Experimental design suggested by RSM, and the result obtained on colour removal.

Run	Dosage of H2O2 (mM)	Independent variables			Colour removal efficiency (%)
		Adsorbent (g L−1)	Reaction time (min)	pH	Fe/AC	Zeolite-Fe/AC
1	120	3	35	6	76.5	43.9
2	40	1	60	9	69.1	24.1
3	200	1	60	9	69.4	42.3
4	40	5	10	3	83.7	86.1
5	120	3	15	6	78.3	43.1
6	200	5	60	9	79.1	55.5
7	40	5	60	9	79.9	40.8
8	200	1	10	9	70.0	41.7
9	280	3	35	6	73.9	54.1
10	120	3	35	6	77.9	44.9
11	40	1	60	3	76.5	62.4
12	200	5	10	3	82.7	87.1
13	40	1	10	9	71.4	21.7
14	120	3	35	12	74.2	67.8
15	120	3	35	6	76.1	45.3
16	120	3	35	6	76.1	44.5
17	200	1	60	3	73.0	68.8
18	200	1	10	3	77.1	66.8
19	120	7	35	6	82.7	66.6
20	200	5	60	3	80.1	93.4
21	120	3	35	6	74.6	46.1
22	40	1	10	3	79.5	59.6
23	200	5	10	9	80.1	55.1
24	40	5	10	9	80.3	47.7
25	120	1	35	6	70.0	30.4
26	40	5	60	3	76.5	93.4
27	40	3	35	6	78.5	25.7
28	120	3	35	0	—	—
29	120	3	35	6	76.7	46.5
30	120	3	85	6	76.1	51.5