The Improvement of Natural Thai Bentonite Modified with Cationic Surfactants on Hexavalent Chromium Adsorption from an Aqueous Solution

Table 6

EXAFS and Fourier transform spectral fitting.

Sample	Shell		(Å)	σ^2
Cr(VI) standard	Cr–O	3.75	1.63	0.004
Cr(III) standard	Cr–O	5.75	1.96	0.003
NTB+Cr(III)	Cr–O	5.60	1.97	0.001
1CPC+Cr(III)	Cr–O	5.41	1.96	0.002
1HDTMA+Cr(III)	Cr–O	5.67	1.97	0.002
1CPC+Cr(VI)	Cr–O	3.65	1.64	0.002
1HDTMA+Cr(VI)	Cr–O	3.69	1.63	0.001

 = number of neighbor atoms;  = interatomic distance;  = Debye–Waller factor.