Fast and high-capacity adsorption of Rb+ and Cs+ onto recyclable magnetic porous spheres

- Recyclable magnetic porous spheres were prepared from O/W Pickering emulsion.
- The s magnetic porous pheres show homogeneous and regular pore structure.
- The spheres have the adsorption capacities of 310 mg/g for Rb+ and 448 mg/g for Cs+.
- The spheres are easy to be separated from solution and regenerated for reuse.

A novel recyclable magnetic porous sphere adsorbent is prepared by grafting acrylic acid (AA) onto hydroxypropyl cellulose (HPC) through a Pickering emulsion integrated precipitation polymerization and used for the enrichment of scattered strategic metals Rb+ and Cs+. The modified Fe3O4 nanoparticles can not only stabilize the Pickering emulsion template for forming pores, but also make the adsorbent easy to be separated from solution by magnetic field. The adsorption results indicate that the adsorption of Rb+ and Cs+ by the sphere adsorbent rapidly reaches equilibrium within 15 and 30 min, respectively. The saturated adsorption capacities reach 310 and 448 mg/g for Rb+ and Cs+, respectively, which are better than that reported in most of literatures. Fourier transform infrared spectra (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses confirm that the chemical complexation of -COO− and -OH with Rb+ and Cs+ contribute mainly to the adsorption. In addition, the adsorbent is very easy to be recovered and regenerated, and the adsorption capacity does not decrease significantly even after five consecutive adsorption-desorption cycles, as compared with the initial adsorption capacity. The results of dynamic adsorption experiments show that the flow rate, initial ion concentration and column height have an effect on the adsorption capacities of Rb+ or Cs+. In a word, this recyclable sphere adsorbent is promising to be used for the efficient adsorption and enrichment of rare metals.

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