Table 2.

CCD matrix for four variables and three responses

Run	Factors				Responses
	A: FeSO4.7H2O (g/L)	B: S0 (g/L)	C: Solid content (g/L)	D: Initial pH (g/L)	In extraction efficiency (%)	Sr extraction efficiency (%)
1	33.53	7.50	19	1.75	100	2.50
2	22.35	0.00	13	2.50	100	1.50
3	11.17	7.50	7	3.25	66	4.30
4	33.53	7.50	7	3.25	72	4.00
5	11.17	2.50	7	1.75	100	4.80
6	33.53	7.50	19	3.25	80	3.50
7	33.53	2.50	19	3.25	74	2.50
8	11.17	7.50	19	3.25	78	3.00
9	11.17	2.50	19	1.75	66	2.00
10	44.70	5.00	13	2.5	65	3.00
11	11.17	7.50	7	1.75	100	5.00
12	11.17	2.50	19	3.25	65	2.00
13	22.35	5.00	13	2.5	100	4.00
14	22.35	5.00	13	4.00	50	4.00
15	0.00	5.00	13	2.50	14	2.00
16	22.35	5.00	13	1.00	100	5.00
17	22.35	5.00	1	2.50	100	7.00
18	11.17	2.50	7	3.25	58	4.00
19	22.35	5.00	13	2.50	100	4.00
20	33.53	7.50	7	1.75	89	4.00
21	33.53	2.50	19	1.75	100	2.50
22	11.17	7.50	19	1.75	98	3.50
23	22.35	5.00	13	2.50	100	3.50
24	22.35	5.00	25	2.50	100	2.50
25	22.35	5.00	13	2.50	100	3.50
26	33.53	2.50	7	1.75	100	4.00
27	22.35	10.00	13	2.50	100	4.00
28	33.53	2.50	7	3.25	97	3.50