GREEN SYNTHESIS OF Fe_xO_y STRUCTURES USING Euterpe oleracea MART EXTRACT FROM THE LEGAL AMAZON, BRAZIL

The synthesis of oxides using plant extracts as precursors has attracted attention as it is an economical, efficient, and ecological route. Euterpe oleracea Mart, available in the Legal Amazon, has great potential due to its composition, rich secondary metabolites. Therefore, this work aimed to investigate the potential of aqueous açaí leaf extract as precursors in synthesizing Fe_xO_y-type oxides. The synthesis was developed in two stages to obtain the hematite phases (step 1) and the magnetite phase (step 2). The effect of pH on phase formation and structure was evaluated in step 1. Then, the material was obtained in step 2 by precipitation with pH adjustment. The powders were characterized by thermal analysis, X-ray diffraction, infrared spectroscopy, and scanning electron microscopy. The results showed that pH played a significant role in the thermal behavior, crystallite sizes, and structural parameters of hematite, with neutral or acidic pH being more attractive for obtaining crystallites between 21 and 24 nm. Magnetite with 21.51 nm crystallites was precipitated, indicating possible capping of the Fe₃O₄ particles and preserving their magnetic characteristics.

Keywords:
green chemistry; açaí; nanostructures; α-Fe₂O₃; Fe₃O₄