Precipitation of struvite (MgNH4PO4·6H2O), a slow-release fertilizer, provides a means of recycling phosphorus from wastewater streams. In this work, a method for high-throughput struvite precipitation is developed to investigate the effects of a peptide additive.
What Did We Do?
The reactions occurred in small volumes (300 μL or less of magnesium, ammonium, and phosphate solutions) in a 96-well plate for 45 minutes. The formation of struvite was monitored by fitting absorbance at 600 nm over time to a first-order model with induction time. The impact of struvite seed dosing was also investigated, highlighting the importance of optimization when peptide is present. The composition of the precipitate was confirmed through Fourier-transform infrared spectroscopy, while morphology and crystal size were analyzed through optical microscopy. Finally, the utility of the high-throughput platform was demonstrated with a 25 full factorial design to capture the effects and interactions of: magnesium dose, mixing time, seed dose, pH, and temperature.
What Have We Learned?
The addition of peptide induced significant changes to the yield parameter and formation constant in the model. Crystals grown in the presence of peptide were morphologically different, having a higher aspect ratio than crystals grown in the absence of peptide. Controlling the shape of the crystal may impact the dissolution properties of struvite.
We anticipate that the general technique investigated can be applied to more complex water matrices (e.g. wastewater), with purity investigated spectroscopically or through other high-throughput assays. Future work will focus on identifying the mechanism by which the peptide acts. The use of a sequence-defined peptide paves the way for further developments in favorably modifying struvite formation and growth. With the effects of shADP5 documented, other similar peptides can be explored via either computational simulations or experimentation to modulate the quality and yield of struvite – potentially increasing its value as a fertilizer. Further computational studies also need to be explored to elucidate the exact mechanism by which shADP5 modulates the thermodynamics of struvite crystallization.
Jacob D Hostert, PhD candidate, Case Western Reserve University
Julie N. Renner, Assistant professor, Case Western Reserve University
Corresponding author email address
Olivia Kamlet, undergraduate, Case Western Reserve University
Zihang Su, Postdoctoral scholar, Columbia University
Naomi S. Kane, B.S., Case Western Reserve University
Hostert, J. D.; Kamlet, O.; Su, Z. H.; Kane, N. S.; Renner, J. N. Exploring the effect of a peptide additive on struvite formation and morphology: a high-throughput method. RSC Advances 2020, 10 (64), 39328-39337, Article. DOI: 10.1039/d0ra06637k.
This work was supported by the United States Department of Agriculture (Award No. 2018-68011-28691) and the National Science Foundation (Award No. 1739473).
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