Synthesis, characterisation, and effect of pH on degradation of dyes of copper-doped TiO₂

Figures & data

Figure 1. XRD patterns of Cu-doped TiO₂ catalysts.

Figure 2. UV–vis diffuse reflectance spectra of Cu-doped TiO₂ catalysts.

Figure 3. TEM micrographs of Cu-doped TiO₂ (a) 0% Cu–TiO₂; (b) 0.15% Cu–TiO₂ and (c) 2.5% Cu–TiO₂.

Figure 4. Variation of zeta potential versus pH for selected Cu-doped TiO₂ catalysts.

Table 1. BET surface area of selected Cu-doped TiO₂ catalysts.

Sample	SBET (m^2/g)
0% Cu–TiO2	79
0.05% Cu–TiO2	65
0.15% Cu–TiO2	49
2.50% Cu–TiO2	38

Table 2. Adsorption amount of methyl orange and methylene blue by using various Cu-doped TiO₂.

	Adsorption amount of dyes in 30 min (mg/g)
	MO			MB
Sample	pH = 3	pH = 6	pH = 9	pH = 3	pH = 6	pH = 9
0% Cu–TiO2	0.57	0.15	NA	NA	0.89	5.05
0.05% Cu–TiO2	0.23	0.06	NA	NA	0.92	5.56
0.10% Cu–TiO2	0.09	0.04	NA	NA	1.05	6.82
0.15% Cu–TiO2	0.06	0.02	NA	NA	1.16	7.71
0.20% Cu–TiO2	0.03	NA	NA	NA	1.33	7.85
0.25% Cu–TiO2	NA	NA	NA	NA	1.53	7.89
0.50% Cu–TiO2	NA	NA	NA	NA	2.36	7.92
2.50% Cu–TiO2	NA	NA	NA	NA	4.48	7.95

Note: NA: no adsorption

Table 3. Rate constant of the decolourisation reaction of methyl orange and methylene blue by using various Cu-doped TiO₂.

	First-order rate constant of the photocatalytic reaction, kapp (×10^−3 min^−1)
	MO			MB
Sample	pH = 3	pH = 6	pH = 9	pH = 3	pH = 6	pH = 9
0% Cu–TiO2	12.5 ± 0.6	5.9 ± 2.1	3.5 ± 0.5	7.9 ± 0.7	10.1 ± 0.6	13.2 ± 0.6
0.05% Cu–TiO2	16.7 ± 0.4	8.4 ± 0.8	3.6 ± 0.7	11.1 ± 0.3	21.0 ± 2.3	26.7 ± 1.2
0.10% Cu–TiO2	15.9 ± 1.5	8.3 ± 0.9	7.0 ± 0.5	15.2 ± 2.2	25.3 ± 1.9	28.3 ± 1.9
0.15% Cu–TiO2	15.0 ± 2.1	8.1 ± 0.4	4.1 ± 0.4	16.9 ± 1.4	28.9 ± 2.6	88.0 ± 4.3
0.20% Cu–TiO2	13.5 ± 0.3	6.8 ± 0.6	3.9 ± 0.2	13.5 ± 0.9	19.3 ± 0.9	67.2 ± 3.5
0.25% Cu–TiO2	10.2 ± 0.8	5.0 ± 0.3	3.0 ± 0.4	8.9 ± 0.3	14.1 ± 0.5	25.1 ± 1.7
0.50% Cu–TiO2	8.5 ± 0.5	2.9 ± 0.6	2.1 ± 0.1	3.2 ± 0.1	7.2 ± 0.3	19.2 ± 0.4
2.50% Cu–TiO2	5.6 ± 0.2	1.1 ± 0.1	1.9 ± 0.2	0.9 ± 0.4	1.1 ± 0.1	15.6 ± 0.9

Figure 5. Photodegradation of methyl orange by 0.05% Cu–TiO₂ catalyst as a function of irradiation time: (a) disappearance of MO by adsorption and photocatalysis and (b) rate constant of the decolourisation reaction.

Figure 6. Photodegradation of methylene blue by 0.15% Cu–TiO₂ catalyst as a function of irradiation time: (a) disappearance of MB by adsorption and photocatalysis and (b) rate constant of the decolourisation reaction.