Calcium Iron Phosphate Research Articles

Hydroxyapatite-magnetite nanocomposites: Synthesis and superior adsorption properties for lead ion removal, with insights into intraparticle diffusion, kinetic modeling, and phase dependency

Multifunctional superparamagnetic magnetite/hydroxyapatite (Fe3O4/Ca10(PO4)6(OH)2 or MHAp) nano-composites were synthesized via a facile two-step co-precipitation method at room temperature. These magnetic nano-composites underwent heat treatment at various temperatures ranging (400°, 600°, and 900 °C), which were subsequently utilized as nanosorbents for removing Pb2+ ions. The XRD data revealed that both the magnetite and hydroxyapatite synthesized were in a pure phase. In the Fe3O4/HAp composites, there was an augmentation in the intensity peak of hydroxyapatite observed up to 600 °C. However, at 900 °C, a calcium iron phosphate phase emerged, and magnetite (Fe3O4) transitioned into the hematite (Fe2O3) phase. Elevating the heat treatment enhanced the crystallinity of the developed Fe3O4/HAp composites while diminishing the surface area. The prepared nanocomposites exhibited high adsorption efficiency across a wide pH range, with an optimal pH of 5.5. Notably, the adsorption rate of Pb2+ reached 94 % within the first 5 min, with complete metal adsorption progressively at 60 min. The kinetic and isotherm analysis of the adsorption process revealed that pseudo-second-order model and Langmuir model agreed well with the adsorption process. Also, FAH0 demonstrated the highest adsorption capacity (263.2 mg/g) for Pb2+ ions. Furthermore, the Fe3O4/HAp composite NPs exhibited remarkable recyclability even after five cycles of reuse; retaining an efficiency of over 96 %, and allowing for easy separation without a significant loss of adsorption efficiency. The results of the current desorption study underscore the promising practical applications of these nano-composites in decontaminating aqueous media.

Formation of Amorphous Iron-Calcium Phosphate with High Stability.

Amorphous iron-calcium phosphate (Fe-ACP) plays a vital role in the mechanical properties of teeth of some rodents, which are very hard, but its formation process and synthetic route remain unknown. Here, the synthesis and characterization of an iron-bearing amorphous calcium phosphate in the presence of ammonium iron citrate (AIC) are reported. The iron is distributed homogeneously on the nanometer scale in the resulting particles. The prepared Fe-ACP particles can be highly stable in aqueous media, including water, simulated body fluid, and acetate buffer solution (pH 4). In vitro study demonstrates that these particles have good biocompatibility and osteogenic properties. Subsequently, Spark Plasma Sintering (SPS) is utilized to consolidate the initial Fe-ACP powders. The results show that the hardness of the ceramics increases with the increase of iron content, but an excess of iron leads to a rapid decline in hardness. Calcium iron phosphate ceramics with a hardness of 4GPa can be achieved, which is higher than that of human enamel. Furthermore, the ceramics composed of iron-calcium phosphates show enhanced acid resistance. This study provides a novel route to prepare Fe-ACP, and presents the potential role of Fe-ACP in biomineralization and as starting material to fabricate acid-resistant high-performance bioceramics.

Microwave processing and characterization of alumina reinforced HA cladding for biomedical applications

The present work comprises of enhancing the bioactivity of the SS-316L substrate by Hydroxyapatite (HA) + 10 wt% Al2O3 (HA10AL) powder using microwave supported surface modifications techniques. The microwave supported surface modified layer has a thickness of around 0.8 mm with the exposure time of 15 min. The surface modified specimens were heat treated at different temperatures (400 °C, 600 °C and 800 °C) for 2 h. Various characterizations tools were employed to characterizing the microwave supported surface modified specimens (as-deposited along with heat-treated). The microstructural study revealed the presence of HA and reaction induced HA phases in the inter-dendritic regions of the Fe-based austenite dendrite matrix. It has been observed that porosity generally decreases after the heat treatments due to faster diffusion of atoms, which fills the pores and voids, whereas the hardness showed the increasing trends with heat-treatment temperature. XRD spectra shows the presence of HA and Al2O3 phases along with iron (Fe), calcium iron phosphate (Ca19Fe2(PO4)14), iron phosphide (Fe2P), along with main iron nickel (Fe-Ni) based matrix at high temperature in all the microwave supported surface modified specimens. The apatite layer was successfully formed on the microwave supported surface modified specimens at all conditions after immersed in simulated body fluid (SBF) test. It was found that apatite formation was reduced with an increase in heat-treatment temperature due to reduction in porosity and amorphous phase (tri-calcium phosphate).

Structure and chemical durability of calcium iron phosphate glasses doped with La2O3 and CeO2

Calcium iron phosphate glasses doped with La2O3 and CeO2 have been prepared by the melting method. The structure and chemical resistance of the glasses were analyzed by XRD, FTIR and SEM. The XRD results showed that the glasses after aqueous corrosion were amorphous, while several crystals emerged after the alkali corrosion. FTIR analysis demonstrated an increase in non-bridging oxygens by adding rare earth oxides and the glass network depolymerized from Q1 to Q0 with the corrosion. Densities increased with increasing La2O3 and CeO2 content. SEM tests displayed that the smooth glass surface became rough with the corrosion time increasing and some cracks emerged at last. Comparing the values of the weight loss ratios of La-doped and Ce-doped glasses, the latter was more corrosion resistant. The least weight loss rate was 10.85% with 2.0 mol% CeO2 addition and the Ce-doped glass had the best alkali resistance in these two series. The addition of La2O3 and CeO2 significantly improved the water and alkali resistance of the glass specimens.

Influences of ZnO on the chemical durability and thermal stability of calcium iron phosphate glasses

This study aims to investigate influences form zinc oxide on glasses in xZnO-(100-x) (54P2O5-36Fe2O3-10CaO) (x = 3,6,9,12,15,18 mol%). Structure analyses were carried by FTIR, and chemical durability tests were introduced to study changes in dissolution rate and weight losses. Thermal stability properties were measured and discussed through DSC. Results from structure changes indicate that glass network turns less compact with more ZnO, the building units gradually evolving into Q0 groups from Q1 tetrahedra, even the whole glass system locates in orthophosphate glasses. Higher melting temperature results in more Fe2+ that would lead to octahedral and disordered octahedral in the prepared glasses also contributing to open glass network in glass structure. The resistance in both alkali and acid solution were deteriorated for the sake of the open network, accompanied with the less strong P-O-Zn bonds when compared with the P-O-P bonds. Reasons accounting for the weak resistance also refer to the transition from [ZnO6] to [ZnO4], larger volume of [ZnO4] than that of [PO4], small particle size in ternary phosphate glasses. Drops in weight loss for each test span with corrosion time might be owing to the formation of alter layer on the surface of glass samples during corrosion. The phenomenon in water also follow the similar trend as those in the other two solutions for the same reasons. The glass transition and crystalline temperatures of all glasses drop as the degree of polymerization in glass becomes small, with four glass stability parameters falling as the amount of ZnO rises.

Fe-doped brushite bone cements with antibacterial property

In present research, Fe-doped brushite bone cements were synthesized. The setting time, microstructure and antibacterial property of samples were investigated. The results showed that the setting time of cements was retarded to about 20 min and 123 min, respectively, as iron doping content increasing from 1 mol% to 5 mol% in β-TCP powder. Moreover, Fe-doped cements had much bigger crystal particles and calcium iron phosphate was identified in them. Furthermore, Fe-doped cements performed well in inhibiting the growth of Staphylococcus aureus and Pseudomonas aeruginosa, and larger inhibition halo was obtained with more iron content. Nevertheless, the Fe-loaded cements were not so sensitive to Escherichia coli as to the other two bacteria.

Effects of barium oxide on structure and properties of calcium iron phosphate glasses

In order to study the effects of barium oxide on the structure and properties of glasses from the glass system of xBaO-(20-x)CaO-32Fe2O3-48P2O5 (x=2,4,6,8,10,12,14,16,18mol%), several methods are applied to the investigation, including XRD, FTIR, DSC and chemical durability tests. Results from FTIR spectra shows that BaO loosens the glass network, with some sorts of crystals forming in the two glass groups depicted in the XRD spectra. However, the glass transition temperature (Tg) and glass crystalline temperature (Tc), as well as the difference between the two(ΔT=Tc-Tg), rise with the addition of BaO. All densities of glasses level up with larger concentration of barium oxide; fluctuations occur in the glass system with the formation of different crystals. When CaO is replaced by BaO, the dissolution rate moves to high level in alkali solution when compared with the basic glass (20CaO-32Fe2O3-48P2O5), while glasses in acid solution possess the inferior resistance than glasses in alkaline solution. It turns out that crystals in these glasses did improve resistance to acid and alkaline ions when they are compared with their base glasses.

Studies of structure of calcium–iron phosphate glasses by infrared, Raman and UV–Vis spectroscopies

Glasses in the ternary CaO–Fe2O3–P2O5 system were prepared and studied by means of density, differential scanning calorimetry, infrared, Raman and UV–Vis spectroscopies. The results showed that density and molar volume in the glass system decreased with increasing substitution of CaO for Fe2O3. The variation of glass transition temperature and thermal stability was strictly related to the nature of bonding in the vitreous network. Spectroscopic analysis showed that substitution of CaO for Fe2O3 induced an evolution of structural units from pyrophosphate to metaphosphate species indicating the polymerization of phosphate chains and the decrease of non-bridging oxygen concentrations. With increasing substitution of CaO for Fe2O3 The P–O–Ca linkage and (P–O− Ca2+ −O–P) chains participated in the glass network by replacing P–O–Fe bonds. The absorption band of the P–O–Ca stretching mode in the glasses with high CaO content (≥32 mol%) was assigned at around 1084 cm−1. The absorption edge would fall in the region between 332 and 420 nm which are the absorption bands of Fe3+ ions.

Effects of Calcium Oxide Addition on the Structure and Thermal Properties of Iron Phosphate Glasses

The calcium iron phosphate glasses were prepared and measured by X-ray diffraction, Fourier transform infrared spectra, Raman spectra, and differential scanning calorimetry. X-ray diffraction analysis has confirmed that all compositions are amorphous. Infrared and Raman spectra indicated that the glass formed the P‒O‒Fe and P‒O‒Ca bonds in Q1 units and (P‒O− Ca2+−O‒P) ionic cross-links in Q2 units. Increasing calcium oxide content in glass compositions was brought about by the Q1 to Q2 conversion, which resulted in the more formation of the non-bridging oxygen (P‒O− Ca2+−O‒P) ionic cross-links. The change of glass transition temperature and thermal stability is consistent with structural modification of the glasses. The analyses of the spectra revealed that calcium oxide played the dual role as a network former and modifier. Oxygen to phosphorus molar ratio about 3.0 would contain the relatively higher concentration of Q1 and Q2 units.

Influence of rare earth addition on the thermal and structural stability of CaO[sbnd]Fe2O3[sbnd]P2O5 glasses

The thermal and structural stability of calcium iron phosphate glasses doped with rare earth oxides has been studied by investigating differential scanning calorimetry, the concentration of modified ions in leachate, Fourier transform infrared spectra, and Raman spectra. The results showed that thermal stability of the rare earth phosphate glasses increased and the release rate of rare earth ions in leachate decreased with the increase of cationic field strength. It related to the known structural units and characteristic bands of these glasses detected by infrared and Raman spectra. Metaphosphate chains by the cross-links of calcium ions and POP linkages were easier to hydrolyze, which converted to orthophosphate units after corrosion. The formation of more chemically resistant REOP bonds with the addition of rare earth leaded to an increased quantity of nonbridging oxygen, which caused consequent variations in the chemical durability of rare earth glasses.

A physicochemical process for fabricating submicrometre calcium iron phosphate spheres

We developed a simple and quick physicochemical process for fabricating calcium iron phosphate submicrometre spheres. Here, pulsed laser irradiation was performed to a calcium phosphate reaction mixture supplemented with ferric ions as a light-absorbing agent. The size and chemical composition of the spheres were controllable through the experimental conditions.

Physical and structural properties of calcium iron phosphate glass doped with rare earth

The physical and structural properties of calcium iron phosphate glasses with different Gd2O3 contents and various rare earth oxides (Y2O3, La2O3, Nd2O3, Sm2O3, Gd2O3) were systematically studied by investigating their density, Vickers-hardness and Raman spectra. The results show that the compositions which contain up to 10mol% of rare earth oxides formed homogeneous glasses and no crystalline phases. The properties of density and molar volume were discussed with different Gd2O3 contents and various rare earth elements, and Y-doped glass is an exception in molar volume. Vickers-hardness increases with the increase of cationic field strength of the corresponding rare earth elements. These physical properties have relations with the rare earth glass structure. The shape of the Raman spectra is affected and a very strong depolymerization appears in studied phosphate glasses with the Gd2O3 addition. The relative area of (PO3)2− bonds in Q1 units with different rare earth glasses increase with increasing cationic field strength of corresponding rare earth ions. The P–O distance and rare earth coordination numbers were discussed to understand further the glass structure.

Structural aspects of calcium iron phosphate glass containing neodymium oxide

Homogeneous glasses of the xNd2O3(100 − x)(12CaO20Fe2O368P2O5) system were obtained within the 0⩽x⩽10mol% composition range. The density and molar volume measurements helped to understand the structural changes occurring in these glasses. Vickers-hardness results showed that addition of Nd2O3 strengthened the crosslinking of the glass network. Spectra analysis indicated that Nd2O3 enters in the structure of the phosphate glasses as a network modifier. The depolymerization of the glass network by the addition of Nd2O3 is characterized by the increase in the concentration of pyrophosphate. The decrease of the Q1 terminal oxygen with increasing Nd2O3 content indicated that PONd bonds participated in the pyrophosphate glass structure, determined from the Raman spectra.

Structure and properties of calcium iron phosphate glasses

The structural properties of xCaO–(100−x) (0.4Fe2O3–0.6P2O5) (x=0, 10, 20, 30, 40, 50mol%) glasses have been investigated by XRD, DTA, IR and Raman spectroscopy. XRD analysis has confirmed that the majority of samples are X-ray amorphous, and EDS analysis indicates that the glass matrix can accommodate ≈30mol% CaO. IR and Raman spectra show that the glass structure consists predominantly of pyrophosphate (Q1) units. IR spectra indicate that the phosphate network is depolymerized with the addition of CaO content. The density and glass transition temperature (Tg) increase with increasing CaO content for the glasses. This behavior indicates that the addition of CaO improves the strength of the cross-links between the phosphate chains of the glass.

Calcium–iron–phosphate features in archaeological sediments: characterization through microfocus synchrotron X-ray scattering analyses

The occurrence of amorphous calcium (Ca)–iron (Fe)–phosphate infilling features in thin-section samples from archaeological stratigraphies is increasingly being reported and used in the cultural interpretations of sites. In some contexts, these materials are the product of dissolution and recrystallization of bone material within pores of the soil or sediment matrix. This study uses transmitted microfocus X-ray scattering to characterize and measure features of known cod fish bone (Gadus morhua) materials, and compare them to archaeological samples of amorphous Ca-Fe-phosphate infilling material found in thin section from early fishing community sites. The analyses characterize the structure of these features for the first time, and allow discussion of the diagenetic processes that lead to their formation.

Characterization by X-ray diffraction, magnetic susceptibility and Mössbauer spectroscopy of a new alluaudite-like phosphate:: Na 4CaFe 4(PO 4) 6

A single crystal of a new sodium calcium iron (III) phosphate, Na 4CaFe 4(PO 4) 6, has been synthesized by a flux method and characterized by X-ray diffraction, Mössbauer spectroscopy and magnetic susceptibility measurements. The compound crystallizes in the monoclinic space group C2/ c( a=12.099(5) Å, b=12.480(5) Å, c=6.404(2) Å, β=113.77(3)°, Z=2, R 1=0.022, R w2=0.066). The crystal structure belongs to the alluaudite type, characterized by the X(2) X(1) M(1) M(2) 2(PO 4) 3 general formula. The open framework results from Fe 2O 10 units of edge-sharing FeO 6 octahedra, which alternate with M(1)O 6 octahedra ( M(1)= 1 2 Na+ 1 2 Ca) that form infinite chains. These chains are linked together through the common corners of PO 4 tetrahedra yielding two distinct tunnels of sodium cation occupation. This compound is antiferromagnetic with a Néel temperature of 35 K. Mössbauer parameters are consistent with the structural results.

Reduction and Re‐Oxidation Behavior of Calcium Iron Phosphate, Ca9Fe(PO4)7.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Crystal structure, magnetic properties and Mössbauer spectroscopy of NaCaFe 3(PO 4) 4

A new sodium and calcium iron phosphate, NaCaFe 3(PO 4) 4, has been synthesized by a flux method and characterized by single crystal X-ray diffraction, magnetic susceptibility and Mössbauer spectroscopy. The compound crystallizes in the orthorhombic space group Pcab with the parameters a=8.706(4) Å, b=9.410(1) Å, c=29.211(6) Å, V=2393 Å 3 and Z=8. The structure consists of discrete FeO 6 octahedra and FeO 5 trigonal bipyramids, corner-sharing with PO 4 tetrahedra that form a [Fe 3P 4O 16] n three-dimensional framework with two distinct cavities which are the Na + and Ca 2+ sites. Mössbauer spectroscopy results confirm those obtained from X-ray diffraction. Magnetic susceptibility indicates an antiferromagnetic behavior with a Néel temperature T N≈26 K.

Development of bioabsorbable glass fibres

Calcium-iron phosphate glasses with an iron oxide content ranging from 5 wt.% to 22 wt.% were prepared to investigate the effect of iron oxide on the properties of the glass. It was found that the dissolution rate, the fibre strength and the glass transition temperature were strongly affected by iron oxide. The glass dissolution rate exhibited a 50-fold reduction while the fibre strength doubled when the iron oxide content was increased from 5 wt.% to 22 wt.%. The phosphate glass containing 22 wt.% of iron oxide had a dissolution rate of about 5μg/(cm 2 day). The fibres drawn from this glass also exhibited the highest tensile strength over 1000 MPa. A cortical bone plug method was used to assess the biocompatibility of the glasses with the hard and soft tissues. The tissues surrounding the samples showed no inflammation at 9 wk. Biomaterials (1994) 15, (13) 1057–1061

Enhanced Phosphorus Removal in Trickling Filters

Phosphorus removal from domestic wastewater was investigated using four synthetic media, pilot trickling filters constructed at the Madison Nine-Springs Sewage Treatment Plant. Phosphorus removal was not correlated with the parameters of the experimental design of: hydraulic load, depth, recirculation, or waste strength; however, greater phosphorus removals were measured than could be attributed to biological requirements for phosphorus. Analysis of filter slime composition and phosphorus release studies suggested this bonus-removal of phosphorus was attributed to chemical precipitates of calcium apatite, aluminum phosphate, and iron (III) phosphate trapped in the filter slime. This trickling filter study supports the enhances-removal mechanism for bonus-removal of phosphorus from hard water wastewaters reported for the activated sludge process.