MORPHOLOGY CHANGES IN BITUMINOUS COAL FLY ASH VIA AQUEOUS SOLUTIONS TREATMENTS (ACIDIC AND NEUTRAL)

Coal Utilities in Israel use ~13Mtons of Bituminous Coal annually producing ~1.3Mtons of coal fly ash and ~120,000 tons of bottom ash as residues. All these residues are utilized in the construction industry either as a cement additive or for concrete production.

In order to upgrade the economic value of the fly ash several studies have been carried out. It has been found that these fly ashes (South African Fly Ash, SAFA, and Colombian Fly Ash, COFA) can act as an efficient scrubber and fixation reagent for acidic wastes. Furthermore, the scrubbed product was found to be an efficient partial substitute to sand and cement in concrete without any danger to the environment. Bricks contain this aggregate products proved to be strong enough according to concrete standards.

During the scrubbing process the fly ashes surface is being affected. Therefore, we have decided to study the interaction of acidic and neutral solutions with the fly ash particles surface. The fly ashes were treated with acidic (0.1M HCl) and ultrapure neutral (UPDI) aqueous solutions. Surface analysis by SEM, TEM, XRD and EDAX of the treated and untreated fly ashes have demonstrated that the treated fly ashes have changed appreciably its' character (morphology and surface). Thus the treatment might change the modes of interaction of trace elements with the surface of the fly ash particles (cation exchange; chemical bonding –coordination; electrostatic adsorption of very fine precipitate).