Lanthanum uptake from water using chitosan with different configurations

Chitosan-based adsorbents (chitosan powder, chitosan film, and chitosan sponge) were prepared and employed for the adsorption of La(III) ions. The materials presented significant differences in their properties, reflected in different La(III) adsorption performances. The adsorption kinetics, isotherms, and thermodynamics were studied. The chitosan materials showed very effective La(III) removal due to their unique characteristics, such abundance of functional groups on their surfaces. In addition, the chitosan sponge's high surface area contributed to La(III) adsorption. The equilibrium data followed the Liu isotherm model. Based on this model, the Q_max values obtained were 85.31 and 93.50 mg g⁻¹ (328 K) for powder and film chitosan, respectively. For chitosan sponges, the equilibrium model followed the Two-step Langmuir model attaining a maximum sorption capacity of 265.6 mg g⁻¹ (298 K). The thermodynamics studies indicate that the adsorption process was spontaneous and endothermic. The adsorption process suggests that electrostatic interactions and coordination/chelation were the main acting mechanisms of La(III) removal. Pore filling also played an important role in the adsorption process for the chitosan sponge. In brief, the CTS materials with different configurations presented a good potential to uptake the rare earth element La(III) from water.