Thermodynamic and Kinetic Analysis of Adsorption of Uranyl Ion by Amidoxime Polyacrylonitrile

Radioactive uranium-containing wastewater will bring environmental pollution risks, it is necessary to properly and effectively treat uranium-containing wastewater. In this paper, a series of adsorption experiments were conducted to investigate the relative adsorption characteristics of amidoxime polyacrylonitrile (AO-PAN) on U(Ⅵ). The effects of adsorption temperature, initial concentration and adsorption time on U(Ⅵ) adsorption on AO-PAN were systematically studied. U(Ⅵ) by AO-PAN increased gradually with the increase of adsorption temperature, and the adsorption amount reached 201.6 mg/g at 343 K. With the increasing of adsorption time under different temperature conditions, the U(Ⅵ) adsorption capacity of AO-PAN also gradually increased, the adsorption rate at initial was faster, as the adsorption progresses gradually, the adsorption curve gradually becomes flat, eventually reaching the equilibrium of adsorption. The U(Ⅵ) adsorption capacity of AO-PAN increased with the initial concentration in the solution. At a temperature of 303 K, the initial uranium concentration in the solution was 500 mg/L, and the U(Ⅵ) adsorption capacity of AO-PAN reached 305.8 mg/g. In addition, the adsorption of uranyl ions by AO-PAN conformed to the Langmuir model. Adsorption thermodynamic analysis shows that the adsorption of uranyl ions by AO-PAN is an endothermic and spontaneous process. The adsorption kinetics analysis showed that the adsorption behavior of uranyl ions by AO-PAN followed a pseudo-second-order kinetics model. The adsorption rate control mechanism analysis shows that the adsorption of U(Ⅵ) by AO-PAN is initially controlled by the intragranular diffusion process. With the continuous adsorption process, the adsorption process gradually changes from intragranular diffusion control to liquid membrane diffusion process control. The adsorption test results show that AO-PAN is an excellent adsorbent and can be used to adsorb U(Ⅵ) in wastewater. The model equation of adsorption process can be used for the analysis and calculation of adsorption process of U(Ⅵ) by AO-PAN.