Biosynthesis of Cube-Shaped Fe.sub.3O.sub.4 Nanoparticles for Removal of Dyes Using Fenton Process

The anti-oxidative potential of Rhamnidium elaeocarpum extract was assessed using a green chemical bottom-up approach to produce ~ 80 nm cubic Fe.sub.3O.sub.4 nanoparticles. The protocol makes use of FeCl.sub.3 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 Fe.sup.3+ reduction to Fe.sup.2+. 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 Fe.sup.3+ to promote the formation of magnetite nanoparticles. In that case, other forms of iron oxide materials, with very low magnetic response, such as hematite ([alpha]-Fe.sub.2O.sub.3) and maghemite ([gamma]-Fe.sub.2O.sub.3) were obtained. The bio-inspired catalyst (Fe.sub.3O.sub.4) was applied in the degradation of Rhodamine-B using H.sub.2O.sub.2. 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.