Bi3+ doping-enhanced optical and photocatalytic activity with stability of cobalt nickel zinc ferrites for wastewater treatment applications

Abstract

In this paper, the spinel ferrite nanoparticles Co0.5Ni0.25Zn0.25BixFe2−xO4 (CNZBF) were prepared by citrate-nitrate auto combustion method. Although the substitution process involves a large ion at the expense of a small one, the lattice constant didn't introduce a regular increment behavior with irregular shifts for the peak position at 34.62°, which is related to the (311) plane. Two hypotheses were introduced to justify this behavior. The crystallite size introduced a peculiar behavior in the span of 20.88–14.78 nm with increasing the Bi3+ content. Morphological study via FE-SEM manifested that the CNZBF nanoferrites have agglomerated spherical shapes. Kubelka-Munk function and Tauc's plot for direct allowed transitions were utilized to determine the band gap of all the CNZBF nanoferrites. The doping of Bi tuned the band gap (within 1.55 to 1.25 eV), boosted the light absorption, induced efficient e/h separation, and ensuing charge migration to the Co0.5Ni0.25Zn0.25BixFe2−xO4 surfaces. On account of the CNZBF advantages, a superb removal efficiency (∼96.41 %) of the sample Co0.5Ni0.25Zn0.25Bi0.08Fe1.92O4 via photocatalytic degradation was achieved. After five reusability cycles the nanocatalyst Co0.5Ni0.25Zn0.25Bi0.08Fe1.92O4 introduced 95.08% degradation which demonstrates a trivial efficiency decline of 1.33 % in the photocatalytic activities. These outcomes of excellent photocatalytic activity with the outstanding stability candidate the novel Co0.5Ni0.25Zn0.25Bi0.08Fe1.92O4 for wastewater treatment applications.