(279a) Recent Advances in the Development of Fly Ash Based Geopolymers for the Adsorption of Aqueous-Phase Heavy Metal Contaminants

Geopolymers are novel inorganic polymeric materials synthesized from aluminosilicate sources via alkaline activation at relatively low temperatures. Although geopolymerisation is not a new concept and has been used as barriers in immobilizing toxic and radioactive metals via the combination of physical encapsulation and chemical stabilization, the application of this technology to produce effective adsorptive materials for mitigation of liquid-phase contaminants is relatively recent. Due to their inorganic structure and stability properties, heavy metals do not decompose in nature and pose risk of accumulation in living species as highly toxic and carcinogenic elements, some even at very low concentrations. The removal of trace toxic heavy metals (TTHMs) from solutions has been commonly carried out by several processes such as adsorption, ion exchange, chemical precipitation, reverse osmosis and solvent extraction. However, recently, adsorption is the one driving most attention among these methods because of simpler equipment and smaller corrosiveness, lower energy consumption, high removal efficiency, reversible nature allowing regeneration of adsorbents and flexibility in design. Adsorption has been regarded as the main interaction mechanism for geopolymers in heavy metal removal investigations. A number of studies on the use of geopolymers derived from fly ash for the sequestration of aqueous and gaseous pollutants has been recently reported. This paper will provide a state-of-the-art overview of the recent scientific advances on geopolymers widely synthesized from abundantly available coal fly ash (CFA) as raw material; and sustainable environmental applications. It focuses on the adsorption of TTHM contaminants in water; evaluating the effectiveness against other adsorption technologies utilizing conventional materials such as activated carbon and zeolites.