Feasibility of Natural Zeolite for Heavy Metal Stabilization in Municipal Solid Waste Incineration Fly Ash: A Novel Approach

The current study investigated the sorption process of heavy metals, especially lead (Pb2+) and Zinc (Zn2+), in Municipal Solid Waste Incineration (MSWI) fly ash applying natural zeolite, namely mordenite, as an inexpensive adsorbent to assess its feasibility for the treatment of fly ash. Batch experiments were performed to investigate the effects of the influential parameters, such as metals initial ion concentration, dosage of adsorbent, liquid to solid (L/S) ratio, and equilibrium concentration of metal on the immobilization of Pb2+ and Zn2+, in a novel approach. Heavy metals removal efficiency increased with increasing the dosage of mordenite influenced by the media-specific surface area. Heavy metals adsorption is ascribed to various mechanisms of ion exchange and adsorption processes. The Langmuir and Freundlich isotherm models were investigated using the adsorption data. The adsorption process describes better in the Freundlich isotherm model compared to the Langmuir isotherm model with a high determination co-efficient (R2), especially for the adsorption of Pb2+. In addition, the affinity of mordenite to Pb2+ was shown to be higher than that of Zn2+. This allows the use of mordenite to capture of Pb2+ in MSWI fly ash. Results raise expectations about using mordenite as a low-cost material for treating MSWI fly ashes. The results show that heavy metal (Pb2+ and Zn2+) removed by mordenite adsorbent is practical and effective. In order to achieve the higher efficiency on heavy metal stabilization in MSWI fly ash, additional experiments are necessary.