Abstract

This work proposed an in-situ method for stabilizing the hazardous calcium arsenic residues (CARs) by introducing small amounts of ferrous (FeII) solution to induce the formation of stable ferrous arsenate minerals. The CARs collected from a copper smelter in China were treated with FeII solution at room temperature, FeII/As molar ratios of 0.5-2 and pH 6-9 under both oxic and anoxic conditions, and the concentrations of aqueous arsenic (As) was monitored during the whole treatment process (up to 760 days). Results showed that As dissolution was significantly inhibited after addition of FeII into the CARs slurries. The concentration of dissolved As was lowered to < 2.0 mg/L from initially similar to 1000 mg/L at pH 6 and 7, and FeII/As >= 1. The resultant solids under these conditions showed TCLP As concentrations of < 1.0 mg/L, which were dramatically lower than that of untreated CARs (862 mg/L). Characterization with X-ray powder diffraction (XRD), scanning/transmission electron microscopy (SEM/TEM), and X-ray absorption spectroscopy (XAS) of the resultant solids revealed that the formation of ferrous arsenates minerals (parasymplesite and/or ferrisymplesite) was the mechanism of the stabilization effects. The FeII treatment method proposed in this work provides an alternative option for in-situ CARs stabilization.

Keywords

Calcium arsenic residues; Ferrous; Parasymplesite; Ferrisymplesite; Circumneutral pH

Published in

Chemical Engineering Journal
2023, Volume: 467, article number: 143294
Publisher: ELSEVIER SCIENCE SA

SLU Authors

• Song, Yu

  • Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
    
  • Chinese Academy of Sciences

UKÄ Subject classification

Inorganic Chemistry


Publication identifier

DOI: https://doi.org/10.1016/j.cej.2023.143294

Permanent link to this page (URI)

https://res.slu.se/id/publ/122949