Optimization of Precious Metals Recovery from Electronic Waste by Chromobacterium violaceum Using Response Surface Methodology (RSM)

Table 4

ANOVA for quadratic model of Au and Ag (%) recovery.

Response	Source	Sum of squares	Df	Mean square	F-value	value	95% CI
Au recovery (%)	Model	6767.03	9	751.89	12.08	0.007
	X1-oxygen level	306.65	1	306.65	4.93	0.077	(0.29, 0.71)
	X2-pulp density	783.68	1	783.68	12.60	0.016	(1.81, 3.69)
	X3-glycine concentration	32.85	1	32.85	0.53	0.500	(1.84, 3.41)
	X1  X1	4356.00	1	4356.00	70.01	0.000
	X2  X2	809.31	1	809.31	13.01	0.015
	X3  X3	1109.23	1	1109.23	17.83	0.008
	X1  X2	18.88	1	18.88	0.30	0.605
	X1  X3	3.65	1	3.65	0.06	0.818
	X2  X3	2.64	1	2.64	0.04	0.845
	Error	311.10	5	62.22
	Lack-of-fit	311.10	3	103.70
	Pure error	0.000	2	0.000
	Total	7078.14	14
	R^2 = 0.956
	Adjusted R^2 = 0.8769
Ag recovery (%)	Model	243.924	9	27.103	4.27	0.062
	X1-oxygen level	0.505	1	0.505	0.08	0.789	(0.29, 0.71)
	X2-pulp density	20.995	1	20.995	3.31	0.129	(1.81, 3.69)
	X3-glycine concentration	13.966	1	13.966	2.20	0.198	(1.84, 3.41)
	X1  X1	131.212	1	131.212	20.67	0.006
	X2  X2	37.074	1	37.074	5.84	0.060
	X3  X3	33.258	1	33.258	5.24	0.071
	X1  X2	0.084	1	0.084	0.01	0.913
	X1  X3	0.011	1	0.011	0.00	0.968
	X2  X3	29.268	1	29.268	4.61	0.085
	Error	31.734	5	6.347
	Lack-of-fit	31.374	3	10/578
	Pure error	0.000	2	0.000
	Total	275.658	14
	R^2 = 0.885
	Adjusted R^2 = 0.6777

Df, degree of freedom; CI, confidence interval.