Sustainable Transportation, Leaching, Stabilization, and Disposal of Fly Ash Using a Mixture of Natural Surfactant and Sodium Silicate

The present study evaluates the transportation, leaching, and stabilization ability of novel saponin extracted from the fruits of Acacia auriculiformis. To enhance the dispersing behavior of the fly ash slurry (FAS) at a lower dosage of sodium silicate, A. auriculiformis was incorporated in FAS. In addition to the rheological study, an attempt has been made to remove heavy metals through leaching for the safe disposal of FAS. Critical factors such as the fly ash (FA) concentration, saponin dosage, surface tension,. potential, temperature, and combination of saponin and sodium silicate, affecting the rheology of FAS, were extensively studied. The addition of a nonionic natural surfactant saponin has been proved to enhance the wettability of FA particles by decreasing the surface tension of FAS. The obtained rheology results were compared with the stabilization yield of the previously reported commercial surfactant cetyltrimethylammonium bromide. The incorporation of sodium silicate in the FAS system was found to be phenomenal in the settling and stabilization of FAS, thereby developing reaction products like sodium aluminum silicate (N-A-S). This facilitates the sustainable disposal of FA preventing air pollution after dewatering. The formation of N-A-S was further supported by scanning electron microscopy (SEM) and X-ray diffraction (XRD) studies.