Brian L. Phillips

Stony Brook University, Stony Brook, New York, United States

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Publications (125)548.11 Total impact

  • Brian L. Phillips · Zelong Zhang · Laura Kubista · Silvia Frisia · Andrea Borsato
    [Show abstract] [Hide abstract] ABSTRACT: Organic phosphorus incorporated in calcite during laboratory precipitation experiments and in natural cave deposits was investigated by solid-state NMR spectroscopy. For calcite precipitated in the presence of organic phosphoesters of varying size and functionality, solid-state 31P{1H} CP/MAS NMR shows that the phosphoesters were incorporated intact into the solid. Systematic changes in the 31P NMR chemical shift of the phosphate group were observed between the solid phosphoester and that incorporated in the solid precipitate, yielding 31P NMR chemical shifts of the coprecipitates in the range of +1.8 to -2.2 ppm. These chemical shifts are distinct from that of similarly prepared calcite coprecipitated with inorganic phosphate, 3.5 ppm. Only minor changes were noted in the phosphoester 31P chemical shift anisotropy (CSA) which suggests no significant change in the local structure of the phosphate group, which is dominated by C-O-P bonding. Close spatial proximity of the organic phosphate group to calcite structural components was revealed by 31P/13C rotational echo double resonance (REDOR) experiments for coprecipitates prepared with 13C-labeled carbonate. All coprecipitates showed significant 31P dephasing effects upon 13C-irradiation, signaling atomic-scale proximity to carbonate carbon. The dephasing rate for smaller organophosphate molecules is similar to that observed for inorganic phosphate, whereas much slower dephasing was observed for larger molecules having long and/or bulky side-chains. This result suggests that small organic molecules can be tightly enclosed within the calcite structure, whereas significant structural disruption required to accommodate the larger organic molecules leads to longer phosphate-carbonate distances. Comparison of 31P NMR spectroscopic data from the synthetic coprecipitates with those from calcite moonmilk speleothems indicates that phosphorus occurs mainly as inorganic orthophosphate in the natural deposits, although small signals occur with characteristics consistent with phosphate monoesters. The results of this study indicate that trace- to minor concentrations of dissolved organic molecules can be effectively taken up during calcite precipitation and incorporated in the structure, leaving a resilient record of materials present during crystallization.
    No preview · Article · Mar 2016 · Geochimica et Cosmochimica Acta
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    [Show abstract] [Hide abstract] ABSTRACT: A series of hexagonal low-OH, F, Cl apatite compositions synthesized by high-temperature reaction is characterized by powder X-ray diffraction (PXRD) and 1H magic-angle spinning (MAS) solid-state NMR methods. Quantitative 1H NMR analysis indicates that the hydroxyl content in all samples is low, less than 2 mol percent, and is due to OH in apatite. 1H{31P} rotational echo double resonance (REDOR) NMR difference spectroscopy indicates that hydroxyl groups are preferentially oriented toward fluorine, probably because of OH–···F– hydrogen bonding. Clustered hydroxyl groups are also observed and may play a significant role in hexagonal solid solution for ternary F, OH, Cl apatites.
    Full-text · Article · Dec 2015 · The Journal of Physical Chemistry C
  • [Show abstract] [Hide abstract] ABSTRACT: Dibromobutadiyne is an extremely unstable compound that explodes at room temperature, even under inert atmosphere. This instability has limited the studies of dibromobutadiyne almost entirely to spectroscopic characterization. Here we report an approach to control the reactivity of dibromobutadiyne, via topochemical reaction in cocrystals, leading to the ordered polymer poly(dibromodiacetylene), PBDA. At low temperatures (-15 to -18 °C), dibromobutadiyne can form cocrystals with oxalamide host molecules containing either pyridyl or nitrile side groups, in which halogen bonds align the dibromobutadiyne monomers for topochemical polymerization. The cocrystals with the bis(nitrile) oxalamide host undergo complete ordered polymerization to PBDA, demonstrated by solid-state MAS-NMR, Raman, and optical absorption spectroscopy. Once formed, the polymer can be separated from the host; unlike the monomer, PBDA is stable at room temperature.
    No preview · Article · Oct 2015 · Angewandte Chemie International Edition
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    [Show abstract] [Hide abstract] ABSTRACT: We present the results of a combined study of shocked labradorite from the Lonar Crater, India, using optical microscopy, micro-Raman spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, high-energy X-ray total scattering experiments, and micro-Fourier transform infrared (micro-FTIR) spectroscopy. We show that maskelynite of shock class 2 is structurally more similar to fused glass than to crystalline plagioclase. However, there are slight but significant differences – preservation of original pre-impact igneous zoning, anisotropy at infrared wavelengths, X-ray anisotropy, and preservation of some intermediate range order – which are all consistent with a solid-state transformation from plagioclase to maskelynite.
    Full-text · Article · Feb 2015 · The Journal of Geophysical Research Planets
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    Ning Ma · Ashaki A. Rouff · Brian L. Phillips
    [Show abstract] [Hide abstract] ABSTRACT: Phosphorus can be reclaimed from nutrient-rich sources as the mineral struvite (MgNH4PO4·6H2O) for reuse as fertilizer. This study determines the impact of initial pH (pHi) from 8 to 11 on the fraction of precipitated struvite from a MgCl2–(NH4)2HPO4–NaCl–H2O system. The rate of P removal from solution increases with pHi and maximizes at pHi 10. Scanning electron microscopy (SEM) of recovered precipitates shows changes in morphology and decreasing particle size with increasing pHi. 31P nuclear magnetic resonance spectroscopy (NMR) confirms that struvite constitutes 96–99% of the phosphate at pHi 8–10, with newberyite (MgHPO4·3H2O) as a minor crystalline phase. At pHi 11, 60% of the solid is struvite, with 22% of the phosphate contained in an amorphous phase and 18% as sodium phosphate. Thermogravimetric analysis (TG) reveals a correlation in the mass loss from the solids with the percentage of struvite detected. Coupling Fourier transform infrared spectroscopy (FT-IR) with TG indicates that the molar concentration of evolved H2O(g) and NH3(g) is influenced by the adsorption of NH4+(aq) at pHi 8–10 and by the low percentage of struvite at pHi 11. Overall, results indicate that both the amount of P recovered and the fraction of struvite are optimized at pHi 10. These findings can be used as a starting point in the selection of a suitable pHi for struvite recovery from nutrient-rich wastes.
    Full-text · Article · Apr 2014 · ACS Sustainable Chemistry & Engineering
  • [Show abstract] [Hide abstract] ABSTRACT: Amorphous calcium carbonate (ACC) is a common transient precursor to biogenic crystalline calcium carbonate, but factors controlling the amorphous to crystalline transformation remain unclear. We present a structural analysis and comparison of hydrated and partially dehydrated, synthetic ACC samples. Thermogravimetric analysis showed total H2O losses of 46% with heating to 115 °C and 75% for heating to 150 °C. The 1H NMR spectra of hydrous ACC, obtained both directly and indirectly, via 13C-detection, contain signals from four principal hydrogen environments: translationally rigid structural H2O, a restrictedly mobile H2O environment, fluidlike mobile H2O that is decoupled from rigid H and C, and hydroxyl. The retention of some restrictedly mobile H2O and lack of change in X-ray total scattering and absorption spectroscopy data for dehydrated ACC suggest that thermal dehydration does not significantly disrupt the calcium-rich ACC framework. NMR results and thermal analyses of samples dehydrated isothermally for extended periods indicate that the H2O loss mechanism is kinetically hindered and occurs in three stages: simultaneous loss of fluidlike mobile, restrictedly mobile, and rigid H2O → loss of restrictedly mobile and rigid H2O → loss of hydroxyl and trapped rigid and mobile components that cannot be removed without transformation to crystalline calcium carbonate.
    No preview · Article · Feb 2014 · Crystal Growth & Design
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    J S Vaughn · D H Lindsley · J M Hughes · H Nekvasil · B L Phillips
    [Show abstract] [Hide abstract] ABSTRACT: Anion (F, OH, Cl) arrangements in apatite are critical to an understanding of its mineral chemistry, relevant not only to the geological sciences but also to numerous technological applications in materials science and biomedical engineering. Although the anion positions in endmember compositions are well described, there exist substantial gaps in our understanding of the anion environments in mixed binary and ternary compositions. Progress in this area has been inhibited due to crystallographic disorder or reversals in the anion column and synthesis problems such as control of composition and growth of sufficiently large crystals for X-ray diffraction analysis. Recently 1 our group reported the crystallographic anion positions in synthetic fluor-chlorapatite {Ca 5 (PO 4) 3 (F 0.5 Cl 0.5)} using single-crystal XRD. A new fluorine site was identified at (0,0,0.167), which yields acceptable F-Cl interatomic distances along the c-axis column, while retaining overall endmember P6 3 /m crystal symmetry. Successful structure analysis required exceptionally low OH-component, which was achieved by high-temperature (1200°C) synthesis under vacuum. Nominal OH occupancy was estimated via solid-state NMR using 31 P{ 1 H} cross-polarization, which indicates ca. 0.5% of P occur in hydroxylapatite-like local environments. Results from 1 H{ 31 P} REDOR showed the presence of two OH environments, giving chemical shifts near 1.6 and 0.2 ppm consistent with OH in mixed-anion and OH-rich local column arrangements, respectively. Only a small fraction of the H in the bulk sample occurs in the apatite structure. We are currently investigating the fluorine environments along the fluor-chlorapatite binary. 19 F spectra for the 50/50 F/Cl sample shows two main peaks, indicating distinct F environments and which are being investigated by 19 F/ 31 P and 19 F/ 35 Cl double resonance methods to provide the local structural relationships to adjacent chlorine sites and nearby phosphate groups. These methods combined with the atomic positions and occupancies from XRD will provide a comprehensive picture of the chemistry in the c-axis column and its variation across the fluor-chlorapatite binary. [1] Hughes, J. M., Vaughn, J. S. et al Am. Mineral. In press.
    Full-text · Conference Paper · Jan 2014
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    Full-text · Dataset · Nov 2013
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    Wei Li · Xionghan Feng · Yupeng Yan · Donald L Sparks · Brian L Phillips
    Full-text · Dataset · Nov 2013
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    Wei Li · Xionghan Feng · Yupeng Yan · Donald L Sparks · Brian L Phillips
    [Show abstract] [Hide abstract] ABSTRACT: Sorption reactions occurring at mineral/water interfaces are of fundamental importance in controlling the sequestration and bioavailability of nutrients and pollutants in aqueous environments. To advance the understanding of sorption reactions, development of new methodology is required. In this study, we applied novel 31P solid-state nuclear magnetic resonance (NMR) spectroscopy to investigate the mechanism of phosphate sorption on Al hydroxides at different environmental conditions, including pH (4 - 10), concentration (0.1 - 10 mM), ionic strength (0.001 M - 0.5 M) and reaction time (15 min - 22 d). Under these conditions, the NMR results suggest formation of bidentate binuclear inner-sphere surface complexes was the dominant mechanism. However, it was found that surface wetting caused a small difference. A small amount (<3%) of monodentate mononuclear inner-sphere surface complexes was observed in addition to the majority of bidentate binuclear surface complexes on a wet paste sample prepared at pH 5, which was analyzed in situ using a double resonance NMR technique, namely 31P{27Al} rotational echo adiabatic passage double resonance (REAPDOR). Additionally, we found that adsorbents can substantially impact phosphate sorption not only on the macroscopic sorption capacity but also on their 31P NMR spectra. Very similar NMR peaks were observed for phosphate sorbed to gibbsite and bayerite, whereas the spectra for phosphate adsorbed to boehmite, corundum and γ-alumina were significantly different. All of these measurements reveal that NMR spectroscopy is a useful analytical tool for studying phosphorus chemistry at environmental interfaces.
    Full-text · Article · Jul 2013 · Environmental Science & Technology
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    [Show abstract] [Hide abstract] ABSTRACT: Total X-ray scattering and pair distribution function analysis are combined with nuclear magnetic resonance spectroscopy to identify key differences in structural properties between biogenic and synthetic samples of amorphous calcium carbonate (ACC). Biogenic samples studied are gastroliths taken from the American lobster and are composed of hydrated ACC containing minor impurities. X-ray pair distribution functions reveal that the short- and medium-range structure found in synthetic ACC also occurs in gastrolith ACC, notably with atomic pair correlations extending up to 10 Å. The 13C NMR spectra of gastrolith ACC show a distribution of carbonate environments as seen in synthetic hydrated ACC. However, 1H NMR spectroscopy reveals that a mobile H2O component and hydroxyl groups found in synthetic hydrated ACC are absent in the gastrolith ACC. This difference may arise from differences in local conditions of ACC formation. The 31P NMR results indicate that inorganic phosphate is the principal form of the minor phosphorus. Gastrolith that was allowed to age shows the presence of calcite and vaterite, as well as residual ACC. 31P NMR also reveals trace amounts of monetite (CaHPO4) in aged samples, raising the possibility that fresh gastrolith ACC may contain a minor component of amorphous calcium phosphate. The findings suggest that important differences in the hydrous components between synthetic and biogenic hydrated ACC influence stability of the amorphous phase and its transformation to crystalline forms, thereby extending the foundation for advanced materials applications in engineered systems.
    Full-text · Article · Jun 2013 · Crystal Growth & Design
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    [Show abstract] [Hide abstract] ABSTRACT: In this research, we investigated the effects of glyphosate (GPS) on Zn sorption/precipitation on γ-alumina using a batch technique, Zn K-edge EXAFS, and 31P NMR spectroscopy. The EXAFS analysis revealed that, in the absence of GPS, Zn adsorbed on the aluminum oxide surface mainly as bidentate mononuclear surface complexes at pH 5.5, whereas Zn-Al layered double hydroxides (LDH) precipitates formed at pH 8.0. In the presence of GPS, the EXAFS spectra of Zn sorption samples at pH 5.5 and 8.0 were very similar, both of which demonstrated that Zn did not directly bind to the mineral surface but bonded with the carboxyl group of GPS. Formation of γ-alumina-GPS-Zn ternary surface complexes were further suggested by 31P solid state NMR data which indicated the GPS binds to γ-alumina via phosphonate group, bridging the mineral surface and Zn. Additionally, we showed the sequence of additional GPS and Zn can influence the sorption mechanism. At pH 8, Zn-Al LDH precipitates formed if Zn was added first and no precipitates formed if GPS was added first or simultaneously with Zn. In contrast, at pH 5.5, only γ-alumina-GPS-Zn ternary surface complexes formed regardless of whether GPS or Zn was added first or both were added simultaneously.
    Full-text · Article · Apr 2013 · Environmental Science & Technology
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    [Show abstract] [Hide abstract] ABSTRACT: Phosphate sorption at the corundum (α-Al2O3)/water interface was investigated as a function of phosphate concentration (0.1–1 mM) and pH (3–11) by 31P solid state NMR spectroscopy, ATR-FTIR, and quantum chemical calculation. The 31P NMR spectra indicate that under these experimental conditions phosphate adsorbs onto corundum mainly as inner-sphere complexes that yield a peak at δP = −2.8 ppm with full width at half maximum (FWHM) of 9.2 ppm, with a small amount aluminum phosphate surface precipitates as suggested by an NMR signal observed from δP = −12 to −20 ppm. We employed 31P{27Al} rotational echo adiabatic passage double resonance (REAPDOR) to further analyze the phosphate adsorption samples prepared at pH 5 and 9 in order to determine the phosphate/Al coordination. To aid interpretation of the NMR data, a series of bidentate and monodentate structural models of phosphate adsorbed on corundum (0 0 1) and (0 1 2) surfaces were calculated using density function theory (DFT). By comparing the experimental REAPDOR curves and those simulated from these models, we can assign the dominant peaks to bidentate binuclear surface complexes. Formation of bidentate binuclear surface complexes is supported by the ATR/FTIR spectra combined with DFT calculation, which further suggests a mixture of non-protonated bidentate and mono-protonated bidentate surface complexes on the corundum surface at pH 5. At pH 9, both NMR and ATR/FTIR indicate the formation of bidentate surface complexes on corundum surface.
    Full-text · Article · Apr 2013 · Geochimica et Cosmochimica Acta
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    [Show abstract] [Hide abstract] ABSTRACT: Variations in speleothem P concentration show cyclic patterns that have important implications for high resolution palaeoclimate and palaeoenvironmental reconstructions. However, little is known about the speciation of P in calcite speleothems. Here we employ solid-state 31P and 1H magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopic techniques as a non-destructive method for analyzing the distribution of P in speleothems. The 31P MAS NMR results show three peaks indicating the presence of three primary types of phosphate species in samples from the Grotta di Ernesto (northeastern Italy): a broad peak at a chemical shift δP-31 = 3.1 to 3.7 ppm from individual phosphate ions incorporated within calcite, a narrow set of peaks near δP-31 = − 0.9 ppm from crystalline monetite and a narrow peak at δP-31 = 2.9 ppm from an unidentified crystalline phosphate phase. Essentially identical results were obtained for a synthetic calcite/phosphate coprecipitate. Spectra collected for a sample from Grotte de Clamouse (southern France) show only a broad peak near 3.5 ppm suggesting a possible limit for phosphate incorporation into the calcite structure. These data suggest that P in this system can interact to form calcium phosphate surface precipitates during infiltration events and are subsequently enclosed during calcite growth.
    Full-text · Article · Jan 2013 · Earth and Planetary Science Letters
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    Wei Li · Xionghan Feng · Yupeng Yan · Donald L Sparks · Brian L Phillips
    [Show abstract] [Hide abstract] ABSTRACT: Sorption reactions occurring at mineral/water interfaces are of fundamental importance in controlling the sequestration and bioavailability of nutrients and pollutants in aqueous environments. To advance the understanding of sorption reactions, development of new methodology is required. In this study, we applied novel 31 P solid-state nuclear magnetic resonance (NMR) spectroscopy to investigate the mechanism of phosphate sorption on aluminum hydroxides under different environ-mental conditions, including pH (4−10), concentration (0.1−10 mM), ionic strength (0.001−0.5 M), and reaction time (15 min−22 days). Under these conditions, the NMR results suggest formation of bidentate binuclear inner-sphere surface complexes was the dominant mechanism. However, it was found that surface wetting caused a small difference. A small amount (<3%) of monodentate mononuclear inner-sphere surface complexes was observed in addition to the majority of bidentate binuclear surface complexes on a wet paste sample prepared at pH 5, which was analyzed in situ by a double-resonance NMR technique, namely, 31 P{ 27 Al} rotational echo adiabatic passage double resonance (REAPDOR). Additionally, we found that adsorbents can substantially impact phosphate sorption not only on the macroscopic sorption capacity but also on their 31 P NMR spectra. Very similar NMR peaks were observed for phosphate sorbed to gibbsite and bayerite, whereas the spectra for phosphate adsorbed to boehmite, corundum, and γ-alumina were significantly different. All of these measurements reveal that NMR spectroscopy is a useful analytical tool for studying phosphorus chemistry at environmental interfaces. ■ INTRODUCTION Phosphate is widely recognized as an essential nutrient for plants and crops and has received extensive attention. However, in the past several decades, overfertilization has caused excessive phosphate mobility from agricultural soils to water bodies, and an adverse consequence is the acceleration of lake and coastal eutrophication. 1 To effectively mitigate phosphate as a non-point-source agricultural pollutant, a good under-standing of phosphate interactions with soil minerals is necessary. In soils, phosphate anions can strongly sorb on metal (hydr)oxides, and the sorption behavior depends on the phosphate concentration, pH, ionic strength, and presence of competing ions (i.e., CO 3 2− , SO 4 2− , etc.). 2 In general, phosphate sorption mechanisms involve formation of inner-sphere surface complexes and surface precipitation. 2 In the surface complexation process, phosphate can either replace two adjacent surface hydroxyl groups (e.g., MeOH) to form bidentate binuclear bonding [(MeO) 2 −PO 2 ] or replace one to form monodentate mononuclear bonding [(MeO)−PO 3 ] (Scheme 1). Surface precipitation occurs when adsorbed phosphate ions interact with the metal ions dissolved from adsorbents 2,3 and form a new solid phase (i.e., surface precipitates). However, many details with respect to the two
    Full-text · Article · Jan 2013 · Environmental Science and Technology
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    [Show abstract] [Hide abstract] ABSTRACT: To better understand the sequestration of toxic metals such as nickel (Ni), zinc (Zn), and cobalt (Co) as layered double hydroxide (LDH) phases in soils, we systematically examined the presence of Al and the role of mineral dissolution during Zn sorption/precipitation on γ-Al(2)O(3) (γ-alumina) at pH 7.5 using extended X-ray absorption fine structure spectroscopy (EXAFS), high-resolution transmission electron microscopy (HR-TEM), synchrotron-radiation powder X-ray diffraction (SR-XRD), and (27)Al solid-state NMR. The EXAFS analysis indicates the formation of Zn-Al LDH precipitates at Zn concentration ≥0.4 mM, and both HR-TEM and SR-XRD reveal that these precipitates are crystalline. These precipitates yield a small shoulder at δ(Al-27) = +12.5 ppm in the (27)Al solid-state NMR spectra, consistent with the mixed octahedral Al/Zn chemical environment in typical Zn-Al LDHs. The NMR analysis provides direct evidence for the existence of Al in the precipitates and the migration from the dissolution of γ-alumina substrate. To further address this issue, we compared the Zn sorption mechanism on a series of Al (hydr)oxides with similar chemical composition but differing dissolubility using EXAFS and TEM. These results suggest that, under the same experimental conditions, Zn-Al LDH precipitates formed on γ-alumina and corundum but not on less soluble minerals such as bayerite, boehmite, and gibbsite, which point outs that substrate mineral surface dissolution plays an important role in the formation of Zn-Al LDH precipitates.
    Full-text · Article · Oct 2012 · Environmental Science & Technology
  • [Show abstract] [Hide abstract] ABSTRACT: [ThB5O6(OH)6][BO(OH)2]·2.5H2O (Notre Dame Thorium Borate-1, NDTB-1) is an inorganic supertetrahedral cationic framework material that is derived from boric acid flux reactions. NDTB-1 exhibits facile single crystal to single crystal anion exchange with a variety of common anions such as Cl−, Br−, NO3−, IO3−, ClO4−, MnO4−, and CrO42−. More importantly, NDTB-1 is selective for the removal of TcO4− from nuclear waste streams even though there are large excesses of competing anions such as Cl−, NO3−, and NO2−. Competing anion exchange experiments and magic-angle spinning (MAS)-NMR spectroscopy of anion-exchanged NDTB-1 demonstrate that this unprecedented selectivity originates from the ability of NDTB-1 to trap TcO4− within cavities, whereas others remain mobile within channels in the material. The exchange kinetics of TcO4− in NDTB-1 are second-order with the rate constant k2 of 0.059 s−1 M−1. The anion exchange capacity of NDTB-1 for TcO4− is 162.2 mg g−1 (0.5421 mol mol−1) with a maximum distribution coefficient Kd of 1.0534 × 104 mL g−1. Finally, it is demonstrated that the exchange for TcO4− in NDTB-1 is reversible. TcO4− trapped in NDTB-1 can be exchanged out using higher-charged anions with a similar size such as PO43− and SeO42−, and therefore the material can be easily recycled and reused.
    No preview · Article · Jun 2012 · Advanced Functional Materials
  • Wei Li · Wenqian Xu · John B. Parise · Brian L. Phillips
    [Show abstract] [Hide abstract] ABSTRACT: The interaction of calcium with phosphate at mineral/water interfaces is of importance for understanding both P sequestration and phosphate mineral formation. We investigated the effect of dissolved calcium on phosphate uptake by boehmite in batch sorption studies as a function of pH. Examination of the solids by 31P NMR spectroscopy and powder X-ray diffraction (XRD) shows evidence for formation of hydroxylapatite from pH 7 to pH 9, which is supported by correlation of Ca and P on particle surfaces at pH 9 observed by scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDX) analysis. At pH 6, two major 31P NMR peaks are observed at δP–31 = 0 and −6 ppm, indicating the presence of bidentate binuclear complexes with surface Al atoms, similar to those found in the absence of dissolved Ca. At higher pH, an additional 31P peak at δP–31 = 2.65 ppm is observed, consistent with hydroxylapatite (Hap). The NMR data indicate that after 30 days most of the phosphate (75%) remained as adsorption complexes at pH 7, but that Hap accounts for most of the phosphate at higher pH, although surface complexes were still evident in CP/MAS NMR spectra. The identification of crystalline Hap is further supported by 31P{1H} heteronuclear correlation (HetCor) experiments in which the 2.65 ppm 31P peak correlates to a narrow 1H peak at δH–1 = 0.2 ppm that is diagnostic of the hydroxyl groups of Hap. In powder X-ray diffraction patterns, two small peaks are observed at slow scan rates that match the major reflections of Hap. Nonetheless, Hap crystals could not be identified in SEM images suggesting small particle size, in agreement with broad XRD peaks. At short reaction times only adsorbed phosphate is observed at pH 7, whereas Hap forms within 15 min at pH 9. These results indicate that the crystallization rate of Hap is enhanced by the boehmite surface, although the detailed mechanisms could not be discerned from these data.
    No preview · Article · May 2012 · Geochimica et Cosmochimica Acta
  • [Show abstract] [Hide abstract] ABSTRACT: Allophane and imogolite neogenesis in soils may occur in the presence of organic matter. To understand this process under conditions relevant to soils, the influence of dissolved organic carbon (DOC) as humic acid (HA), on aluminosilicate formation was studied at 25 C ∘ , pH 6, and low-DOC concentrations. For solutions with initial Al/Si ratios of 1–2.1, and 0–6 mg/L DOC, precipitates recovered after 20 h had Al/Si ratios of 2.2–2.7. The formation of allophane, imogolite-like material, and aluminosilicate gel was confirmed by XRD, FTIR, and NMR. The effect of DOC was to produce a small, but systematic increase in imogolite-like Si in the precipitate, and a decrease in the formation of aluminosilicate gel. Results suggest that the presence of DOC as HA slows the otherwise rapid polymerization of Al and Si at low temperature, and may also promote the formation of imogolite. The high C content of these precipitates indicates that this process may facilitate the sequestration of organic matter, slowing C cycling in soils.
    No preview · Article · Mar 2012 · Applied and Environmental Soil Science
  • B.L. Phillips · Y.J. Lee · R.J. Reeder
    No preview · Article · Jan 2012

Publication Stats

3k Citations
548.11 Total Impact Points

Institutions

  • 2005-2015
    • Stony Brook University
      • Department of Geosciences
      Stony Brook, New York, United States
  • 2002-2013
    • State University of New York
      New York City, New York, United States
  • 2010
    • University of Notre Dame
      • Department of Civil and Environmental Engineering and Earth Sciences
      South Bend, Indiana, United States
  • 2006
    • Temple University
      • Department of Chemistry
      Filadelfia, Pennsylvania, United States
  • 1997-2006
    • University of California, Davis
      • • Department of Chemistry
      • • Department of Chemical Engineering and Materials Science
      Davis, California, United States
  • 2000-2001
    • Carnegie Mellon University
      • Department of Materials Science and Engineering
      Pittsburgh, Pennsylvania, United States
  • 1988-1995
    • University of Illinois, Urbana-Champaign
      • Department of Geology
      Urbana, Illinois, United States