Phosphate Recovery by a Surface-Immobilized Cerium Affinity Peptide

Cerium oxide/hydroxide adsorbents have emerged as promising phosphate removal materials due to their excellent performance and stability. In this study, an engineered cerium affinity peptide immobilized on a metal surface was utilized to synthesize a novel, nanoscale, and bio-enabled phosphate adsorbent. The goal of this work was to characterize the binding of phosphate and potential competing ions to the novel material, demonstrating the potential utility of the engineered peptide in biotemplating applications. Phosphate binding and competing ion binding with time were investigated via a quartz crystal microbalance with dissipation (QCM-D). Kinetic modeling of the QCM-D data revealed that the bio-enabled material facilitated strong phosphate adsorption behavior in a wide pH range of 3–7. Changing the media from simple phosphate solutions to more complex synthetic wastewater solutions did not negatively impact the observed binding constants. The main phosphate adsorption mechanism likely followed a ligand exchange process, with enhanced adsorption achieved by increasing the number of surficial hydroxide groups. The strong binding behavior observed with phosphate was not observed when the material was exposed to common competing ions. Overall, this study presents a sequence-defined peptide as a promising tool for the engineering of advanced phosphate capture materials.