Pumice Adsorption of Radionuclides from Liquids: Optimization and Modeling

Abstract

Nuclear operations generate significant amounts of radioactive liquids (RLs), posing a severe threat to the environment. Effective decontamination of RLs remains a challenge. This study introduces pumice as a novel, sustainable, and economical adsorbent for radionuclides removal. The characteristics of pure pumice were verified through X-ray diffraction, a scanning electron microscopy (SEM), a Fourier-transform infrared spectroscopy (FTIR), and X-ray fluorescence spectrometry. Batch experiments were conducted to evaluate the effectiveness of pumice in removing radionuclides from RLs. The gross alpha, beta, and gamma technique was used to concurrently radiologically characterize the RLs before and after decontamination. The operating conditions for the process included a 5-min stirring time, stirring speed at 100 rpm, mass of pumice 3 g/L, and a pH of 5. Initial gross beta and gamma activities were 29,766 and 4623 Bq/L, respectively, while the experiments were conducted at room temperature. The batch experiments demonstrated that pumice effectively removed 65.77% of gross beta and 61.73% of gross gamma radioactivity. The Freundlich isotherm model and the pseudo-second-order kinetic model accurately represented the adsorption process, suggesting a heterogeneity of surfaces and a chemical reaction between radionuclides and active pumice sites. System energy was endothermic and resulted in a decrease in energy dissipation and an increase in system order.

Graphical abstract