Transformation of arsenic during realgar tailings stabilization using ferrous sulfate in a pilot-scale treatment

Xin Wang, He Zhang, Linling Wang, Jing Chen, Shiqi Xu, Huijie Hou, Yao Shi, Jingdong Zhang, Miao Ma, Daniel C.W. Tsang, John C. Crittenden

Research output: Journal article publicationJournal articleAcademic researchpeer-review

16 Citations (Scopus)

Abstract

Massive realgar tailings abandoned in mining areas in China have caused serious arsenic (As) pollution seeking for urgent disposal. Stabilization treatment is a feasible strategy, however, stabilization technologies for realgar tailings, that are Fe-deficient, Ca-rich and S-rich, have not been well developed to date. In this study, we conducted a pilot-scale stabilization treatment of realgar tailings via ferrous sulfate addition to evaluate the transformation of As during stabilization. We found that Si, As, Ca, and S were the predominant elements in the raw realgar tailings with a low content of Fe, and realgar (As II 4 S 4 ) and pharmacolite (CaHAs V O 4 ·2H 2 O) were the main As-bearing minerals. After the ferrous sulfate treatment, the As leaching concentration of realgar tailings was successfully reduced from 135 mg/L to a level below the Chinese regulatory limit (2.5 mg/L). Based on the results of leaching tests, sequential extraction analysis, XRD, SEM-EDS, XPS, and thermodynamic modeling, we concluded that ferrous sulfate addition enhanced the transformation of Ca–As and S–As species to more stable Fe–As species, e.g., crystalline symplesite and amorphous Fe–As complex. Dissolution of pharmacolite was facilitated by H + and SO 4 2− derived from the hydrolysis and oxidation of ferrous sulfate, and oxidation of realgar could be promoted by reactive oxygen species (ROSs) from Fe(II) oxygenation. This study improved our understanding of As transformation pathways in realgar tailings during ferrous sulfate treatment, which could serve as an alternative scheme for realgar tailings stabilization.

Original languageEnglish
Pages (from-to)32-39
Number of pages8
JournalScience of the Total Environment
Volume668
DOIs
Publication statusPublished - 10 Jun 2019

Keywords

  • Arsenic stabilization
  • Ferrous sulfate treatment
  • Pharmacolite dissolution
  • Realgar oxidation
  • Realgar tailings

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • Waste Management and Disposal
  • Pollution

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