Mechanistic Insights Into Red Mud, Blast Furnace Slag, or Metakaolin-Assisted stabilization/solidification of Arsenic-Contaminated Sediment

Environ Int. 2019 Dec;133(Pt B):105247. doi: 10.1016/j.envint.2019.105247. Epub 2019 Oct 31.

Abstract

Elevated level of arsenic (As) in marine sediment via deposition and accumulation presents long-term ecological risks. This study proposed a sustainable stabilization/solidification (S/S) of As-contaminated sediment via novel valorization of red mud waste, blast furnace slag and calcined clay mineral, which were selected to mitigate the increased leaching of As under alkaline environment of S/S treatment. Quantitative X-ray diffraction and thermogravimetric analyses illustrated that stable Ca-As complexes (e.g., Ca5(AsO4)3OH) could be formed at the expense of Ca(OH)2 consumption, which inevitably hindered the hydration process and S/S efficiency. The 29Si nuclear magnetic resonance analysis revealed that incorporation of metakaolin for As immobilization resulted in a low degree of hydration and polymerization, whereas addition of red mud promoted Fe-As complexation and demonstrated excellent compatibility with As. Transmission electron microscopy and elemental mapping further confirmed the precipitation of crystalline Ca-As and amorphous Fe-As compounds. Therefore, red mud-incorporated S/S binder achieved the highest efficiency of As immobilization (99.9%), which proved to be applicable for both in-situ and ex-situ S/S of As-contaminated sediment. These results advance our mechanistic understanding for the design of green and sustainable remediation approach for effective As immobilization.

Keywords: Arsenic leachability; Green/sustainable remediation; Hydration and polymerization; Potentially toxic element; Precipitation chemistry; Waste valorization/recycling.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arsenic / chemistry*
  • Calcium Compounds / chemistry*
  • Clay / chemistry*
  • Environmental Restoration and Remediation
  • Geologic Sediments / chemistry*
  • Green Chemistry Technology
  • Hong Kong
  • Humans
  • Industrial Waste*
  • Mining*
  • Silicates / chemistry*
  • X-Ray Diffraction

Substances

  • Calcium Compounds
  • Industrial Waste
  • Silicates
  • Arsenic
  • calcium silicate
  • Clay