Ca Phosphate Research Articles

Magnesium-Assisted Continuous Growth of Strongly Iron-Enriched Incisors.

Teeth are an excellent example where optimally designed nanoarchitectures with precisely constructed components consist of simple compounds. Typically, these simple constituent phases with insignificant properties show mechanical property amplifications when formed into composite architectures. Material properties of functional composites are generally regulated on the nanoscale, which makes their characterization particularly demanding. Using advanced analytical and imaging transmission electron microscopy techniques, we identified innovative microstructural adjustments combined with astonishing compositional adaptations in incisors of coypu. Unique constituents, recognized as an additional amorphous Fe-rich surface layer followed by a transition zone covering pigmented enamel, provide the required structural stability to withstand repeated mechanical load. The chemically diverse Fe-rich surface layer, including ferrihydrite and iron-calcium phosphates, gives the typical orange-brown coloration to the incisors. Within the spaces between elongated hydroxyapatite crystals in the pigmented enamel, only ferrihydrite was found, implying that enamel pigmentation is a very strictly controlled process. Most significantly, an unprecedentedly high amount of Mg was measured in the amorphous flake-like material within the dentinal tubules of the incisors, suggesting the presence of a (Mg,Ca) phosphate phase. This unusually high influx of Mg into the dentin of incisors, but not molars, suggests a substantial functionality of Mg in the initial formation stages and constant growth of incisors. The present results emphasize the strong mutual correlation among the microstructure, chemical composition, and mechanical properties of mineralized dental tissues.

A mineralogical view of apatitic biomaterials

Biomaterials are synthetic compounds and composites that replace or assist missing or damaged tissue or organs. This review paper addresses Ca phosphate biomaterials that are used as aids to or substitutes for bones and teeth. The viewpoint taken is that of mineralogists and geochemists interested in (carbonated) hydroxylapatite, its range of compositions, the conditions under which it can be synthesized, and how it is used as a biomaterial either alone or in a composite. Somewhat counter-intuitively, the goal of most medical or materials science researchers in this field is to emulate the properties of bone and tooth, rather than the hierarchically complex materials themselves. The absence of a directive to mimic biological reality has permitted the development of a remarkable range of approaches to apatite synthesis and post-synthesis processing. Multiple means of synthesis are described from low-temperature aqueous precipitation, sol-gel processes, and mechanosynthesis to high-temperature solid-state reactions and sintering up to 1000 °C. The application of multiple analytical techniques to characterize these apatitic, frequently nanocrystalline materials is discussed. An online supplement 1 details the specific physical and chemical forms in which synthetic apatite and related Ca phosphate phases are used in biomaterials. The implications from this overview are the enhanced recognition of the structurally and chemically accommodating nature of the apatite phase, insight into the effects of synthesis techniques on the specific properties of minerals (specifically apatite), and the importance of surface chemistry of apatite nanocrystals. The wide range of synthesis techniques, types of analytical characterization, and applications to human health associated with apatite are a non-geological demonstration of the power of mineralogy.

Extractability and availability index of sulphur in selected soils of Odisha

We aimed to evaluate the extractability of two reagents viz.0.15% CaCl2 & 0.01M Ca (H2PO4) for sulphur along with the sulphur availability index of mixed red and black soils. For this 86 soil samples were collected from mixed red and black soil regions and extracted with these solutions. Results showed that both these solutions ex-tracted nearly similar amount of sulphur in black soils while the Ca phosphate solution extracted higher amount (13.9mgkg-1) compared to Ca chloride solution (11.5mgkg-1) in red soil regions. Considering all the 86 soil samples tested, there was an excellent correlation between the extractable sulphur, the highest correlation being reported from black soils (R2= 0.97). Sulphur availability index was found to be higher in black soils (mean 6.6) compared to red soils (mean 5.1). Also the content of adsorbed sulphur was found to be high in red soils (2.4mgkg-1) compared to black soils (1.5mgkg-1). Correlation matrix and regression equations (Ca phosphate S= 5.00+ 0.77 Ca chloride S) were worked out between the extractable sulphur and soil properties to justify the results.

Fly ash as reactive sorbent for phosphate removal from treated waste water as a potential slow release fertilizer

There is interest in recovering phosphate (P(V)) from secondary sources, such as waste water streams for potential use as fertilizers reducing the environmental impacts of P(V) discharges and providing alternative phosphorus sources. The goal of this work was to provide an understanding of P(V) removal by fly ash (FA) from coal power plants. Phosphate removal using Ca(II) rich FA was evaluated in terms of i) sorption equilibrium, ii) sorption kinetics under the expected pH values and P(V) concentrations in wastewaters effluents, and iii) P(V) availability of the FAs in agricultural applications. At the pH values (6–9) expected for wastewater effluents, P(V) removal proceeds as a combination of CaO(s) dissolution and brushite (CaHPO4(s)) formation on the FA particles. This process avoids the formation of relatively insoluble Ca–phosphates, such as, hydroxyapatite (Hap) with limited fertilizing properties. High P-loadings were achieved (up to 50mgP-PO4/g FA (5% P(V) by weight)) at a pH of 8. The removal kinetics data were well described as a diffusion-based process of phosphate ions (H2PO4− and HPO42−) on FA particles, and the CaO(s) dissolution process was discarded as the rate controlling step. The P(V) availability from loaded samples was determined via an agronomical assay with NaHCO3 solutions with P(V) release ratios of 10–30mgP-PO4/g in FA, confirming the appropriateness of this material as a potential fertilizer, even in calcareous soils.

Dissolution and storage stability of nanostructured calcium carbonates and phosphates for nutrition

Rapid calcium (Ca) dissolution from nanostructured Ca phosphate and carbonate (CaCO3) powders may allow them to be absorbed in much higher fraction in humans. Nanosized Ca phosphate and CaCO3 made by flame-assisted spray pyrolysis were characterized by nitrogen adsorption, X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscopy. As-prepared nanopowders contained both CaCO3 and CaO, but storing them under ambient conditions over 130 days resulted in a complete transformation into CaCO3, with an increase in both crystal and particle sizes. The small particle size could be stabilized against such aging by cation (Mg, Zn, Sr) and anion (P) doping, with P and Mg being most effective. Calcium phosphate nanopowders made at Ca:P ≤ 1.5 were XRD amorphous and contained γ-Ca2P2O7 with increasing hydroxyapatite content at higher Ca:P. Aging of powders with Ca:P = 1.0 and 1.5 for over 500 days gradually increased particle size (but less than for CaCO3) without a change in phase composition or crystallinity. In 0.01 M H3PO4 calcium phosphate nanopowders dissolved ≈4 times more Ca than micronsized compounds and about twice more Ca than CaCO3 nanopowders, confirming that nanosizing and/or amorphous structuring sharply increases Ca powder dissolution. Because higher Ca solubility in vitro generally leads to greater absorption in vivo, these novel FASP-made Ca nanostructured compounds may prove useful for nutrition applications, including supplementation and/or food fortification.

Synthesis of composite calcium-phosphate coatings via pulsed photon processing

The phase composition and mechanical properties of coatings generated on a Ti surface via the ion sputtering of a hydroxyapatite (HA) target and a compound (hydroxyapatite and Ti) target with subsequent pulsed photon processing (PPP) with incoherent xenon lamp radiation are investigated. It is found for the first time that pulsed photon processing accelerates the crystallization of amorphous films of Ca–P–O–H and Ca–P–O–H–Ti compositions, during which tricalcium phosphate Ca3(PO4)2, titanium oxide TiO2 (rutile, anatas), and perovskite CaTiO3 are formed, depending on the radiation dose and the ratio between Ti and Ca phases (Ti/Ca) with hydroxyapatite structure. It is found that pulsed photon processing of initial amorphous coatings greatly increases their hardness (up to 10.9 GPa) and adhesion (up to 29.0 MPa).

The environmental sustainability of calcined calcium phosphates production from the milling of eggshell wastes and phosphoric acid

Industrial waste shells of egg cause environmental and health issues. Diversion of eggshells from landfill to a useful product or used in a better way towards the fabrication of marketable/valuable products is of high economic and ecologic interest. Different structures of calcium phosphates were prepared by milling eggshells with different amounts of phosphoric acid (H3PO4) in the presence of gelatin. The amounts of H3PO4 were varied over wide ranges (2.90 ml–8.73 ml), and the impact of such variations on calcined samples was investigated through the characterization of their morphologies by field emission scanning electron microscopy (FESEM). Long milling time is associated with size reduction of the eggshell powders. It was demonstrated that addition of 8.73 ml H3PO4 reduced the d50 eggshell particles from ∼ 1 μm to 0.96 μm after being milled for 8 h. X-ray diffraction (XRD) has been used to identify the crystalline phases present after milling and also after heat treatment for various times of up to 5 h at temperatures in the range 700–1200 °C. Monetite (CaHPO4) is the characteristic phase of ball-milled samples over the whole ranges of phosphoric acid. The thermal treatment applied to the ball-milled samples led to the interaction between the constituents, causing a modification in the proportion of calcium phosphate structures. At 2.90 and 3.88 ml of H3PO4, both tri-calcium phosphate Ca3(PO4)2 and hydroxyapatite Ca5(PO4)3OH phases are the major crystalline structures developed at 1000 and 1200 °C, while Ca2P2O7 and Ca3(PO4)2 were mainly the observed phases at lower sintering temperatures. The present work is establishing a treatment strategy to produce tailor-made calcium phosphate structures for bio-applications.

Bacterial strains from floodplain soils perform different plant-growth promoting processes and enhance cowpea growth

Certain nodulating nitrogen-fixing bacteria in legumes and other nodule endophytes perform different plant-growth promoting processes. The objective of this study was to evaluate 26 bacterial strains isolated from cowpea nodules grown in floodplain soils in the Brazilian savannas, regarding performance of plant-growth promoting processes and ability to enhance cowpea growth. We also identified these strains by 16S rRNA sequencing. The following processes were evaluated: free-living biological nitrogen fixation (BNF), solubilization of calcium, aluminum and iron phosphates and production of indole-3-acetic acid (IAA). The abilities to nodulate and promote cowpea growth were evaluated in Leonard jars. Partial sequencing of the 16S rRNA gene identified 60 % of the strains as belonging to genus Paenibacillus. The following four genera were also identified: Bacillus, Bradyrhizobium, Enterobacter and Pseudomonas. None of the strains fixed N2 free-living. Among the strains, 80 % solubilized Ca phosphate and one solubilized Al phosphate and none solubilized Fe phosphate. The highest IAA concentrations (52.37, 51.52 and 51.00 μg mL−1) were obtained in the 79 medium with tryptophan by Enterobacter strains UFPI B5-7A, UFPI B5-4 and UFPI B5-6, respectively. Only eight strains nodulated cowpea, however, all increased production of total dry matter. The fact that the strains evaluated perform different biological processes to promote plant growth indicates that these strains have potential use in agricultural crops to increase production and environmental sustainability.

Soft Tissue Augmentation of the Face With Autologous Platelet-Derived Growth Factors and Tricalcium Phosphate. Microtomography Evaluation of Mice.

The platelets used in oral, maxillofacial, and plastic surgery are generally grouped as concentrated platelet-rich plasma. The general principle of production consists of a centrifugation, making it possible to eliminate red blood cells, then acellular plasma, to preserve only the concentrated platelets. The aim of the present study was that micro porous tricalcium phosphate (β-TCP) mixed with autologous platelet-derived growth factors could be an alternative to fat and hyaluronic acid which are widely used for oral and maxillofacial soft tissue augmentation. Ten female, 6 to 8-week-old black-haired mice were selected. On 1 cheek was injected the gel of tricalcium phosphate/autologous platelet-derived growth factors, while on the other cheek, was left empty and was used as control. The animals were killed after 8 weeks. Investigator evaluation was based on microtomography observation and comparison of control and test. The microtomography technique demonstrated amorphous radiopaque images projected in the soft tissue parts of each paramedian region of the right cheek, in those sites corresponding to the injection of the gel of tricalcium phosphate/autologous platelet-derived growth factor. Eight weeks after surgery, β-TCP granules were clearly visible with most remaining within the cheek. The margins of the β-TCP granules were clear and not diffused within the vicinity of the tissues. The results indicate that micro β-tricalcium phosphate Ca3(PO4)2 mixed with autologous platelet-derived growth factors material was able to create a lasting three-dimensional soft tissue augmentation and is a promising biomaterial for soft tissue augmentation as a scaffold for cells.

Femtosecond laser ablation of enamel.

The surface topographical, compositional, and structural modifications induced in human enamel by femtosecond laser ablation is studied. The laser treatments were performed using a Yb:KYW chirped-pulse-regenerative amplification laser system (560 fs and 1030 nm) and fluences up to 14 J/cm2. The ablation surfaces were studied by scanning electron microscopy, grazing incidence x-ray diffraction, and micro-Raman spectroscopy. Regardless of the fluence, the ablation surfaces were covered by a layer of resolidified material, indicating that ablation is accompanied by melting of hydroxyapatite. This layer presented pores and exploded gas bubbles, created by the release of gaseous decomposition products of hydroxyapatite (CO2 and H2O) within the liquid phase. In the specimen treated with 1-kHz repetition frequency and 14 J/cm2, thickness of the resolidified material is in the range of 300 to 900 nm. The micro-Raman analysis revealed that the resolidified material contains amorphous calcium phosphate, while grazing incidence x-ray diffraction analysis allowed detecting traces of a calcium phosphate other than hydroxyapatite, probably β-tricalcium phosphate Ca3(PO4)2, at the surface of this specimen. The present results show that the ablation of enamel involves melting of enamel’s hydroxyapatite, but the thickness of the altered layer is very small and thermal damage of the remaining material is negligible.

Phosphorus dynamics in Swedish agricultural soils as influenced by fertilization and mineralogical properties: Insights gained from batch experiments and XANES spectroscopy

The soil chemistry of phosphorus (P) is important for understanding the processes governing plant availability as well as the risk of environmental losses of P. The objective of this research was to investigate both the speciation and the pH-dependent solubility patterns of P in clayey agricultural soils in relation to soil mineralogy and fertilization history. The study focused on soil samples from six fields that were subjected to different P fertilization regimes for periods of 45 to 57years. Soil P speciation was analyzed by P K-edge XANES spectroscopy and chemical fractionation, sorption isotherms were constructed, and dissolved P was measured as a function of pH. The XANES fitting results showed that organic P and P adsorbed to Fe and Al (hydr)oxides were common P constituents in all soils. Calcium phosphates were identified in five of six soil samples. The XANES results also indicated an increase in P adsorbed to Al and to a lesser extent Fe (hydr)oxides as a result of fertilization. Moreover, the fluorescence intensity from the P K-edge XANES analysis was most strongly correlated with HCl-digestible P (r=0.81***). Consistent with the XANES analysis, laboratory sorption isotherm models showed that the Freundlich sorption coefficient (KF) was most closely related to oxalate-extractable Al. Greater proportions of Ca phosphate in two of the heavily fertilized soils in combination with enhanced PO4 solubilization upon sample acidification indicated neoformation of Ca-phosphate precipitates. The results for the unfertilized soil samples generally showed a minimum in dissolved PO4 between pH6.5 and 7.5, with increases particularly at lower pH. This behavior can be explained either by the dissolution of Al-hydroxide-type sorbents or Ca phosphates at lower pH. In fertilized soils, there was no consistent trend in pH-dependent solubilization of P, with a complex relationship to solid-phase speciation. To conclude, inorganic P species changed most dynamically in agricultural clay soils over a period of several decades, and the role of pH in the solubilization of P depended mainly on P fertilization history and the content of reactive Ca phosphates.

Design Strategy for the Multilayer Core–Shell Bioceramics with Controlled Chemistry

New strategies for fabricating multiphase bioceramic porous scaffolds with time‐dependent biodegradation and pore network enlargement are of fundamental importance in the advancement of bioceramics. Here, we developed a one‐step preparation of core–shell bioceramic microspheres (~2 mm in diameter) with single‐ or double‐shell structure through a coaxially aligned multilayer capillary system. The Ca‐phosphate (CaP) and Ca‐silicate (CaSi) ceramic phase distribution could be also adjusted by extruding through different capillaries, and thus the biodegradation rate would be readily tailored over time. When the polystyrene (PS) microbeads of ~15 μm in diameter were premixed into the CaP‐ or CaSi‐containing alginate slurry, the tailorable porous structures could be introduced into the core or different shell layers of the microspheres. These micropores may potentially maximize the permeability for rapid exchange of guest molecules or inorganic ions from the bioceramics. Totally, such strategy is promising because the ceramic phases with different biological properties can be assembled into the core–shell bioceramic microspheres, and thus the macropore structure evolution may be readily manipulated in the closely packed microsphere systems. We believe our gradient hybrid methodology will have potential in various categories of advanced biomaterials of organic–inorganic composites.

Managing the value of composts as organic amendments and fertilizers in sandy soils

Nutrient rich composts are employed at low rates to minimize risks of N and P losses; this limits their value as soil improvers through C addition and the build up of soil organic matter. Blending with nutrient-poor composts such as those from the organic fraction of municipal solid waste could reduce the risks of nutrient losses while maintaining the positive effects on soil organic matter. We conducted a 2-yr experiment with composts of diverse origin: organic fraction of municipal solid waste (MC), cattle feedlot manure (FC), poultry litter (PC) and biosolids (BC), alone or blended (FC-MC, PC-MC) in a sandy soil under the humid warm climatic conditions of NE Argentina. We studied the effects of a single application (40 Mg ha−1) on the surface soil (0–10cm) properties of a permanent subtropical pasture through annual chemical and biological analyses. On five dates, available N and P were also determined at 0–10cm and 55–65cm. Soil total C and N increased over time while potential N mineralization and CO2 emission decreased. All amendments resulted in similar increments of soil C and N despite marked differences in quantity and quality of organic matter inputs. Because MC had substantial amounts of Ca carbonates, it contributed to a reduction of available P from manure composts through dilution and precipitation. The release of available P from biosolids composts (where P is bound to Fe and Al) was lower than from manure composts (where P is bound by Ca phosphates). The highest environmental risk from compost application would likely be the leaching of soluble N produced during the composting process and released immediately after field application. Blending with N-poor MC would contribute to nitrate dilution.

The paradoxical role of urinary macromolecules in the aggregation of calcium oxalate: a further plea to increase diuresis in stone metaphylaxis.

This study was designed to get information on aggregation (AGN) of urinary calcium oxalate crystals (CaOx) which seems to occur in stone formation despite a protecting coat of urinary macromolecules (UMs). CaOx crystallization was directly produced in urine, control and albumin solution by Ox titration and was spectrophotometrically followed. A rapid decrease of optical density indicating AGN was absent in 14 of 15 freshly voided urines of 5 healthy controls. However, in the presence of UM-coated hydroxyapatite all urines with relative high sodium concentration, being an indicator of concentrated urine, showed a pronounced AGN which was abolished when these urines were diluted. Albumin relatively found to be an inhibitor of AGN showed after temporary adsorption on Ca Phosphate (CaP) massive self-AGN and changed to a promoter of CaOx AGN. Self-AGN after adsorption on surfaces especially of CaP, being an important compound of Randall’s plaques, can thus explain this paradoxical behavior of UMs. Aggregated UMs probably bridge zones of electrostatic repulsion between UM-coated crystals with identical electrical surface charge. These zones extend by urine dilution which decreases ionic strength. Diminution of urinary concentration by increasing diuresis seems, therefore, to be important in stone metaphylaxis.

Compressive strength and biomineralisation improvement by water glass coating on porous calcium phosphate scaffolds

Calcium phosphate (Ca–P) based scaffolds were found to be a favourable alternative for orthopaedic applications because of their similar chemical composition to natural bone. In this study, porous triphasic Ca–P scaffolds containing macropores (∽200 μm) interconnected with micropores (∽20 μm) were fabricated using an extrusion method. The hydroxyapatite/tricalcium phosphate ratio of the porous scaffolds was varied using different ratios of starting materials while keeping the Ca/P ratio fixed (1.5). A water glass coating on the porous Ca–P scaffolds increased the compressive strength by 45% without significantly decreasing the porosity of the H100D50 scaffold. The maximum compressive strength, ∼15 MPa, was achieved on the H100D50 scaffold. The ability for apatite formation in simulated body fluid was amplified by the water glass coating on the sintered Ca–P scaffolds. Therefore, a water glass coating can be used to enhance the mechanical properties as well as the biomineralisation of the porous ceramic scaffolds.

Correlations and zoning patterns of phosphorus and chromium in olivine from H chondrites and the LL chondrite Semarkona

AbstractPhosphorus zoning is observed in olivines in high‐FeO (type IIA) chondrules in H chondrites over the entire range of petrologic grades: H3.1–H6. Features in P concentrations such as oscillatory and sector zoning, and high P cores are present in olivines that are otherwise unzoned in the divalent cations. Aluminum concentrations are low and not significantly associated with P zoning in chondrule olivines. In highly unequilibrated H chondrites, phosphorus zoning is generally positively correlated with Cr. Atomic Cr:P in olivine is roughly 1:1 (3:1 for one zone in one olivine in RC 075), consistent with Cr3+ charge‐balancing P5+ substituting for Si4+. Normal igneous zonation involving the dominant chrome species Cr2+ was observed only in the LL3.0 chondrite Semarkona. In more equilibrated chondrites (H3.5–H3.8), Cr spatially correlated with P is occasionally observed but it is diffuse relative to the P zones. In H4–H6 chondrites, P‐correlated Cr is absent. One signature of higher metamorphic grades (≥H3.8) is the presence of near matrix olivines that are devoid of P oscillatory zoning. The restriction to relatively high metamorphic grade and to grains near the chondrule–matrix interface suggests that this is a response to metasomatic processes. We also observed P‐enriched halos near the chondrule–matrix interface in H3.3–H3.8 chondrites, likely reflecting the loss of P and Ca from mesostasis and precipitation of Ca phosphate near the chondrule surface. These halos are absent in equilibrated chondrites due to coarsening of the phosphate and in unequilibrated chondrites due to low degrees of metasomatism. Olivines in type IA chondrules show none of the P‐zoning ubiquitous in type IIA chondrules or terrestrial igneous olivines, likely reflecting sequestration of P in reduced form within metallic alloys and sulfides during melting of type IA chondrules.

Influence of Engine Age on Morphology and Chemistry of Diesel Soot Extracted from Crankcase Oil

In this study, the role of engine age on the structure and chemistry of crankcase soot was studied using X-ray diffraction, high-resolution transmission electron microscopy, energy-dispersive spectroscopy, and Raman spectroscopy. Results indicate that the basic structure of the carbonaceous species remains the same in all cases and is composed of turbostratic carbon. However, there are some very subtle changes in the structure of the soot as the age of the engine increases. Older engines have a greater proportion of non-crystalline amorphous carbonaceous constituents in the soot relative to newer engines. In addition, the wear-induced debris increase with the age of the engine, with a larger proportion of phosphates of Ca and Zn as well as sulfates of Ca in the soot of older engines. The presence of these wear debris particles incorporated in the soot extracted from the crankcase indicates that they arise from three-body abrasive wear between the soot and the tribofilms formed within the engine.

Reference spectra of important adsorbed organic and inorganic phosphate binding forms for soil P speciation using synchrotron-based K-edge XANES spectroscopy.

Direct speciation of soil phosphorus (P) by linear combination fitting (LCF) of P K-edge XANES spectra requires a standard set of spectra representing all major P species supposed to be present in the investigated soil. Here, available spectra of free- and cation-bound inositol hexakisphosphate (IHP), representing organic P, and of Fe, Al and Ca phosphate minerals are supplemented with spectra of adsorbed P binding forms. First, various soil constituents assumed to be potentially relevant for P sorption were compared with respect to their retention efficiency for orthophosphate and IHP at P levels typical for soils. Then, P K-edge XANES spectra for orthophosphate and IHP retained by the most relevant constituents were acquired. The spectra were compared with each other as well as with spectra of Ca, Al or Fe orthophosphate and IHP precipitates. Orthophosphate and IHP were retained particularly efficiently by ferrihydrite, boehmite, Al-saturated montmorillonite and Al-saturated soil organic matter (SOM), but far less efficiently by hematite, Ca-saturated montmorillonite and Ca-saturated SOM. P retention by dolomite was negligible. Calcite retained a large portion of the applied IHP, but no orthophosphate. The respective P K-edge XANES spectra of orthophosphate and IHP adsorbed to ferrihydrite, boehmite, Al-saturated montmorillonite and Al-saturated SOM differ from each other. They also are different from the spectra of amorphous FePO4, amorphous or crystalline AlPO4, Ca phosphates and free IHP. Inclusion of reference spectra of orthophosphate as well as IHP adsorbed to P-retaining soil minerals in addition to spectra of free or cation-bound IHP, AlPO4, FePO4 and Ca phosphate minerals in linear combination fitting exercises results in improved fit quality and a more realistic soil P speciation. A standard set of P K-edge XANES spectra of the most relevant adsorbed P binding forms in soils is presented.

Underlining the complexity of the structural and chemical characteristics of ectopic calcifications in breast tissues through FE-SEM and μFTIR spectroscopy

Abstract Breast calcifications, defined as calcium deposits within breast tissue, can arise from a vast number of aetiologies. Diffuse or scattered distribution is typically seen in benign entities. Approximately 95% of all Ductal carcinoma-in-situ, which represents 25–30% of all reported breast cancers are diagnosed because of mammographically detected microcalcifications. In this investigation dedicated to breast calcifications, we assessed at the micrometer scale their chemical nature through last generation micro-Fourier transform Infrared microspectroscopy and their structural characteristics through last generation field emission scanning electron microscopy. Several striking results have been obtained. Heavily mineralized deposits seem to be the result of the agglomeration of micrometer scale spherules and for the first time, we show that micrometer scale spherules display very different internal structure. Moreover, while Ca phosphate apatite and calcium oxalate dihydrate are the two chemical phases usually reported, we underline the presence of a third chemical phase namely amorphous carbonated calcium phosphate. In the case of duct carcinoma in situ (DCIS), the chemical composition as well as the carbonate level are very inhomogeneous even inside micrometer scale breast calcifications. Moreover, for some samples related to DCIS, special features at the micrometer scale seem to be related to this pathology because they were not found for the other pathologies.

Powdered Ca‐activated zeolite for phosphate removal from treated waste‐water

AbstractBACKGROUNDA powdered zeolitic material synthesised from fly ash (FA) (NaP1‐FA) and its calcium modified form (CaP1‐NA) were studied as sorbent materials for the recovery of phosphate from treated waste‐water effluents. Phosphate‐sorption equilibrium experiments were performed by varying the experimental conditions, including solution pH, phosphate concentration, and the presence of competing ions.RESULTSThe maximum phosphate‐sorption capacities were 57 ± 5 and 203 ± 11 mgP–PO4 g−1 for NaP1‐FA and CaP1‐NA, respectively. The sorption capacities of both zeolites in the pH range expected for waste‐water effluents (pH 7 to 9) were slightly dependent on pH, exhibiting maxima at pH 8. Phosphate removal proceeds through two main mechanisms: (a) surface complexation with ≅AlOH and ≅FeOH groups of the zeolitic structure or unreacted minerals from the FA; and (b) the formation of Ca–phosphate phases, mainly brushite.CONCLUSIONSThe removal mechanisms were confirmed by XRD analyses and P speciation. The stabilities of the phosphate‐loaded zeolite samples evaluated by the extraction experiments confirmed their potential availabilities in soil applications. Finally, the higher solubility of brushite compared with that of Hap makes this zeolitic material promising as a novel inorganic zeolite/CaP1‐NA/brushite fertiliser. © 2015 Society of Chemical Industry