[Preparation of Bamboo-based N, P Co-doped Activated Carbon and Its Lanthanum Ion Adsorption Performance]

Using diammonium hydrogen phosphate as an activator and N and P source and and bamboo chips as the carbon source, N, P co-doped activated carbon was prepared by one-step pyrolysis and used to efficiently remove La³⁺ in aqueous solutions. The effects of activation temperature and pH value on the adsorption performance of La³⁺ were analyzed, and the activation and adsorption mechanisms were explored using TG-IR, SEM-EDX, pore structure, XPS, and hydrophilicity. The results showed that diammonium hydrogen phosphate easily decomposed at a high temperature to produce ammonia and phosphoric acid, which activated the material and promoted the increase in the specific surface area and pore volume of the activated carbon. As an N and P source, the addition of diammonium hydrogen phosphate successfully achieved the N, P co-doping of activated carbon, and the introduction of N- and P-containing functional groups was the key to enhance the adsorption of La³⁺. Among them, graphitic nitrogen could provide interactions between La³⁺-π bonds, and C-P=O and C/P-O-P could provide active sites for the adsorption of La³⁺ through complexation and electrostatic interaction. The adsorption of La³⁺ on N, P co-doped activated carbons was endothermic and spontaneous, and the adsorption process conformed to the Langmuir isotherm and secondary kinetic model. Under the process conditions of an activation temperature of 900℃ and pH=6, the adsorption capacity of the N, P co-doped activated carbon was as high as 55.18 mg·g^-1, which was 2.53 times higher than that of the undoped sample, and its adsorption selectivity for La³⁺ in the La³⁺/Na⁺and La³⁺/Ca²⁺ coexistence systems reached 93.49% and 82.49%, respectively. Additionally, the removal efficiency remained above 54% after five successive adsorption-desorption cycle experiments.