Effective Factor Analysis for Chromium(VI) Removal from Aqueous Solutions and Its Application to Tunçbilek Lignite Using Design of Experiments

Table 5

Freundlich and Langmuir isotherm constants, chromium(VI) adsorption values, and model performances at different temperatures (pH = 2).

ppm	PAC, 298 K		PAC, 323 K		CAC, 298 K		CAC, 323 K
	Ce (mg/L)	qe (mg/g AC)	Ce (mg/L)	qe (mg/g AC)	Ce (mg/L)	qe (mg/g AC)	Ce (mg/L)	qe (mg/g AC)
25	3.775	0.840	3.050	0.880	7.100	0.720	6.142	0.740
50	9.849	1.580	7.551	1.680	16.349	1.310	12.610	1.440
100	23.796	3.160	19.028	3.310	37.728	2.550	28.565	2.950
200	70.785	5.180	61.090	5.620	89.769	4.520	72.402	5.230
300	121.013	6.950	104.855	7.570	152.051	5.710	111.059	7.200
400	177.218	8.560	151.290	9.600	210.195	7.210	165.639	9.100
500	230.679	10.590	211.710	11.480	294.145	8.180	216.393	11.090
900	521.468	15.880	437.564	19.170	582.513	13.320	491.390	16.770
1200	716.433	20.590	676.762	22.960	817.680	16.780	695.273	22.060
Freundlich isotherm
KF	0.415		0.498		0.219		0.244
n	1.690		1.688		1.540		1.427
R^2	0.996		0.996		0.996		0.992
χ^2	0.150		0.160		0.140		0.590
Langmuir isotherm
Q0	23.923		27.624		21.322		28.986
b	0.005		0.005		0.003		0.003
R^2	0.895		0.893		0.898		0.942
χ^2	2.220		2.880		1.250		0.810
DOE
R^2	0.988		0.988		0.988		0.988
χ^2	3.210		2.500		0.990		1.280