efficiency. Geopolymers were further applied to solidify pure Cr(III)/Cr(VI) compounds to elucidate solidification mechanism. Density Functional Theory (DFT) calculations identified a substantial energy difference (-212.17 kJ/mol) during polymerization between [SiO(OH)₃]⁻ and [Cr(OH)₄]⁻, confirming thermodynamic favorability of Cr(III) incorporation. Both of experimental and DFT results revealed that Cr(III), in form of [Cr(OH)₄]⁻, chemically reacted with [SiO(OH)₃]⁻ monomers to integrate into the geopolymer network, while Cr(VI) was physically encapsulated. The life cycle assessment (LCA) confirms the excellent performance of the proposed solidification for COPR in environmental feasibility.

Keywords: Chromite ore processing residue; Density Function Theory; Geopolymer; Life cycle assessment; Solidification.