State-of-the-art Technology to Stabilize Heavy Metal in Municipal Solid Waste Incineration Fly Ash Using Natural Zeolite

Abstract

Stabilizing heavy metals in Municipal Solid Waste Incineration (MSWI) fly ash by using natural zeolite is one of the state-of-the-art technologies. The current study focused on the sorption process of heavy metals by applying mordenite, an inexpensive natural zeolite adsorbent, and assessing the efficacy of the treatment of fly ash. Batch experiments were conducted to investigate the effects of the influential parameters, such as the initial metal ion concentration, the liquid-to-solid (L/S) ratio, the dosage of the adsorbent, and the equilibrium concentration of the metal, on the immobilization of Pb²⁺ and Zn²⁺. Heavy metal stabilization efficiency increased with increasing the dosage of mordenite, influenced by the media-specific surface area. Heavy metal adsorption is attributed to various adsorption processes and ion exchange mechanisms. The Langmuir and Freundlich isotherm models were investigated using the adsorption data. The adsorption process is better in the Freundlich isotherm model with a high determination coefficient (R²), especially for the adsorption of Pb²⁺. The outcomes raise hopes for the use of mordenite as a low-cost substance to treat MSWI fly ash. The findings indicate that heavy metal (Pb²⁺ and Zn²⁺) immobilization by mordenite is technically feasible and seems to be very effective. Furthermore, treated fly ash can be used as a construction material.