Biosynthesis of Cube-Shaped Fe₃O₄ Nanoparticles for Removal of Dyes Using Fenton Process

Abstract

The anti-oxidative potential of Rhamnidium elaeocarpum extract was assessed using a green chemical bottom-up approach to produce ~ 80 nm cubic Fe₃O₄ nanoparticles. The protocol makes use of FeCl₃ as the only precursor of magnetite, and it allows the obtaining of the material using water as solvent, and urea as a pH regulator. Besides, since the bark extract functions as both the capping and reducing agents, no unfriendly extra chemicals are required to promote the Fe³⁺ reduction to Fe²⁺. For comparison purposes, we also obtained iron oxide materials in the absence of the biomass, and it was observed that urea alone could not reduce Fe³⁺ to promote the formation of magnetite nanoparticles. In that case, other forms of iron oxide materials, with very low magnetic response, such as hematite (α-Fe₂O₃) and maghemite (γ-Fe₂O₃) were obtained. The bio-inspired catalyst (Fe₃O₄) was applied in the degradation of Rhodamine-B using H₂O₂. Under the studied conditions, a single portion of the catalyst could promote the dye degradation for at least 5 cycles (degradation > 94%), and the material could be rapidly isolated in between batches using a small neodymium magnet. We also found out that the iron oxides obtained in the absence of extract and urea exhibited a lower degradation efficiency, and could not be recycled in successive runs. An investigation on the toxicity of this new catalyst was also carried out on three model organisms and no toxicity enhancement could be induced by the presence of the as-synthesized magnetite nanoparticles.