Search

CoAl4(OH)12(SO4)·3H2O is a 0D magnet and MAl4(OH)12(SO4)·3H2O with M = Ni2+ and Cu2+ are ferromagnetic spin chains (no magnetic ordering > 2 K) based on magnetic susceptibility, neutron scattering, NMR, and first-principles calculations.

The variation in phosphorus (P) speciation of sewage sludge throughout three wastewater treatment plants (WWTPs) was obtained by combining sequential P extraction with optical and scanning electron microscopy (SEM), chemical analyses, powder X-ray diffraction (PXRD), and

Membrane-Aerated Biofilm Reactors (MABRs) are becoming a popular process intensification alternative within wastewater treatment plants (WWTP). Indeed, the nitrogen removal capacity of aerobic/anoxic/anaerobic reactors can be substantially enhanced with reduced energy consumption and footprint requirements. However, little is known about how oxidation–reduction potential (ORP) may impact their overall process performance. This study aims to report some of these effects by showing the results of almost three years of monitoring of two hybrid MABRs (R1, R2) adjacent to an existing Biodenipho™ facility. In Period 1 (P1), R1 and R2 were fed with anaerobic mixed liquor from the selector for the biological phosphorus removal zone. In Period 2 (P2), external aeration was introduced to increase ORP values (R1, R2), and membranes were replaced (R1) or cleaned (R2). Results show an increase in nitrification rates: from 0.27 and 0.33 g N m−2 d−1 in R1/R2 during P1 to 1.0 and 0.80 g N m−2 d−1 in R1/R2 during P2. 16 s rRNA amplicon sequencing analysis revealed that the relative abundance of nitrifying organisms increased from 0.2 to 6.7 % in R1 and 0.8 to 5.3 % in R2 in P2 (in detriment of microbes with fermenting capabilities). Energy dispersive X-ray spectroscopy confirmed the presence of coating substances under the lowest ORP (P1), which could be pyrite and its precursors like mackinawite. Overall, it is hypothesized that low ORP conditions (P1) had a detrimental effect on nitrification performance, as it promoted the reduction of different iron and sulfur compounds, which in turn a) precipitate in the biofilm as FeS increasing mass transfer limitations and competing with biomass for space; b) re-oxidize increasing the internal oxygen demand; c) inhibit nitrifiers growth.

The synthesis and thermal degradation of MAl4(OH)12SO4·3H2O layered double hydroxides with M = Co2+, Ni2+, Cu2+, and Zn2+ ("MAl4-LDH") were investigated by inductively coupled plasma-optical emission spectroscopy, thermogravimetric analysis, powder X-ray diffraction, Rietveld refinement, scanning electron microscopy, scanning tunnel electron microscopy, energy-dispersive X-ray spectroscopy, and solid-state 1H and 27Al NMR spectroscopy. Following extensive synthesis optimization, phase pure CoAl4- and NiAl4-LDH were obtained, whereas 10-12% unreacted bayerite (Al(OH)3) remained for the CuAl4-LDH. The optimum synthesis conditions are hydrothermal treatment at 120 °C for 14 days (NiAl4-LDH only 9 days) with MSO4(aq) concentrations of 1.4-2.8, 0.7-0.8, and 0.08 M for the CoAl4-, NiAl4-, and CuAl4-LDH, respectively. A pH ≈ 2 for the metal sulfate solutions is required to prevent the formation of byproducts, which were Ni(OH)2 and Cu3(SO4)(OH)4 for NiAl4- and CuAl4-LDH, respectively. The thermal degradation of the three MAl4-LDH and ZnAl4-LDH in a nitrogen atmosphere proceeds in three steps: (i) dehydration and dehydroxylation between 200 and 600 °C, (ii) loss of sulfate between 600 and 900 °C, and (iii) formation of the end products at 900-1200 °C. For CoAl4-LDH (ZnAl4-LDH), these are α-Al2O3 and CoAl2O4 (ZnAl2O4) spinel. For NiAl4-LDH, a spinel-like NiAl4O7 phase forms, whereas CuAl4-LDH degrades by a redox reaction yielding a diamagnetic CuAlO2 (delafossite structure) and α-Al2O3.

Lithium vanadium fluorophosphate, LiVPO4F, is a promising cathode material for Li-ion batteries because of its high intercalation potential (4.24 V vs Li/Li+) and high stability. However, recent studies show that as-synthesized LiVPO4F very often contains oxygen defects on the fluoride site giving rise to a general composition of LiVPO4F1−yOy with vanadium in a mixed +III/+IV valence state. The inclusion of oxygen naturally influences the electrochemical properties greatly, and a thorough material characterization is necessary to understand the performance. In this study, we synthesize lithium vanadium fluorophosphate by two common strategies: solid-state and hydrothermal synthesis. We show that solid-state synthesis provides LiVPO4F, while the hydrothermal method, in contrast to previous reports, leads to the inclusion of ca. 35% oxygen on the fluoride site and significant disorder in the material. The different electrochemical properties were probed by operando synchrotron X-ray powder diffraction to investigate the effects of oxygen inclusion on the structural evolution during electrochemical lithiation and delithiation. This reveals that while LiVPO4F exhibits a typical biphasic phase evolution, the sample with oxygen inclusion on the fluoride site displays extended solid-solution behavior. This explains previous observations of improved capacity retention due to defects.

Large amounts of phosphorus (P) are present in activated sludge from municipal wastewater treatment plants, where it exists in the form of metal salt precipitates or biologically bound into the biomass as nucleic acids, cell membrane components, and the extracellular polymeric substances or, in special polyphosphate-accumulating organisms (PAOs), as intracellular polyphosphate. Only recently, methods that reliably allow an absolute quantification of the different P-fractions, such as sequential extraction, Raman microspectroscopy, solid-state 31P magic angle spinning (MAS) NMR, and solution state 31P NMR have been developed. This study combines these techniques to obtain a comprehensive P mass-balance of activated sludge from four wastewater treatment plants with enhanced biological phosphate removal (EBPR). The total content of P and various cations was measured by chemical analysis (ICP-OES), and different P fractions were extracted for chemical characterization. Chemically bound P constituted 38-69% of total P, most likely in the form of Fe, Mg, or Al minerals, while organically bound P constituted 7-9%. By using Raman microspectroscopy and solution state 31P NMR and 31P MAS NMR spectroscopy before and after anaerobic P-release experiments, poly-P was quantified and constituted 22-54% of total P in the activated sludges and was found in approx. 25% of all bacterial cells. Moreover, Raman microspectroscopy in combination with fluorescence in situ hybridization (FISH) was used to quantify the species-specific intracellular poly-P of known PAO genera (Tetrasphaera, Ca. Accumulibacter, Dechloromonas) and other microorganisms known to possess high level of poly-P, such as the filamentous Ca. Microthrix. They were all abundant, as measured by quantitative-FISH and amplicon sequencing, and accumulated large amount of poly-P, depending on their cell-size, contributing substantially to the P-removal. Interestingly, in all four EBPR plants investigated, only 1-13% of total poly-P was stored by unidentified PAO, highlighting that most PAOs in the full-scale EBPR plants investigated are now known.HighlightsExhaustive P mass-balance of main organic and inorganic P-species in four EBPR plantsQuantification of poly-P of FISH-defined PAO and other species with high P contentTotal P content was 36-50 mgP/gSS of which 31-62% was in biomass and as poly-PA high fraction of all cells (25-30%) contained a high content of poly-PKnown PAOs contained almost all poly-P in the EBPR plants investigated

P-glycoprotein inhibitors, like zosuquidar, have widely been used to study the role of P-glycoprotein in oral absorption. Still, systematic studies on the inhibitor dose-response relationship on intestinal drug permeation are lacking. In the present study, we investigated the effect of 0.79 nM-2.5 μM zosuquidar on etoposide permeability across Caco-2 cell monolayers. We also investigated etoposide pharmacokinetics after oral or IV administration to Sprague Dawley rats with co-administration of 0.063–63 mg/kg zosuquidar, as well as the pharmacokinetics of zosuquidar itself. Oral zosuquidar bioavailability was 2.6–4.2%, while oral etoposide bioavailability was 5.5 ± 0.9%, which increased with increasing zosuquidar doses to 35 ± 5%. The intestinal zosuquidar concentration required to induce a half-maximal increase in bioavailability was estimated to 180 μM. In contrast, the IC50 of zosuquidar on etoposide permeability in vitro was only 5–10 nM, and a substantial in vitro-in vivo discrepancy of at least four orders of magnitude was thereby identified. Overall, the present study provides valuable insights for future formulation development that applies fixed dose combinations of P-glycoprotein inhibitors to increase the absorption of poorly permeable P-glycoprotein substrate drugs., Graphical abstract Unlabelled Image

Vivianite (Fe

Polyphosphate (poly-P) is a major constituent in activated sludge from wastewater treatment plants with enhanced biological phosphorus removal due to poly-P synthesis by poly-P accumulating organisms where it plays an important role for recovery of phosphorus from waste water. Our aim was to develop a reliable protocol for poly-P quantification by 31 P NMR spectroscopy. This has so far been complicated by the risks of inefficient extraction and poly-P hydrolysis in the extracts. A protocol for complete extraction, identification and quantification of poly-P in activated sludge from a waste water treatment plant was identified based on test and evaluation of existing extraction protocols in combination with poly-P determination and quantification by solution and solid state 31 P NMR spectroscopy. The total poly-P middle group content was quantified by solid state NMR for comparison with the poly-P middle groups quantified by solution NMR, which is novel. Three different extraction protocols previously used in literature were compared: 1) a single 0.25 M NaOH-0.05 M EDTA extraction, 2) a 0.05 M EDTA pre-extraction followed by a 0.25 M NaOH main extraction and 3) a 0.05 M EDTA pre-extraction followed by a 0.25 M NaOH-0.05 M EDTA main extraction. The results showed that the extraction protocol 2 was optimal for fresh activated sludge, extracting 10.8 ± 0.4 to 11.4 ± 1.2 mgP/gDW poly-P. Extraction protocols 1 and 3 extracted less than 9.4 ± 0.5 mgP/gDW poly-P. A comparison of the quantification of poly-P by 31 P solution NMR and by 31 P solid state NMR spectroscopy of lyophilised activated sludge showed 86 ± 9% extraction efficiency of poly-P, which confirms that the extraction protocol recovered most of the poly-P from the samples without pronounced poly-P degradation.

Lithium fluoride (LiF) and fluoride additives in carbon-based materials are currently under research as electrode materials for energy storage applications. Herein we demonstrate a simple and novel method for the in situ fabrication of fluorinated carbon-LiF nanocomposites both as powder and as supported thin films. The starting solution of polyvinylidene fluoride (PVDF) and lithium nitrate (LiNO3) in N,N‑Dimethylformamide is poured into a mould or applied to a thermally resistant substrate as a thin film. Pre-tempering and further pyrolysis at 550 °C yield LiF doped amorphous and fluorinated carbon (AC) powder or film. The precursor solution can be additionally modified with multi-walled carbon nanotubes (MWCNT) to yield porous AC-MWCNT-LiF-nanocomposites. Structural and morphological characterization (scanning electron and energy dispersive X-ray spectroscopy, X-ray diffraction as well as solid-state 7Li magic angle spinning nuclear magnetic resonance spectroscopy) show a fine dispersion of faceted LiF-nanoparticles in the carbon matrix or decorating the MWCNTs. The formation mechanism involves the thermally activated reaction of Li-ions with the fluorine of the polymer during pyrolysis thus allowing an in situ nanocomposite to be obtained. Finally the electrochemical capacitance properties in a two-electrode set-up using LiNO3 in ethylene glycol as electrolyte are reported and discussed in comparison to LiF-free electrodes. Keywords: Lithium fluoride, Fluorinated carbon, Lithium nitrate, Nanocomposite, Pyrolysis, Prelithiation

Layered double hydroxides (LDH) are a versatile group of materials, which receive significant attention due to their many applications within catalysis, energy conversion and storage, drug delivery, environmental remediation, and carbon dioxide sequestration. Moreover, many LDH exists as minerals in Nature. Their properties can be tuned by the choice of chemical composition as well as by, e.g., delamination to form two dimensional materials or nanohybrid materials, which further increases their potential applications. However, LDH are notorious for their low crystallinity and often inherent structural disorder, which render their characterization challenging. This review illustrates how solid-state NMR spectroscopy (SSNMR) has provided detailed insight into the atomic level structure of LDH including the distribution of metal ions in the cation layer, the dynamics of the interlayer water and anions, the formation and reactivity of LDH as well as is becoming a core analytical technique, when the properties of LDH are investigated. The review focusses on studies, where demanding SSNMR experiments often combined with detailed data analyses has been reported and/or when SSNMR in combination with other methods have provided detailed insight into the LDH structure and/or properties. Moreover, it highlights some of the practical aspects in relation to SSNMR studies of LDH materials.

Calcium controls important processes in fungal metabolism, such as hyphae growth, cell wall synthesis, and stress tolerance. Recently, it was reported that calcium affects polyphosphate and lipid accumulation in fungi. The purpose of this study was to assess the effect of calcium on the accumulation of lipids and polyphosphate for six oleaginous Mucoromycota fungi grown under different phosphorus/pH conditions. A Duetz microtiter plate system (Duetz MTPS) was used for the cultivation. The compositional profile of the microbial biomass was recorded using Fourier-transform infrared spectroscopy, the high throughput screening extension (FTIR-HTS). Lipid content and fatty acid profiles were determined using gas chromatography (GC). Cellular phosphorus was determined using assay-based UV-Vis spectroscopy, and accumulated phosphates were characterized using solid-state31P nuclear magnetic resonance spectroscopy. Glucose consumption was estimated by FTIR-attenuated total reflection (FTIR-ATR). Overall, the data indicated that calcium availability enhances polyphosphate accumulation in Mucoromycota fungi, while calcium deficiency increases lipid production, especially under acidic conditions (pH 2–3) caused by the phosphorus limitation. In addition, it was observed that under acidic conditions, calcium deficiency leads to increase in carotenoid production. It can be concluded that calcium availability can be used as an optimization parameter in fungal fermentation processes to enhance the production of lipids or polyphosphates.

Rechargeable aqueous zinc-ion battery (ZIB) is considered as a promising energy storage device due to the low cost, high obtainable output voltage, non-toxicity, and environmental friendliness. To achieve an excellent energy storage performance, morphology engineering of cathode materials for aqueous ZIBs is regarded as an important strategy. The impact of dimension and orientation of the cathode material on the electrochemical performance are, however, less studied. Herein, we compare two types of zinc pyrovanadate (Zn3V2O7(OH)2•2H2O, ZnVO) in nanowires and nanoflakes with the same crystal type but different orientations. ZnVO nanowires expose mostly the (001) plane lattice, in contrast to (020) and (110) lattice for ZnVO flakes. Interestingly, nanowires exhibit an excellent specific discharge capacity of 108 mAh g−1 after 700 cycles at 2 A g−1, contributed from Faradic and diffusion-controlled capacity. In contrast, nanoflakes deliver a very poor capacity of 1.5 mAh g−1 after 700 cycles at 0.1 A g−1 with only diffusion-controlled capacity. Density functional theory (DFT) reveals significantly different Zn2+ ion diffusion rates in ZnVO along different orientations.

Environmental science is an interdisciplinary field, which integrates chemical, physical, and biological sciences to study environmental problems and human impact on the environment. This article highlights the use of solid-state NMR spectroscopy (SSNMR) in studies of environmental processes and remediation with examples from both laboratory studies and samples collected in the field. The contemporary topics presented include soil chemistry, environmental remediation (e.g., heavy metals and radionuclides removal, carbon dioxide mineralization), and phosphorus recovery. SSNMR is a powerful technique, which provides atomic-level information about speciation in complex environmental samples as well as the interactions between pollutants and minerals/organic matter on different environmental interfaces. The challenges in the application of SSNMR in environmental science (e.g., measurement of paramagnetic nuclei and low-gamma nuclei) are also discussed, and perspectives are provided for the future research efforts.

Potassium chromium jarosite, KCr3(OH)(6)(SO4)(2) (Cr-jarosite), is considered a promising candidate to display spin liquid behavior due to the strong magnetic frustration imposed by the crystal structure. However, the ground state magnetic properties have been debated, since Cr-jarosite is notoriously non-stoichiometric. Our study reports the magnetic properties for deuterated KCr3(OD)(6)(SO4)(2) on chemically well-defined samples, which have been characteried by a combination of powder X-ray diffraction, neutron diffraction, solid state NMR spectroscopy, and scanning electron microscopy with energy dispersive spectroscopy. Eight polycrystalline samples, which all contained only 1-3% Cr vacancies were obtained. However, significant substitution (2-27%) of potassium with H2O and/or H3O+ was observed and resulted in pronounced stacking disorder along the c-axis. A clear second-order transition to an antiferromagnetically ordered phase at T-N = 3.8(1) K with a small net moment of 0.03 mu(B) per Cr3+-ion was obtained from vibrating sample magnetometry and temperature dependent neutron diffraction. The moment is attributed to spin canting caused by the Dzyaloshinskii-Moriya interaction. Thus, our experimental results imply that even ideal potassium chromium jarosite will exhibit magnetic order below 4 K and therefore it does not qualify as a true spin liquid material.

Potassium chromium jarosite, KCr

13C solid-state MAS NMR spectra of a series of paramagnetic metal acetylacetonate complexes; [VO(acac)2] (d1, S = ½), [V(acac)3] (d2, S = 1), [Ni(acac)2(H2O)2] (d8, S = 1), and [Cu(acac)2] (d9, S = ½), were assigned using modern NMR shielding calculations. This provided a reliable assignment of the chemical shifts and a qualitative insight into the hyperfine couplings. Our results show a reversal of the isotropic 13C shifts, δiso(13C), for CH3 and CO between the d1 and d2versus the d8 and d9 acetylacetonate complexes. The CH3 shifts change from about -150 ppm (d1,2) to roughly 1000 ppm (d8,9), whereas the CO shifts decrease from 800 ppm to about 150 ppm for d1,2 and d8,9, respectively. This was rationalized by comparison of total spin-density plots and computed contact couplings to those corresponding to singly occupied molecular orbitals (SOMOs). This revealed the interplay between spin delocalization of the SOMOs and spin polarization of the lower-energy MOs, influenced by both the molecular symmetry and the d-electron configuration. A large positive chemical shift results from spin delocalization and spin polarization acting in the same direction, whereas their cancellation corresponds to a small shift. The SOMO(s) for the d8 and d9 complexes are σ-like, implying spin-delocalization on the CH3 and CO groups of the acac ligand, cancelled only for CO by spin polarization. In contrast, the SOMOs of the d1 and d2 systems are π-like and a large CO-shift results from spin polarization, which accounts for the reversed assignment of δiso(13C) for CH3 and CO.

13C solid-state MAS NMR spectra of a series of paramagnetic metal acetylacetonate complexes; [VO(acac)2] (d1, S = ½), [V(acac)3] (d2, S = 1), [Ni(acac)2(H2O)2] (d8, S = 1), and [Cu(acac)2] (d9, S = ½), were assigned using modern NMR shielding calculations. This provided a reliable assignment of the chemical shifts and a qualitative insight into the hyperfine couplings. Our results show a reversal of the isotropic 13C shifts, δiso(13C), for CH3 and CO between the d1 and d2versus the d8 and d9 acetylacetonate complexes. The CH3 shifts change from about -150 ppm (d1,2) to roughly 1000 ppm (d8,9), whereas the CO shifts decrease from 800 ppm to about 150 ppm for d1,2 and d8,9, respectively. This was rationalized by comparison of total spin-density plots and computed contact couplings to those corresponding to singly occupied molecular orbitals (SOMOs). This revealed the interplay between spin delocalization of the SOMOs and spin polarization of the lower-energy MOs, influenced by both the molecular symmetry and the d-electron configuration. A large positive chemical shift results from spin delocalization and spin polarization acting in the same direction, whereas their cancellation corresponds to a small shift. The SOMO(s) for the d8 and d9 complexes are σ-like, implying spin-delocalization on the CH3 and CO groups of the acac ligand, cancelled only for CO by spin polarization. In contrast, the SOMOs of the d1 and d2 systems are π-like and a large CO-shift results from spin polarization, which accounts for the reversed assignment of δiso(13C) for CH3 and CO.

In this paper, we experimentally study and model the electron donating character of an axial diamagnetic Pd2+ ion in four metalloligated lanthanide complexes of formula [PPh4][Ln{Pd(SAc)4}2] (SAc- = thioacetate, Ln = Tb, Dy, Ho, and Er). A global model encompassing inelastic neutron scattering, torque magnetometry, and dc magnetometry allows to precisely determine the energy level structure of the complexes. Solid state nuclear magnetic resonance reveals a less donating character of Pd2+ compared to the previously reported isostructural Pt2+-based complexes. Consequently, all complexes invariably show a lower crystal field strength compared to their Pt2+-analogues. The dynamic properties show an enhanced single molecule magnet behavior due to the suppression of quantum tunneling, in agreement with our model.

Layered double hydroxides (LDH) and their magnetic composites have been intensively investigated as recyclable high-capacity phosphate sorbents but with little attention to their stability as function of pH and phosphate concentration. The stability of a Fe3O4@SiO2-Mg3Fe LDH P sorbent as function of pH (5–11) and orthophosphate (Pi) concentration (1–300 mg P/L) was investigated. The composite has high adsorption capacity (approx. 80 mg P/g) at pH 5 but with fast dissolution of the LDH component resulting in formation of ferrihydrite as evidenced by Mössbauer spectroscopy. At pH 7 more than 60% of the LDH dissolves within 60 min, while at alkaline pH, the LDH is more stable but with less than 40% adsorption capacity as compared to pH 5. The high Pi sorption at acid to neutral pH is attributed to Pi bonding to the residual ferrihydrite. Under alkaline conditions Pi is sorbed to LDH at low Pi concentration while magnesium phosphates form at higher Pi concentration evidenced by solid-state 31P MAS NMR, powder X-ray diffraction and chemical analyses. Sorption as function of pH and Pi concentration has been fitted by a Rational 2D function allowing for estimation of Pi sorption and precipitation. In conclusion, the instability of the LDH component limits its application in wastewater treatment from acid to alkaline pH. Future use of magnetic LDH composites requires substantial stabilisation of the LDH component.

The various hydrogen species present in a series of synthetic hydroniumjarosite ((H3O)Fe3(SO4)2(OH)6), and ammonioalunite ((NH4)Al3(SO4)2(OH)6) as well synthetic potassium (Cr3+ and V3+) and hydronium (V3+, Cr3+, and Ga3+) analogues were identified and quantified by 1H and 2H MAS NMR spectroscopy. The results confirm the defect mechanism proposed for alunite Nielsen et al. (Am Miner 92: 587–597, 2007), and allow for identification and quantification of even a few percent structural defects. For the paramagnetic samples, the isotropic shift for G2-OH group (V3+, Cr3+, and Fe3+) span more than 1100 ppm, which is related to different d-electron configuration (d2, d3, and d5). Analysis of the 1H and 27Al MAS NMR spectra shows that the synthetic ammonioalunite contains small amounts (5–10%) of hydronium. Furthermore, the close structural relationship between of hydronium and gallium alunite is reflected by the 27Al and 71Ga quadrupole coupling parameters. Thus, the current work demonstrates the applicability of solid state NMR spectroscopy for identification and quantification of hydrogen species in both dia- and paramagnetic minerals.

In the small intestine, P-glycoprotein (P-gp) may limit the permeability of its substrates, which lead to reduced oral absorption. To circumvent the effect of P-gp, a nanocomposite material termed montmorillonite-surfactant hybrid particles was developed. The particles consisted of montmorillonite, the P-gp-inhibiting, nonionic surfactant, polysorbate 20, and the P-gp substrate, digoxin. The present study aimed to investigate if montmorillonite-surfactant hybrid particles could modulate the absorption of digoxin in vivo. Montmorillonite-surfactant hybrid particles were prepared by lyophilising an aqueous suspension of the constituents. Scanning electron microscopy, thermogravimetric analysis, and powder X-ray diffraction revealed an altered surface morphology, decreased water content, and intercalation of polysorbate 20 between montmorillonite layers. The particles were administered orally to Sprague Dawley rats, and digoxin was quantified by liquid chromatography-tandem mass spectrometry. Control digoxin-containing montmorillonite decreased the exposure of digoxin. In contrast, montmorillonite-surfactant hybrid particles increased AUC and C max by 31 and 91%, respectively, compared to digoxin in solution. It was hypothesised that montmorillonite-surfactant hybrid particles increased digoxin exposure by forming mucosa-localised elevated concentrations of polysorbate 20 and digoxin, which enhanced the inhibitory effect of polysorbate 20 on P-gp.

Thermodynamic data for the arsenates of various metals are necessary to calculate their solubilities and to evaluate their potential as arsenic storage media. If some of the less common arsenate minerals have been shown to be less soluble than the currently used options for arsenic disposal (especially scorodite and arsenical iron oxides), they should be further investigated as promising storage media. Furthermore, the health risk associated with arsenic minerals is a function of their solubility and bioavailability, not merely their presence. For all these purposes, solubilities of such minerals need to be known. In this work, a complete set of thermodynamic data has been determined for mansfieldite, AlAsO4·2H2O; angelellite, Fe4(AsO4)2O3; and kamarizaite, Fe3(AsO4)2(OH)3·3H2O, using a combination of high-temperature oxide-melt calorimetry, relaxation calorimetry, solubility measurements, and estimates where possible and appropriate. Several choices for the reference compounds for As for the high-temperature oxide-melt calorimetry were assessed. Scorodite was selected as the best one. The calculated Gibbs free energy of formation (all data in kJ·mol–1) is –1733.4 ± 3.5 for mansfieldite, –2319.2 ± 7.9 for angelellite and –3056.8 ± 8.5 for kamarizaite. The solubility products for the dissolution reactions are –21.4 ± 0.5 for mansfieldite, –43.4 ± 1.5 for angelellite and –50.8 ± 1.6 for kamarizaite. Available, but limited, chemical data for the natural scorodite–mansfieldite solid-solution series hint at a miscibility gap; hence the non-ideal nature of the series. However, no mixing parameters were derived because more data are needed. The solubility of mansfieldite is several orders of magnitude higher than that of scorodite. The solubility of kamarizaite, on the other hand, is comparable to that of scorodite, and kamarizaite even has a small stability field in a pH-pε diagram. It is predicted to form under mildly acidic conditions in acid drainage systems that are not subject to rapid neutralization and sudden strong supersaturation. The solubility of angelellite is high, and the mineral is obviously restricted to unusual environments, such as fumaroles. Its crystallization may be enhancedviaits epitaxial relationship with the much more common hematite. The use of the scorodite–mansfieldite solid solution for arsenic disposal, whether the solid solution is ideal or not, is not practical. The difference in solubility products of the two end-members (scorodite and mansfieldite) is so large that almost any system will drive the precipitation of essentially pure scorodite, leaving the aluminium in the aqueous phase.

The sustainable exploitation of phosphorus (P) is essential for food and water security. However, our current poor management of this essential nutrient represents a pressing challenge, which cause global scale pollution of water resources(2) while failing to achieve equitable access to fertilizers to support food production worldwide.(3) This is, in part, due to poor uptake of advances, for example, in new technologies to reduce losses of P from agriculture, in our understanding of P thresholds for ecosystem functioning, and in sustainable urban development approaches focused on nutrient recycling systems. We identify, here, a pressing need to develop a new generation of nutrient sustainability professionals working collectively to implement diverse and interdiciplinary approaches within large scale urban and rural planning, for example, following the UNESCO Global Action Programme on Education for Sustainable Development, to meet the diverse needs of communities and countries.

Vivianite (Fe3(PO4)2⋅8H2O) is a potential phosphorus (P) recovery product from wastewater treatment plants (WWTPs). However, routine methods for quantification of vivianite bound P (vivianite-P) are needed to establish the link between vivianite formation and operating conditions, as current approaches require specialized instrumentation (Mössbauer or synchrotron). This study modified a conventional sequential P extraction protocol by insertion of an extraction step (0.2% 2,2′-bipyridine + 0.1 M KCl) targeting vivianite-P (Gu et al., Water Research, 2016, 103, 352–361). This protocol was tested on digested and dewatered sludge from two WWTPs, in which vivianite (molar Fe:P ratios of 1.0–1.6) was unambiguously identified by optical microscopy, powder X-ray diffraction, and scanning electron microscopy with energy dispersive X-ray spectroscopy. The results showed that vivianite-P was separated from iron(III)-bound P (Fe(III)-P) in the sludge. Vivianite-P constituted about half of the total P (TP) in the sludge from a Fe dosing chemical P removal (CPR) WWTP, but only 16–26% of TP in the sludge from a WWTP using a combination of Fe dosing CPR and enhanced biological P removal (EBPR). The modified protocol revealed that Fe-bound P (Fe-P, i.e., vivianite-P + Fe(III)-P) was the dominant P fraction, in agreement with quantitative 31P nuclear magnetic resonance (NMR) experiments. Moreover, it was shown that the conventional P extraction protocol underestimated the Fe-P content by 6–35%. The established protocol represents a reliable in-house analytical method that can distinguish and quantify vivianite-P and Fe(III)-P in sludge, i.e. facilitate optimized vivianite production at WWTPs.

Recent advances in computational methodology allowed for first-principles calculations of the nuclear shielding tensor for a series of paramagnetic nickel(II) acetylacetonate complexes, [Ni(acac)2L2] with L = H2O, D2O, NH3, ND3, and PMe2Ph have provided detailed insight into the origin of the paramagnetic contributions to the total shift tensor. This was employed for the assignment of the solid-state 1,2H and 13C MAS NMR spectra of these compounds. The two major contributions to the isotropic shifts are by orbital (diamagnetic-like) and contact mechanism. The orbital shielding, contact, as well as dipolar terms all contribute to the anisotropic component. The calculations suggest reassignment of the 13C methyl and carbonyl resonances in the acac ligand [Inorg. Chem. 53, 2014, 399] leading to isotropic paramagnetic shifts of δ(13C) ≈ 800–1100 ppm and ≈180–300 ppm for 13C for the methyl and carbonyl carbons located three and two bonds away from the paramagnetic Ni(II) ion, respectively. Assignment using three different empirical correlations, i.e., paramagnetic shifts, shift anisotropy, and relaxation (T1) were ambiguous, however the latter two support the computational results. Thus, solid-state NMR spectroscopy in combination with modern quantum-chemical calculations of paramagnetic shifts constitutes a promising tool for structural investigations of metal complexes and materials.

The system Fe2O3-SO3-H2O contains the most important minerals of acid mine drainage (AMD), iron oxides, and iron sulfates. For geochemical modeling of the AMD systems, reliable thermodynamic data for these phases are needed. In this work, we have determined thermodynamic data for the most acidic sulfates rhomboclase [(H5O2)Fe(SO4)2·2H2O or (H3O)Fe(SO4)2·3H2O] and the phase (H3O)Fe(SO4)2. The actual compositions of the studied phases are (H3O)1.34Fe(SO4)2.17(H2O)3.06 (molecular mass of 344.919 g/mol) and (H3O)1.34Fe(SO4)2.17 (289.792 g/mol). Structural details for both phases were refined from synchrotron powder X-ray diffraction data. Enthalpies of formation were determined by acid-solution calorimetry. Low-temperature heat capacity was measured for rhomboclase by relaxation calorimetry but a critical analysis of entropies for several oxysalts showed that these data are too high. Entropies for both phases were estimated from a Kopp-rule algorithm. The enthalpies of formation and entropies were combined with previously published temperature-relative humidity brackets to generate an internally consistent thermodynamic data set for rhomboclase: ΔfH° = -3202.03 kJ/mol, S° = 378.7 J/(mol·K); and for (H3O)1.34Fe(SO4)2.17 : ΔfH° = -2276.25 kJ/mol, S° = 253.2 J/(mol·K). Solubility experiments at room temperature and at T = 4 °C agree well with previously reported data in the system Fe2O3-SO3-H2O. An inspection of the extended Pitzer model for Fe3+-SO4 solutions shows that this model reproduces the general topology of the phase diagram, but the position of the calculated solubility curves deviates substantially from the experimental data. Solid-state 2H MAS NMR spectra on deuterated rhomboclase show two isotropic chemical shifts δiso(2H) = of 8 ± 1 and 228 ± 1 ppm, assigned to D5O2 + and Fe-OD2 groups, respectively. Canonical ensemble (NVT) molecular dynamics simulations for (H3O)Fe(SO4)2 at T = 300 K showed that the H3O+ groups maintain their trigonal pyramidal geometry and perform different types of motion.

The phosphate (P) adsorption properties of three magnesium aluminum layered double hydroxides (LDH) intercalated with nitrate and/or carbonate (MgAl-NO3/CO3 LDH) with targeted Mg/Al ratios of 2, 3, and 4 were investigated to understand how phosphate interacts with the LDH using powder X-ray diffraction (PXRD), solid-state NMR spectroscopy, vibrational spectroscopy, scanning electron microscopy, and inductively coupled plasma-optical emission spectrometry. The solid products after phosphate exposure contained four different phosphate species which were quantified by 31P MAS NMR: phosphate intercalated in the interlayer (A), phosphate adsorbed to the surface of the LDH particles (B and C), and phosphate adsorbed to amorphous aluminum hydroxide (D). Their relative concentrations depend on the Mg/Al ratio, the phosphate loading, and the intercalated anion in the parent LDH. Surprisingly, phosphate intercalated by anion exchange, which has been assumed to be the dominant mechanism of P adsorption, is less than 30%. Instead phosphate adsorbed to the surface of the LDH particles is the predominant site (52-88%). Moreover, a non-negligible fraction (8-39%) of phosphate is adsorbed to an amorphous aluminum hydroxide (AOH) impurity (site D) especially at high phosphate concentrations and exposure time. AOH is a known impurity in LDH prepared by co-precipitation at constant pH, the most commonly used method in phosphate removal studies. This indicates that MgAl-LDH have higher affinity for phosphate than AOH. Furthermore, no significant dissolution of the LDH followed by precipitation of phosphate minerals was observed by PXRD and 27Al and 31P MAS NMR.

Capture of phosphorus from runoff and wastewater is of high priority in order to reclaim phosphorus for food security and to prevent water pollution. Here we report an environmentally friendly method to synthesize ultrathin MgAl layered double hydroxide (LDH)nanoparticles for phosphorus adsorption. Fast co-precipitation of magnesium and aluminum at 25–80 °C in the presence of urea resulted in the desired LDH with variable admixtures of amorphous aluminum hydroxide (16–38%)quantified from solid state 27 Al MAS NMR. Freshly synthesized particles appeared as exfoliated single layers that upon drying stacked to form particles with thickness of 3 to 5 nm (four to six LDH layers)and lateral sizes of ~30 nm, as seen by XRD, SEM, TEM, and AFM. Phosphate adsorption on LDH nanoparticles synthesized at room temperature (LDHns-U25)was very fast and reaction reached equilibrium within 15 min at pH 8.5. The freeze-dried LDHns-U25 nanoparticles exhibited phosphate sorption capacity of 98 ± 15 mg P·g −1 , which is 55% higher than for conventional LDH. Phosphate was bound to LDH electrostatically and via inner-sphere surface complexation as evidenced from a combination of 31 P MAS NMR spectroscopy, surface potential measurements, IR spectroscopy, and ionic strength effects on phosphate sorption. This study demonstrates that urea-facilitated synthesis of LDH nanoparticles provides high capacity phosphate sorbents with potentials for phosphate recovery from waste waters.

This study reports the mechanism of reactivity of phosphate anions (HPO4 2−) with Ca2Al-NO3 LDH. Sequestration of PO4 by Ca2Al-NO3 was quantified by fitting the adsorption isotherm with a Langmuir model. Adsorption capacity (65.2 mgP·g−1 of LDH) is greater than the theoretical anion exchange capacity indicating further mechanism of sequestration. Partial dissolution of CaAl-NO3 results in precipitation of multiple Ca-PO4 phases. Combined characterizations by XRD, 27Al and 31P NMR, FTIR/Raman and SEM highlight the competitive precipitation of hydroxyapatite and brushite within the LDH structure. Multiple environment of PO4 anions offer promising perspective for CaAl-NO3/PO4 as slow release fertilizer.

The phase purity of a series of ZnAl

The phase purity of a series of ZnAl 4(OH) 12SO 4· nH 2O layered double hydroxides (ZnAl 4-LDH) obtained from a reaction of bayerite (Al(OH) 3) with an excess of zinc(II) sulfate under hydrothermal conditions was investigated as a function of the reaction temperature, the duration of the hydrothermal treatment, and the zinc(II) concentration. The product quality, i.e., crystalline impurities, Al impurities, and bulk Zn:Al ratio, were assessed by powder X-ray diffraction (PXRD), 27Al MAS NMR, and elemental analysis. Structural characterization of a stoichiometric ZnAl 4-LDH (120 °C, 9 days, and 2.8 M Zn(II)) showed a well-defined structure of the metal ion layer as evidenced by a single, well-defined Zn environment: i.e., no Zn substitution on the Al sites according to Zn k-edge EXAFS and PXRD. Furthermore, nearly all of the 12 different 1H atoms in the -OH groups and 4 27Al resonances could be assigned using 1H, 27Al NMR correlation experiments recorded with ultrafast MAS. The interlayer water content is variable on the basis of thermogravimetric analysis and changes in the 1H MAS NMR spectra with temperature. A composition of ZnAl 4(OH) 12(SO 4)·2.6H 2O was obtained from a combination of these techniques and confirmed that ZnAl 4-LDH is isostructural with the mineral nickelalumite (NiAl 4(OH) 12SO 4·3H 2O).

The reactivity and thermal decomposition of γ-Mg(BH4)2-MHx, M = Li, Na, Mg, and Ca composites has been examined with the objective of studying the hydrogen storage capability of the composites. The samples were prepared by manual grinding γ-Mg(BH4)2 with a metal hydride to obtain homogenous mixtures. In-situ synchrotron radiation powder X-ray diffraction (SR-PXD) and simultaneous thermogravimetric analysis, differential scanning calorimetry, and mass spectrometry was performed to analyse the decomposition mechanism, whereas solid-state 11B nuclear magnetic resonance spectroscopy and SR-PXD was used to investigate the decomposition products. Interestingly, substitution reactions take place between magnesium borohydride and lithium, sodium and calcium hydride forming the more stable metal borohydrides, M(BH4)x, M = Li, Na or Ca. The composite γ-Mg(BH4)2-LiH has a hydrogen release at T ∼380–420 °C, which indicates the formation of amorphous LiBH4 during decomposition. For the composites γ-Mg(BH4)2-NaH, formation of crystalline NaBH4 is observed by SR-PXD from T = 150–450 °C, and hydrogen release ascribed to NaBH4 is observed in MS data at T = 460–480 °C. γ-Mg(BH4)2-MgH2 composite decomposes as the individual constituents. β-Ca(BH4)2 is formed at T = 175–375 °C in the composites of γ-Mg(BH4)2-CaH2. Bragg diffraction from CaB6 at T > 370 °C is detected by SR-PXD for γ-Mg(BH4)2-CaH2 (1:0.5) but not for samples richer in CaH2. Release of diborane was not observed for any of the magnesium borohydride metal hydride composites.

Polyphosphate (poly-P) is a major constituent in activated sludge from wastewater treatment plants with enhanced biological phosphorus removal due to poly-P synthesis by poly-P accumulating organisms where it plays an important role for recovery of phosphorus from waste water. Our aim was to develop a reliable protocol for poly-P quantification by

In this work, we determined thermodynamic properties of a suite of tin perovskites □ 2 (BSn 4 + )(OH,O) 6 that correspond to the minerals burtite (B = Ca), jeanbandyite (Fe 3 + ), schoenfliesite (Mg), wickmanite (Mn), vismirnovite (Zn), and mushistonite (Cu). Purity of the samples was verified by powder X-ray diffraction, chemical analysis (ICP-OES), solid state 119 Sn magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy, 57 Fe Mossbauer spectroscopy, thermogravimetry (TG), and Karl-Fischer titration. Enthalpies of formation ( Δ f H o ) were determined by acid-solution calorimetry (in 5 N HCl at T = 298 K, with SnCl 4 as the reference phase), that for jeanbandyite also in high-temperature oxide-melt calorimetry (in sodium molybdate at T = 973 K, with SnO 2 as the reference phase). For the two methods, the difference for the Δ f H o values is 10.7 kJ · mol − 1 , a fair agreement. Because of the high H 2 O content of the studied phases, acid-solution calorimetry was given preference as it is less sensitive to errors in H 2 O determination. Entropy was estimated, including configurational or magnetic contribution. The resulting Δ f G o (kJ · mol − 1 ) and log K s p values are: CaSn(OH) 6 − 1885.8 ± 7.6, 7.7; FeSn(OH) 5 O − 1425.4 ± 7.6, − 5.8 ; MgSn(OH) 6 − 1812.4 ± 7.5, 3.3; ZnSn(OH) 6 − 1519.6 ± 7.6, 0.7; MnSn(OH) 6 − 1598.7 ± 7.7, 1.0; CuSn(OH) 6 − 1311.2 ± 7.9, 0.0. The log K s p value relate to reaction MSn(OH) 6 + 6H + → M 2 + + Sn 4 + + 6H 2 O or FeSn(OH) 5 O + 7H + → Fe 3 + + Sn 4 + + 6H 2 O. The solid solution between vismirnovite and mushistonite was found to be thermodynamically non-ideal, with a mixing parameters W = − 15.38 kJ · mol − 1 . Calculations of Gibbs free energies of selected reactions show that the tin perovskites are stabilized at basic pH. For example, burtite becomes stable with respect to cassiterite (SnO 2 ) in systems buffered by calcite, gypsum or the C-S-H phase from cement at pH > 9–10.5. Similarly, jeanbandyite is stabilized in systems buffered by ferrihydrite [Fe(OH) 3 ] but not in those buffered by goethite (FeOOH). Saturation indices calculated from polluted water in field settings show the same trend; the tin perovskites are stable under alkaline conditions and the solutions become supersaturated with respect to the tin perovskites. Hence, under alkaline conditions, such phases could take up and retain tin in the environment.

Para-amino salicylate (PAS), a tuberculosis drug, was intercalated in three different layered double hydroxides (MgAl, ZnAl, and CaAl-LDH) and the samples were studied by multi-nuclear ((1)H, (13)C, and (27)Al) solid state NMR (SSNMR) spectroscopy in combination with powder X-ray diffraction (PXRD), elemental analysis and IR-spectroscopy to gain insight into the bulk and atomic level structure of these LDHs especially with a view to the purity of the LDH-PAS materials and the concentration of impurities. The intercalations of PAS in MgAl-, ZnAl-, and CaAl-LDH's were confirmed by (13)C SSNMR and PXRD. Moreover, (13)C MAS NMR and infrared spectroscopy show that PAS did not decompose during synthesis. Large amounts (20-41%) of amorphous aluminum impurities were detected in the structure using (27)Al single pulse and 3QMAS NMR spectra, which in combination with (1)H single and double quantum experiments also showed that the M(II):Al ratio was higher than predicted from the bulk metal composition of MgAl-PAS and ZnAl-PAS. Moreover, the first high-resolution (1)H SSNMR spectra of a CaAl LDH is reported and assigned using (1)H single and double quantum experiments in combination with (27)Al{(1)H} HETCOR.

A combined field and laboratory scale study of 10 European lakes treated between 2006 and 2013 with a lanthanum (La) modified bentonite (LMB) to control sediment phosphorus (P) release was conducted. The study followed the responses in sediment characteristics including La and P fractions and binding forms, P adsorption capacity of discrete sediment layers, and pore water P concentrations. Lanthanum phosphate mineral phases were confirmed by solid state (31)P MAS NMR and LIII EXAFS spectroscopy. Rhabdophane (LaPO4 · nH2O) was the major phase although indications of monazite (LaPO4) formation were also reported, in the earliest treated lake. Molar ratios between La and P in the sediments were generally above 1, demonstrating excess La relative to P. Lanthanum was vertically mixed in the sediment down to a depth of 10 cm for eight of the ten lakes, and recovery of La in excess of 100% of the theoretical aerial load indicated translocation of the LMB towards the deepest areas of the lakes. Lanthanum was generally recovered from bed sediment samples following sequential chemical extraction from the HCl fraction. Soluble reactive P (SRP) release experiments on intact sediment cores indicated conditions of P retention (with the exception of two lakes) by sediments, indicating effective control of sediment P release, i.e. between two and nine years after treatment.

The phosphate adsorption properties including kinetics and uptake pathway of MgxFe layered double hydroxides (LDH) with targeted x values of 2 and 3 and intercalated with nitrate (NO3 −) and chloride (Cl−) anions were investigated at a phosphate concentration of 16.31 mgP·L−1 and pH (pH = 5, 7, and 9) similar to wastewater conditions. The synthesized MgxFe-LDH show fast adsorption (90–98%) of the final phosphate removal within 3 h and remove 68–73% of the total phosphate content after 24 h. The pristine MgxFe-LDH and solid products after phosphate exposure were characterized by PXRD, FT-IR, zeta-potential, SEM, and solid-state 31P MAS NMR spectroscopy to investigate the phosphate removal pathway. Interestingly, the four MgxFe-LDH phase had similar Mg:Fe ratios irrespective of the Mg:Fe ratio of the reactants based on PXRD. The MgxFe-LDH plate-like morphology was preserved after phosphate exposure and no sign of phosphate intercalation were evident by PXRD, FT-IR, and SEM albeit a small amount of the MgxFe LDH was dissolved based on ICP-OES, PXRD and the final pH. Partial dissolution of the LDH was clearly evident by SEM for Mg2Fe-LDH exposed to 200% theoretical P capacity. The FT-IR spectra and zeta-potential values indicated that the phosphate ions are adsorbed by surface complexation. The 31P MAS NMR spectra of MgxFe-LDH exposed to phosphate has an intense spinning sideband manifold and only minor paramagnetic shifts (xFe-LDH is surface complexation similar to MgAl-LDH and possible the formation of ill-defined magnesium phosphate due to partial dissolution of the MgFe-LDH, especially at high P loading.

Our immediate and future food security agenda requires sustainable phosphorus (P) management, and recovered P products such a struvite form part of the solution. Waste recovered struvite is generated from different waste streams and precipitation technologies. In this study, we compare P speciation and bioavailability of nine struvite products with traditional/granulated chemical fertilisers to investigate performance characteristics across soil types in the Irish ecoregion. Elemental-analysis/P-speciation of the struvites was examined by ICP-OES, 31P solid state NMR, PXRD and P-solubility tests. The fertiliser dose effect and bioavailability of the different struvite products were tested in 4-week and 3-month rhizotron experiments with perennial ryegrass (Lolium perenne). In addition to calculating plant-P offtake, bioavailability was assessed by Olsen-P and Diffusive-Gradients-in-Thin-Films (DGT). The struvites differed markedly in colour/appearance, texture, metal content and solubility. Struvites all had similar P-speciation, but minor impurity phases were detected. There was no significant difference between the struvite samples and triple-super-phosphate (TSP) with respect to either plant growth performance or P-bioavailability. The struvite products are produced from different wastewater streams/processes, yet possess a uniformity in overall fertilising performance within our experiments. Encouragingly, no appreciable agronomic difference in terms of yield was observed between the struvite and chemical fertilisers, which provides further evidence in support of struvite as a sustainable alternative to mined rock-phosphate derived products. Importantly the struvite samples analysed within this study contained both significantly fewer impurities than TSP and lower concentrations of toxic metals such as cadmium.