Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
}
TY - JOUR
T1 - Time-dependent sorption of Cd2+ on CaX zeolite : experimental observations and model predictions.
AU - Ahmed, Imad A. M.
AU - Young, Scott D.
AU - Crout, Neil M. J.
PY - 2006/10/1
Y1 - 2006/10/1
N2 - 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.
AB - 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.
KW - Zeolite
KW - model prediction
KW - Speciation
KW - Free ion activity
KW - chabazite
KW - intra-particle diffusion
KW - kinetic model
KW - diffusion model
U2 - 10.1016/j.gca.2008.12.018
DO - 10.1016/j.gca.2008.12.018
M3 - Journal article
VL - 70
SP - 4850
EP - 4861
JO - Geochimica et Cosmochimica Acta
JF - Geochimica et Cosmochimica Acta
SN - 0016-7037
IS - 19
ER -