RT Journal Article
T1 Octahedral cation distribution in palygorskite
A1 Chryssikos, Georgios D.
A1 Gionis, Vassilis
A1 Kacandes, Georges H.
A1 Stathopoulou, Elizabeth T.
A1 Súarez Barrios, Mercedes
A1 García Romero, Emilia
A1 Sánchez del Río, Manuel
AB The OH speciation of 18 palygorskite samples from various localities were evaluated by near infrared spectroscopy (NIR) and compared to the corresponding octahedral composition derived from independent, single-particle analytical electron microscopy (AEM). NIR gives evidence for dioctahedral-like (AlAlOH, AlFe3+OH, Fe3+Fe3+OH) and trioctahedral-like (Mg3OH) species. Therefore, palygorskite can be approximated by the formula yMg5 Si8O20(OH)2·(1 – y)[xMg2Fe2·(1 – x)Mg2Al2]Si8O20(OH)2, where x is the Fe content of the dioctahedral component, and y is the trioctahedral fraction. The values of x estimated from the NIR data are in excellent agreement with the Fe/(VIAl + Fe) ratio from AEM (R2 = 0.98, σ = 0.03), thus suggesting that all octahedral Al and Fe in palygorskite participate in M2M2OH (dioctahedral-like) arrangements. Furthermore, y values from AEM can be compared to NIR (R2 = 0.90 and σ = 0.05) after calibrating the relative intensity of the Mg3OH vs. (Al,Fe)2OH overtone bands using AEM data. The agreement between the spectroscopic and analytical data are excellent. The data show that Fe3+ for Al substitution varies continuously in the analyzed samples over a broad range (0 < x < 0.7), suggesting that fully ferric dioctahedral palygorskites (x = 1) may exist. On the other hand, the observed upper trioctahedral limit of y = 0.50 calls for the detailed structural comparison of Mg-rich palygorskite with sepiolite.
PB Mineralogical Society of America
SN 0003-004X
YR 2009
FD 2009
LK https://hdl.handle.net/20.500.14352/50678
UL https://hdl.handle.net/20.500.14352/50678
LA eng
DS Docta Complutense
RD 6 abr 2025