Lanthanides diffusion through pH-responsive reverse osmosis membranes

ABSTRACT

The adsorption of some lanthanides in the trivalent state, namely trivalent Ce, Pr, Sm, Gd, Dy, and Ho, was identified onto polyacrylamide zirconium titanosilicate (PAm-ZTS) composite membranes. Numerous opportunities for reverse osmosis-type separations involving organics that might become practical as suitable membrane systems became available. A theoretical framework for analysis of experimental data in terms of fundamental parameters was developed, to study the effect of the transport of the solute and solvent in the polymer membrane. Different theoretical modeling approaches were tested; Langmuir and Freundlich models appeared to have various regressions, so that Langmuir model was taken as the best fit theoretical model. During the polymer enhanced ultrafiltration, the tested retained lanthanides were ordered as Ce⁴⁺ > Pr³⁺ > Sm³⁺ > Gd³⁺ > Dy³⁺ > Ho³⁺. Upon competing conditions, the Q_max values were decreased to nearly 50%.

Keywords:

• Adsorption
• Reverse osmosis
• Lanthanides
• Diffusion
• Solvent and pressure
• Isotherms