Turning waste into a resource: coal fly ash as a sustainable approach for heavy metal removal in contaminated waters

ABSTRACT Image showing mound of fly ash being used to treat water contaminated with heavy metals with various results shown Effective, low-cost water treatment approaches are needed to address increasing heavy metal contamination, particularly in the developing world. This study evaluates the use of fly ash, a waste byproduct from coal combustion, as a sustainable adsorbent to remove cadmium (Cd2+), cobalt (Co2+), and lead (Pb2+) from aqueous solutions. Two types of fly ash sourced from different power plants in the southeastern United States were evaluated in this study: Belews Creek fly ash (BFA), which was untreated, and Wateree Station fly ash (WFA), which was processed using a proprietary carbon burnout method. The removal kinetics followed the pseudo-second order model, with equilibrium being achieved within 2 h. The experimental data best fit the Freundlich isotherm model, compared with the Linear isotherm model, suggesting that multilayer adsorption occurred on the fly ash surfaces. The results showed that Pb2+ exhibited the highest removal efficiency for each adsorbent (BFA: 99%; WFA: >99%), followed by Co2+ (BFA: 98%; WFA: 94%) and Cd2+ (BFA: 93%; WFA: 56%). Removal efficiency was influenced by pH and was negatively impacted by increasing ionic strength and total organic carbon content. The findings demonstrate that fly ash is a viable, low-cost alternative for heavy metal removal for use in resource-limited areas.