Microwave mediated precipitation and aging of iron oxyhydroxides at low temperature for possible hydrometallurgical applications

This preliminary study examined the role of microwave radiation on precipitation and aging of iron oxyhydroxides at 60 °C. It was observed that due to rapid heating under microwave, transformation of two line ferrihydrite to α-Fe2O3 takes place within 4–10 h. This is in contrast to the usual aging temperature of > 100 °C adopted in most conventional studies, and several days of aging. Besides rapid transformation, microwave helps forming nanoparticles, with crystallite size of ~ 60 nm as determined from X-ray diffractograms, and < 100 nm particles as observed under TEM. Rapid transformation also promotes formation of α-Fe2O3 without the formation of intermediate γ-Fe2O3. This study brought out the advantages of low temperature microwave assisted precipitation/aging as a low energy process to transform iron oxyhydroxides, with likely applications in slurry rheology, synthesis of nanoparticles, and adsorption.

► Precipitation of iron hydroxide under ambient condition
► Aging of the precipitate under microwave at 60 °C
► Characterisation of the precipitate through XRD, TG, TEM, and BET
► The α-Fe2O3 formed after aging was of nanosize.
► A low temperature method to prepare fine iron oxide particles