Efficient recovery of gadolinium from magnetic resonance imaging patient urine using a diglycolamide ligand-functionalized sorbent system

Abstract

Gadolinium-based contrast agents are used in more than 30 million magnetic resonance imaging procedures worldwide each year. These gadolinium complexes are excreted in urine and then end up polluting wastewater, leading to gadolinium concentration increase in rivers, known as the ‘gadolinium anomaly.’ Here we studied gadolinium recovery from patient urine using ligand-associated organosilica media impregnated with N,N,N′,N′-tetraoctyl-diglycolamide, a chelating agent traditionally used in separating lanthanides from actinides in nuclear waste applications. Gadolinium-containing urine was acidified with nitric acid and tested in batch and packed bed column experiments. Sorbent media and precipitate solids were analyzed using advanced characterization tools. Results show that more than 85% of the gadolinium was recovered with a 12.8 mg g⁻¹ sorption capacity. A two-cycle column study produced over 99% pure gadolinium through stripping, oxalic acid precipitation, and calcination. A binding mechanism with a 1:3 chelation and matching kinetics for a pseudo-second-order rate model can help design scaled-up systems.