A Novel Approach to Heavy Metal Immobilization in Municipal Solid Waste Incineration Fly Ash: Investigating the Use of Chicken Eggshell Waste and CaO Addition

Municipal solid waste incineration (MSWI) fly ash is a significant byproduct of waste-to-energy processes, and poses substantial environmental and health hazards if not treated properly. The process of Stabilization/Solidification (S/S) efficiently immobilizes hazardous elements present in the fly ash through a combination of physical and chemical mechanisms. The objective of this research is to thoroughly examine the feasibility of using chicken eggshell waste powder as a stabilizing agent for heavy metals, specifically targeting Pb, in MSWI fly ash. Experimental analysis involved varying eggshell waste to fly ash weight proportions, extending from 0.0 (control group), 7:3 up to 9.5:0.5 ratio, with designated curing durations of 2 and 72hours, and maintaining a liquid-to-solid (L/S) ratio at 1.0mL/g. In the two-hour curing period, the immobilization efficiency of Pb reached 100% with the addition of only 1.5% eggshell waste. Optimal ratios for Pb stabilization in MSWI fly ash were identified: maximum 2% eggshell waste for 2-hour curing and 1.5% for 72hours due to elevated Pb and Cd levels of 7:3 ratio. Adding CaO mitigated these levels, enhancing stabilization and compliance with landfill criteria. The results demonstrated that the addition of CaO led to efficient immobilization of Pb, achieving approximately 99%. In addition, the observed enhancement in compressive strength resulting from the incorporation of CaO highlights its effectiveness in enhancing the stabilizing process of MSWI fly ash. By demonstrating the effectiveness of eggshell waste and CaO in stabilizing hazardous elements, this study advocates for scalable solutions and further research on long-term stability and environmental impacts.