Solar light-facilitated oxytetracycline removal from the aqueous phase utilizing a H₂O₂/ZnWO₄/CaO catalytic system

Peer review under responsibility of Taibah University.

Figures & data

Fig. 1 (a, b) SEM image of pure CaO and (c, d) SEM images of ZnWO₄/CaO composites.

Fig. 2 TEM images of ZnWO₄/CaO composites.

Fig. 3 (a) UV–vis absorbance spectra of ZnWO₄/CaO composites. (b) X-ray diffraction pattern of pure CaO and ZnWO₄/CaO composites. (c, d) EDX pattern of pure CaO and ZnWO₄/CaO composites.

Fig. 4 FTIR spectra of pure CaO and ZnWO₄/CaO composites.

Fig. 5 (a, b) Time profile of OTC degradation in the H₂O₂/CaO/ZnWO₄ system under different reaction conditions (a) solar and (b) in the dark. (c) Time profile for adsorptional photocatalytic degradation of OTC. (d) The plot of log (absorbance) vs. time. Experimental conditions: [OTC] = 1 × 10⁻⁴ M, [H₂O₂] = 1 × 10⁻⁴ M, Catalyst dosage = 50 mg/50 ml, pH 5, temperature = 30 ± 0.3 °C and time = 70 min.

Fig. 6 (a–d) Effect of different reaction parameters, OTC (a), catalyst (b), H₂O₂ (c), pH (d) on OTC removal. Reaction conditions [OTC] = 1 × 10⁻⁴ M, catalyst dosage = 50 mg/50 ml, [H₂O₂] = 1 × 10⁻⁴ M, pH 5, temperature = 30 ± 0.3 °C, reaction time = 60 min and solar light intensity = 35 × 10³ ± 1000 lx.

Fig. 7 (a) COD removal efficiency and (b) mineralization kinetics during degradation of OTC. Reaction conditions [OTC] = 1 × 10⁻⁴ M, catalyst dosage = 50 mg/50 ml, [H₂O₂] = 1 × 10⁻⁴ M, pH 5, temperature = 30 ± 0.3 °C and solar light intensity = 35 × 10³ ± 1000 lx.

Fig. 8 The proposed mechanism for OTC degradation under the solar/H₂O₂/ZnWO₄/CaO system.

Fig. 9 Recycle catalytic activity of ZnWO₄/CaO. Reaction conditions: [OTC] = 1 × 10⁻⁴ M, [H₂O₂] = 1 × 10⁻⁴ M, catalyst dosage = 50 mg/50 ml, pH 5 and temperature = 30 ± 1 °C, reaction time = 60 min and solar light intensity = 35 × 10³ ± 1000 lx.