An XPS and EDS Investigation of Portland Cement Doped with Pb<sup>2+</sup> and Cr<sup>3+</sup> Cations

Cocke, David L.; McWhinney, Hylton; Dufner, D. C.; Horrell, Ben; Ortego, J. Dale

doi:10.1089/hwm.1989.6.251

Cited by 42 publications

(13 citation statements)

References 9 publications

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“…Moreover the association of both elements existed in other matrices and iron oxihydroxides are known to strongly fix lead. The EXAFS and ì-XRF data on the Si-Pb relations confirmed previous studies indicating the strong affinity between Pb and C-S-H. [1][2][3][4][5][6] Both in the unaltered core and the altered layer, some of the Pb atoms could be retained by C-S-H, probably linked to a Q 1 or a Q 2P silicate 5,6 (Fig. 7).…”

Section: Evolution Of Pb Retention Site With Leachingsupporting

confidence: 88%

Modelling of Pb release during Portland cement alteration

Benard

Rose

Hazemann

et al. 2009

Advances in Cement Research

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Complex cementitious matrices undergo weathering with environmental exchange and can release metallic pollutants during alteration. The molecular mechanisms responsible for metal release are difficult to identify, though this is necessary if such processes are to be controlled.The present study determines and models the molecular mechanisms of Pb release during Portland cement leaching. Since Pb release is strongly related to its speciation (i.e. atomic environment and nature of bearing phases), the first objective of the present work is to investigate the evolution of Pb retention sites together with the evolution of the cement mineralogy during leaching. Complementary and efficient investigation tools were used, namely XRD, µ-XRF and XAFS. The second goal is to reproduce our results with a reactive transport code (CHESS/HYTEC) in order to test the proposed speciation model of Pb.Combined results indicate that both in the unaltered core and altered layer of the leached cement, Pb(II) would be retained through C-S-H "nano-structure", probably linked to a Q 1 or Q 2P silicate tetrahedra. Moreover in the altered layer, the presence of Fe atoms in the atomic environment of Pb is highly probable. Unfortunately little is known about Fe phases in cement, making the interpretation difficult. Can Fe-substituted hydrogranet (C 3 AH 6 ) be responsible for Pb retention? Modelling results are consistent with Pb retention through C-S-H in layers and also in an additional, possibly Fe-containing, Pb-retention phase in the altered layer.

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Section: Evolution Of Pb Retention Site With Leachingsupporting

confidence: 88%

Modelling of Pb release during Portland cement alteration

Benard

Rose

Hazemann

et al. 2009

Advances in Cement Research

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show abstract

“…This was also assumed by other authors. 4,5 Cocke et al 7 have shown evidence for Pb adsorption on cement for cement doped with Pb nitrate up to 10 wt % using XPS. Thus, to build a cluster simulating adsorbed Pb, the structure of the C 3 S surface must be used.…”

Section: Speciation Of Lead Mixed With C 3 S and Hydrated In Lime Watmentioning

confidence: 99%

X-ray Absorption Spectroscopy Study of Immobilization Processes for Heavy Metals in Calcium Silicate Hydrates: 1. Case of Lead

et al. 2000

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Trace amounts of heavy metals can be detected in cement. The major source is due to heavy metals naturally present in some of the raw materials used for clinkers manufacture. One way to predict the long-term behavior of these metals is to know which types of links occur between heavy metals and major elements (Ca, Si, Al, Fe). Since tricalcium silicate (C3S) is the major phase of cement-base material, a XAS study at the Pb-LIII edge has been carried out to elucidate the binding mechanisms of Pb by calcium silicate. At low concentration, under the precipitation of the oxide and oxy-hydroxide, a strong retardation of the hydration of the C3S has been observed for C3S doped with Pb. EXAFS results confirmed by XANES at the Pb-LIII edge indicate that Pb is chemically adsorbed at the surface of the C3S. This Pb layer acts as a diffusional barrier to water and leads to the retardation of C3S hydration. When C3S is previously hydrated without Pb, lead is strongly retained by the hydrated C3S (called CSH for calcium silicate hydrate). A previous 29 Si NMR 1 study has demonstrated that Pb is chemically fixed to the CSH structure through a Pb-O-Si bond. XAS experiments have confirmed that Pb is incorporated within the matrix of CSH and directly linked at the end of the silicate chains through Pb-O-Si bonds. The Pb-Si distance is ≈3.75 Å. All EXAFS results have been confirmed by ab initio calculation including multiple scattering.

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“…Sequential extraction indicated that the majority of Si (\ 90%) was distributed in residual fraction (not presented schematically) as reported by Tessier (1979), suggesting that the shifted Cr was bound into silicate. Cocke et al [18] concluded that Cr in cement-based systems was different from other metals for its size and charge, which allowed it to be incorporated throughout the solid material during hydration. Bishop [17] reported that Cr was bound into the silica matrix.…”

Section: Sequential Extractionmentioning

confidence: 99%

Characteristics of four alkaline biosolids produced from sewage sludge

Hsiau¹,

Lo²

1997

Resources, Conservation and Recycling

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An XPS and EDS Investigation of Portland Cement Doped with Pb²⁺ and Cr³⁺ Cations

Cited by 42 publications

References 9 publications

Modelling of Pb release during Portland cement alteration

Modelling of Pb release during Portland cement alteration

X-ray Absorption Spectroscopy Study of Immobilization Processes for Heavy Metals in Calcium Silicate Hydrates: 1. Case of Lead

Characteristics of four alkaline biosolids produced from sewage sludge

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An XPS and EDS Investigation of Portland Cement Doped with Pb2+ and Cr3+ Cations

Cited by 42 publications

References 9 publications

Modelling of Pb release during Portland cement alteration

Modelling of Pb release during Portland cement alteration

X-ray Absorption Spectroscopy Study of Immobilization Processes for Heavy Metals in Calcium Silicate Hydrates: 1. Case of Lead

Characteristics of four alkaline biosolids produced from sewage sludge

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An XPS and EDS Investigation of Portland Cement Doped with Pb²⁺ and Cr³⁺ Cations