We. Dubbin et Tb. Goh, SORPTIVE CAPACITY OF MONTMORILLONITE FOR HYDROXY-CR POLYMERS AND THE MODE OF CR COMPLEXATION, Clay Minerals, 30(3), 1995, pp. 175-185
Separate montmorillonite suspensions were treated with CrCl3 to give s
even Cr(III) concentrations. Each suspension was then titrated with 0.
1 N NaOH to give a NaOH/Cr3+ molar ratio of 2.5. Montmorillonite was a
n effective sorbent for hydroxy-Cr species up to 1200 cmol(+)/kg; abov
e that concentration, sorption continued, though less efficiently. How
ever, N-2-BET specific surfaces and cation exchange capacity measureme
nts indicated that the montmorillonite could sorb significantly more t
han 1200 cmol(+)/kg. There was virtually no exchangeable Cr in any of
the clays, suggesting that this element was covalently bonded to the s
iloxane surface. Infrared spectroscopy revealed a vibration at 1015-10
20 cm(-1) in the Cr clays which was not present in the control. This n
ew absorption band was attributed to an attenuation of the Si-O a(1)(1
) vibration caused by inner-sphere complexation of the interlayer Cr w
ith the siloxane oxygen. Because Cr was strongly held and efficiently
sorbed, montmorillonite was shown to be an effective sorbent for hydro
xy-Cr polymers.