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. 2013 Aug 2;11:24. doi: 10.1186/2052-336X-11-24

Table 2.

Experimental design and results of the central composite design

Run X 1 X 2 X 3 Con. (mg/L) pH Time (min) Efficiency (%)
1
 0
 0
 0
 50
 7
 7.5
 65.8
2
 1
 1
 −1
 75
 10
 3
 40.0
3
 0
 0
 0
 50
 7
 7.5
 65.4
4
 1
 −1
 1
 75
 4
 12
 76.6
5
 −1
 −1
 1
 25
 4
 12
 75.0
6
 0
 0
 0
 50
 7
 7.5
 66.2
7
 −1.68
 0
 0
 7.95
 7
 7.5
 59.0
8
 0
 0
 +1.68
 50
 7
 15
 95.0
9
 1
 −1
 −1
 75
 4
 3
 15.2
10
 1
 1
 1
 75
 10
 12
 82.6
11
 0
 0
 0
 50
 7
 7.5
 65.8
12
 −1
 1
 1
 25
 10
 12
 90.0
13
 −1
 −1
 −1
 25
 4
 3
 15.0
14
 0
 +1.68
 0
 50
 12
 7.5
 62.5
15
 0
 0
 −1.68
 5
 7
 0
 0.0
16
 +1.68
 0
 0
 92
 7
 7.5
 58.1
17
 0
 0
 0
 50
 7
 7.5
 66.0
18
 0
 0
 0
 50
 7
 7.5
 65.6
19
 −1
 1
 −1
 25
 10
 3
 30.8
20 0 −1.68 0 50 2 7.5 52.5