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

Table 7

The comparison of chemical and physical characteristics.

No.	Clay	Agent	CEC	-spacing (Å)	New FTIR bands (cm^-1)	Reference
1	Bentonite	CPC	0	14.99	1465, 1490, 2852, 2926	Banik et al. [68]
			1	16.97
2	Montmorillonite	CPC	0	14.70	1468, 2847, 2916	Zou et al. [23]
			1	19.30
3	Montmorillonite	CPC	0	15.30	1468, 2847, 2916	Liu et al. [24]
			1	23.60
4	Montmorillonite	HDTMA	0	12.67	2850, 2920	Zawrah et al. [69]
			1	19.80
5	Montmorillonite	HDTMA	0	12.60	—	Abdel-Wahhab et al. [70]
			1	19.80
6	Montmorillonite	HDTMA	0	15.17	2850, 2918	Hu and Luo [37]
			1	22.50
7	Bentonite	CPC	0	14.85	1465, 1486, 2851, 2924	This study
			1	20.48
8	Bentonite	HDTMA	0	14.85	1465, 1486, 2851, 2924	This study
			1	18.79

0CEC = natural clay without modification; -spacing = the value from XRD. FTIR bands at 1465–1468, 1486–1490, 2847–2852, and 2916–2926 cm^-1 corresponded to CH₂ scissoring, N–CH₃ scissoring, C–H symmetric stretching, and C–H asymmetric stretching, respectively.