Stabilization of Red Mud Using Mineral Precursors by Geopolymerization Process

Abstract

Red mud (RM) is an alkaline industrial waste product generated during the processing of bauxite by Bayer’s process. Red mud is high alkaline, exceedingly caustic and harmful to soil and biological forms posing a significant disposal challenge. The alkalinity of red mud can be successfully utilized to initiate geopolymeric reaction with industrial waste materials rich in alumino-silicates to stabilize the red mud. In this study using mineral precursors like granulated blast furnace slag (GBFS) and rice husk ash (RHA), an attempt has been made to stabilize red mud. The quantity of GBFS and RHA is varied as 0, 5, 10, 15, and 20% by weight of the RM–GBFS and RM–RHA mixes. Further, additional doses of alkali (NaOH) solutions of 1, 2, and 4 M concentrations are added to accelerate the geopolymerization process. The plasticity properties, compaction characteristics, swelling, and strength properties of treated red mud were determined at different curing periods. A noticeable increase in strength was observed with addition of mineral precursors, doses of alkali, and curing period. Mineralogical analysis endorses the formation of geopolymeric products which improve the geotechnical properties in addition to encapsulating the metallic ions present in virgin red mud. Atomic absorption spectroscopy (AAS) analysis also confirms reduction in the concentration of metals in leachate of stabilized red mud.