Adsorption of Cr(VI) in Aqueous Solution Using a Surfactant-Modified Bentonite

Table 2

Factorial design for the independent variables used in this study along with the observed response.

Test	Code values		Real values		Response; Cr(VI) removal, (%)
	A	B	A (mg)	B
1	−1	−1	0.30	2.0	82.33 ± 3.16
2	0	−1	0.40	2.0	86.93 ± 1.28
3	1	−1	0.50	2.0	89.00 ± 2.15
4	−1	0	0.30	4.0	87.04 ± 0.25
5	0	0	0.40	4.0	92.28 ± 0.96
6	1	0	0.50	4.0	87.71 ± 5.63
7	−1	1	0.30	6.0	70.31 ± 1.11
8	0	1	0.40	6.0	78.07 ± 0.81
9	1	1	0.50	6.0	77.28 ± 4.54