Intensification of Azo Dye Removal Rate in the Presence of Immobilized TiO_𝟐 Nanoparticles and Inorganic Anions under UV-C Irradiation: Optimization by Response Surface Methodology

Table 4

The four-factor central composite design matrix and the value of the response function (𝑅%).

Run	[NO3^−] (mM)	[HCO3^−] (mM)	[H2PO4^−] (mM)	[Cl^−] (mM)	Removal efficiency (%)
					Experimental	Predicted
1	−1	−1	−1	−1	34.394	35.180
2	1	−1	−1	−1	61.432	65.392
3	−1	1	−1	−1	51.023	48.756
4	1	1	−1	−1	85.646	88.019
5	−1	−1	1	−1	28.299	27.683
6	1	−1	1	−1	48.023	49.524
7	−1	1	1	−1	36.013	32.998
8	1	1	1	−1	63.727	63.892
9	−1	−1	−1	1	35.902	35.180
10	1	−1	−1	1	65.375	65.392
11	−1	1	−1	1	48.998	48.756
12	1	1	−1	1	88.119	88.019
13	−1	−1	1	1	29.110	27.683
14	1	−1	1	1	48.287	49.524
15	−1	1	1	1	33.731	32.998
16	1	1	1	1	63.892	63.892
17	−2	0	0	0	5.887	10.120
18	2	0	0	0	75.686	71.225
19	0	−2	0	0	42.957	41.045
20	0	2	0	0	66.262	68.988
21	0	0	−2	0	75.474	70.829
22	0	0	2	0	40.503	39.204
23	0	0	0	−2	54.416	55.016
24	0	0	0	2	53.965	55.016
25	0	0	0	0	53.066	55.016
26	0	0	0	0	55.525	55.016
27	0	0	0	0	55.066	55.016
28	0	0	0	0	54.268	55.016
29	0	0	0	0	55.147	55.016
30	0	0	0	0	54.591	55.016