Batch adsorption and desorption investigations of Cs(I) and Sr(II) from simulated reactor waste by humic acid

This work focused on cost-effective and collective adsorption of radionuclides followed by their subsequent selective desorption, which is necessary for separation. The potential of humic acid, a low-cost adsorbent, for the removal and recovery of Cs(I) and Sr(II) from simulated reactor waste, was investigated Experimental parameters like solution pH, adsorbent dose, contact time, and temperature were optimized. FT-IR of humic acid before and after adsorption was compared. Selective desorption of both the radionuclides was achieved with desorbing agents – citric acid and HCl The process was governed by rapid kinetics where 91±2% of Cs(I) and 83±2% of Sr(II) was adsorbed within 10 min. Data modelling revealed that the process follows pseudo-second-order kinetics, and is spontaneous, feasible, and exothermic, with positive entropy indicating a high affinity of humic acid for the metallic ions. Maximum desorption of 97±2% was obtained for Sr(II), and 82±2% for Cs(I) Thus, the adsorption of investigated radionuclides by humic acid and their desorption was time-efficient, economical and environmentally a benign alternative for the removal and recovery of Cs(I) and Sr(II).