Real-time characterization of mineral nucleation and growth phenomena is becoming increasingly significant in understanding how nanominerals nucleate, grow, transform, and interact with their surrounding environments. The complexity of the mechanisms involved in the formation of iron oxides and oxyhydroxides has drawn increasing attention due to implications regarding biogeochemical transport of contaminants. Evidence indicates the importance of non-classical growth mechanisms, potentially in conjunction with classical growth at various stages of the formation process. Furthermore, it has been shown that evidence for these early processes is often effectively erased in later stages of the mineral growth pathway, making the need for in situ characterization increasingly apparent. The use of mixed flow reactor systems allows for precise tuning of reaction conditions (flow rate, residence times, solution chemistry, etc.) and thus when coupled with in situ techniques such as small angle x-ray scattering (SAXS), valuable mechanistic information can be obtained. This project is fabricating new 3D printed mixed flow reactors designed specifically for in situ crystallization experiments. However, before we can comfortably deploy these designs, thorough analysis of the chemical stability/compatibility of the polymer, a commercial polymethyl-methacrylate (PMMA) derivative, is required. To that end, we are performing tests at various post-processing stages of our material and assessing if the custom reactors are stable at a range of pH (1-12) and temperature (25-50 °C) conditions. Thermogravimetric analysis with Fourier transform infrared spectroscopy (TGA-FTIR) is being used to analyze the chemistry of volatile compounds included unreacted monomers and oligomers at various temperatures. Differential scanning calorimetry (DSC) is providing information on polymeric thermal transitions/degradation and dynamic mechanical analysis (DMA) is being used to evaluate changes in mechanical properties. Once the material has been properly scrutinized for the relevant reaction conditions, we will begin using the reactors in studies on crystallization of ferric oxyhydroxides and hydroxylsulfates to probe the complex formation mechanisms involved. By employing these 3D printed mixed flow reactors, we aim to introduce an increased capacity for time-resolved studies, experiment design versatility, as well as cost efficiency to laboratory-based geochemical research.

3D printed mixed flow reactors: In situ characterization of ferric oxyhydroxides nanoparticles

254th National Meeting (2017)

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