Synergistic action of multiple functional groups enhanced uranium extraction from seawater of porous phosphorylated chitosan/coal-based activated carbon composite sponge

Abstract

A new porous phosphorylated chitosan/coal-based activated carbon composite sponge (PPCCS) was designed and synthesized to achieve selective uranium extraction from seawater. The effects of initial pH and initial uranium concentration, adsorption time and temperature, and competitive ions on the adsorption of uranium by PPCCS were studied. The adsorption reaction accords with the pseudo-second-order model and is a spontaneous endothermic reaction. The maximum adsorption capacity of PPCCS for uranium is 639.77 mg g−1 at 308 K and pH = 6. In addition, PPCCS has good reusability and stable adsorption capacity after adsorption and desorption for 5 times. The mechanism characterization and group masking results show that uranium is adsorbed by complexing with –OH, –NH2, and PO on the superficies of PPCCS, and the synergistic action of the three functional groups can significantly enhance the selective adsorption of uranium by the PPCCS, especially in uranium (5 mg L−1)–vanadium (5 mg L−1) solutions, the distribution coefficients of PPCCS for uranium can reach 13,980.47 mL g−1, and for uranium and vanadium are significantly different (distribution coefficient (Kd) of uranium is 63 times higher than that of vanadium). The adsorption capacity of PPCCS for 1 L real seawater to uranium is 130 μg g−1. These conclusions demonstrate that PPCCS has great potential for uranium extraction from seawater.