偕胺肟聚丙烯腈对铀酰离子吸附热力学及动力学过程分析

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

  • 摘要: 放射性含铀废水会带来环境污染风险,合理有效处理含铀废水十分必要。本研究通过吸附实验探究偕胺肟聚丙烯腈(AO-PAN)对U(Ⅵ)的吸附特性,系统研究吸附温度、初始浓度、吸附时间对AO-PAN吸附U(Ⅵ)的影响。结果表明,随着吸附温度升高,AO-PAN对U(Ⅵ)的吸附量逐渐增加,在343 K温度时吸附量达201.6 mg/g。不同温度条件下随着吸附时间增加,AO-PAN对U(Ⅵ)的吸附量逐渐升高,吸附初始时吸附速率较快,随着吸附逐渐进行吸附曲线逐渐趋于平缓,最终达到吸附平衡。AO-PAN对铀的吸附量随溶液中初始浓度的增加而升高,温度为303 K,溶液中初始铀浓度为500 mg/L时,AO-PAN对U(Ⅵ)的吸附量达305.8 mg/g。此外,AO-PAN对铀酰离子的吸附符合朗格缪尔(Langmuir)模型,吸附热力学分析表明AO-PAN对铀酰离子的吸附是吸热和自发过程,吸附动力学分析表明AO-PAN对铀酰离子的吸附行为遵循准二级动力学模型,吸附速率控制机理分析表明AO-PAN对U(Ⅵ)的吸附初始受颗粒内扩散过程控制,随着吸附不断进行吸附过程逐渐由颗粒内扩散控制变为液膜扩散过程控制。吸附实验结果表明,AO-PAN是一种优良的吸附剂,可以用于吸附废水中U(Ⅵ),吸附过程的模型方程可以用于AO-PAN对U(Ⅵ)吸附过程的分析和计算。

     

    Abstract: 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.

     

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