Preparation of polysulfone based rubidium ion imprinted membrane and its selective adsorption and separation performance

A novel Rb⁺ imprinted membrane was fabricated via non-solvent inversion phase separation method by blending template RbCl, poly(styrene-co-4-hydroxylstyrene) (P(S-co-VPh)) and polysulfone, where the phenolic hydroxyl groups of P(S-co-VPh)) spontaneously coordinated with template Rb⁺ in the casting solution to form an imprinted Rb⁺ site. Gel permeation chromatography, FTIR and ¹H NMR results indicated that the (P(S-co-VPh) had been synthesized successfully. The characterization of water contact angle, scanning electron microscope and membrane performance tests indicated that the blending membranes had better hydrophilicity, more porous structure and higher pure water flux. The adsorption behaviors of Rb⁺ on the blending membranes were investigated depending on the parameters of solution pH, temperature, ions interference, Rb⁺ concentration and contact time. The results indicated that the maximum Rb⁺ adsorption capacity can be obtained when the solution pH is 9.0, and low temperature is favorable for adsorption because it is an exothermic process. As compared to Na⁺, Ca²⁺, and Mg²⁺, K⁺ has the greatest ion interference effect, causing up to 58.1% decline in Rb⁺ adsorption capacity for non-imprinted membranes but only 7.4% for imprinted membranes. The adsorption process conforms to Langmuir isothermal model and pseudo-second-order kinetic model, and the theoretical maximum adsorption of Rb⁺ is 70.12 mg/g. Furthermore, the Rb⁺ imprinted membrane can be reused at least five times using 0.1 M HCl solution as the eluent, indicating that membrane has potential application value in the separation and extraction of rubidium.