INFEWS N/P/H2O: Chemical and structural transformations at low solubility magnesium mineral-wastewater interface during struvite formation and growth

Lehigh University, Bethlehem PA

Investigators

Abstract

In this project funded by the Environmental Chemical Sciences program in the Division of Chemistry, Professor Jonas Baltrusaitis and his students study reactions of magnesium-containing, low solubility mineral surfaces with aqueous ammonium and phosphate ions from model wastewater streams. The goal is to develop new, highly efficient nitrogen (N) and phosphorus (P) immobilization routes for use of these minerals as slow release fertilizers. The project utilizes readily available magnesium-containing minerals (e.g., magnesium oxide, magnesium carbonate, dolomite and serpentinite) as substitutes for low abundance, high solubility magnesium chlorides and sulfates that are currently used. Outcomes of this work are expected to guide the development of nutrient recovery and recycling systems by providing fundamental understanding of mineral surface chemistry. Thus, this project addresses critical challenges of adequately managing nutrients at the nexus of food, energy and water. The project provides training opportunities for graduate and undergraduate students in the areas of surface science and environmental catalysis. Furthermore, the principal investigator actively participates in efforts to promote understanding of environmental science research in the local community via the Lehigh University Summer Engineering Institute and Summer CHOICES Engineering Camp. This project uses spectroscopic techniques to investigate reactive surface intermediates and products under diffusion-limited conditions on single crystal surfaces. This provides information on the detailed reaction kinetics, solid surface transformation and growth mechanisms, and insights into the nature of reactive sites. Iron- and calcium-doped MgO nanoparticles are synthesized in the laboratory. Ammonium and phosphate ion adsorption from aqueous solutions is performed to monitor the growth of slow nutrient release fertilizer mineral, such as struvite or hydroxyapatite, under interface limited conditions. Model magnesium mineral surfaces, their growth, and adsorption are characterized using Raman and diffuse reflectance infrared spectroscopy. Structural surface details of the synthesized MgO nanoparticles are interrogated using X-ray photoelectron spectroscopy and high resolution transmission electron microscopy. Growth kinetics of slow nutrient release fertilizer materials from ammonium and phosphate containing model wastewater solutions is measured using ion chromatography.