Increase In Phosphate Content Research Articles

Rapid subsidence as a driver of phosphate deposition in the later Ordovician: Case study from the Alabama Appalachians

An increase in accumulation of phosphate-enriched sediment occurred in several areas of Earth's oceans during the later Ordovician, suggesting that some fundamental change (s) in seawater and/or pore water chemistry were taking place, either syndepositionally or during early diagenesis. One hypothesis is that widespread cooling of the water column led to this increase, but another is that the increase could have been forced primarily by changes in seawater chemistry that accompanied an influx of siliciclastic sediments associated with tectonically driven subsidence. Here, we report on findings from study of the upper ~30 m of the >200 m of Middle and Late Ordovician strata exposed near Tidwell Hollow, Blount County, Alabama, and what the results suggest about the competing hypotheses. This Ordovician sequence, deposited along the southeastern margin of Laurentia during the initial (Blountian) stage of the Taconic Orogeny, records the transition from a restricted peritidal carbonate shelf environment (the “Black River lithofacies”) into a more normal marine carbonate environment (the “Trenton lithofacies”). In particular, the younger carbonate strata are notable for their measurably higher amounts of secondary phosphate minerals. This stratigraphic interval is also well-constrained chronostratigraphically by the presence of the Deicke and Millbrig K-bentonite beds (altered volcanic tephra layers), thus it is ideal for a focused geochemical, petrographic, and stratigraphic investigation of the increased phosphate content of a specific Upper Ordovician sequence. Analyses of bulk rock samples and of extracted collophane grains (via x-ray fluorescence, XRF, and in-situ laser ablation inductively coupled plasma mass spectrometer, ICPMS) suggest that phosphogenesis in these strata was episodic rather than slow and steady, with a depositional pattern of abrupt increases followed by abrupt declines. Observed trace element changes in the 12 m to 18 m sample interval include the occurrence of elevated Th/U ratios (maximum of 5.7) accompanied by Y/Ho ratios that range from 27 (base) to 51 (top). We attribute these changes to increasing silicate influx into the basin and an accompanying increase in available Fe, which would preferentially scavenge MREEs and then release them to the pore waters leading to MREE enrichment, which we also observe in this interval. In a rapidly subsiding basin, MREE enrichment could have resulted from initial restriction of bottom water circulation followed by gradually more open marine conditions. Some allochems and textures that are more characteristic of the older Black River lithofacies than the younger Trenton lithofacies (e.g. framework grains of calcareous green algae and Type 1 and Type 2 oncoids, fenestral lime mudstones, and associated small framestones of Tetradium sp. buildups) persist in relative abundance upsection into the ~10 m interval of strata above the Millbrig K-bentonite Bed, and this persistence supports the hypothesis that the Trenton transgression was not initially accompanied by widespread cooling of the Laurentian epicontinental sea. Instead, we propose that variable weathering rates, turbidity, and nutrient supply accompanied by relatively rapid subsidence could have governed the observed variability in phosphate deposition and elemental abundances in these sediments, and that this subsidence of the Laurentian margin could have been the driver of an uptick in phosphate deposition during the later Ordovician here, and perhaps at other locations as well where subsidence was occurring, given that increased phosphate deposition is a globally recognized and globally significant change in many Upper Ordovician sequences beyond eastern Laurentia.

Investigation of physical, mechanical and in-vitro bioactivity of bioactive glass-ceramics fabricated from waste soda-lime-silica glass doped P2O5 by microwave irradiation sintering

The ever-increasing generation of waste glass, poses a major environmental challenges due to its large volume and limited recycling options. This research explores a novel sustainable approach to repurposing this waste by transforming it into silicate based bioactive glass-ceramics (SBGCs). The glass waste was recycled into powder form and homogeneously mixed with sodium dihydrogen orthophosphate (NaH2PO4) in the step of 2, 4, 6, 8 and 10 wt % respectively with addition of organic binder and sintered by microwave irradiation approach. The obtained SBGCs were then characterized for its phase constituents, microstructure, physical, mechanical, and in-vitro bioactivity behaviour. The results showed that the samples exhibited considerable density and porosity while both the micro-hardness and compressive strength decreased with increased phosphate content. Sample SLP2% showed optimum hardness and compressive strength of 7.3 GPa and 87 MPa respectively. Combeite was obtained as the major phase while wollastonite and quartz were also detected. The developed SBGCs also showed increased hydroxyapatite (HA) formation after immersion in simulated body fluid (SBF) and displayed good antibacterial capacity when reacted with four bacteria strains. The results obtained indicate that the developed SBGCs might be considered a potential candidate for biomedical applications. However, sample SLP8% is the best sample to serve as bioactive glass-ceramics considering the combination of its high HA and good CHA formation, besides its considerable density and mechanical properties.

Influence of Phosphate on Network Connectivity and Glass Transition in Highly Polymerized Aluminosilicate Glasses.

Melt-derived metaluminous (Al/Na = 1) aluminosilicate glasses in the system SiO2-Al2O3-Na2O-P2O5 were prepared with P2O5 and SiO2 contents varying from 0 to 7.5 and 50 to 70 mol %, respectively. The glass structure was investigated by X-ray absorption near edge structure, far- and medium-infrared, and polarized Raman spectroscopic techniques. The results indicate the incorporation of phosphate into the aluminosilicate network not only as partially depolymerized groups but also as fully polymerized groups charge-balanced by aluminate units in Al-O-P bonds. A new analysis method based on polarized Raman spectra in the bending frequency range indicates a preference of phosphate to reorganize the smallest ring structures. Changes in the glass transition temperature with the increase in phosphate content were found to be consistent with the depolymerization of the network structure shown by spectroscopy. By contrast, increasing the silica content by substituting SiO4 for AlO4 tetrahedra, while keeping the phosphate content constant, was found to have a negligible effect on network polymerization. Still, the glass transition temperature decreased and correlated with a far-infrared sodium band shift to higher frequency. This was interpreted as local changes in bond strength caused by complex interactions between the different network formers and sodium ions.

Concentration‐dependent response of soil parameters and functions to trifluoroacetic acid

AbstractDespite growing environmental concerns about perfluoroalkyl and polyfluoroalkyl substances (PFAS) worldwide, the ultra‐short‐chain PFAS, for example, trifluoroacetic acid (TFA), have been largely neglected in the context of soil pollution. Given the persistence and increasing occurrence of TFA in the soil environment, accumulated TFA could impact soil properties and functions. Therefore, we investigated the effects of a wide range of concentrations of TFA (0.001–100 μg g−1) on chemical, physical and biological indicators of soil health, using a six‐week microcosm experiment. Our results showed that TFA treatments decreased soil pH, sulphate content, soil respiration, litter decomposition and bacterial abundance, and increased phosphate content (p < 0.05). These effects were observed for TFA concentrations ≥1 μg g−1. As expected, because of its strong acidity, TFA decreased soil pH, and this change likely contributed to effects on other soil parameters and functions, for example, reducing bacterial abundance and soluble nutrients. However, importantly, TFA clearly also affected soil parameters at concentrations at which soil pH was not changed. Soil aggregation, fungal abundance, and enzyme activities were not affected by TFA in this study. Considering the current reported environmental levels of TFA of <2.4 μg g−1, only litter decomposition would be affected under current field conditions. Our data also show that future accumulation of higher concentrations, or hotspots of TFA, will likely negatively affect soils with similar properties as our test soil. Thus, we demonstrated that microbial processes can be impacted by the accumulation of the ‘forever chemical’ TFA in the tested sandy, low organic matter soil.Highlights Trifluoroacetic acid (TFA) decreased soil pH, respiration, litter decomposition and bacterial abundance. TFA affected soil soluble nutrients. TFA affected litter decomposition at 1 μg g−1 with no change in soil pH. Effects of TFA on soil enzyme activity and aggregation and fungal abundance were negligible.

Electrical Conductivity Enhancement of V2O5-P2O5-Bi2O3 Glasses by Nanocrystallization

The structural and electrical properties of the xP2O5-(40 − x) Bi2O3-60V2O5 (0 ≤ x ≤ 20) glass system have been investigated. The samples were prepared by the conventional melt-quenching technique. X-ray diffraction (XRD) patterns confirmed the amorphous nature of the present glasses. Nanocrystalline grains were found due to the annealing of the glass samples under study. Nanocrystals with an average grain size of 22 nm were implanted in the glass structure and estimated from the XRD patterns of the glass–ceramic samples. DC conductivity of the glass system has been determined in the temperature range 300–500 K. It was found that the general behavior of electrical conductivity was similar for all the glass compositions and found to decrease with increasing phosphate content. The electrical conductivity of the glass–ceramic nanocrystals obtained by annealing at crystallization temperature (Tc) was much higher than the initial glass. The activation energy (W) was enhanced by annealing and was obtained from plots of temperature-dependent DC conductivity, and found to be 0.23–0.31 eV for glasses and 0.19–0.23 eV for the glass–ceramic nanocrystals.

Nano-imaging confirms improved apatite precipitation for high phosphate/silicate ratio bioactive glasses

Bioactive glasses convert to a biomimetic apatite when in contact with physiological solutions; however, the number and type of phases precipitating depends on glass composition and reactivity. This process is typically followed by X-ray diffraction and infrared spectroscopy. Here, we visualise surface mineralisation in a series of sodium-free bioactive glasses, using transmission electron microscopy (TEM) with energy-dispersive X-ray spectroscopy (EDXS) and X-ray nano-computed tomography (nano-CT). In the glasses, the phosphate content was increased while adding stoichiometric amounts of calcium to maintain phosphate in an orthophosphate environment in the glass. Calcium fluoride was added to keep the melting temperature low. TEM brought to light the presence of phosphate clustering and nearly crystalline calcium fluoride environments in the glasses. A combination of analytical methods, including solid-state NMR, shows how with increasing phosphate content in the glass, precipitation of calcium fluoride during immersion is superseded by fluorapatite precipitation. Nano-CT gives insight into bioactive glass particle morphology after immersion, while TEM illustrates how compositional changes in the glass affect microstructure at a sub-micron to nanometre-level.

Abstract 3046: In situ analysis of microenvironmental glycogen in Ewing's sarcoma patient samples by mass spectrometry imaging

Abstract Ewing's sarcoma (ES) is a rare pediatric cancer of the bone and soft tissues affecting adolescents and young adults, with peak incidence from ages 10 to 15 years. A clinical feature of ES is the accumulation of Periodic acid-Schiff positive (PAS+) aggregates. PAS+ staining in ES histopathology analysis has been speculated to be glycogen accumulation, however, this has not been confirmed. To interrogate these aggregates, we developed a novel workflow for the high-sensitive detection of in situ glycogen via enzymatic release of glycogen substrates coupled to matrix assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS) from formalin-fixed patient tissues. We utilized this method to study the nature of PAS+ staining in a cohort of ES patient samples surgically removed from tibia, rib, chest, shoulder, abdomen and testicle tissues. Using this innovative technique, we discovered profound intra-tumoral glycogen accumulation compared to adjacent stroma, normal, muscle and/or necrotic tissue. Further, intra-tumoral glycogen also has an increased phosphate content and distinct chain length profile compared to normal glycogen found in adjacent and patient-matched tissue. Notably, genetic manipulation and pharmacological inhibition of glycogen synthesis, or removal of glycogen phosphates, blunted ES tumor growth in xenografted mouse models. These findings suggest an important role of ES glycogen aggregates in tumor growth. Together, application of this novel MALDI-IMS technique, and the insights provided by formalin-fixed ES patient samples, reveals a distinct role of ES glycogen aggregates and uncovers a new therapeutic opportunity for this rare pediatric cancer. Citation Format: Lyndsay E. Young, Lindsey R. Conroy, Harrison A. Clarke, Derek B. Allison, Richard R. Drake, Matthew S. Gentry, Ramon C. Sun. In situ analysis of microenvironmental glycogen in Ewing's sarcoma patient samples by mass spectrometry imaging [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 3046.

EVALUATING THE ANTHROPOGENIC IMPACT ON THE PRUT RIVER NEAR YAREMCHE-TOWN ON THE POLLUTION LEVEL INDICES OF BOTTOM SEDIMENTS

Introduction. One of the most objective and reliable indicators of the state of pollution of the aquatic environment and the overall level of technological load on it is the content of pollutants in bottom sediments (BS). There are no large industrial enterprises in and around Yaremche-town (Ivano-Frankivsk region), so there are no significant discharges of toxic substances into the sewage system, especially directly into the river. However, every year in this picturesque cornerof Prykarpattia the number of sanatoriums, recreation centres, cottage towns and just residential buildings grows. Accord-ingly, the Prut River, which is the pearl of this region, quite often gets untreated runoff, which pollutes not only water but also settles on bottom sediments.The purpose of this study was to assess the anthropogenic load on the Prut River based on a comprehensive environmental analysis of the state of pollution of the bottom sediments of this river upstream and downstream from Yaremche.Methods. Water extracts from bottom sediments were prepared by the recommendations of the relevant regula-tions in the ratio "bottom sediments - water" as 1: 5 in terms of the dry mass of bottom sediments. Laboratory study of hydrochemical parameters of selected samples was performed by gravimetric, titrimetric, photometric and other methods of analysis.Research results. The accumulation of ammonium salts, nitrites and nitrates, which are easily soluble, in the far above the discharge site of wastewater, is obviously due to the significant sorption properties of river sludge, which prevents these ions from being washed away by the flow. At the point of discharge of wastewater from the city, the content of these ions increases and reaches a maximum at point 3 - at a distance of approx. 100 m below the discharge site. Further downstream, their number systematically decreases. A similar distribution of concentrations is observed in the case of phosphates. Their source of getting into the river also, for the most part, belongs to the housing and communal services. A significant contribution to the increased phosphate content in the sample below the discharge is made by urban wastewater, in which even after treatment the concentration of phosphate ions remains quite high. The fact of the presence of oil products in the bottom sediments at the investigated area was revealed. The constant increase in the number of road transport on the banks of this resort river inevitably leads to the ingress of products of incomplete combustion of fuel, uncontrolled spills.Conclusions. Upstream from the place of discharge into the Prut River of treated wastewater in the city of Yaremche, the concentrations of salts-pollutants of the biogenic group are formed due to uncontrolled sources of domestic sew-age. In this area, the pollution of bottom sediments is insignificant, slightly higher at the discharge site, and they are of the greatest importance below the discharge. This fact indicates the growing anthropogenic impact of coastal cities on the state of the river and in general, and pollution of bottom sediments, in particular. For the first time oil products were found in bottom sediments in the studied area. The reason for this phenomenon is the constant increase in the number of vehicles on the banks of this river.

Supplementation With Phytogenic Compounds Modulates Salivation and Salivary Physico-Chemical Composition in Cattle Fed a High-Concentrate Diet.

Saliva facilitates feed ingestion, nutrient circulation, and represents an important pH buffer for ruminants, especially for cattle fed high-concentrate diets that promote rumen acidification. This experiment evaluated the short-term effects of nine phytogenic compounds on salivation, saliva physico-chemical composition as well as ingested feed boli characteristics in cattle. A total of nine ruminally cannulated Holstein cows were used. Each compound was tested in four of these cows as part of a high-concentrate meal (2.5 kg of total mixed ration in dry matter basis for 4 h) in low or high dose, and was compared to a control meal without compound. Saliva was sampled orally (unstimulated saliva) for physico-chemical composition analysis. Composition of the ingested saliva (stimulated saliva), salivation and feed boli characteristics were assessed from ingesta collected at the cardia during the first 30 min of the meal. Analysis of unstimulated saliva showed that supplementation with capsaicin and thyme oil increased buffer capacity, while supplementation with thymol, L-menthol and gentian root decreased saliva pH. In addition, supplementing angelica root decreased saliva osmolality. Regression analysis on unstimulated saliva showed negative associations between mucins and bicarbonate as well as with phosphate when garlic oil, thyme oil or angelica root was supplemented. Analysis of stimulated saliva demonstrated that supplementation with garlic oil increased phosphate concentration, thyme oil tended to increase osmolality, capsaicin and thymol increased buffer capacity, and ginger increased phosphate content. Furthermore, salivation rate increased with ginger and thymol, and tended to increase with garlic oil, capsaicin, L-menthol and mint oil. Feed ensalivation increased with capsaicin. A positive association was found between feed bolus size and salivation rate when any of the phytogenic compounds was supplemented. Overall, our results demonstrate positive short-term effects of several phytogenic compounds on unstimulated and stimulated saliva physico-chemical properties, salivation or feed boli characteristics. Thus, the phytogenic compounds enhancing salivary physico-chemical composition have the potential to contribute to maintain or improve ruminal health in cattle fed concentrate-rich rations.

Phosphate hinders the complexation of dissolved organic matter with copper in lake waters.

The properties of phosphate in lakes and their ability to cause eutrophication have been well studied; however, the effects of phosphate on the environmental behavior of other substances in lakes have been ignored. Dissolved organic matter (DOM) and heavy metals may coexist with phosphate in lakes. Herein, the mechanisms underlying the influence of phosphate on heavy metals complexation with DOM were investigated using multi-spectroscopic tools. Overall, the amount of DOM-bound Cu(Ⅱ) decreased with the increasing phosphate content. Furthermore, the fluorescence excitation and emission matrix results combined with parallel factor analysis showed that when the Cu(Ⅱ) concentration increased from 0 to 5mg/L and 50μM phosphate to the reaction of DOM and copper, the fluorescence intensity of tyrosine (component 1), humic-like (component 2) and tryptophan (component 3) decreased by 36.46%, 57.34%, and 74.70% compared with the treatment with no phosphate addition, respectively. This finding indicates that the binding of different fluorescent components to Cu(Ⅱ) was restricted by phosphate. Furthermore, different functional groups responded differently to Cu(Ⅱ) under different phosphate concentrations. The binding sequence of different functional groups under high concentration of phosphate (phenolic hydroxyl group＞amide (Ⅰ) ＞carbohydrates) was completely opposite to that with no phosphate. These results demonstrated that phosphate could restrict the binding affinity of heavy metals with different fluorescent substances or organic ligands of DOM, suggesting that the comigration of DOM-bound heavy metals in lakes is hindered by phosphate and the risk of heavy metal poisoning in aquatic organisms is therefore diminished.

High phosphate content in bioactive glasses promotes osteogenesis in vitro and in vivo

ObjectivesHigh phosphate content was found to significantly increase apatite formation of bioactive glasses (BGs) in vitro. However, there is very limited understanding of the effect of phosphate contents on osteogenesis which is important for clinical applications. The aims of this study were to investigate how phosphate content influences apatite formation ability of bioactive glasses in α-MEM culture medium and whether high phosphate content in bioactive glasses promotes osteogenesis in vitro and in vivo. MethodsFour phosphate containing bioactive glasses were synthesized via a melt-quench method and characterized using X-ray powder Diffraction (XRD), TGA-DSC and Fourier transform infra-red spectroscopy (FTIR). The apatite formation ability in α-MEM culture medium and the in vitro and in vivo osteogenic potential of these bioactive glass were explored. ResultsFTIR spectra confirmed faster apatite formation with an increase in phosphate content. The culture media containing ions released from the BGs showed enhanced cell viability and alkaline phosphatase activity of osteoblasts. Osteoblasts cultured with extracted BGs culture media generally showed increased proliferation, mineralized nodule formation, osteogenic and angiogenic genes expression with an increase in phosphate content in the glass compositions. An in vivo study demonstrated a larger amount of new bone formation in the calvarial defects implanted with high phosphate containing BG granules compared with that of BG without the presence of phosphate at 8 weeks post-surgery. SignificantThe presence of higher phosphate content accelerates apatite formation and promotes osteogenesis, indicating that both apatite formation and osteogenesis of bioactive glasses can be tailored by varying phosphate content for specific clinical needs and personalized treatments.

Effect of the phosphate content on the spectroscopic and lasing properties of Er3+/Yb3+-doped fluorophosphate glasses

The influence of phosphate content on the formation and luminescent properties of Er3+/Yb3+-doped fluorophosphate glass has been studied. Using the Judd-Ofelt theory the phenomenological intensity parameters Ωt (t = 2; 4; 6) were obtained. The change of Judd-Ofelt parameters indicates minor differences in Er3+environment with increase in the phosphates content up to 10 mol.%. It was shown that in the studied fluorophosphates glasses erbium ions remain in the fluoride environment. The increase in phosphate content leads to lifetime change of erbium laser level from 9.4 ms to 7.8 ms. Using the Judd-Ofelt intensity parameters Ωt the stimulated emission cross-section of the 4I13/2→4I15/2 transition has been calculated. The gain shape of the glasses with lower (2–10 mol. %) phosphate content has been found to be smoother than for phosphate glasses with 20 mol.% Ba(PO3)2, which makes former very attractive gain material.

Niobium containing bioactive glasses as remineralizing filler for adhesive resins

ObjectiveThe aim of this study was to incorporate sol–gel-derived bioactive glass as filler into experimental adhesive resins and evaluate the influence of glass composition on the physicochemical and biological properties of the developed adhesives. Materials and methodsSol–gel particles were produced with or without the addition of niobium (BAGNb or BAG, respectively). The produced particles were incorporated (2wt%) into experimental adhesive resins formulated with 66wt% bisphenol A-glycidyl methacrylate and 33wt% hydroxyethyl methacrylate. Ethyl dimethyl-4-aminobenzoate and camphorquinone were used as photoinitiator system. Two experimental groups were produced: ABAGNb and ABAG. The adhesive without particles was used as control (ACG). The materials were tested for their degree of conversion, softening in solvent, and cytotoxicity. The mineral deposition was analyzed by Raman spectroscopy. Flexural strength and immediate and 1-year microtensile bond strength were evaluated. ResultsNo statistical difference was found in degree of conversion. ABAGNb showed reduced softening and higher mineral deposition than ACG and ABAG after 28 days. ABAG and ABAGNb resulted in higher cell viability and lower flexural strength when compared to ACG. After 1-year, ABAGNb and ABAG presented statistically significant lower μTBS values. SignificanceSol–gel-derived bioactive glasses promoted increased mineral deposition and cell viability for experimental adhesives with increased phosphate content and longitudinal μTBS values for the ABAGNb group. These results suggest the potential of the studied particles to be applied as bioactive fillers for dental adhesives. Reductions in longitudinal μTBS and flexural strength, however, were observed for both glasses compositions and must be considered.

Regulated micro-leaf like nickel pyrophosphate as a cathode electrode for asymmetric supercapacitor

In present work, nickel pyrophosphate (Ni2P2O7.8H2O) thin film on stainless steel substrate synthesized using facile chemical bath deposition method and used as cathode electrode for asymmetric supercapacitor. Three compositions of nickel phosphate with varying of nickel:phosphate (2:1, 1:1 and 1:2) molar ratio are prepared to study composition effect on microstructure and subsequently on supercapacitive performance. Morphology changes with composition from microflower to leaf like, consequently supercapacitive performance influences with increasing phosphate content in material. The well dispersed leaf like microstructure (nickel:phosphate;1:2) of nickel pyrophosphate offers more active sites and it shows maximum specific capacitance of 482 F g−1 at current density of 3 mA cm-2 along with 99.73% capacitive retention over 2500 cycles. Moreover, an asymmetric device fabricated using nickel pyrophosphate and reduced graphene oxide as a positive and negative electrode, respectively. Prepared asymmetric supercapacitor offers specific capacitance of 74.81 F g-1 at 0.9 mA cm-2 current density with 26.6 Wh kg-1 energy density at a moderately high power density of 870.6 W kg-1. Also, exhibits 87.35% of capacitive retention over 5500 cycles at 4 mA cm-2 current density.

Network structure and thermal properties of bioactive (SiO2\u2013CaO\u2013Na2O\u2013P2O5) glasses

Ca- and P-based bioactive glasses are excellent candidates for design and manufacture of biomaterials. Understanding the structure and physico-chemical–thermal behaviour of bioactive glasses is a fundamental step towards the design of a new generation of biocompatible materials. In this study, the structure of SiO2–CaO–Na2O glasses and its derivatives, obtained by substituting Na2O with P2O5 and prepared by melt–quench technique, was studied with neutron and electron diffraction techniques combined with thermal analysis, high-resolution electron microscopy and X-ray photoelectron spectroscopy. Neutron and electron diffraction data were analysed with reverse Monte Carlo simulation and pair distribution function analysis, respectively. Bioactivity of P2O5 substituted glasses was also investigated and proven in vitro using simulated body fluid. Based on the structural analysis, it was found that Si and P atoms are in well-defined tetrahedral units with a bond distance of 1.60 Å for both Si–O and P–O bonds, although P exhibits a higher average coordination number than Si. With increasing phosphate content, tendentious changes in the glass behaviour were observed. Linear increase in Tg, supported by the changes in the average coordination numbers of Si and P, indicates strengthening of network structure with increasing P content and formation of P–O–Ca atomic linkages, which lead to Ca–P-rich atomic environments in the silicate network. These Ca–P-rich environments trap volatile elements and thus decrease the total weight loss during heating at higher P concentrations. In the case of the highest investigated P2O5 content (5 mol%), nanoscale structural inhomogeneity and the formation of Ca–P-rich clusters were also revealed by electron diffraction and atomic resolution imaging. This type of Ca–(Na)–P clustering has a key role in the behaviour of phosphate-substituted silicate glasses under physiological conditions.

Mobilisation of arsenic, selenium and uranium from Carboniferous black shales in west Ireland

The fixation and accumulation of critical elements in the near surface environment is an important factor in understanding elemental cycling through the crust, both for exploration of new resources and environmental management strategies. Carbonaceous black shales are commonly rich in trace elements relative to global crustal averages, many of which have potential environmental impacts depending on their speciation and mobility at surface. This trace element mobility can be investigated by studying the secondary mineralisation (regolith) associated with black shales at surface. In this study, Carboniferous shales on the west coast of Ireland are found to have higher than average shale concentrations of As, Cd, Cu, Co, Mo, Ni, Se, Te and U, similar to the laterally equivalent Bowland Shales, UK. Groundwater penetration and oxidative weathering of these pyritic black shales produces oxide deposits, dominated by goethite and jarosite, which are significantly enriched in As (44–468 ppm), Se (12–184 ppm), U (6–158 ppm) and other trace elements, compared to concentrations in the parent shales. Major elemental abundances vary in composition from 3.5 to 29.4% sulphate, 0.6–9.1% phosphate and 36.6–47.2% iron-oxide. Phosphate substitution within jarosite is observed in these samples, formed under ambient pressure and temperature conditions.The major and trace elements forming these secondary deposits are predominantly sourced from the underlying black shales through mobilisation by groundwater. This discovery is critical for the environmental assessment of black shale lithologies during shale gas exploration and production, where the demonstrated mobility of in situ elemental enrichments may indicate a significant source of produced- and groundwater contamination during and after hydraulic fracturing processes. The proportions of the major oxide phases exhibit a clear control on the trace elemental enrichments within the secondary deposits, where increasing Se and As concentrations correlate with increasing phosphate content of the jarosite mineralisation. This has implications for the remediation of acid mine drainage seeps, where phosphate-rich jarosite phases could be utilised for more efficient trace element removal.

Characterization and reactivity of zirconia-doped phosphate ion catalyst prepared by sol–gel route and mechanistic study of acetic acid esterification by ethanol

Phosphated zirconia prepared by sol–gel method has been used as catalyst in esterification reaction of acetic acid with ethanol. Optimization of different preparation parameters on the catalyst was studied, such as the effect of molar ratio n P/n Zr, surfactant assisted synthesis, calcination temperature, and the effect of the drying mode. Catalysts were characterized by N2 physisorption at −196 °C, X-ray diffraction, FTIR spectroscopy, and 31P MAS NMR spectroscopy. The obtained results show that an increase in phosphate content partially inhibits the development of tetragonal t-ZrP phase and leads to a rise of both specific area and pore size of the catalyst. Besides, the introduction of the surfactant in the preparation step develops this phase and enhances the size of pores, but decreases specific area. However, calcination of the catalyst allows the development of tetragonal ZrO2 phase and causes the disappearance of ZrP phase. The evacuation of the solvent at its supercritical conditions promotes the development of both tetragonal phase of zirconia and pore size but slows that of the phases related to the ZrP species. Catalytic properties of acid esterification by ethanol were correlated to catalyst characteristic data, suggesting that t-ZrP phase and doping agent-support interaction stabilize active sites of the catalyst. Kinetic and mechanism study shows that catalytic reaction occurs with a first order and takes place through Eley–Rideal mechanism in which adsorbed acetic acid species react with ethanol in fluid phase to form corresponding ester. Application of Eyring theory shows that the adsorption step is characterized by an endothermic character and a rapid associative mechanism occurs between adsorbed species and the second reactant. Eley–Rideal mechanism of acetic acid esterification by ethanol over xerogel catalyst XZrP0.05

Investigation on the thermal properties, density and degradation of quaternary iron and titanium phosphate based glasses

The possibility of producing phosphate based glasses (PBG) with tailored degradation profile allows for unique utilisation in biomedical application. Various compositions in the phosphate based glass (PBG) system of (50-x)P2O5-40Ca-(5+x)Na-5TiO2 and (50-x)P2O5-40Ca- (5+x)Na-5Fe2O3, where x= 5 and 10 were prepared and characterised. Method as differential scanning calorimetry (DSC) has been used to characterise the thermal properties of these phosphate based glasses. It was observed that both glass transition temperature (Tg) and onset of crystalisatisation temperature (Tx) increased with increasing phosphate content. In addition, Tg values were found to be higher for the P2O5-CaO-Na2O-TiO2 glass system compared to P2O5- CaO-Na2O-Fe2O3 glass system. The density result showed that increasing the P2O5 content at the expense Na2O led to a decrease in density for both glass systems. The dissolution study of these glasses was conducted in phosphate buffered saline (PBS). It was observed that the dissolution rate of P2O5-CaO-Na2O-Fe2O3 glass system was higher than the P2O5-CaO-Na2O-TiO2 glass system. The dissolution rate for both glass systems was in the order of 10-6 g cm-2 hr-1.

The Glass Transition Temperature of Iron and Titanium Containing Phosphate Based Glasses

In this study various compositions in the phosphate based glass (PBG) system of (50-x)P2O5-40Ca-(5+x)Na-5TiO2 and (50-x)P2O5-40Ca-(5+x)Na-5Fe2O3, where x= 5 and 10 were investigated for glass transition temperature (Tg) via thermo mechanical analyser (TMA) and differential scanning calorimetry (DSC). The amorphous nature of the glasses was confirmed via XRD. The Tg measured via DSC was consistently higher by 19°C-29°C compared to TMA and was due to the thermal history and the heating rate of the samples. The Tg increased with increasing phosphate content in both glass systems. The Tg for Ti containing PBG was found to be in the range of 453°C-500°C whilst Tg for Fe containing PBG was in the range of 449°C-494°C. Consistently higher Tg for the Ti containing glass series compared to the Fe containing glasses may be attributed to the smaller ionic radius and therefore higher field strength of Ti4+.

Enhancing the Protonic Conductivity of Tin Pyrophosphates by Increasing Phosphate Content

Indium-doped tin pyrophosphate materials were synthesized with varying metal to phosphate ratios to assess the influence of the excess amorphous polyphosphate phase on conductivity. Total conductivity at 250¢ªC was found to increase with increasing P:M ratio, with a maximum conductivity of 10-1.8 Scm-1 in dry N2 and 10-0.8 Scm-1 in humidified N2. These results combined with supporting spectroscopy, suggest that a grain-boundary polyphosphate phase is required to achieve high conductivity at low-intermediate temperatures. The conductivity of the excess phosphorous content materials was stable in both dry and humidified environments at 250¢ªC. The use of this material as a promising fuel cell electrolyte was demonstrated with a maximum power density of 11 mWcm-2 obtained for the highest P:M ratio material at 300¢ªC without humidification. This value is an order of magnitude lower than what has been reported previously in the literature. However the conductivity of the electrolyte in the operating fuel cell was 0.075 Scm-1 and the poor performance is attributable to cathodic overpotentials.