Utilization of mill scale and recycled MoO3 from spent acid for economic synthesis of nanocrystalline intermetallic Fe–Mo alloys

This paper deals with an economic and clean route for the synthesis of ferro-alloys through utilization of waste materials (mill scale and spent acid). The molybdic oxide, MoO3 is successfully synthesized from the spent acid by ammonia gas neutralization method. MoO3/mill scale powder mixture was isothermally reduced in pure hydrogen at 700–1100 °C. Based on thermogravimetric analysis, the reduction behavior of the synthesized Fe–Mo alloy and the kinetics reaction mechanism were studied. The initial oxides powder and the various reduction products were characterized by XRD and SEM to reveal the effect of hydrogen reduction on composition, microstructure and reaction kinetics of synthesized ferro-alloys. The activation energy values were calculated using the Arrhenius equation. The approved mathematical formulations for the gas–solid reaction were applied to confirm the estimated rate controlling reaction mechanism. Complete reduction of mixed oxides powder was achieved with synthesis of nanocrystalline Fe–Mo alloys.