Table 1 Analysis of variance (ANOVA) of the response surface quadratic model.

From: Coagulation of trace arsenic and cadmium from drinking water using titanium potassium oxalate

Source a

Mean squares b

F value b

p value b

Mean squares c

F value c

p value c

Model

1734.49

29.31

<0.0001

2339.59

19.99

<0.0001

X1

6583.89

111.24

< 0.0001

10.46

0.0894

0.7675

X2

4.59

0.0776

0.7828

221.79

1.89

0.1809

X3

8626.19

145.75

< 0.0001

5974.61

51.04

<0.0001

X4

6.60

0.1114

0.7413

12.54

0.1071

0.7461

X5

9810.02

165.75

< 0.0001

35106.38

299.92

<0.0001

X1X2

19.21

0.3246

0.5739

13.95

0.1192

0.7328

X1X3

0.0191

0.0003

0.9858

196.86

1.68

0.2065

X1X4

0.2135

0.0036

0.9526

1.86

0.0159

0.9008

X1X5

5.51

0.0930

0.7629

28.07

0.2398

0.6286

X2X3

0.0576

0.0010

0.9753

345.18

2.95

0.0983

X2X4

2.73

0.0462

0.8315

63.29

0.5407

0.4690

X2X5

3.05

0.0515

0.8223

5.85

0.0500

0.8249

X3X4

1.86

0.0314

0.8607

3.40

0.0290

0.8660

X3X5

1002.95

16.95

0.0004

47.58

0.4065

0.5296

X4X5

2.22

0.0375

0.8480

25.54

0.2182

0.6445

X1²

1056.72

17.85

0.0003

58.20

0.4972

0.4873

X2²

12.96

0.2189

0.6439

245.45

2.10

0.1600

X3²

1062.22

17.95

0.0003

1132.61

9.68

0.0046

X4²

6.48

0.1095

0.7434

0.8217

0.0070

0.9339

X5²

4887.34

82.58

< 0.0001

2461.13

21.03

0.0001

Residual

59.18

  

117.05

  

Lack of Fit

73.02

19.01

0.0020

141.62

7.54

0.0170

Pure Error

3.84

  

18.79

  
 

R2 = 0.9591

R2 = 0.9411

  1. aX1-Initial As(III) concentration, X2-Initial Cd concentration, X3-K2TiO(C2O4)2 dose, X4-CaCl2 dose, and X5-pH.
  2. bAs(III) removal efficiency.
  3. cCd removal efficiency.
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