Efficient Separation and Enrichment of Rubidium in Salt Lake Brine Using High-Performance PAN-KCuFC-PEG Adsorption Composite

Salt lake brine contains abundant rubidium resources; however, the separation of rubidium from brine with a high K content remains a significant challenge in metallurgical processes and materials science. In this study, PAN-KCuFC-PEG particles were synthesized by phase transformation, using hydrophilic polyacrylonitrile (PAN) as the skeleton structure, potassium cupric ferricyanide (KCuFC) as the active component and water-soluble polymer polyethylene glycol (PEG) as the pore regulator. Characterization revealed that the addition of PEG increased the pore volume of PAN-KCuFC-PEG by 63% and the BET surface area by 172%. KCuFC powder was uniformly dispersed in PAN-KCuFC-PEG, and its crystal structure remained stable after loading. In static adsorption experiments, the maximum adsorption capacity of PAN-KCuFC-PEG for Rb+ reached 190 mg/g. The adsorption behavior followed a pseudo-second-order kinetic model, with the rate jointly controlled by external diffusion, intraparticle diffusion, and chemical reaction. In the column experiment, PAN-KCuFC-PEG was used to adsorb Qarhan Salt Lake brine (K: 26,000 mg/L, Rb: 65 mg/L). NH4Cl was employed for elution and desorption of PAN-KCuFC-PEG. During the adsorption–desorption process, the separation factor between Rb and K reached 160, the desorption rate reached 96.6%, and the overall yield was 68.3%. The enrichment and separation of Rb were successfully achieved.