Wei-fan Chu,Zhouzhou Yuan,Peihua Lin,Guan-Ping Jin
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+.
Rubidium (Rb), a critical strategic metal with extensive applications in energy storage, electronics, and nuclear medicine, faces extraction challenges due to its low natural abundance and dispersed occurrence. To address the inefficiency and selectivity limitations of conventional extraction methods, this study synthesized a core-shell composite metal-organic framework (MOF) material, KCoFC@UiO-66, via a solvothermal coordination strategy. The material synergistically integrates the ion-exchange capability of potassium cobalt hexacyanoferrate (KCoFC) with the hierarchical porosity and structural stability of zirconium 1,4-dicarboxybenzene MOF (UiO-66). Structural characterization confirmed the core-shell architecture, where the KCoFC core facilitates selective Rb capture via ion exchange and cyano coordination, while the UiO-66 shell enhances Rb enrichment through electrostatic interactions and size-selective sieving. Adsorption kinetics followed a pseudo-second-order model, indicating chemisorption dominance, while isotherm studies aligned with Freundlich and Dubinin-Radushkevich models, revealing heterogeneous multilayer adsorption. The composite demonstrated remarkable selectivity for rubidium, achieving a recovery rate of 98.7 % from lithium tailing leachates, along with notable regeneration stability, retaining 86.2 % of its capacity after five cycles. This performance can be ascribed to the ability of UiO-66 to inhibit the aggregation of KCoFC and to the effects of pore confinement. This work establishes a multi-mechanistic adsorption paradigm combining ion exchange, electrostatic attraction, and pore confinement, offering a scalable solution for Rb recovery from complex matrices.
A novel composite adsorbent, AMP@MIL-101(Cr), has been successfully synthesized by integrating ammonium phosphomolybdate (AMP) with the metal–organic framework MIL-101(Cr) for the efficient adsorption of rubidium ions (Rb+) from aqueous solutions. The results of structural characterizations confirmed that the crystalline framework of the adsorbent remained intact after Rb+ adsorption, indicating excellent structural stability. Adsorption kinetics, isotherm, and thermodynamics studies revealed that the adsorption process followed a single-layer chemisorption mechanism and was an endothermic reaction and spontaneous adsorption process with negligible influence from solution pH. The adsorbent exhibited a remarkable Rb+ adsorption capacity, reaching 69.4 mg·g–1 within 5 min in a solution containing 250 mg·L–1 Rb+ at 45 °C. In the Nanyi Mountain Oilfield, the adsorption rate of adsorbent for Rb+ (10.69%) exceeded that of other ions (Li+: 0.75%; Na+: 0; K+: 0.95%; Mg2+: 0.67%). Furthermore, the adsorbent still maintained 86.72% of its initial adsorption capacity after 5 consecutive adsorption–desorption cycles. These findings highlighted the great potential of AMP@MIL-101(Cr) as an efficient and stable adsorbent for the selective recovery of rubidium from aqueous environments.
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