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Products and stability of phosphate reactions with lead under freeze-thaw cycling in simple systems.

Authors
  • Hafsteinsdóttir, Erla G1
  • White, Duanne A
  • Gore, Damian B
  • Stark, Scott C
  • 1 Department of Environment & Geography, Macquarie University, NSW 2109, Australia. [email protected] , (Australia)
Type
Published Article
Journal
Environmental pollution (Barking, Essex : 1987)
Publication Date
Dec 01, 2011
Volume
159
Issue
12
Pages
3496–3503
Identifiers
DOI: 10.1016/j.envpol.2011.08.026
PMID: 21907472
Source
Medline
License
Unknown

Abstract

Orthophosphate fixation of metal contaminated soils in environments that undergo freeze-thaw cycles is understudied. Freeze-thaw cycling potentially influences the reaction rate, mineral chemical stability and physical breakdown of particles during fixation. This study determines what products form when phosphate (triple superphosphate [Ca(H(2)PO(4))(2)] or sodium phosphate [Na(3)PO(4)]) reacts with lead (PbSO(4) or PbCl(2)) in simple chemical systems in vitro, and assesses potential changes in formation during freeze-thaw cycles. Systems were subjected to multiple freeze-thaw cycles from +10 °C to -20 °C and then analysed by X-ray diffractometry. Pyromorphite formed in all systems and was stable over multiple freeze-thaw cycles. Low temperature lead orthophosphate reaction efficiency varied according to both phosphate and lead source; the most time-efficient pyromorphite formation was observed when PbSO(4) and Na(3)PO(4) were present together. These findings have implications for the manner in which metal contaminated materials in freezing ground can be treated with phosphate.

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