M. Sc. Rebecca Volkmann

PhD Student
M. Sc. Rebecca Volkmann
Building A 71, Room 226
Telegrafenberg
14473 Potsdam

Function and Responsibilities:

Doctoral student in the Interface Geochemistry section 3.5

Co-maintainer of X-ray diffractometry lab of Interface Geochemistry Section 3.5

GeoGraduate representative GFZ Potsdam

First aid worker Interface Geochemistry Section 3.5

Research Interests:

In my doctoral project I investigate the nucleation and growth kinetics of the phosphate mineral struvite (MgNH4PO4*6H2O). Struvite occurs in sewage sludge systems, guano-rich soils, and in human and animal kidney stones (so-called infectious stones). Previous studies investigated the formation conditions of struvite, particularly in wastewater, to avoid clogging pipelines and to recover the precipitates to use as phosphorus- and nitrogen-rich fertilizer.

I am studying nucleation and crystal growth in the pure (NH4)2HPO4 - MgCl2*6H2O system with UV-Vis turbidity measurements and monitoring of pH during struvite synthesis in solution. Little is known about the temperature dependence of formation, so I perform the experiments at various temperatures in the low-temperature range.

Under atmospheric conditions, struvite is unstable and transforms in air into the phases newberyite (MgPO3(OH)*3H2O) and dittmarite (MgNH4PO4*H2O). Using ex-situ X-ray diffraction (XRD) of powder samples and Rietveld analyses, I determine the kinetic rates of this process and the influence of temperature. Optical microscopy and Raman spectroscopy of single crystals gives me information about textural relationships transformation phases to struvite. For the use as fertilizer, knowledge about the transformation of struvite is important, since nitrogen is lost in the process.  For further information see also struvite crystallization.


Career:

2020 - recent: PhD student, section 3.5, German Research Centre for Geosciences Potsdam

2017 - 2020:    Research assistant, petrology working group, Ruhr University Bochum

2017:                 Student assistant, petrology working group, Ruhr University Bochum

Education:

2017 - 2020:  M.Sc. Geosciences, majoring petrology, Ruhr University Bochum

                          Topic of master's thesis: "Carbonate minerals associated with the volcano-sedimentary iron-ores of the Lahn-Dill type:
                          A petrographic and geochemical study"

2013 - 2017:  B.Sc. Geosciences, Ruhr University Bochum

                          Topic of bachelor's thesis: "Petrographie und Geochemie an Metapeliten der Buchan-Zone in Nordost-Schottland"

Research Boards and Committees:

2021 - recent: Member of the "GetStarted" project group within the German Mineralogical Society to support students and young
                     researchers in the fields of  geochemistry, mineralogy, crystallography and petrology in their professional careers

2017 - recent: Member of the German Mineralogical Society (DMG)

Awards:

2022 | Receiver of bursary for Zurich School of Crystallography 2022

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