Phosphate Matrix Research Articles

Non-fluoride dissolution of tantalum and niobium oxides and their separation using ion exchange

The study involved the separation of Ta and Nb in a phosphate matrix using ion exchange chromatography. Experimental variations included different types of Ta/Nb containing samples, types of resin, phosphoric acid concentration as eluent, flow rate and column dimensions. Experimental conditions were developed and refined using a pure 1:1 (Ta/Nb)2O5 synthetic mixture and the optimum conditions were then applied to a real tantalite mineral sample. Experimental results indicated the successful separation of the Ta and Nb in the synthetic sample using the weak basic Dowex Mathon and Dowex 66 free base resins. Almost complete recovery of Nb was achieved with 200mL of 8M H3PO4. It was found that Ta was more strongly absorbed but by using a stronger acid concentration of 10M H3PO4, almost complete recovery was also obtained for Ta. Excellent elemental separation (α=11.5) and recoveries were also obtained with tantalite mineral as sample under identical experimental conditions. Almost complete recoveries for both Nb and Ta were obtained after elution with 8.0M and 10.0M H3PO4 respectively. Apart from the complete separation of Ta and Nb, minor elements which are also present in tantalite like Fe, Mn and U could also be successfully separated and quantitatively recovered. However, the Nb fraction was contaminated with Ti because under these conditions these two elements are simultaneously eluted.The successful separation and recovery of both Ta and Nb from a phosphate matrix suggest a possible alternative to the conventional fluoride beneficiation methods. This method also has the potential of industrial applications.

Study on Dielectric Properties of Aluminum Borate Whisker Reinforced Aluminum Phosphate Composite

Aluminum borate whisker with different ratios (20wt%, 30wt%, 40wt%, 50wt%, 70wt%) was added to the aluminum phosphate matrix. The composite was sintered at 750 ℃ -1400 ℃ temperature, then the dielectric constant ( e ) and the dielectric loss tangent (tan δ ) of the composite was measured. The results show that when the whisker content is the same, the dielectric constant of the sample increases with increasing of relative density, but the dielectric loss decreases with increasing of relative density. The dielectric loss of the composite is mainly caused by the relaxation polarization.

Electrocatalytic Oxidation of Glucose at Nickel Phosphate Nano/Micro Particles Modified Electrode

Here is a first study of the electrocatalytic oxidation of glucose by nickel phosphate nano/micro particles (NiPh) modified glassy carbon electrode (NiPh/GC). The NiPh is fabricated by a simple reflux method. The morphology and structure of the NiPh particles have been studied using field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), BET surface area measurement and Fourier transfer Infrared spectroscopy (FTIR). According to the above measurements, a needle-like morphology with average particle dimensions of 200 × 800 nm is obtained. The phase structure of the NiPh particles is found to be Ni3(PO4)2.8H2O and having BET surface area of 20.0 m2/g. Electrochemical measurements like cyclic voltammetry (CV) are used to characterize the NiPh/GC electrode. Potential cycling in the range of −0.1 to 0.7 V (Ag/AgCl/KCl(sat)) is used to activate the phosphate matrix. After ~75 cycles, two redox peaks are emerged which were assigned for the redox transform NiPh (II)/NiPh (III) due to invasion of the OH− ions into the NiPh matrix. The NiPh/GC demonstrates electrocatalytic activity towards glucose oxidation in alkaline solution. The glucose reaction is analyzed and characterized in the light of the collected experimental data.

Co-delivery of cisplatin and doxorubicin from calcium phosphate beads/matrix scaffolds for osteosarcoma therapy

Bone substitute materials with a controlled drug release ability can fill cavities caused by the resection of bone tumours and thereby combat any leftover bone cancer cells. The combined release of different cytostatics seems to enhance their toxicity. In this study, calcium phosphate beads and matrix scaffolds are combined for a long-term co-delivery of cis-diamminedichloroplatinum (cisplatin, CDDP) and doxorubicin hydrochloride (DOX) as clinical relevant model drugs. Tricalcium phosphate/alginate beads as additional drug carrier are produced by droplet extrusion with ionotropic gelation and incorporated in scaffold matrix by freeze gelation without sintering. CDDP shows a short burst release while DOX has a continuous release measurable over the entire study period of 40days. Drug release from matrix is decreased by ~30% compared to release from beads. Nevertheless, all formulations follow the Korsmeyer-Peppas release kinetic model and show Fickian diffusion. Cytotoxic activity was conducted on MG-63 osteosarcoma cells after 1, 4, and 7days with WST-1 cell viability assay. Co-loaded composites enhance activity towards MG-63 cells up to ~75% toxicity while reducing the released drug quantity. The results suggest that co-loaded beads/matrix scaffolds are highly promising for osteosarcoma therapy due to synergistic effects over a long period of more than a month.

Non-homogeneous distribution of Al3+ in doped phosphate glasses revealed by 27Al/31P solid state NMR

Solid state NMR is applied in this contribution on the xAl2O3-(50-x/2)Na2O-(50-x/2)P2O5 composition line (with 0<x<5mol%) in order to investigate the distribution of Al3+ ions in Al2O3-doped sodium phosphate glasses. The structure was analysed by (i) 27Al 1D-, 3Q-, DQ- MAS-NMR analysis and (ii) 1D 31P, 27Al(31P) 2D D-HMQC MAS-NMR and 2D 31P R-INADEQUATE technique. The 27Al NMR results confirm the presence of six-coordinated aluminate as major aluminate species and indicate that Al3+ ions are fully dissociated in the glass network. The 31P NMR data show the simultaneous presence of five different phosphate units connected to 0, 1 but also 2 Al3+ ions and offer a new vision of the doping mechanism by highlighting a non-homogeneous distribution of Al3+ ions in the phosphate matrix. This study indicates that the glass networks contain Al3+-rich and -poor domains and present thus a significant structural disorder beyond the local order.

Preparation and photocatalytic activity of chemically-bonded phosphate ceramics containing TiO2

Titanium dioxide was incorporated into chemically-bonded phosphate ceramic for use as photocatalytic inorganic coating. The coatings obtained were applied to unglazed ceramic tiles and cured at 350°C. The surfaces were characterized by photocatalytic activity, determined in aqueous medium, based on the degradation of methylene blue dye. The effects of the percentage of TiO2 and the thickness of the layer on the photocatalytic efficiency were evaluated. The influence of the incorporation of TiO2 on the consolidation of the phosphate matrix coating was investigated using the wear resistance test. The crystalline phases of the coatings obtained were determined by XRD. The microstructure of the surfaces was analyzed by SEM. The thermal curing treatment did not cause a phase transition from anatase to rutile. An increase in the photocatalytic activity of the coating was observed with an increase in the TiO2 content. The dye degradation indices ranged from 14.9 to 44.0%. The photocatalytic efficiency was not correlated with the thickness of the coating layer deposited. The resistance to wear decreased with an increase in the TiO2 content. Comparison with a commercial photocatalytic ceramic coating indicated that there is a range of values for the TiO2 contents which offer potential for photocatalytic applications.

Grain size effect in conductive phosphate / carbon nanotube ceramics

Composite materials based on aluminium phosphate matrix with different grain sizes and small inclusions of carbon nanotubes were studied by means of broadband dielectric spectroscopy in a wide frequency (20Hz to 36GHz) and temperature (25–600K) ranges. The highest electrical percolation threshold was observed for ceramics with the grain size of 0.8µm, which is higher than the carbon nanotubes cluster size. The electrical transport in ceramics occurs due to the thermal activation at higher temperatures (above room temperature) and the tunneling at lower temperatures. The potential barrier for electron hopping is the lowest in nanosized ceramics. The distance for electron tunneling is also lowest in nanosized ceramics. The electrical properties of ceramics are stable up to 560K.

CLINOPTILOLITE WITH CESIUM IMMOBILIZATION TO POTASSIUM MAGNESIUM PHOSPHATE MATRIX

The possibility of potassium magnesium phosphate (PMP) matrix application for immobilization of clinoptilolite with simulator of radioactive cesium isotopes was investigated. X-ray phase analysis of the natural clinoptilolite sample has shown that it includes two main phases of clinoptilolite (Na,K)4CaAl6Si30O72·24H2O, and mordenite (Na2Ca, K2) 4Al8Si40O96 · 28H2O. In addition, impurities of SiO2, Fe2O3 and TiO2 phases are observed. To saturate clinoptilolite with cesium, 0.5 M solution of cesium chloride was used. A chemical analysis of clinoptilolite after saturation with cesium has demonstrated that the content of cesium in clinoptilolite was about 2 wt.%. After the introduction of clinoptilolite with cesium in the PMP matrix, the obtained material was identified as potassiummagnesium phosphate with the presence of clinoptilolite, mordenite, TiO2 and unreacted MgO phases. The results of the electron microscopy analysis have shown that cesium was dislocated between PMP matrix and clinoptilolite, incorporated into the PMP matrix. Normalized leaching rate of cesium from PMP matrix with 25wt.% clinoptilolite was about 3.2.10-4 g / cm2 per day after 7 days testing.

Synthesis and characterization of PLD glass phosphate films doped with CdS

In the present work, optical, structural and morphological properties of CdS-doped phosphate films obtained by pulsed laser deposition (PLD) method were investigated. In the deposition process, a target based on a mixture composed of Li2O-Al2O3-BaO-La2O3-ZnO-P2O5 glass and CdS powder as dopant was used. The phosphate glass target was obtained by non-conventional wet route of raw reagents processing followed by melt-quenching technique. The complex oxide composition of the glass as well as the final PLD target consisting in a mixture of glass and CdS powder followed by pressing and heat treatment represents the novelty of the work. CdS dopant particles were highlighted by X-ray diffraction analysis as well as by Raman spectroscopy. Thus, cubic CdS particles having less than 10 nm size corroborated with specific LO (longitudinal optical phonons) and 2LO CdS Raman peaks from 300 and 600 cm−1, respectively, certified the presence of the dopant in the deposited films. Specific vibration modes for the vitreous phosphate matrix were revealed by fourier transform infrared spectroscopy, and spherulitic units characteristic to PLD technique were found by scanning electron microscopy and atomic force microscopy analyses. A relative large luminescence band located around 430 nm was provided by UV excitation, representative for CdS nanoparticles having about 9–10 nm size.

Synthesis and Characterization of a Nanostructured Matrix of Hydrated Calcium Phosphate

Bone reconstruction biomaterials are topics of interest in dentistry, orthopedics, scientific, commercial. The most popular bone repairing and reconstruction biomaterials are calcium phosphates. The demand for biomaterials is associated with the chemical and crystallographic characteristics of the human bone apatite. The wet synthesis method is common in the production of nanostructured powders of hydrated calcium phosphates, providing nanoparticles with sizes less than 50nm. This study aimed to synthesize and characterize hydrated calcium phosphate powders in the molar ratio of Ca/P = 1.67. After calcination at temperature 900°C/2h, these powders provide nanostructured hydroxyapatite matrix. The characterization studies were performed with Scanning Electron Microscopy, X-rays diffraction and Infrared Spectroscopy by Fourier Transform. The results show that the synthesis method provides hydrated calcium phosphate powders formed by aggregated and agglomerated nanoparticles. The thermal treatment of hydrated calcium phosphate powder led to formation of hydroxyapatite matrix.

Synthesis and Characterization of a Hydrated Calcium Phosphate Matrix and Biphasic Compositions with MgO and α-Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;

The calcium phosphate bioceramics are characterized by chemical and crystallographic similarity with the human skeleton. The wet synthesis method was used in the preparation of hydrated calcium phosphate nanostructured powders and biphasic compositions of calcium phosphate matrix. This study aimed the synthesis and characterization of a hydrated calcium phosphate matrix in the ratio Ca/P 1.67 molar and two biphasic compositions of hydrated calcium phosphate matrix, with 1% MgO and 5% α-Al2O3. Scanning Electron Microscopy (SEM) helped with the powders morphological characterization, X-ray diffractometry (XRD) served for crystallographic characterization of powders and Fourier Transformed Infrared Spectroscopy (FTIR) gave support to the identification of H2O, CO32- and PO43- grouping vibrational bands. The work showed that the presence of 1% MgO inside the hydrated calcium phosphate matrix provided brushite formation and the presence of 5% α-Al2O3 in the matrix provided the hydrated calcium phosphate powder.

Titanium Dioxide/Lithium Phosphate Nanocomposite Derived from Atomic Layer Deposition as a High‐Performance Anode for Lithium Ion Batteries

Atomic layer deposition (ALD) is considered as a powerful technique to synthesize novel electrode materials for lithium‐ion batteries (LIBs), because not only the compositions can be specifically designed to achieve higher battery performances, but also the materials can be deposited on various substrates for different purposes. Herein, a novel design of active material/electrolyte mixture electrode, i.e., titanium dioxide/lithium phosphate (TLPO) nanocomposite, has been successfully developed by ALD and deposited on carbon nanotube substrates (CNTs@TLPO) at 250 °C, by combining the ALD recipes of TiO2 and lithium phosphate (LPO). In the nanocomposite, TiO2 forms anatase nanocrystals, embedded in a matrix of amorphous lithium phosphate. CNTs@TLPO has been examined as an anode material for LIBs, exhibiting a similar electrochemical response as anatase TiO2 in the cyclic voltammetry testing. CNTs@TLPO presents an outstanding capacity of 204 mA h g−1 upon 200 cycles in charge and discharge cycling measurements, as well as a significantly improved rate capability compared with ALD deposited TiO2 on CNTs without LPO ALD cycles. This work shows that the in situ addition of solid‐state electrolyte (e.g., lithium phosphate), which introduces higher Li+ ionic conductivity, is an efficient way to achieve high‐performance electrode materials for LIBs by ALD.

Magnesium inhibits the calcification of the extracellular matrix in tendon-derived stem cells via the ATP-P2R and mitochondrial pathways

Tendon calcification has been widely regarded by researchers to result from the osteogenic differentiation of Tendon-Derived Stem Cells (TDSCs) and ectopic mineralization caused by the calcification of cellular matrix. Recent studies have revealed a correlation between the Mg2+/Ca2+ balance and the degeneration or calcification of tendon tissues. Furthermore, the ATP–P2X/P2Y receptor pathway has been shown to play a decisive role in the process of calcification, with calcium exportation from mitochondria and calcium oscillations potentially representing the cohesive signal produced by this pathway. Our previous study demonstrated that matrix calcification is inhibited by magnesium. In this study, we examined the effects of extracellular Mg2+ on the deposition of calcium phosphate matrix and cellular pathways in TDSCs. The suppression of the export of calcium from mitochondria has also been detected. We found that a high concentration of extracellular Mg2+ ([Mg2+]e) inhibited the mineralization of the extracellular matrix in TDSCs and that 100 μM ATP reversed this inhibitory effect in vitro. In addition, the spontaneous release of ATP was inhibited by high [Mg2+]e levels. A high [Mg2+]e suppressed the expression of P2X4, P2X5 and P2X7 and activated the expression of P2Y1, P2Y2, P2Y4 and P2Y14. The interaction between Mg2+ and Ca2+ is therefore contradictory, Mg2+ inhibits mitochondrial calcium concentrations, meanwhile it reverses the opening of mPTP that is induced by Ca2+. JC-1 staining verified the protective effect of Mg2+ on mitochondrial membrane potential and the decrease induced by Ca2+. Taken together, these results indicate that high [Mg2+]e interferes with the expression of P2 receptors, resulting in decreased extracellular mineralization. The balance between Mg2+ and Ca2+ influences mitochondrial calcium exportation and provides another explanation for the mechanism underlying matrix calcification in TDSCs.

Distarch Phosphate as a Matrix for the Generation of Quantum Dots

Generation of ZnS, CdS, CaS and MgS quantum dots (QDs) was attempted in the matrix of distarch phosphate, an anionic polysaccharide. Based on the analysis of FTIR spectra, thermograms and Differential Scanning Calorimetry, interactions of QDS with the matrix could be excluded. On generation of MgS QDs and also, to a certain extent, CaS QDs, hydrolysis of the salts generating these QDs took place. That process had an impact on the partial destruction of the matrix. Molecular weight and radii of gyration of the products showed that the generation of QDs was dependent on the properties of the matrix polysaccharide. The elasticity, plasticity and viscosity of the gels containing QDs were significantly lower than those of plain distarch phosphate. Generally these values changed with time similarly to gels free of QDs.

Strengthening of bone cements based on tribasic calcium phosphate by calcium carbonate granules

The influence of the size and number of calcium carbonate granules introduced to the cement matrix of an alpha-tribasic calcium phosphate–orthophosphoric acid solution on the compression strength of the composite material was studied. A potential increase in strength by a factor of six by the introduction of an optimal amount of granules into the matrix was determined.

Effect of recombinant PDGF-BB on bone formation in the presence of β-tricalcium phosphate and bovine bone mineral matrix: a pilot study in rat calvarial defects.

BackgroundSupplementation of bone substitutes with recombinant platelet-derived growth factor-BB (PDGF-BB) can enhance bone regeneration. The aim of the study was to evaluate the effect of PDGF-BB on bone formation in the presence of β-tricalcium phosphate and bovine bone mineral matrix in a rat calvaria defect model.MethodsThe authors examined 5 mm rat calvarial defects treated with β-tricalcium phosphate (TCP) or demineralized bovine bone mineral (DBBM) with and without 0.3 mg/ml recombinant PDGF-BB. Calvaria defects were randomly divided into the following treatment groups (n = 5); TCP; TCP plus PDGF-BB; DBBM; DBBM plus PDGF-BB; and untreated empty control. After 45 days, bone formation was evaluated by histomorphometry and fluorescence microscopy.ResultsThe authors report that the area of newly formed bone was similar between the empty controls and the two bone substitutes, TCP and DBBM. Supplementation of TCP and DBBM with PDGF-BB had no significant impact on bone formation. Fluorochrome staining revealed no visible changes in the pattern of bone formation in defects filled with TCP and DBBM, irrespective of PDGF-BB. Furthermore, supplementation with PDGF-BB did not influence biomaterial degradation.ConclusionsThe authors concluded that PDGF-BB had no impact on bone formation and degradation of bone substitutes in the respective rodent models. Thus, possible beneficial effects of PDGF-BB may require other model situations.

HIGH LEVEL WASTES IMMOBILIZATION IN CERAMIC AND HYDRATED PHOSPHATE MATRIX

The results of experimental research for obtaining of phosphate matrix materials: fluorapatite Ca10(PO4)6F2, sodium zirconium phosphate NaZr2(PO4)3 and potassium magnesium phosphate KMgPO4·6H2O were presented. The evolution of phase composition in their synthesis was investigated. The optimal parameters for obtaining monophasic phosphate matrix materials were found. Possibility of obtaining powders of calcium Ca10(PO4)6F2 and strontium-containing Ca9Sr(PO4)6F2 fluorapatites by both solid phase reaction method with subsequent heat treatment and chemical co-precipitation method from solutions of the initial components was investigated. Nanosized zirconium orthophosphate powders NaZr2(PO4)3 were synthesized by the sol-gel method. Hydrated phosphatic matrices KMgPO4·6H2O by a chemical reaction between MgO and KH2PO4 in water at a room temperature were obtained. The requirements for high-level waste matrix were presented. The suitability of the use of synthetic phosphate materials as a matrix for the immobilization of high level nuclear wastes was determined.

Extraction of rare earth elements from upgraded phosphate flotation tailings

Phosphate rock contains traces of rare earth elements (REEs) and can be a secondary source of these critical materials as large tonnages of phosphate rock are mined annually. Attention has mostly focused on the extraction of REEs from phosphogypsum, which contains more than 70 percent of the REEs reporting to phosphate concentrate, with only limited work conducted on REE extraction from sand tailings and slime even though they account for 16 percent and 15 percent, respectively, of REEs mined with phosphate matrix. In this work, phosphate flotation tailings were upgraded by gravity separation and froth flotation. Gravity separation was conducted using a laboratory shaking table, while flotation was conducted in a Denver D-12 flotation cell. The concentrated tailings were then leached by nitric acid followed by REE extraction with solvent and ion-exchange resin. The sand tailings were assayed as having 2.6 percent phosphate (P2O5) and 198.1 µg/g REEs. It was found that the shaking table could produce tailing concentrate assayed as having 8.6 percent P2O5 and 616 µg/g REEs but with only 20 percent REE recovery, while the froth flotation produced froth concentrate assayed as having 8.1 percent P2O5 and 368.2 µg/g REEs with 63.5 percent REE recovery. Leaching the flotation concentrate with 5.2 M (25 percent) nitric acid followed by extraction with solvent and ion-exchange resin yielded precipitates with REE contents of 0.926 and 0.314 percent, respectively, compared with 0.716 and 0.213 percent when table concentrate was used.

Bioelectrochemical Systems for Clean Environment

The aim of this work is to introduce bacteria into the matrix of natural phosphate to catalyze the phenol oxidation. The results showed that the NP-bacteria-CPE exhibited excellent electro catalytic activity to phenol. The appearance of three peaks of oxidation shows that the degradation of the phenol was total.

Overcoming Molecular Sample Processing Limitations: (a) New Platform Technologies, (b) RNA and DNA Extraction Strategies, and (c) Fiber-Optic Biosensors

Overcoming Molecular Sample Processing Limitations: (a) New Platform Technologies, (b) RNA and DNA Extraction Strategies, and (c) Fiber-Optic Biosensors