Phosphorylated-CNC/MWCNT thin films-toward efficient adsorption of rare earth La(III)

The purpose of the paper is to achieve adsorption and secondary application of La(III) through strong coordination ability of phosphate groups and La(III). Firstly, cellulose nanocrystals (CNCs) were phosphorylated in two solvents (water and molten urea). p-CNC(water)/MWCNT and p-CNC(urea)/MWCNT thin films were successfully synthesized by using p-CNCs as film units based on EISA method. The addition of multi-wall carbon nanotube was to improve thermal stability and repeatability of films and carboxyl groups thereon could also involve in the coordination of La(III). Adsorption experiments show that, at pH 4.0, adsorption capacities of p-CNC(water)/MWCNT and p-CNC(urea)/MWCNT films were 21.23 and 44.71 mg g⁻¹, with half equilibrium time (t_1/2) of 23.06 and 4.87 min. Repeatability tests show that the adsorption capacities of films remained above 82% of the maximum adsorption capacities after five adsorption–desorption cycles.