Recovery of Rubidium Using Hydrogel Beads Encapsulating Potassium Copper Hexacyanoferrate from Saline Lake Brines

A handy hydrogel bead adsorbent of graphene oxide/poly(vinyl alcohol)/sodium alginate/carboxymethyl cellulose encapsulating potassium copper hexacyanoferrate (KCuFC) was fabricated via injection devices (GPSC-KCuFC), which can be employed for recovering rubidium (Rb) resources from saline lake brines. The successful loading of KCuFC on GPSC was substantiated by the microstructure observed using scanning electron microscopy, the chemical composition derived with Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, and the lattice structure analyzed by X-ray diffraction. Depending on diverse pH values, adsorption times, temperatures, initial concentrations, and types of competing ions, batch tests were carried out. The GPSC-KCuFC has been shown to acquire a maximum adsorption capacity of 242.91 mg/g for Rb+ at 45 °C with pH = 8, and the Langmuir isotherm model can explain the adsorption behavior. Likewise, the process of Rb+ adsorption is in accordance with the pseudo-second-order model, while manifesting the three-stage intraparticle diffusion model. The GPSC-KCuFC exhibits remarkable reusability as evidenced by five adsorption–desorption cycles. Besides, the GPSC-KCuFC shows promising selectivity for Rb+ adsorption from saline lake brines. Subsequently, anion exchange membrane electrolysis can derive a higher purity solution of Rb+.