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Coordination of Cd2+ ions in the internal pore system of Zeolite-X : a combined EXAFS and isotopic exchange study.

Research output: Contribution to journalJournal article


<mark>Journal publication date</mark>15/03/2009
<mark>Journal</mark>Geochimica et Cosmochimica Acta
Issue number6
Number of pages11
Pages (from-to)1577-1587
<mark>Original language</mark>English


The effect of prolonged contact time (up to 130 days) on the immobilization of Cd by sorption to calcium exchanged zeolite-X (CaX), under environmentally relevant conditions, was studied using both isotopic exchange and extended X-ray absorption fine structure spectroscopy (EXAFS). Sorption and isotopic exchange measurements revealed time-dependent Cd sorption and indicated the movement of Cd2+ ions into less accessible sites due to ageing. EXAFS suggested progressive fixation of Cd in the double six-ring (D6R) unit of the CaX structure. Proportional allocation of the apparent Cd–Si bond distance to two ‘end-members’, across all contact times, indicated that the bond distance for labile Cd was 3.41 Å and for non-labile (or fixed) Cd was 3.47 Å.

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