The overabundance of phosphate ions (HPO42-) in environmental systems can lead to eutrophication and the hyper-production of algae, which can ultimately modify aquatic ecosystems. This project utilizes the coordination chemistry of gadolinium (Gd) complexes to capture phosphate ions from water. Lanthanide ions, such as Gd, typically have 8-10 coordination sites. So, when chelated by hexadentyl tripodal ligands, like Gd-Tren-MAM and and Gd-Tren-HOPO, open coordination sites remain to bind phosphate. As Gd complexes alter the relaxation time of bound water molecules, phosphate binding can be investigated by measuring longitudinal (T1) relaxation times via Nuclear Magnetic Resonance Spectroscopy. Several ligands are investigated to optimize phosphate binding, ensure the selective binding of phosphate, and achieve a reversible phosphate binding that is pH dependent. Once the phosphate has been bound at neutral pH, its release upon exposure to an acidic solution is evaluated. The thermodynamics and pH dependence of phosphate binding is determined along with the stability of the metal complex. Ultimately, phosphate binding Gd-complexes can be incorporated into a membrane designed to capture phosphate from water systems, and the released phosphate can be repurposed to make a fertilizer.

Gadolinium complexes for catch-and-release of phosphates

253rd National Meeting (2017)

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