Synthesis of magnetic bentonite-based nanocellulose composites for the removal of La(Ⅲ) ions in aqueous solutions

Untreated rare earth wastewater contains large quantities of rare earth elements (REE), which can cause serious harm if they enter the human body or the environment. Therefore, the treatment of these wastewaters is of paramount importance. This study developed a novel type of bentonite composite material by grafting nanocellulose crystals onto the surface of magnetic bentonite for better adsorption properties of rare earth ions, especially La(III) ions. A suite of characterization techniques was employed, including SEM-EDS, XPS, FT-IR, XRD, and VSM. The results demonstrate that the nanocellulose crystals were successfully integrated with magnetic bentonite. And its BET specific surface area increased from 54.96 m²/g to 114.07 m²/g, which further enhanced its adsorption performance. Under optimal conditions (pH 6 and 303 K), where 0.9 g/L CMB was added to a 30 mg/L La(III) solution for the adsorption of rare earth ions for 360 min, the maximum adsorption removal rate was 97.52%. Furthermore, the experimental fitting curve conforms to the pseudo-second-order kinetic model and the Langmuir model. The results reveal that the adsorption process of La(III) ions by CMB is a chemisorption process that is influenced by both intraparticle diffusion and liquid film diffusion. The maximum adsorption capacity of CMB was 41.32 mg/g. Moreover, in the coexisting ion experiment, the lowest removal of La(III) ions by CMB was achieved at a Gd(III) ion concentration of 15 mg/L, which decreased to 82%. After seven sorption-desorption cycles, the removal rate of La(III) ions by CMB remained at 68.18%, indicating that it possessed excellent reusability.