TY - JOUR A1 - Hoevelmann, J. A1 - Stawski, T. M. A1 - Besselink, R. A1 - Freeman, H. M. A1 - Dietmann, K. M. A1 - Mayanna, S. A1 - Pauw, Brian Richard A1 - Benning, L. G. T1 - A template-free and low temperature method for the synthesis of mesoporous magnesium phosphate with uniform pore structure and high surface area N2 - Mesoporous phosphates are a group of nanostructured materials with promising applications, particularly in biomedicine and catalysis. However, their controlled synthesis via conventional template-based routes presents a number of challenges and limitations. Here, we show how to synthesize a mesoporous Magnesium phosphate with a high surface area and a well-defined pore structure through thermal decomposition of a crystalline struvite (MgNH4PO4·6H2O) precursor. In a first step, struvite crystals with various morphologies and sizes, ranging from a few micrometers to several millimeters, had been synthesized from supersaturated aqueous solutions (saturation index (SI) between 0.5 and 4) at ambient pressure and temperature conditions. Afterwards, the crystals were thermally treated at 70–250 °C leading to the release of structurally bound water (H2O) and ammonia (NH3). By combining thermogravimetric analyses (TGA), scanning and transmission electron microscopy (SEM, TEM), N2 sorption analyses and small- and wide-angle X-ray scattering (SAXS/WAXS) we show that this decomposition process results in a pseudomorphic transformation of the original struvite into an amorphous Mg-phosphate. Of particular importance is the fact that the final material is characterized by a very uniform mesoporous structure with 2–5 nm wide pore channels, a large specific surface area of up to 300 m2 g−1 and a total pore volume of up to 0.28 cm3 g−1. Our struvite decomposition method is well controllable and reproducible and can be easily extended to the synthesis of other mesoporous phosphates. In addition, the so produced mesoporous material is a prime candidate for use in biomedical applications considering that Magnesium phosphate is a widely used, non-toxic substance that has already shown excellent biocompatibility and biodegradability. KW - Struvite KW - SAXS KW - Scattering KW - Nanoporous KW - Geology PY - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-477130 VL - 11 IS - 14 SP - 6939 EP - 6951 PB - Royal Society of Chemistry AN - OPUS4-47713 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Karafiludis, Stephanos A1 - Stawski, Tomasz A1 - Scoppola, E. A1 - Kochovski, Z. A1 - Retzmann, Anika A1 - Emmerling, Franziska T1 - Crystallization study of transition metal phosphates: Characterization of a non-classical crystallization pathway N2 - Industrial and agricultural waste streams (waste waters, sludges, tailings etc.), which contain high concentrations of NH4+, PO43- and transition metals, are environmentally harmful due to their toxic pollutants. At the same time, phosphorus and selective transition metals such as Cobalt could be potentially depleted as a critical raw material due to the high demand and rapidly declining natural ore deposits. Therefore, due to simultaneous scarcity and abundance, the phosphorus and 3d metal recovery from agricultural, industrial, mining, or urban wastewaters have been an important factor in sustaining our global consumption and preservation of the natural environment. Typically, separate pathways have been considered to extract hazardous substances such as transition metals or phosphate, independently from each other. Here, we investigate the crystallization of transition metal phosphate (TMP) compounds (NH4MPO4∙6H2O, M3(PO4)2∙8H2O with M = Ni2+, Co2+, NixCo1-x2+ M-struvite and M-phosphate octahydrate) out of aqueous solutions, which allow for P, ammonia and metal co-precipitation. The precipitation of these compounds from industrial and agricultural waste waters has high potential as a P- and 3d metal recovery route. For this purpose, a detailed understanding of the crystallization process beginning from combination of solved ions and ending in a final crystalline product is required. Through adjusting the reaction conditions, the stability, crystallite size and morphology of the as-obtained TMPs could be controlled. Detailed investigations of the precipitation process in time using ex- and in-situ techniques provided new insights into their non-classical crystallization mechanism/crystal engineering of these materials. These TMPs involve transitional colloidal nanophases during the crystallization process. Over time, their complex amorphous framework changes significantly resulting simultaneously in an agglomeration and densification of the compound. After extended reaction times these colloidal nanophases condensed to a final crystal. However, the reaction kinetics of the formation of a final crystalline product and the lifetime of these intermediate phases vary significantly depending on the metal cation involved in the precipitation process. Ni-struvite is stable in a wide reactant concentration range and at different metal/phosphorus (M/P)-ratios, whereas Co tends to form Co-struvite and/or Co-phosphate octahydrate depending on the (M/P)-ratio. The mixed NixCo1-x system shows a significantly different crystallization behavior and reaction kinetics of the precipitation compared to the pure endmembers. The observed various degree of stability could be linked to the octahedral metal coordination environment in these compounds. The achieved level of control over the precipitates, is highly desirable for 3d- and P-recovery methods. Under this paradigm, the crystals can be potentially upcycled as precursor materials for (electro)catalytical applications. T2 - HZB Usermeeting 2023 CY - Berlin, Germany DA - 22.06.2023 KW - Struvite KW - Transition metal KW - Phosphates KW - Crystallization KW - Amorphous phases PY - 2023 AN - OPUS4-57775 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Karafiludis, Stephanos A1 - Scoppola, E. A1 - Wolf, S.E. A1 - Kochovski, Z. A1 - Matzdorff, D. A1 - Van Driessche, A. E. S. A1 - Hövelmann, J. A1 - Emmerling, Franziska A1 - Stawski, Tomasz M. T1 - Evidence for liquid-liquid phase separation during the early stages of Mg-struvite formation N2 - The precipitation of struvite, a magnesium ammonium phosphate hexahydrate (MgNH₄PO₄ · 6H₂O) mineral, from wastewater is a promising method for recovering phosphorous. While this process is commonly used in engineered environments, our understanding of the underlying mechanisms responsible for the formation of struvite crystals remains limited. Specifically, indirect evidence suggests the involvement of an amorphous precursor and the occurrence of multi-step processes in struvite formation, which would indicate non-classical paths of nucleation and crystallization. In this study, we use synchrotron-based in situ x-ray scattering complemented by cryogenic transmission electron microscopy to obtain new insights from the earliest stages of struvite formation. The holistic scattering data captured the structure of an entire assembly in a time-resolved manner. The structural features comprise the aqueous medium, the growing struvite crystals, and any potential heterogeneities or complex entities. By analysing the scattering data, we found that the onset of crystallization causes a perturbation in the structure of the surrounding aqueous medium. This perturbation is characterized by the occurrence and evolution of Ornstein-Zernike fluctuations on a scale of about 1 nm, suggesting a non-classical nature of the system. We interpret this phenomenon as a liquid-liquid phase separation, which gives rise to the formation of the amorphous precursor phase preceding actual crystal growth of struvite. Our microscopy results confirm that the formation of Mg-struvite includes a short-lived amorphous phase, lasting >10 s. KW - Physical and theoretical chemistry KW - Non-classical crystallization KW - Struvite KW - Liquid-liquid-phase-separation KW - Nucleation KW - Crystallization KW - In-situ scattering PY - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-584766 SN - 1089-7690 VL - 159 IS - 13 SP - 1 EP - 12 PB - AIP Publishing CY - Woodbury, NY AN - OPUS4-58476 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stawski, Tomasz A1 - de Oliveira Guilherme Buzanich, Ana A1 - Emmerling, Franziska T1 - Evolution of mesoporous frameworks from precipitated struvite-structured metal phosphate materials N2 - Mesoporous transition metal phosphates (TMPs) have attracted major interest due to their high (electro-)catalytic activity suitable for H2 generation, supercapacitors or batteries. Typically, mesoporous materials are synthesized via a template-based route. This way is in the case of TMP because the surfactants used are difficult to remove due to the sensitivity of the mesoporous framework. We present a template-free method including the formation of a precursor phase called M-struvite (NH4MPO4•6H2O, M = Mg2+, Ni2+, Co2+, Ni2+xCo2+1-x) to synthesize mesoporous and amorphous metal phosphates. This method relies on the thermal decomposition of crystalline M-struvite precursors to an amorphous and simultaneous mesoporous phase associated with the degassing of NH3 and H2O. The temporal evolution of mesoporous frameworks and the response of the coordination metal coordination environment was followed with diffraction and spectroscopy based in-situ and ex-situ methods. We highlight the systematic differences in absolute surface area, pore shape, pore size, and phase transitions between the chemical systems. In a complex amorphous structure, thermal decomposed Mg-, Ni- and NixCo1-x-struvites exhibit high surface areas and pore volumes for phosphate materials with a spherical to channel-like pore geometry (240 m²g-1 and 0.32 cm-3 g-1 for Mg and 90 m²g-1 and 0.13 cm-3 g-1 for Ni). In addition to this low-cost, environmentally friendly and simple synthesis, M-struvites could grow as a recycling product from industrial and agricultural wastewaters. These waste products could be upcycled through a simple thermal treatment for further applications. T2 - ECCG7, European Conference on Crystal Growth CY - Paris, France DA - 25.07.2022 KW - Transition metals KW - Phosphates KW - Struvite KW - Amorphous phases KW - Mesoporosity PY - 2022 AN - OPUS4-55491 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Karafiludis, Stephanos A1 - Stawski, Tomasz A1 - de Oliveira Guilherme Buzanich, Ana A1 - Emmerling, Franziska T1 - Evolution of mesoporous frameworks from precipitated struvite-structured metal phosphate materialsls N2 - Mesoporous transition metal phosphates (TMPs) have attracted major interest due to their high (electro-)catalytic activity suitable for H2 generation, supercapacitors or batteries. Typically, mesoporous materials are synthesized via a template-based route. This way is in the case of TMP because the surfactants used are difficult to remove due to the sensitivity of the mesoporous framework. We present a template-free method including the formation of a precursor phase called M-struvite (NH4MPO4•6H2O, M = Mg2+, Ni2+, Co2+, Ni2+xCo2+1-x) to synthesize mesoporous and amorphous metal phosphates. This method relies on the thermal decomposition of crystalline M-struvite precursors to an amorphous and simultaneous mesoporous phase associated with the degassing of NH3 and H2O. The temporal evolution of mesoporous frameworks and the response of the coordination metal coordination environment was followed with diffraction and spectroscopy based in-situ and ex-situ methods. We highlight the systematic differences in absolute surface area, pore shape, pore size, and phase transitions between the chemical systems. In a complex amorphous structure, thermal decomposed Mg-, Ni- and NixCo1-x-struvites exhibit high surface areas and pore volumes for phosphate materials with a spherical to channel-like pore geometry (240 m²g-1 and 0.32 cm-3 g-1 for Mg and 90 m²g-1 and 0.13 cm-3 g-1 for Ni). In addition to this low-cost, environmentally friendly and simple synthesis, M-struvites could grow as a recycling product from industrial and agricultural wastewaters. These waste products could be upcycled through a simple thermal treatment for further applications. T2 - SNI 2022 - German Conference for Research with Synchrotron Radiation, Neutrons and Ion Beams at Large Facilities CY - Berlin, Germany DA - 05.07.2022 KW - Struvite KW - Transition metal KW - Phosphate KW - Amorphous phases KW - Mesoporosity PY - 2022 AN - OPUS4-55911 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Karafiludis, Stephanos A1 - Kochovski, Z. A1 - Retzmann, Anika A1 - Scoppola, E. A1 - Emmerling, Franziska A1 - Stawski, Tomasz T1 - How do transition metal phosphates crystallise? N2 - Industrial and agricultural waste streams (waste waters, sludges, tailings etc.), which contain high concentrations of NH4+, PO43- and transition metals, are environmentally harmful due to their toxic pollutants. At the same time, phosphorus and selective transition metals such as Cobalt could be potentially depleted as a critical raw material due to the high demand and rapidly declining natural ore deposits. Therefore, due to simultaneous scarcity and abundance, the phosphorus and 3d metal recovery from agricultural, industrial, mining, or urban wastewaters have been an important factor in sustaining our global consumption and preservation of the natural environment. Typically, separate pathways have been considered to extract hazardous substances such as transition metals or phosphate, independently from each other. Here, we investigate the crystallization of transition metal phosphate (TMP) compounds (NH4MPO4∙6H2O, M3(PO4)2∙8H2O with M = Ni2+, Co2+, NixCo1-x2+ M-struvite and M-phosphate octahydrate) out of aqueous solutions, which allow for P, ammonia and metal co-precipitation. The precipitation of these compounds from industrial and agricultural waste waters has high potential as a P- and 3d metal recovery route. For this purpose, a detailed understanding of the crystallization process beginning from combination of solved ions and ending in a final crystalline product is required. Through adjusting the reaction conditions, the stability, crystallite size and morphology of the as-obtained TMPs could be controlled. Detailed investigations of the precipitation process in time using ex- and in-situ techniques provided new insights into their non-classical crystallization mechanism/crystal engineering of these materials. These TMPs involve transitional colloidal nanophases during the crystallization process. Over time, their complex amorphous framework changes significantly resulting simultaneously in an agglomeration and densification of the compound. After extended reaction times these colloidal nanophases condensed to a final crystal. However, the reaction kinetics of the formation of a final crystalline product and the lifetime of these intermediate phases vary significantly depending on the metal cation involved in the precipitation process. Ni-struvite is stable in a wide reactant concentration range and at different metal/phosphorus (M/P)-ratios, whereas Co tends to form Co-struvite and/or Co-phosphate octahydrate depending on the (M/P)-ratio. The mixed NixCo1-x system shows a significantly different crystallization behavior and reaction kinetics of the precipitation compared to the pure endmembers. The observed various degree of stability could be linked to the octahedral metal coordination environment in these compounds. The achieved level of control over the precipitates, is highly desirable for 3d- and P-recovery methods. Under this paradigm, the crystals can be potentially upcycled as precursor materials for (electro)catalytical applications. T2 - Granada Münster Discussion Meeting (GMDM) CY - Granada, Spain DA - 30.11.2022 KW - Struvite KW - Transition metal KW - Phosphates KW - Amorphous phases KW - Non-classical crystallization PY - 2022 AN - OPUS4-56478 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Karafiludis, Stephanos A1 - de Oliveira Guilherme Buzanich, Ana A1 - Kochovski, Z. A1 - Feldmann, Ines A1 - Emmerling, Franziska A1 - Stawski, Tomasz T1 - Ni- and Co-Struvites: Revealing Crystallization Mechanisms and Crystal Engineering toward Applicational Use of Transition Metal Phosphates N2 - Industrial and agricultural waste streams (waste water, sludges, tailings, etc.) which contain high concentrations of NH4+, PO43–, and transition metals are environmentally harmful and toxic pollutants. At the same time, phosphorous and transition metals constitute highly valuable resources. Typically, separate pathways have been considered to extract hazardous transition metals or phosphate independently from each other. Investigations on the simultaneous removal of multiple components have been carried out only to a limited extent. Here, we report the synthesis routes for Ni- and Co-struvites (NH4MPO4·6H2O, M = Ni2+ and Co2+), which allow for P, ammonia, and metal co-precipitation. By evaluating different reaction parameters, the phase and stability of transition metal struvites as well as their crystal morphologies and sizes could be optimized. Ni-struvite is stable in a wide reactant concentration range and at different metal/phosphorus (M/P) ratios, whereas Co-struvite only forms at low M/P ratios. Detailed investigations of the precipitation process using ex situ and in situ techniques provided insights into the crystallization mechanisms/crystal engineering of these materials. M-struvites crystallize via intermediate colloidal amorphous nanophases, which subsequently aggregate and condense to final crystals after extended reaction times. However, the exact reaction kinetics of the formation of a final crystalline product varies significantly depending on the involved metal cation in the precipitation process: several seconds (Mg) to minutes (Ni) to hours (Co). The achieved level of control over the morphology and size makes precipitation of transition metal struvites a promising method for direct metal recovery and binding them in the form of valuable phosphate raw materials. Under this paradigm, the crystals can be potentially up-cycled as precursor powders for electrochemical or (electro)catalytic applications, which require transition metal phosphates. KW - Crystallization KW - Struvite KW - Nickel KW - Cobalt KW - Phosphorous recovery KW - Up-cycling KW - Aqueous synthesis PY - 2022 U6 - https://doi.org/10.1021/acs.cgd.2c00284 VL - 22 IS - 7 SP - 4305 EP - 4315 PB - ACS Publications CY - Washington D.C. AN - OPUS4-55286 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Karafiludis, Stephanos A1 - Ryll, T. W. A1 - Buzanich, Ana Guilherme A1 - Emmerling, Franziska A1 - Stawski, Tomasz Maciej T1 - Phase stability studies on transition metal phosphates aided by an automated synthesis N2 - Transition metal phosphates (TMPs) have attracted interest as materials for (electro-) catalysis, and electrochemistry due to their low-cost, stability, and tunability. In this work, an automated synthesis platform was used for the preparation of transition metal phosphate crystals to efficiently explore the multidimensional parameter space, determining the phase selection, crystal sizes, shapes. By using X-ray diffraction and spectroscopy-based methods and electron microscopy imaging, a complete characterization of the phase stability fields, phase transitions, and crystal morphology/sizes was achieved. In an automated three-reactant synthesis, the individual effect of each reactant species NH4+, M2+, and PO43- on the formation of transition metal phosphate phases: M-struvite NH4MPO4·6H2O, M-phosphate octahydrate M3(PO4)2·8H2O with M = Ni, Co and an amorphous phase, was investigated. The NH4+ concentration dictates the phase composition, morphology, and particle size in the Ni-system (crystalline Ni-struvite versus amorphous Ni-PO4 phase), whereas in the Co-system all reactant species - NH4+, Co2+, and PO43- - influence the reaction outcome equivalently (Co-struvite vs. Co-phosphate octahydrate). The coordination environment for all crystalline compounds and of the amorphous Ni-PO4 phase was resolved by X-ray absorption spectroscopy, revealing matching characteristics to its crystalline analogue, Ni3(PO4)2·8H2O. The automated synthesis turned out to be significantly advantageous for the exploration of phase diagrams due to its simple modularity, facile traceability, and enhanced reproducibility compared to a typical manual synthesis. KW - Automated synthesis KW - Phase diagrams KW - Transition metals KW - Phosphates KW - Local structure KW - Struvite PY - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-579151 VL - 25 IS - 30 SP - 4333 EP - 4344 PB - CrystEngComm CY - London AN - OPUS4-57915 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Karafiludis, Stephanos A1 - de Oliveira Guilherme Buzanich, Ana A1 - ten Elshof, Johan E. A1 - Emmerling, Franziska A1 - Stawski, Tomasz T1 - Recycled transition metal phosphates as functional materials for electrochemistry N2 - In the last decade transition metal phosphates (TMPs) captured major interest due to their high electrochemical activity useful for electrode materials, supercapacitors or batteries. Importantly, TMPs are known to exhibit high proton conductivity of the order of >10-2 -10-5 S/cm from 25°C to temperatures as high as 400°C. The crucial milestone in the research on the applicational use of TMPs in all their varieties is an ability to obtain, explore and optimize different compositions and structures, both crystalline and amorphous. Thus, we elucidate the structures of amorphous and crystalline Ni- and Co phosphate phases, as they develop upon heating. This method relies on the thermal decomposition of a crystalline M-struvite precursor, i.e. NH4MPO4•6H2O (M = Mg, Ni, Co, NixCo1-x etc. Here, coincidently volatile components such as H2O or NH3 degas out of the compound resulting in a phase transformation to amorphous or crystalline metal phosphate phases depending on the reaction conditions. For this we used a suite of advanced methods such as FTIR, FT-RS and synchrotron-based XAS. Ni-struvite transforms to amorphous phases over a broad range of temperatures (90°C < T < 600°C) in which it remains in an octahedral coordination environment. On the other hand, Co-struvite treatment leads to multiple crystalline phases with only small amounts of short-lived amorphous phases. Importantly, the occurring amorphous phases exhibit uniform mesoporous frameworks (2–5 nm wide pore channels, specific surface area of 100 m2g−1 and a pore volume of 0.13 cm3g−1) at low temperatures (<200°C) while the crystalline compounds can be used as proton conductors demonstrating values of >10-4 S/cm at 25°C. Consequently, we investigated the amorphization/evolution of mesoporosity, the proton-conducting properties and the complex local structure with in- and ex-situ approaches during thermal treatment. Additionally, to this low cost, environmentally friendly and simple one pot synthesis, the precursor M-struvites could grow as a recovery product from industrial waste waters. In such a way, they would to a recycling economy of sought-after commodities like phosphorus or transition metals. T2 - E-MRS Spring Conference 2023 CY - Strasbourg, France DA - 29.05.2023 KW - Struvite KW - Transition metals KW - Phosphates KW - Functional materials KW - Mesoporosity KW - Proton conductivity PY - 2023 AN - OPUS4-57587 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Karafiludis, Stephanos A1 - de Oliveira Guilherme Buzanich, Ana A1 - Heinekamp, Christian A1 - Smales, Glen Jacob A1 - Hodoroaba, Vasile-Dan A1 - ten Elshof, J. E. A1 - Emmerling, Franziska A1 - Stawski, Tomasz T1 - Template-free synthesis of mesoporous, amorphous transition metal phosphate materials N2 - We present how mesoporosity can be engineered in transition metal phosphate (TMPs) materials in a template-free manner. The method involves a transformation of a precursor metal phosphate phase, called M-struvite (NH4MPO4·6H2O, M = Mg2+, Ni2+, Co2+, NixCo1-x2+). It relies on the thermal decomposition of crystalline M-struvite precursors to an amorphous and simultaneously mesoporous phase, which forms while degassing of NH3 and H2O. The temporal evolution of mesoporous frameworks and the response of the metal coordination environment were followed with in-situ and ex-situ scattering and diffraction, as well as X -ray spectroscopy. Despite sharing the same precursor struvite structure, different amorphous and mesoporous structures were obtained depending on the involved transition metal. We highlight the systematic differences in absolute surface area, pore shape, pore size, and phase transitions depending on a metal cation present in the analogous M-struvites. The amorphous structures of thermally decomposed Mg-, Ni- and NixCo1-x-struvites exhibit high surface areas and pore volumes (240 m²g-1 and 0.32 cm-3 g-1 for Mg and 90 m²g-1 and 0.13 cm-3 g-1 for Ni). We propose that the low-cost, environmentally friendly M-struvites could be obtained as recycling products from industrial and agricultural wastewaters. These waste products could be then upcycled into mesoporous TMPs through a simple thermal treatment for further applications, for instance, in (electro)catalysis. KW - Struvite KW - Pphosphates KW - Transition metal KW - In-situ SAXS/WAXS KW - Mesoporosity PY - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-569503 SN - 2040-3364 SP - 1 EP - 15 PB - Royal Society of Chemistry (RSC) AN - OPUS4-56950 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -