Leaching Behavior and Immobilization of Heavy Metals in Geopolymer Synthesized from Red Mud and Fly Ash

Abstract

Fly ash is an industrial waste from coal-fired thermal power plants whereas red mud is an industrial waste generated during aluminum production from bauxite. If both fly ash and red mud are not properly managed, they could cause negative impact on the environment. This study utilized red mud and fly ash in combination with sodium silicate solution to produce a geopolymer-based material which can be used as building materials. This study focussed on the leachability of heavy metals in the raw materials and the geopolymer as this would be significant in assessing the environmental impact of the product. Leachability of heavy metals such as Cu, Zn, Cd, Pb, Fe, and Cr was evaluated based on European standard (EN 124572 – 2, EU CEN TC292/ CEN TC 308) with pH values at 7. The results showed that raw materials (red mud and fly ash) have higher leachability than geopolymer specimens. And the values of leaching tests for heavy metals in the geopolymer - based materials belonged to limits of EULFD and USEPA.