Europium adsorption by granulated Cr-MIL-PMIDA metal−organic frameworks and dynamic fixed bed column modelling

Cr-MIL-PMIDA adsorbent exhibits high selectivity for Rare Earth Elements (REE) over competing transitional metals. However, shaping of this highly efficient material is necessary for industrial applications. Therefore, this paper focuses on the treatment of mining wastewater using a dynamic column adsorption process. In this study, Cr-MIL-PMIDA was successfully granulated for the first time using alginic acid and CaCl2. Divalent calcium ions (Ca2+) acts as the cross-linking agent with carboxyl groups, enabling the encapsulation of Cr-MIL-PMIDA powder and controlled release. The prepared material was characterised using XRD, SEM and FTIR measurements to validate successful granulation. Adsorption capacity of powdered Cr-MIL-PMIDA of 56.01 mg/g decreased to 31.05 mg/g after granulation due to reduction of surface area and pore volume. However, granulated Cr-MIL-PMIDA recorded only an 8 % reduction in selectivity towards Eu in a multi component solution compared to the powdered state. The material exhibited the ability to be reused for five cycles while maintaining over 90 % of its initial adsorption capacity. Furthermore, this study demonstrates that the dynamic column model developed for a novel granulated Cr-MIL-PMIDA can be reliably utilized to design industrial-scale systems for resource recovery from mining wastewater with a single adsorption column experiment.