Synthesis of composite zeolite-layered double hydroxides using ultrasonic neutralized red mud

In this study, red mud (RM) treated by sonication was used to form zeolite-layered double hydroxide composite (LTA-LDH). RM is a waste material primarily composed of iron oxides-hydroxides. LDH (layered double hydroxides) is a family of layered materials with a brucite structure characterized by ion-exchange capability and high specific surface area. The synthesis of composite LTA-LDH was performed by NaOH pre-fused RM treatment. The results indicate that ultrasonic process changes the RM mineralogical composition thus neutralizing this waste material by forming large amount of LDH. The addition of this modified RM to the conventional LTA synthesis, determines the formation of a composite zeolite which combines the properties of both LTA and LDH. Scanning electron microscopy (SEM) data show the presence of LDH plate shaped crystals on the synthetic zeolite surface. Preliminary LTA-LDH characterization for its adsorption properties was performed testing the efficiency with Reactive Orange 16 (RO16).