Iron colloidal transport mechanisms and sequestration of As, Ni, and Cu along AMD-induced environmental gradients

Lijun Fan; Tao Zhu; Yixuan Yang; Tiancheng Han; Zhuang Qiao; Xianxing Huang; Weiwei Zhai; Xiangliang Pan; Daoyong Zhang

doi:10.1016/j.scitotenv.2023.165513

Iron colloidal transport mechanisms and sequestration of As, Ni, and Cu along AMD-induced environmental gradients

Sci Total Environ. 2023 Nov 10:898:165513. doi: 10.1016/j.scitotenv.2023.165513. Epub 2023 Jul 13.

Authors

Lijun Fan¹, Tao Zhu¹, Yixuan Yang¹, Tiancheng Han¹, Zhuang Qiao¹, Xianxing Huang¹, Weiwei Zhai¹, Xiangliang Pan¹, Daoyong Zhang²

Affiliations

¹ Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou 310000, China.
² Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou 310000, China. Electronic address: zhangdaoyong@zjut.edu.cn.

PMID: 37451442
DOI: 10.1016/j.scitotenv.2023.165513

Abstract

Colloids are common in mine waters and their chemistry and interactions are critical aspects of metal(loid)s cycling. Previous studies mostly focus on the colloidal transport of metal(loid)s in zones where rivers and soil profiles receive acid mine drainage (AMD). However, there is limited knowledge of the colloid and the associated toxic element behavior as the effluent flows through the coal waste dump, where a geochemical gradient is produced due to AMD reacting with waste rocks which have high acid-neutralization effects. Here, we investigated the geochemistry of Fe and co-occurring elements As, Ni, and Cu along the coal waste dump, in aqueous, colloidal, and precipitate phases, using micro/ultrafiltration combined with STEM, AFM-nanoIR, SEM-EDS, XRD, and FTIR analysis. The results demonstrated that a fast attenuation of H⁺, SO₄^2-, and metal(loid)s happened as the effluent flowed through the waste-rock dump. The Fe, As, Ni, and Cu were distributed across all colloidal sizes and primarily transported in the nano-colloidal phase (3 kDa-0.1 μm). An increasing pH induced a higher percentage of large Fe colloid fractions (> 0.1 μm) associated with greater sequestration of trace metals, and the values for As from 39.5 % to 54.4 %, Ni from 40.8 % to 75.7 %, and Cu from 43.7 % to 56.0 %, respectively. The Fe-bearing colloids in AMD upstream (pH ≤ 3.0) were primarily composed of Fe-O-S and Fe-O-C with minor Al-Si-O and Ca-O-S, while in less acidic and alkaline sections (pH ≥ 4.1), they were composed of Fe-O with minor Ca-O-S. The iron colloid agglomerates associated with As, Ni, and Cu precipitated coupling the transformation of jarosite, and schwertmannite to ferrihydrite, goethite, and gypsum. These results demonstrate that the formation and transformation of Fe-bearing colloids response to this unique geochemical gradient help to understand the natural metal(loid)s attenuation along the coal waste dump.

Keywords: AMD geochemical gradients; Coal waste dump; Contaminant mobility; Fe-bearing colloids; Mine remediation.