Variation in defects and properties in composite of ZnO and {\alpha}-Fe2O3 for methyl blue dye removal

TL;DR

This study investigates how annealing temperature affects the defect states, structural properties, and dye removal efficiency of ZnO and { extalpha}-Fe2O3 composite, revealing optimal conditions for wastewater treatment applications.

Contribution

It provides new insights into the relationship between annealing-induced structural changes and dye degradation performance in ZnO-Fe2O3 composites.

Findings

Pristine ZF-W achieved 86% methyl blue adsorption.

Optimal annealing at 300°C resulted in 84% degradation.

Defect evolution correlates with improved dye removal efficiency.

Abstract

The plasma deposition wall coated composite of ZnO and {\alpha}-Fe2O3 (ZF-W) after exposure to ~ 2000 {\deg}C, mostly considered as waste-materials and cleaned out from the deposition unit, was subjected to anneal at 300, 500 and 1000 {\deg}C to manipulate the structural properties. An evolution of defect states along with the structural changes has been identified as annealing temperature was varied. As a consequence, an unstable state of ZnFe2O4 was found to be stabilized at 500 {\deg}C and migration of Zn from ZnO causes the phase transformation from the {\alpha}-Fe2O3 to ZnFe2O4. While implemented for methyl blue adsorption/degradation without the effect of any external sources, the degradation for ZF-W annealed at 300 {\deg}C, 500 {\deg}C and 1000 {\deg}C were 84%, 68% and 82%, respectively. Compared to annealed structures, pristine ZF-W delivered the highest methyl blue adsorption efficiency of 86%. The changes in adsorption/degradation properties have been correlated with the simultaneous evolution of defects and structural properties of ZF-W as annealed at different temperatures. The plausible mechanism on the interaction of methyl blue with the composites on the adsorption/degradation is proposed. These findings give a clear indication on the importance of defects presence in the mixed metal oxide composite to obtain high-performance degradation/adsorption properties for sustainable wastewater treatment.