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

Table 4

Results of the regression analysis.

Analysis of variance for qe (coded units)
Source	DF	Seq SS	Adj SS	Adj MS	F	P
Main effects	3	1074.84	1074.84	358.279	432.36	0
Temp	1	10.91	10.91	10.915	13.17	0.003
Ppm	1	990.57	990.57	990.569	1195.4	0
pH	1	73.35	73.35	73.353	88.52	0
2-way interactions	2	75.86	75.86	37.929	45.77	0
Temp  ppm	1	9.71	9.71	9.711	11.72	0.005
ppm  pH	1	66.15	66.15	66.146	79.82	0
Residual error	12	9.94	9.94	0.829
Curvature	1	0.21	0.21	0.208	0.23	0.637
Lack of fit	2	0.77	0.77	0.385	0.39	0.69
Pure error	9	8.97	8.97	0.996
Total	17	1160.64
Estimated effects and coefficients for qe (coded units)
Term	Effect	Coef	SE coef	T	P
Constant		8.519	0.2146	39.7	0
Temp	1.652	0.826	0.2276	3.63	0.003
ppm	15.737	7.868	0.2276	34.57	0
pH	−4.282	−2.141	0.2276	−9.41	0
Temp  ppm	1.558	0.779	0.2276	3.42	0.005
ppm  pH	−4.067	−2.033	0.2276	−8.93	0
S	0.910304	PRESS	24.5778
R-Sq	99.14%	R-Sq(pred)	97.88%	R-Sq(adj)	98.79%