纳滤膜对稀土离子的动态吸附行为及截留特性

The dynamic adsorption behavior and retention characteristics of rare earth ions by nano-filtration membrane

  • 摘要: 采用经碳纳米管改性的亲水化纳滤膜浓缩提取稀土浸出液中的稀土离子,探究纳滤膜表面对La3+、Nd3+、Pr3+、Ce3+和Y3+5种稀土离子吸附动力学行为,考察稀土离子半径的大小对纳滤膜吸附性能和截留性能的影响.结果表明,Freundlich吸附方程比Langmuir方程能更好地描述稀土离子在纳滤膜表面上的动态吸附行为,用Freundlich吸附方程拟合后的结果相关度系数R2能达到0.999以上;在初始浓度为5×105 μg/L,温度为25 ℃,运行压力为0.6 MPa的实验条件下,纳滤膜对稀土离子的浓缩提取过程中,初始阶段的截留机理取决于纳滤膜表面的吸附作用和膜孔的机械筛分效应,膜面吸附达到平衡后以膜孔的机械筛分效应为主,此时La3+、Nd3+、Pr3+、Ce3+和Y3+的截留率分别为94.21 %、81.25 %、85.80 %、89.90 %和81.18 %,表明经碳纳米管改性的亲水化纳滤膜能高效浓缩截留稀土浸出液中的稀土离子.

     

    Abstract: The concentration of rare earth ions in the rare earth leaching solution was reduced by using the hydrophilic nanofiltration membrane modified by carbon nano-tubes. The adsorption kinetics of La3+, Nd3+, Pr3+, Ce3+and Y3+ rare earth ions on the surface of nano-filtration membrane was investigated. The effects of the radius of rare earth ion on the adsorption and retention properties of nano-filtration membrane were also explored. The experimental results show that the Freundlich adsorption equation is better than Langmuir equation to describe the dynamic adsorption behavior of nano-filtration membrane on rare earth ions. The correlation coefficient R2 of the fitting results are above 0.999. Under the condition of initial concentration of 5×105 μg/L, temperature of 25 ℃ and operating pressure of 0.6 MPa, the retention of rare earth ions in the initial stage was characterized by membrane surface adsorption and mechanical sieving effect of the membrane pore, the adsorption to achieve the balance of the mechanical effect of the membrane pore-based. The rejection ratios of La3+, Nd3+, Pr3+, Ce3+ and Y3+ were 94.21 %, 81.25 %, 85.8 %, 89.90 % and 81.18 % respectively, which indicated that hydrophilic nano-filtration films modified by carbon nanotubes could be highly effective concentration of rare earth ions in REE leaching solution.

     

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