Preparation of nano-scale ferric hexacyanoferrate using coal ash by microwave-assisted hydrothermal process for cesium removal

Abstract

The removal of radioactive cesium (Cs+) has received considerable attention owing to its chemotoxicity and radiotoxicity. This study presents a method for producing ferric hexacyanoferrate nanoparticles (Prussian blue, PB), using recycled magnetic coal ash (M-CA) as an effective and selective adsorbent for Cs+ removal. A microwave-assisted hydrothermal technique was employed to recover the Fe solution from M-CA and a simple sol–gel technique was used to synthesize PB nanoparticles. The PB nanoparticles exhibited cubic cluster structures with an average size of 20.67 nm. Their Cs+ adsorption capacity reached 213.061 mg/g, significantly surpassing the capacities of absorbents reported in previous studies. Cs+ was observed to be associated with localized adsorption sites on the PB surfaces, with minimal internal diffusion. In addition, the hydrated radius of Cs+ emerged as a critical factor influencing its adsorption onto PB surfaces, enabling the efficient removal of Cs+ even in the presence of competing ions. These findings offer valuable insights for the straightforward synthesis of highly efficient and selective adsorbents for radioactive substances, as well as the recovery of valuable materials from industrial solid waste.