Electrochemical Struvite Precipitation Enhanced by an Amelogenin Peptide for Nutrient Recovery

Precipitation of struvite (MgNH4PO4 center dot 6H2O) from wastewater is a promising method for recycling phosphorous, which results in a slow-release fertilizer and improves wastewater treatment costs. While chemical struvite precipitation is commercialized, electrochemical precipitation can improve the process from an energy and materials standpoint. However, new methods are needed to increase electrochemical recovery at pH values near typical wastewater conditions (6-9). Here, a surface-bound amelogenin peptide was explored in a model electrochemical system to control struvite growth at neutral pH. Molecular dynamics simulations indicated that the peptide enables favorable Mg2+ conformations, which facilitate struvite crystallization. Chronoamperometric studies conducted with a range of immobilized peptides in synthetic wastewater at pH 7.1 produced precipitates characterized as struvite. Peptides loaded onto a gold mesh at a concentration of 19 mu g mL-1 led to a 21% increase in struvite precipitation. Longer crystals formed in the presence of surface-bound peptide compared to when no peptide was present, showing that dendritic crystal growth can be achieved at neutral pH. The peptide does not appear to bind to struvite, maintaining struvite purity. Our findings show the viability of electrochemical struvite precipitation for relevant wastewater pH values and highlights how peptides can modulate crystal growth.