Evaluation of microwave acid baking on Indian red mud sample

Abstract

The present study validates the application of microwave heating for acid baking of red mud and the dissolution of metallic values during water leaching. The effect of microwave power and exposure time is evaluated on the sulfation and decomposition mechanism of the constituent phases present in the red mud. It is inferred that the processing time can be significantly reduced to less than 3 min for the enrichment of Fe (~41%) and Ti (~15%) in the residue by employing microwaves as a heating source. The low solution pH value (<2) for baking experiments with less than 90 s synergized to improve metal dissolution during the leaching stage. The metallic values in the solution were precipitated and calcined to produce a product containing refractory phases such as mullite, alumina, and hematite, which can be segregated using a conventional magnetic separation process. The dissolved titanium values interact with iron values and occur in ilmenite and pseudobrookite phases in the calcined precipitate. The microwave-assisted acid baking process is a potential first step process for the complete utilization of red mud and separation of iron and titanium values.