[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 La in aqueous solutions. The effects of activation temperature and pH value on the adsorption performance of La 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 La. Among them, graphitic nitrogen could provide interactions between La-π bonds, and C-P=O and C/P-O-P could provide active sites for the adsorption of La through complexation and electrostatic interaction. The adsorption of La 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, which was 2.53 times higher than that of the undoped sample, and its adsorption selectivity for La in the La/Naand La/Ca coexistence systems reached 93.49% and 82.49%, respectively. Additionally, the removal efficiency remained above 54% after five successive adsorption-desorption cycle experiments.