High activity of ZnFe₂O₄ nanoparticles for photodegradation of crystal violet dye solution in the presence of sunlight

Figures & data

Figure 1. XRD patterns of the MFe₂O₄ nanocomposite photocatalysts.

Table 1. Crystalline, interplanar spacing, particle sizes and lattice constant of MFe₂O₄ nanostructures calcined at 973 K for 24 h.

MFe2O4 samples	Intense peak position (deg.)	Crystalline size (nm)	Interplanar spacing (nm)	Average particle size (nm)	Lattice constant (Å)
ZnFe2O4	35.54	21.71	0.19	26.00	7.20
CoFe2O4	35.53	21.69	0.16	32.00	7.20
CuFe2O4	35. 53	23.86	0.12	26.00	6.10
NiFe2O4	35.74	18.30	0.19	28.00	5.80

Figure 2. FT-IR spectra of MFe₂O₄ nanocomposite photocatalysts, calcined at 973 K for 24 h.

Figure 3. SEM images of (a) NiFe₂O_4; (b) CoFe₂O_4; (c) CuFe₂O_4; (d) ZnFe₂O_4, calcined at 973 K for 24 h.

Figure 4. EDS analysis of (a) NiFe₂O_4; (b) CoFe₂O_4; (c) CuFe₂O_4; (d) ZnFe₂O_4, calcined at 973 K for 24 h.

Figure 5. HRTEM results and particle size distributions of (a) NiFe₂O₄; (b) CoFe₂O₄; (c) CuFe₂O_4; (d) ZnFe₂O_4, calcined at 973 K for 24 h.

Figure 6. Particle size distributions of (a) NiFe₂O₄; (b) CoFe₂O₄; (c) CuFe₂O_4; (d) ZnFe₂O_4, calcined at 973 K for 24 h.

Figure 7. Nitrogen adsorption-desorption isotherms and pore size distribution of MFe₂O₄ photocatalysts.

Table 2. Textural properties of MFe₂O₄ nanoparticles.

Photocatalyst	Calcination temperature (K)	SBET (m^2g^−1)	Pore volume (cm^3g^−1)	Pore diameter (nm)	Optical band gap (eV)
ZnFe2O4	973	03.715	0.015	130.254	1.69–2.55
CoFe2O4	973	16.180	0.130	55.278	2.40
CuFe2O4	973	30.576	0.140	21.75	2.48
NiFe2O4	973	23.651	0.126	17.795	2.53

Figure 8. UV-Vis absorption spectra of MFe₂O₄ nanostructures.

Figure 9. Plots of (Ahν)ⁿ as a function of photon energy (hν).

Figure 10. Photodegradation vs time of MFe₂O_4, calcined at 973 K for 24 h.

Figure 11. (a) Effect of calcination temperature of ZnFe₂O₄. (b) Effect of calcination duration upon photocatalytic activity of ZnFe₂O₄ (1:2) nanoparticles calcined at 873 K on the photodegradation of CV dye using 15 mg of photocatalyst, 10 ml of 10-ppm CV solution in sunlight and pH 7.

Figure 12. (a) effect of ratio of Zn/Fe, (b) effect of load of ZnFe₂O₄ (1:2) nanoparticles calcined at 873 K on the photodegradation of CV dye using 15 mg of photocatalysts, 10 ml of 10 ppm CV solution under sunlight radiation and at pH 7 for 30 min.

Figure 13. Time-dependent spectral changes to CV dye solution (a) dark reaction catalyzed by ZnFe₂O_4, calcined at 973 K; (b) blank reaction; (c) catalyzed reaction by ZnFe₂O_4, calcined at 873 K; (d) catalyzed reaction by ZnFe₂O_4, calcined at 973 K.

Figure 14. (a) C/C_o vs time plot for the photocatalytic degradation of CV dye, and (b) the plot of ln (C/C_o) vs time for the kinetic study by MFe₂O₄ photocatalysts.

Table 3. Kinetic studies of photocatalytic degradation of CV dye using MFe₂O₄ nanostructures.

Photocatalyst	kapp (s^−1)	t1/2 (s^−1)
NiFe2O4, 973 K (30 mg)	1.2	0.58
CoFe2O4, 973 K (30 mg)	3.0	0.23
CuFe2O4, 973 K (30 mg)	4.2	0.17
ZnFe2O4, 973 K (15 mg)	5.4	0.13
ZnFe2O4, 973 K (30 mg)	7.2	0.10
ZnFe2O4, 873 K (15 mg)	21.6	0.03

Figure 15. Degradation efficiency ZnFe₂O₄ per run, measured as the percentage of CV dye degraded by photocatalysts.

Figure 16. (a) XPS spectra; (b) Mott–Schottky plots; (c) scheme of energy with reduction potentials vs. NHE of ZnFe₂O₄ photocatalyst.

Figure 17. The rate of photocatalytic degradation of CV dye over ZnFe₂O₄ in the presence of active species.

Figure 18. Scheme of the photocatalytic degradation mechanism of CV dye over ZnFe₂O₄ photocatalyst under sunlight irradiation.

Data availability statement

Not applicable.