Characterization and Optimization of Calcination Process Parameters for Extraction of Aluminum from Ethiopian Kaolinite

Table 7

ANOVA for the surface quadratic model (response: extracted aluminum).

Source	Sum of squares	Df	Mean square	F value	value; Prob > F	Remark
Model	113.77	9	12.64	1495.52	<0.0001	Significant
X1, temperature	13.56	1	13.56	1604.31	<0.0001	Significant
X2, time	2.85	1	2.85	336.77	<0.0001	Significant
X3, particles size	53.71	1	53.71	6354.20	<0.0001	Significant
X1X2	0.050	1	0.050	5.87	0.0359	Significant
X1X3	1.20	1	1.20	142.36	<0.0001	Significant
X2X3	1.391 × 10^−4	1	1.391 × 10^−4	0.016	0.9005	Not significant
	31.86	1	31.86	3769.00	<0.0001	Significant
	6.15	1	6.15	728.12	<0.0001	Significant
	10.86	1	10.86	1285.11	<0.0001	Significant
Residual	0.085	10	8.452 × 10^−3
Lack of fit	0.048	5	9.568 × 10^−3	1.30	0.3889	Not significant
Pure error	0.037	5	7.337 × 10^−3
Cor total SS	113.85	19