Repurposing Non-toxic and Cost-effective Organic Ligancds to Enhance the Removal of Uranium and Thorium From Wastewater

Cheap, effective and industrially practical remediation methods for uranium and thorium are of utmost importance. Electrocoagulation is a cheap but only mildly effective method for the remediation of these elements. It was recently shown that chelating ligands enhance this process. Unfortunately, few ligands have been tested for this enhancement. Of these, the most effective, Alizarin Red S, had a 99.2% uranium removal efficiency but was expensive ($3.6 / g), toxic to humans and environmentally harmful. Therefore, ligands that avoid these downsides are needed before any industrial application can occur. Potential ligands were found via exhaustive searches of MilliporeSigma’s database. Over 3000 ligands were examined ranging from the histological stains (486 potentials) to organic building blocks (>3000 potentials). From these ligands, it was narrowed down on four criteria. The price must be below $2 / 1 gram, non-toxic to humans, environmentally friendly and selectively chelate to uranium or thorium. Four potential ligands were found from the over 3000 which fit all four qualities well. The differences however included the solubility in water, charge and price. Pamoic acid ($1.33 / g) and quercetin ($1.88 / g) are neutral molecules with low water solubility. Acid blue 40 ($1.6 / g) contains a single negative charge and Acid blue 80 ($1.5 / g) and contains two negative charges. Both have excellent water solubility due to their ionic charges. Herein, we effectively found four potential ligands for use in the removal of uranium or thorium from water via ligand enhanced electrocoagulation.