Supermagnetic Mn-substituted ZnFe2O4 with AB-site hybridization for the ultra-effective catalytic degradation of azoxystrobin

Spinel ferrites with magnetic properties have great potential for the decontamination of aqueous systems due to their ease of recycling by magnetic separation. Herein, the purpose is to enhance ZnFe2O4 spinel properties in terms of magnetization and catalytic performance via Mn substitution into the crystal structure. Zn1-xMnxFe2O4 (x = 0-1) nanoclusters were successfully synthesized via an optimal hydrothermal process, in which additives (i.e., citric acid and ammonia) play key roles in inhibiting impurity phase formation via homogenizing the distribution of metal ions and slowing down the reaction rate. At a Zn/Mn ratio of 1 : 3, the nanocluster Zn0.25Mn0.75Fe2O4 (ZMF(0.75)) composed of nanoparticles with sizes ranging from 5 to 10 nm shows the highest saturation magnetization (Ms = 68 emu g(-1), which is similar to 5 times greater than that of ZnFe2O4) and the best catalytic performance, with >99% azoxystrobin (AZX) degradation in a Fenton-like system. Moreover, the findings unveiled that the balance of Zn and Fe occupation in the polyhedron centres in the spinel crystal is broken upon replacing Zn with Mn. In all probability, the Zn/Fe/Mn cross-occupation phenomenon is essential for enhancing the activity of Fe and Mn multivalent metal atoms. A plausible mechanism for the synergistic effect of multiple active sites in ZMF(0.75) on the formation of HO and HO2 radicals is proposed. This work proves that Mn-substituted ZnFe2O4 could be an efficient heterogeneous Fenton-like catalyst for EOC decontamination in aqueous systems with ease for recycling via magnetic separation.

Automated summary

This study aims to enhance the magnetic and catalytic properties of ZnFe2O4 spinel through Mn substitution. Zn1-xMnxFe2O4 nanoclusters were synthesized via an optimized hydrothermal process, with additives playing a key role in impurity phase inhibition. The Zn0.25Mn0.75Fe2O4 nanocluster demonstrated the highest saturation magnetization and catalytic performance.