Investigating the crystallization pathways of struvite using in-situ liquid-phase and cryogenic transmission electron microscopy

• Applicant: Helen Freeman, Ph.D.
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 389508713

Natural supplies of phosphorus are depleting worldwide and rock phosphorous is considered a critical resource. This situation has led to the exploration of new methods to extract phosphorus from alternative sources. One such abundant resource of phosphate is in municipal and industrial wastewaters where phosphorous is abundant and can be extracted via crystallization of the mineral struvite (magnesium ammonium phosphate). Struvite can then directly be used in fertilizers, thus helping to conserve finite phosphorus resources. However, the efficiency of this recovery process depends on an improved understanding of struvite crystallisation mechanisms and pathways. Only with such knowledge will the recovery of phosphate from wastewater be efficient and the environmental impact of phosphorous on the aquatic environment and the demand on phosphorus resources be reduced.The formation of struvite from aqueous media has been studied before, but mostly via non-direct methods which have been proven to suffer from various artefacts. Thus an efficient and simple mechanistic understanding of the process is still lacking. I propose here to use a combination of in-situ liquid-phase and cryogenic transmission electron microscopy to follow in real time all the crystallisation stages of struvite from initial ions to final solids. Recent advances in both techniques have improved our knowledge in nucleation and growth, but never before have they been applied to the same system. Together, liquid-phase and cryogenic transmission electron microscopy can be used to derive highly dynamic (both at high temporal and spatial resolution) information through imaging and micro-spectroscopic analyses of a process as it unfolds. With this science network I aim to bring together world class experts in liquid-cell and cryo technologies and processes and apply them to gain a better understanding of the crystallisation pathways of struvite.

• DFG Programme: Scientific Networks