Fabrication and performance of the ammonium molybdophosphate/polysulfone mixed matrix membranes for rubidium adsorption in aqueous solution

Abstract

The separation of the rare and precious metal rubidium is still a challenge to hydrometallurgy and material science. A novel ammonium molybdophosphate (AMP)/polysulfone (PSf) mixed matrix membrane for rubidium adsorption and separation was prepared successfully by NIPs method via immobilizing AMP into the PSf porous membrane. FTIR, XRD, SEM tests indicate that AMP is embedded into the PSf matrix, and its crystalline structure remains intact. WCA tests show that the membrane surfaces are more and more hydrophilicity with the AMP blending content increasing. The fluxes increase approximately linearly from 210.2 to 370.2 L m À2 h À1 with the AMP content while the bovine serum albu rejections decrease from 97.8% to 88.5%. The Rb + adsorption capacities of the membranes studied as a function of contact time, pH, Rb + concentration, temperature, presence of various interference ions, and the Rb + capacity is up to 98.4 mg g À1 at the optimal adsorption conditions. The Rb + adsorption on the AMP/PSf porous membrane complies with Langmuir adsorption isotherms and pseudo-second-order kinetic model. Finally, the reusability in Rb + adsorption of the AMP/PSf porous membrane is investigated, and the recovery rate can still be maintained above 95% after five adsorption-desorption recycles.

Efficient Selective Adsorption of Rubidium and Cesium from Practical Brine Using a Metal–Organic Framework-Based Magnetic Adsorbent

“…With comparison of pseudo-first-order, pseudo-second-order linear, and nonlinear fitting parameters, as can be seen from Tables S2 and S4, the correlation coefficient ( R 1 2 ) of the pseudo-first-order kinetic model ranges from 0.885 to 0.971, and the correlation coefficient ( R 2 2 ) of the pseudo-second-order kinetic model ranges from 0.997 to 0.999. The results show that the adsorption system conforms to the pseudo-second-order kinetic model and the adsorption process belongs to chemisorption process. , …”

“…Moreover, the n value calculated by the Hill model (0.553) shows that the number of Rb + and Cs + adsorbed at each adsorption site on Fe 3 O 4 @ZIF-8@AMP surface is 0.553. 52 These results indicate that the adsorption mechanism of Fe 3 O 4 @ZIF-8@AMP on Rb + and Cs + is monomolecular layer adsorption. 53 A comparison of the adsorption capacity of Fe 3 O 4 @ZIF-8@ AMP with similar adsorbents in the literature is shown in Table S12.…”

“…This suggests that both three-parameter Redlich–Peterson and Hill isotherms are close to the Langmuir isotherm model, which is consistent with the results of the two-parameter isotherm analysis. Moreover, the n value calculated by the Hill model (0.553) shows that the number of Rb + and Cs + adsorbed at each adsorption site on Fe 3 O 4 @ZIF-8@AMP surface is 0.553 . These results indicate that the adsorption mechanism of Fe 3 O 4 @ZIF-8@AMP on Rb + and Cs + is monomolecular layer adsorption …”

“…The results show that the adsorption system conforms to the pseudo-second-order kinetic model and the adsorption process belongs to chemisorption process. 51,52 The results of fitting parameters obtained by combining the five adsorption kinetics models show that for the adsorption of Rb + and Cs + , the phase relation values decrease from pseudosecond-order, in-particle diffusion, Elovich, and pseudo-firstorder equations to Boyd equation, indicating that the adsorption process depends on both the surface properties of the adsorbent and the solute concentration. 47,48 The rate control step may involve chemisorption between Rb + /Cs + and Fe 3 O 4 @ZIF-8@ AMP.…”

“…The experimental data were analyzed based on experimental data and fitted by Langmuir, Freundlich, Temkin, Redlich− Peterson and Hill models. 45,46,50,52 The forms of Langmuir and Freundlich empirical equations are expressed as where q e (mmol g −1 ) is the amount of adsorption when the adsorbent reaches equilibrium and C e (mmol L −1 ) is the equilibrium concentration of the solution when the adsorbent reaches equilibrium. q m is the maximum monolayer adsorption (mmol g −1 ).…”