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

Erla G. Hafsteinsdóttir*, Duanne A. White, Damian B. Gore, Scott C. Stark

*Corresponding author for this work

    Research output: Contribution to journalArticle

    18 Citations (Scopus)

    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 2PO 4) 2] or sodium phosphate [Na 3PO 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 3PO 4 were present together. These findings have implications for the manner in which metal contaminated materials in freezing ground can be treated with phosphate.

    Original languageEnglish
    Pages (from-to)3496-3503
    Number of pages8
    JournalEnvironmental Pollution
    Volume159
    Issue number12
    DOIs
    Publication statusPublished - Dec 2011

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