Simultaneous Photocatalytic Reduction of Cr(VI) and Oxidation of Benzoic Acid in Aqueous N-F-Codoped TiO₂ Suspensions: Optimization and Modeling Using the Response Surface Methodology

Table 1

Central composite design matrix and experimental results for benzoic acid (BA) and Cr(VI) photocatalytic degradation.

Exper. no.	CTiO2-𝑥1; (mg L^−1)	Cr/BA; ratio-𝑥2	pH-𝑥3	(%) removal; Cr(VI)	(%) degradation; BA
1	200	5	10	32.36	2.5
2	600	15	4	55.22	49.47
3	400	1.59	7	100	17.5
4	400	18.41	7	36.41	32.78
5	600	5	10	54.95	5.1
6	600	5	4	100	36.61
7	400	10	1.95	58.9	47.84
8	400	10	7	45.96	9.49
9	200	5	4	76.16	23.07
10	200	15	10	4.58	6.56
11	400	10	12.05	4.85	2.79
12	200	15	4	24.06	30.34
13	400	10	7	45.57	8.18
14	63.64	10	7	18.85	2.7
15	736.36	10	7	65.82	17.24
16	400	10	7	47.44	8.66
17	600	15	10	32.92	12.08