Fabrication of hypercrosslinked hydroxyl-rich solid phase extractants for cesium separation from the salt lake brine

In this work, two hypercrosslinked hydroxyl-rich polymers (HCP-P and HCP-R) were facilely prepared through a one-pot Friedel-Crafts polymerization of phenol, resorcinol and formaldehyde dimethyl acetal, respectively. HCP-P and HCP-R were investigated for their ability to separate Cs+ from the salt lake brine via ion-exchange reaction between Cs+ and O−Na+. The Cs+ adsorption isotherms of HCP-P and HCP-R follow the Langmuir model, and their adsorption capacities reach 249.64 mg g−1 and 259.97 mg g−1, surpassing most of commercial materials like AMP-PAN (81 mg g−1) and TAM-5 (191.8 mg g−1). The Cs+/K+ separation factors (S.F.) of HCPs can reach 12.4 even in the presence of high concentrations of K+ (C(K+)/C(Cs+) = 712.5). Notably, HCPs could retain more than 90% of the adsorption capacities after 5 successive adsorption-desorption cycles. Besides, X-ray photoelectron spectroscopy (XPS), FT-IR spectra and TEM-EDS analysis revealed the ion exchange mechanism of the Cs+ adsorption process. This work demonstrated the excellent application potential of hypercrosslinked hydroxyl-rich polymer adsorbents in separating Cs+ from the salt lake brine.