Abstract
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•Ni1-xZnxFe2O4 inverse spinel ferrite photocatalyst prepared by combustion route.•Dopant determined CB shifting-higher thermodynamic O2− generation potential.•Superior photo-degradation of levofloxacin under visible and solar light.•Higher charge separation and transfer capacity-metal redox.•Suitable degradation pathway for levofloxacin proposed.
Spinel ferrites with a compatible electronic band structure are always excellent candidates for photo-catalytic environmental detoxification employing visible light and solar energy. However, the potential is not harnessed to its fullest owing to unnerving charge carrier recombination. In this work, we report the synthesis of Ni1-xZnxFe2O4 (x = 0, 0.1, 0.3, & 0.5) mixed spinel ferrites via combustion route. As prepared samples were characterized for phase identification using X-ray diffraction (XRD) and Reitveld refined pattern confirms the formation of single phased cubic structure with a nano-metric crystallite size.
The homogeneous distribution of grains and particles is evidenced by shape and size morphological studies. Raman spectroscopy reveals the presence of motion of oxygen in tetrahedral and octahedral voids. The dc electrical resistivity measured using the two probe method is found to be in the range of 107 to 108 Ω-cm. The optical band gap measured for all photo-catalysts resides at 2.11–2.53eV. The ferrite photocatalyst exhibits high visible absorption, superior charge transfer capacity, and highly suppressed recombination as suggested by electrochemical impedance spectroscopy and photoluminescence results. The change in band structure with variable Zn content was monitored by shifting of conduction and valence bands. The photo-catalyst Ni0.7Zn0.3Fe2O4 (N2) exhibited 96.8% levofloxacin (LEV) degradation in 90 min of visible light exposure. The effect of parameters such as pH, catalyst dosage, electrolytes and water matrix was analysed in detail. The photo-catalytic degradation rate was enhanced in the presence of persulfate and H2O2. Furthermore, the high magnetic character of the catalysts aids in their retrieval post utilization in catalysis. In terms of band structure analysis, role of dopants, metal redox, and scavenging studies, a suitable photo-catalytic process was proposed. Degradation intermediates discovered by liquid chromatography–mass spectrometry analysis were also recommended as a pathway of degradation. These findings open up exciting possibilities for developing novel solar active photo-catalytic systems based on spinel ferrites for efficient environmental cleanup.