New insights into chelator recycling by a chelating resin: From molecular mechanisms to applicability

As part of the project of developing a "green" and highly feasible soil remediation process, recycling an eco-friendly chelating agent, glycine, using Chelex-100 chelating resin, was studied. Two model complexes, copper and nickel glycinates, were tested under various conditions, including equivalent viscosity but different temperature conditions. Two similar complexes demonstrated very different reactivity towards Chelex-100. An in-depth study led to the discovery of unusual metal-dependent mechanisms of the complex-to-resin metal transfer. Particularly, nickel transfer proceeds via a dissociative mechanism, whereas copper transfer does not require pre-dissociation of the complexes, and proceeds via the associative ligand-exchange mechanism. Both processes result in the recovery of the used chelator. The glycine solution was applied on the spiked soil, then recovered on Chelex-100 resin and successfully reused, thus demonstrating a proof of the concept. These findings contribute to the science, strategies, and methodology of both water purification and chelator recycling fields.