坡缕石对Sr(Ⅱ)的吸附热力学研究

Thermodynamic Study on Adsorption of Sr(Ⅱ) on Palygorskite

  • 摘要: 采用静态吸附法研究了坡缕石对水溶液中Sr(Ⅱ)的吸附热力学特征,并考察了时间、溶液pH值和离子强度对吸附效果的影响。结果表明:Sr(Ⅱ)在坡缕石上的吸附受pH值和离子强度的影响明显;坡缕石对Sr(Ⅱ)的吸附主要通过表面络合和离子交换进行;吸附过程符合Lagergren准二级速率方程;吸附等温线符合Freundlich和D-R模型,升高温度有利于吸附反应的进行;热力学参数ΔH°、ΔS°和ΔG°的计算结果表明,坡缕石对Sr(Ⅱ)的吸附是自发进行的吸热反应。

     

    Abstract: The adsorption thermodynamics of Sr(Ⅱ) on palygorskite in aqueous solutions was investigated. In addition, the effects of contact time, ionic strength and pH were also investigated by static adsorption method. The results indicate that the adsorption of Sr(Ⅱ) on palygorskite is strongly affected by pH and ionic strength, and the ion exchange and surface complexation are the main adsorption mechanisms in the adsorption process. The adsorption kinetics of Sr(Ⅱ) on palygorskite can be described by Lagergren pseudo-second reaction rate model very well. The adsorption isotherm is fitted well by Freundlich and D-R models. Raising temperature is beneficial to adsorption reaction. The thermodynamic parameters, such as enthalpy (ΔH°), entropy (ΔS°) and Gibbs free energy (ΔG°) were calculated using adsorption equilibrium constant obtained from the Langmuir isotherm. The results indicate that the adsorption of Sr(Ⅱ) on palygorskite is a spontaneous and endothermic process.

     

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