Fly Ash as a Potential Adsorbent for Removing Radionuclides from Aqueous Solutions in an Adsorption-Membrane Assisted Process Compared to Batch Adsorption

The paper deals with checking the possibility of using fly ash (FA) as a sorbent in the batch adsorption method of removing radionuclides from aqueous solutions. An adsorption-membrane filtration (AMF) hybrid process with a polyether sulfone ultrafiltration membrane with a pore size of 0.22 μm was also tested as an alternative to the commonly used column-mode technology. In the AMF method, metal ions are bound by the water-insoluble species prior to the membrane filtration of the purified water. Thanks to the easy separation of the metal-loaded sorbent, it is possible to improve water purification parameters using compact installations and reduce operating costs. This work evaluated the influence of such parameters on cationic radionuclide removal efficiency (EM): initial pH and composition of the solution, contact time of the phases, and the FA doses. A method for removing radionuclides, ordinarily present in an anionic form (e.g., TcO(4)(−)), from water, has also been presented. The results show, that both batch adsorption of radionuclides and adsorption-membrane filtration (AMF) using the FA as an adsorbent can be effectively used for water purification and in the form of a solid directed to long-term storage.