Activation of Coal Fly Ash for Cadmium Wastewater Remediation

Industrial wastewater contamination by heavy metals is a major environmental issue. Various techniques and materials have been proposed to address this problem, including those related to the adsorption process. However, new, improved, and low-cost materials must be developed and proposed in order for these strategies to be competitive. This study aims to investigate the remediation of water contaminated with cadmium, i.e., Cd(II), using activated coal fly ash, a low-cost sorbent, as it is the byproduct of an industrial process. Coal fly ash was chemically treated in acidic and alkaline mediums and activated using ultrasonic energy to enhance the materials and increase the uptake of Cd(II). Controlling the pH was found to be crucial, as the maximum sorption capacity occurred at pH 6. The materials activated in an alkaline medium with ultrasound were able to adsorb more significant amounts of Cd(II) under the studied experimental conditions and over four cycles of adsorption experiments. Finally, the kinetics of the adsorption process were analyzed, and some mathematical kinetics models were proposed to simulate the experimental data. After statistical discrimination, the Elovich isotherm was selected to represent the adsorption of Cd(II) in the different materials studied.