Rare earth elements (REEs), particularly lutetium (Lu) and yttrium (Y), are increasingly vital in green energy technologies such as super-magnets, fluorescent lighting, optical glasses, and catalysts in oil refining. Their growing demand, coupled with supply constraints due to geopolitical factors—especially China’s export restrictions—has elevated their status as critical raw materials. This has prompted global efforts to secure sustainable recovery methods from industrial waste streams. Among various techniques, adsorption stands out for its simplicity, low cost, reusability, and high selectivity in recovering trace REEs from acidic solutions. In this study, two advanced adsorbents were developed: 1,4-phthaloyl diamido-propyltriethoxysilane (1,4-PA-APTES)-functionalized SBA-15 and N-(phosphonomethyl) iminodiacetic acid (PMIDA)-modified MIL-101(Cr). The former is a mesoporous silica material with tunable surface chemistry, while the latter is a chromium-based metal-organic framework (MOF) known for its exceptional surface area and functional versatility.
The synthesis of functionalized SBA-15 began with hydrothermal preparation of the parent mesoporous silica using tetraethyl orthosilicate (TEOS) and P123 as a structure-directing agent. After calcination to remove surfactants, the material was modified via grafting of 1,4-PA-APTES ligands through a reaction between APTES and terephthaloyl dichloride in dry toluene. This introduced amide and amine groups capable of chelating REE ions. For MIL-101(Cr), Cr(NO₃)₃·9H₂O and 2-aminoterephthalic acid were used to form the MOF precursor Cr-MIL-NH₂, which was then functionalized with PMIDA using DCC as a coupling agent.284028-89-3 Biological Activity The resulting MIL-101-PMIDA exhibited enhanced affinity for Lu and Y due to the presence of phosphonic and carboxylic acid groups that act as strong coordination sites for trivalent REE cations.
Characterization confirmed structural integrity and successful modification. XRD analysis revealed the retention of hexagonal symmetry in SBA-15 after functionalization, although peak intensity decreased due to pore blocking. In contrast, MIL-101-PMIDA displayed sharp diffraction peaks at 5.0°, 9.0°, and 16.5° 2θ, confirming its crystalline structure. FTIR spectra showed new absorption bands at ~1500 cm⁻¹ and ~2900 cm⁻¹ corresponding to N–H vibrations, and peaks at ~1600 cm⁻¹ (C=O stretch) and ~900 cm⁻¹ (P–OH and –PO₃H₂), confirming the presence of PMIDA. Nitrogen adsorption-desorption isotherms indicated significant changes in porosity: BET surface area dropped from 810 m²/g (SBA-15) to 510 m²/g (1,4-PA-SBA), while MIL-101-PMIDA maintained a high surface area of 1050 m²/g with a narrow pore size distribution (mean diameter 1.99 nm), indicating effective preservation of microporosity despite functionalization.
Batch adsorption experiments were conducted at pH 5.0 ± 0.2, optimal for REE speciation and minimal hydrolysis. Initial results showed negligible adsorption on pristine SBA-15, but after modification, Langmuir maximum capacities reached 17.0 mg/g for Lu and 17.9 mg/g for Y. In comparison, MIL-101-PMIDA achieved much higher capacities—63.4 mg/g for Lu and 25.3 mg/g for Y—demonstrating superior performance attributed to its larger surface area and abundant phosphonic groups. Equilibrium data fitted well to Langmuir, Freundlich, and Sips models (R² > 0.96), indicating monolayer adsorption and favorable interactions. Notably, Lu exhibited greater affinity than Y, likely due to stronger ion exchange with phosphonic acid groups.
Kinetic studies revealed faster uptake on MIL-101-PMIDA, achieving 96% removal within 120 minutes versus only 69% for 1,4-PA-SBA.CST2 Antibody web Pseudo-second-order and surface diffusion models provided excellent fits (R² = 0.PMID:34894201 99), suggesting chemisorption-dominated kinetics and surface-controlled diffusion. The surface diffusion coefficient (Ds) and film mass transfer coefficient (ks) derived from numerical simulations enabled predictive modeling under varying conditions.
Regeneration tests over five cycles demonstrated robust reusability. Both adsorbents retained over 90% of their initial capacity after repeated acid desorption (0.1 M HCl) and base reactivation (0.1 M NaOH), highlighting excellent structural stability. This resilience supports long-term application in industrial wastewater treatment systems.
In conclusion, functionalized MIL-101(Cr)-PMIDA emerges as a highly efficient, reusable adsorbent for selective recovery of Lu and Y from aqueous solutions. Its combination of high surface area, tailored functional groups, and excellent regenerability makes it a promising candidate for scalable resource recovery technologies. These findings contribute significantly to advancing circular economy strategies for rare earth elements, reducing dependency on primary mining, and enabling sustainable utilization in emerging green technologies.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com