Novel Co–Fe–O micro/nano structures manipulated by urea and their applications in degradation of hexachlorobenzene

Abstract

Four microsized composite materials containing oxides of cobalt and iron were prepared via a polyol-mediated process involving aggregation of nanoparticles that formed initially. Two alkoxide precursors with different morphologies were obtained by controlling the amount of urea during the synthesis stage and calcinate each precursor in nitrogen and air afford four products. Hexagonal flower-like particles were formed in the absence of urea, while tetragonal brick-like structures were obtained in the presence of urea. The morphologies were retained during calcination. However, the compositions of the materials depend on the presence of air or nitrogen during calcination. In the absence of urea during initial synthesis, CoFe₂O₄ was formed when calcined in air, but a mixture of Fe₃O₄, Fe₂O₃, CoO and a small amount of Co₃O₄ was obtained when calcined in nitrogen. In the presence of urea, CoFe₂O₄/Fe₂O₃ was formed when calcined in air and a mixture, Co_0.62Fe_2.38O₄/Fe₃O₄, was formed when calcined in nitrogen. In the catalytic degradation of hexachlorobenzene, the two products synthesised by calcination under nitrogen display much higher catalytic activity that is attributed to the lower valence of the metals. The two products calcined in air possess magnetic properties, while the products synthesised in the presence of urea show weaken magnetic properties because of the partial substitution of CoFe₂O₄ by Fe₂O₃.

Keywords:

• Urea
• Co–Fe–O micro/nanostructure
• morphology
• magnetism
• HCB
• degradation

Notes on contributors

Jian Yang is a master degree candidate of College of Biological and pharmaceutical Sciences in China Three Gorges University. His main research interests are about the preparation of high efficient catalysts for the degradation of organic pollutants.

Manke Jia is an associate professor in College of Biological and pharmaceutical Sciences, China Three Gorges University. Her main research interests are about the preparation of thermal catalysts and photocatalysts and their application in the degradation of environmental organic pollutants.

Disclosure statement

No potential conflict of interest was reported by the authors.