Interfacial Adsorption Behavior of a Structurally Optimized AMP@MIL-101(Cr) Composite for Efficient Rubidium Recovery...

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.