Biomimetic Synthesis of Hydroxyapatite in Presence of Imidazole-4,5-dicarboxylic Acid Grafted Chitosan for Removing Chromium(VI)

Table 2

Orthogonal experimental design and results.

Number	pH	Initial concentration of Cr(VI) (mg·L^−1)	Dosage of HAP (mg·L^−1)	Adsorption time (min)	Removal rate η (%)
1	3	25	200	90	80.85
2	3	50	400	120	86.32
3	3	100	800	150	91.73
4	3	200	1000	180	94.45
5	5	25	400	150	82.05
6	5	50	200	180	85.71
7	5	100	1000	90	89.83
8	5	200	800	120	88.36
9	7	25	800	180	88.67
10	7	50	1000	150	93.26
11	7	100	200	120	73.95
12	7	200	400	90	80.28
13	9	25	1000	120	87.45
14	9	50	800	90	83.62
15	9	100	400	180	74.37
16	9	200	200	150	69.25
Verifying test	3	50	1000	180	95.66
ADR1^∗	88.34	84.76	77.44	83.65
ADR2^∗	86.49	87.23	80.76	84.02
ADR3^∗	84.04	82.47	88.10	84.08
ADR4^∗	78.67	83.09	91.25	85.80
Range	9.67	4.76	13.81	2.15
IF^∗	Secondary	Tertiary	Primary	General