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

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.