Synthesis of Mullite Using Fine Sand Generated in Recycling Process of Waste Foundry Sand

Abstract

Fine sand generated in a recycling process of waste foundry sand is used as raw material for cement. In order to find more effective use for the fine sand, we attempted to synthesize mullite using the sand as a silica source. Self-propagating high-temperature synthesis was carried out by adding thermite powder, a mixture of aluminum and iron oxide (III) with a molar ratio of 2:1, to the fine sand. A mixture containing 20 wt% of fine sand was heated to a maximum temperature of approximately 1660 K by an exothermic reaction, and the major products of this reaction were mullite and iron. The maximum combustion temperature of a mixture with more than 20 wt% of fine sand decreased with an increase in the fine sand content. In these cases, not all of the fine sand reacted: the reaction products were corundum, hematite, mullite and iron.