Metallurgical and Materials Transactions B

, Volume 37, Issue 2, pp 189–197 | Cite as

Acidity, valency and third-ion effects on the precipitation of scorodite from mixed sulfate solutions under atmospheric-pressure conditions

  • Shalabh Singhania
  • Qiankun Wang
  • Dimitrios Filippou
  • George P. Demopoulos
Article
Received:

Abstract

The present study is focused on the precipitation of scorodite from mixed sulfate media at 95 °C under atmospheric pressure. In particular, this study explores the effects of acidity (pH), valency [Fe(II)/Fe(III), As(III)/As(V)], and solution composition (third cation/anion) on the yield, crystallinity, and stability (leachability) of scorodite precipitates. Thus, it was found that the precipitation of crystalline scorodite can be achieved without stringent pH control once the precipitation has started. Nonetheless, the selection of the initial pH is critical to avoid the formation of an amorphous precipitate. A leachability as low as 0.5 mg/L As at pH 5 and 22 °C (TCLP-like test) is obtained when the initial molar ratio Fe(III):As(V) is increased to 3:1, but the precipitation yield is very low. When Fe(II) is used as excess iron, the precipitate solubility drops to 0.2 mg/L As with a yield exceeding 80 pct in 2.5 hours. The stability of the product is not measurably affected by the presence of Cu2+, Zn2+, Ni2+, Co2+, Mn2+, SO 4 2− , and NO 3 − . The presence of PO 4 3− , however, leads to the formation of crystalline phosphate-containing scorodite precipitates of somewhat reduced stability. In most cases, the TCLP leachability of the precipitate was found to be between 1 and 3 mg/L As, and never exceeded the regulatory limit of 5 mg/L As.

Keywords

Arsenic Material Transaction Arsenic Removal Initial Molar Ratio Ferric Arsenate 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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Copyright information

© ASM International & TMS-The Minerals, Metals and Materials Society 2006

Authors and Affiliations

  • Shalabh Singhania
    • 1
  • Qiankun Wang
    • 2
  • Dimitrios Filippou
    • 3
  • George P. Demopoulos
    • 4
  1. 1.Telarix, Inc.Vienna
  2. 2.Inco Ltd.MississaugaCanada
  3. 3.Rio Tinto Iron & Titanium Inc.TracyCanada
  4. 4.the Department of Mining, Metals and Materials EngineeringMcGill UniversityMontrealCanada

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