EGU2020-21866
https://doi.org/10.5194/egusphere-egu2020-21866
EGU General Assembly 2020
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

In situ AFM imaging of dissolution and growth of struvite surface

Aikaterini Vavouraki1, Helen King2, Christine Putnis3,4, and Petros Koutsoukos5,6
Aikaterini Vavouraki et al.
  • 1Technical University of Crete, School of Mineral Resources Engineering, GREECE, Greece (avavouraki@isc.tuc.gr)
  • 2Department of Earth Sciences, Utrecht University, Netherlands
  • 3Institut für Mineralogie, Universität Münster, Münster, Germany
  • 4The Institute for Geoscience Research (TIGeR), Department of Chemistry, Curtin University, Perth, Australia
  • 5Department of Chemical Engineering, University of Patras, Patras, Greece
  • 6Institute of Chemical Engineering & High Temperature Chemical Processes, Patras, Greece

Phosphorus removal from wastewaters is a great interest to avoid eutrophication of natural waters (i.e. rivers, lakes). Additionally phosphorus recovery is also important due to increasingly limited nutrient resources. Struvite (MgNH4PO4*6H2O) is of current interest as it is considered an alternative way for water remediation and potential use as a renewable fertilizer. Towards environmental sustainability, phosphorus and nitrogen removal and recovery from domestic, industrial, and/ or agricultural inputs, in the form of struvite may be an attractive alternative for the valorization of wastewaters (Mpountas et al., 2017).

Direct observations of crystal dissolution and growth process at the nano- level are possible through the use of Atomic Force Microscopy (AFM). A considerable number of studies have investigated mineral dissolution and growth by in-situ AFM imaging in a fluid-cell (Vavouraki et al., 2008; 2010). These direct observations and measurements allow the investigation of possible process mechanisms at the mineral-solution interface. Previous study on AFM imaging indicated struvite micro- to nanocrystal morphology. Hövelmann & Putnis (2016) investigated the interactions of ammonium-phosphate solutions with brucite (Mg(OH)2) cleavage surfaces by AFM suggesting coupled brucite dissolution and struvite precipitation at the mineral-fluid interface. To the best of our knowledge, there are no records of nanoscale observations of dissolution and/ or growth of struvite surfaces. The aim of this study is to perform in situ AFM experiments using freshly cleaved struvite surfaces at flow conditions. Step retreat and/ or etch pit spreading were observed. Dissolution rates of struvite using doubly deionized water at different pH values were determined  whereas growth rates at different saturation values and pH using magnesium and ammonium-phosphate bearing solutions were also measured . Raman and SEM analyses were carried out to assess chemical structure and morphology of the obtained struvite crystals before and after AFM experiments.

Acknowledgments: The work has been supported by IKY-DAAD (2018-4) and KRHPIS II (Action PERAN).                                                                                

References: Hövelmann & Putnis, 2016. Env. Sci. Technol. 50, 13032−13041; Mpountas et al., 2017. J. Chem. Technol. Biotechnol. 92, 2075–2082; Vavouraki et al., 2008. Chem. Geol. 253, 243–251; Vavouraki et al., 2010. Cryst. Growth Des. 10, 60–69.

How to cite: Vavouraki, A., King, H., Putnis, C., and Koutsoukos, P.: In situ AFM imaging of dissolution and growth of struvite surface, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21866, https://doi.org/10.5194/egusphere-egu2020-21866, 2020.

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