Modification of the Adsorption Capacity of Brick Industry Fly Ash for the Removal of Cd(II)

Fly ash, a byproduct of coal burning and gasification, is a significant source of global pollution and is classified as hazardous waste. However, physicochemical treatments can improve their adsorption capacity by increasing their surface area. This research aimed to enhance the adsorption capacity of fly ash from the brick manufacturing industry to remove Cd(II) ions by optimizing its surface area. The treatment process was designed with two factors: sodium hydroxide concentration and stirring time, each evaluated at three levels. The modification was confirmed through X-ray diffraction analysis of its mineralogical composition. Using the BET method, the initial fly ash exhibited a surface area of 8.59 m2/g, which increased to a maximum of 33.99 m2/g after treatment. The proposed modification method successfully quadrupled the surface area under optimal conditions: 2.0 M NaOH concentration and 60 min of stirring. The 32 factorial design shows that the highest degree of Cd(II) removal is 99.75%, which is achieved using the modified fly ash with a surface area of 33.99 m2/g under favorable operating conditions of 30 min and 600 rpm stirring speed.