A magnetic adsorbent with metal-organic framework based on ammonium phosphomolybdenum heteropoly tungstate (AWP): Selective adsorption of Rb+ and Cs+ from aqueous resources and stripping with ammonium salts

In the process of in situ synthesis of the metal-organic framework ZIF-8, the active component ammonium phosphomolybdenum heteropoly tungstate (AWP) was introduced and magnetized to obtain a composite magnetic adsorbent (Fe3O4@ZIF-8@AWP). The adsorption isotherms of Fe3O4@ZIF-8@AWP on Rb+ and Cs+ conform to the Langmuir model, with maximum adsorption of 0.78 and 0.85 mmol g−1 of Rb+ and Cs+, respectively. The ion exchange mechanism of Rb+ and Cs+ adsorption was elucidated in detail by experimental data and characterization analysis. Remarkably, the adsorbent can retain more than 86% of the adsorption capacity after 5 consecutive adsorption-desorption cycles. In addition, the developed adsorbent has good saturation magnetization (54.3 emu g−1) and can be quickly and easily separated from Rb+ and Cs+ solutions after the adsorption process. The adsorbent can be used for the adsorption of Rb+ and Cs+ from Nanyi Mountain oil field brine which indicates that it has good prospects for application in separation of Rb+ and Cs+ from liquid resources in the future.