Preparation and characterization of carbonated barium-calcium hydroxyapatite solid solutions

Particles of carbonated barium-calcium hydroxyapatite solid solutions (BaCaHap) with different Ba/(Ba+Ca) (X(Ba)) atomic ratios were prepared by a wet method at 100 degrees C and characterized by various means. The crystal phases and structures of the products strongly depended on the composition of the starting solution, that is, the Ba/(Ba+Ca) atomic ratio ([X(Ba)]) and H3PO4 concentration ([H3PO4]) in the solution. BaCaHap with X(Ba)0.43 could be prepared at [X(Ba)]0.7 by changing [H3PO4], but could never be obtained at [X(Ba)]=0.8-0.95 regardless of [H3PO4]. The carbonated calcium hydroxyapatite particles prepared at [X(Ba)]=0 were fine and short rod-shaped particles (ca. 14x84 nm). With increasing [X(Ba)] from 0 to 0.8, the particles obtained became large spherical agglomerates. The carbonated barium hydroxyapatite particles formed at [X(Ba)]=1 were long rod-shaped agglomerates (ca. 0.2x2 microm) of fine primary particles. The amount of CO2 adsorbed irreversibly on a series of BaCaHaps showed a minimum at (Ba+Ca)/(P+C) atomic ratio of around 1.56, which agreed well with the minimum cation/P ratio obtained for the other hydroxyapatites, as already reported.     

Effect of K(+) on the Stoichiometry of Carbonated Hydroxyapatite Obtained by the Hydrolysis of Monetite

This study investigates the stoichiometry and the thermal stability of K(+)- and CO(3)(2)(-)-containing apatites (KCAp's) obtained by the hydrolysis of monetite. The analysis results of the samples after drying reveal that the KCAp's start to lose carbonate at temperatures V(Ca) + CO(3)(2)(-) + V(OH)] and [Ca(2+) + PO(4)(3)(-) <--> K(+) + CO(3)(2)(-)], where V(X) stands for a vacancy in the X-sublattice. Moreover, a small part of the CO(3)(2)(-) ions are presumably incorporated according to [Ca(2+) + 2PO(4)(3)(-) <--> V(Ca) + 2CO(3)(2)(-)]. A comparison of the contributions of these fundamental mechanisms with the results for precipitated Na(+)- and CO(3)(2)(-)-containing apatites shows that no intrinsic coupling whatsoever exists between these mechanisms.     

The formation mechanism of cobalt silicide on silica from Co(SiCl3)(CO)4 by in situ Fourier transform infrared spectroscopy

Silica supported CoSi particles were synthesized by metal organic chemical vapor deposition of the Co(SiCl(3))(CO)(4) precursor carried in hydrogen at atmospheric pressure and moderate temperature in a fluidized bed reactor. In contrast, CoCl(2) supported on silica was formed by using argon as the carrier gas. The samples were characterized by X-ray diffraction, transmission electron microscopy, ultraviolet-visible spectroscopy, and thermogravimetric/differential thermogravimetric analysis. The precursor Co(SiCl(3))(CO)(4) reacted with the hydroxyl groups of amorphous silica via loss of HCl and introduced cobalt species onto the surface. The decomposition mechanism of the supported precursor on silica was investigated by in situ Fourier transform infrared spectroscopy from room temperature to 300 °C in a hydrogen or argon atmosphere. The results showed that CO and HCl elimination occurred in a hydrogen atmosphere, while only CO elimination occurred in Ar. All of the results showed that it was possible to prepare supported CoSi at lower temperatures via changing the carrier gas.     

Particle-particle chemistry between micrometer-sized PbSO4 and CaCO3 particles in turbulent flow initiated by liquid water

A mixture of natural and anthropogenic particles is ubiquitous in the troposphere and exerts an important influence on air quality. This work reports the study of mixing and heterogeneous chemistry of particles of natural-like mineral dust (CaCO(3)) and anthropogenic-like microparticle (PbSO(4)) in turbulent air flow under varying relative humidity. Sparse monolayers of laboratory-generated particles were collected on substrates using impaction. The grain size distribution and chemistry of micrometer-sized particles were determined as CaCO(3)-PbSO(4) internal and external mixtures by Raman imaging, scanning electron microscopy, and time-of-flight static secondary ionization mass spectrometry. The condensation of a thin water layer on mixed aggregates initiates the formation of complex internal mixtures of Pb(3)(CO(3))(2)(OH)(2), PbCO(3), CaSO(4)·2H(2)O, CaCO(3), and PbSO(4) fine particles. These heterogeneous chemistry processes which may occur in ambient air can increase dramatically the amounts of hazardous breathable particles.     

垃圾衍生燃料流化床燃烧过程中HCl和NOx的排放研究

在床总高为4040mm的变截面流化床中试规模装置内，研究垃圾衍生燃料(RDF)在气化和燃烧不同阶段中NOx和HCl的生成特性。含NaCl的垃圾衍生燃料在流化床内燃烧，燃烧低于640℃时，Ca(OH)2的脱氯效果比较好;但随着温度升高，烟气中HCl的体积分数迅速增长，但脱氯效果明显受到CaCl2化学反应平衡的限制。燃烧状况特别是氧的体积分数对NOx的生成影响比较大。含氮量高的RDF燃烧产生NOx的体积分数明显高于低含氮燃料所产生的。     

Simultaneous fermentation and separation of lactic acid in a biparticle fluidized-bed bioreactor

A bioreactor configuration has been tested for simultaneous fermentation and separation of the desired inhibitory product, lactic acid. The bioreactor is a fluidized bed of immobilized Lactobacillus delbreuckii. Another solid phase of denser sorbent particles (a poly-vinyl pyridine resin) was added to this fluidized bed. These sorbent particles fell through the bed, absorbed the product, and were removed. In test fermentations, the addition of the sorbent enhanced the fermentation and moderated the fall of the pH. The biparticle fluidized-bed bioreactor utilizing immobilized microorganisms and adsorbent particles has been shown to enhance the production of lactic acid fourfold in this nonoptimized system.

     

Elements of metabolic evolution

Research into the origin of evolution is polarized between a genetics-first approach, with its focus on polymer replication, and a metabolism-first approach that takes aim at chemical reaction cycles. Taking the latter approach, we explored reductive carbon fixation in a volcanic hydrothermal setting, driven by the chemical potential of quenched volcanic fluids for converting volcanic C1 compounds into organic products by transition-metal catalysts. These catalysts are assumed to evolve by accepting ever-new organic products as ligands for enhancing their catalytic power, which in turn enhances the rates of synthetic pathways that give rise to ever-new organic products, with the overall effect of a self-expanding metabolism. We established HCN, CO, and CH(3)SH as carbon nutrients, CO and H(2) as reductants, and iron-group transition metals as catalysts. In one case, we employed the "cyano-system" [Ni(OH)(CN)] with [Ni(CN)(4)](2-) as the dominant nickel-cyano species. This reaction mainly produced α-amino acids and α-hydroxy acids as well as various intermediates and derivatives. An organo-metal-catalyzed mechanism is suggested that mainly builds carbon skeletons by repeated cyano insertions, with minor CO insertions in the presence of CO. The formation of elemental nickel (Ni(0)) points to an active reduced-nickel species. In another case, we employed the mercapto-carbonyl system [Co(2)(CO)(8)]/Ca(OH)(2)/CO for the double-carbonylation of mercaptans. In a "hybrid system", we combined benzyl mercaptan with the cyano system, in which [Ni(OH)(CN)] was the most productive for the double-carbon-fixation reaction. Finally, we demonstrated that the addition of products of the cyano system (Gly, Ala) to the hybrid system increased productivity. These results demonstrate the chemical possibility of metabolic evolution through rate-promotion of one synthetic reaction by the products of another.     

Mechanistic origin of antagonist effects of usual anionic bases (OH-, CO3(2-)) as modulated by their countercations (Na+, Cs+, K+) in palladium-catalyzed Suzuki-Miyaura reactions

The mechanism of the reaction of trans-ArPdBrL(2) (Ar=p-Z-C(6)H(4), Z=CN, H; L=PPh(3)) with Ar'B(OH)(2) (Ar'=p-Z'-C(6)H(4), Z'=H, CN, MeO), which is a key step in the Suzuki-Miyaura process, has been established in N,N-dimethylformamide (DMF) with two bases, acetate (nBu(4)NOAc) or carbonate (Cs(2)CO(3)) and compared with that of hydroxide (nBu(4)NOH), reported in our previous work. As anionic bases are inevitably introduced with a countercation M(+) (e.g., M(+)OH(-)), the role of cations in the transmetalation/reductive elimination has been first investigated. Cations M(+) (Na(+), Cs(+), K(+)) are not innocent since they induce an unexpected decelerating effect in the transmetalation via their complexation to the OH ligand in the reactive ArPd(OH)L(2), partly inhibiting its transmetalation with Ar'B(OH)(2). A decreasing reactivity order is observed when M(+) is associated with OH(-): nBu(4)N(+) > K(+) > Cs(+) > Na(+). Acetates lead to the formation of trans-ArPd(OAc)L(2), which does not undergo transmetalation with Ar'B(OH)(2). This explains why acetates are not used as bases in Suzuki-Miyaura reactions that involve Ar'B(OH)(2). Carbonates (Cs(2)CO(3)) give rise to slower reactions than those performed from nBu(4)NOH at the same concentration, even if the reactions are accelerated in the presence of water due to the generation of OH(-). The mechanism of the reaction with carbonates is then similar to that established for nBu(4)NOH, involving ArPd(OH)L(2) in the transmetalation with Ar'B(OH)(2). Due to the low concentration of OH(-) generated from CO(3)(2-) in water, both transmetalation and reductive elimination result slower than those performed from nBu(4)NOH at equal concentrations as Cs(2)CO(3). Therefore, the overall reactivity is finely tuned by the concentration of the common base OH(-) and the ratio [OH(-)]/[Ar'B(OH)(2)]. Hence, the anionic base (pure OH(-) or OH(-) generated from CO(3)(2-)) associated with its countercation (Na(+), Cs(+), K(+)) plays four antagonist kinetic roles: acceleration of the transmetalation by formation of the reactive ArPd(OH)L(2), acceleration of the reductive elimination, deceleration of the transmetalation by formation of unreactive Ar'B(OH)(3)(-) and by complexation of ArPd(OH)L(2) by M(+).     

用于流化床燃烧脱硫的石灰石的反应活性评价和测试研究

对用于燃煤流化床燃烧脱硫的脱硫剂石灰石的反应活性进行了研究，提出了易于进行数学处理的石灰石硫盐化模型，得出了评价石灰石反应活性的两个指标－最大转化率和反应速率常数。研究方法除采用了传统的热天平法和鼓泡流化床外，还根据循环流化床燃烧技术的特点，发展了提出了湍流床法和石英棉法，并进行了不同试验条件下的实验研究，对不同反应活性温度技术进行了试验比较。     

Room temperature fabrication of hollow ZnS and ZnO architectures by a sacrificial template route

Hollow ZnS and ZnO architectures are fabricated by employing Zn(5)(CO(3))(2)(OH)(6) microspheres as the sacrificial template. Zn(5)(CO(3))(2)(OH)(6) microspheres can be effectively converted into the core/shell structured ZnO/ZnS composites (in the Na(2)S solution) and hollow ZnO architectures (in the KOH solution), by a spontaneous ion replacement reaction at room temperature. Removing the core by the KOH treatment of core/shell structured ZnO/ZnS, hollow ZnS spheres with different shell thicknesses can be effectively achieved. The obtained hollow ZnO architectures exhibit unique geometrical shapes, and their walls are composed of nanocrystals, which are connected to each other to form their hemispherical or circular shape. A possible formation process from Zn(5)(CO(3))(2)(OH)(6) microspheres to core/shell structured ZnO/ZnS composites is proposed by arresting a series of intermediate morphologies.     

Controlled synthesis of hydroxyapatite-supported palladium complexes as highly efficient heterogeneous catalysts

Achieving precise control of active species on solid surfaces is one of the most important goals in the development of highly functionalized heterogeneous catalysts. The treatment of hydroxyapatites with PdCl(2)(PhCN)(2) gives two new types of hydroxyapatite-bound Pd complexes. Using the stoichiometric hydroxyapatite, Ca(10)(PO(4))(6)(OH)(2), we found that monomeric PdCl(2) species can be grafted on its surface, which are easily transformed into Pd(0) particles with narrow size distribution in the presence of alcohols. Such metallic Pd species can effectively promote alcohol oxidation using molecular oxygen and are shown to give a remarkably high TON of up to 236 000. Another monomeric Pd(II) phosphate complex can be generated at a Ca-deficient site of the nonstoichiometric hydroxyapatite, Ca(9)(HPO(4))(PO(4))(5)(OH), affording a catalyst with Pd(II) structure and high activity for the Heck and Suzuki reactions. To the best of our knowledge, the PdHAP are one of the most active heterogeneous catalysts for both alcohol oxidation under an atmospheric O(2)() pressure and the Heck reaction reported to date. These Pd catalysts are recyclable in the above organic reactions. Our approach to catalyst preparation based on the control of Ca/P ratios of hydroxyapatites represents a particularly attractive method for the nanoscale design of catalysts.     

The calcite/water interface II. Effect of added lattice ions on the charge properties and adsorption of sodium polyacrylate

The origin of the surface potential of calcium carbonate in aqueous dispersions and the dissolution of calcite in systems containing excess Ca(2+) and CO(3)(2-) have been the subjects of this study. In addition, stabilization of calcite particles with an anionic polyelectrolyte (sodium polyacrylate (NaPA)) and the effect on surface potential and dissolution of calcite have been studied. Preferential dissolution of either Ca(2+) or CO(3)(2-) from the surface, which is governed by the partial pressure of CO(2) in solution and the pH of the solution, mainly determines the surface potential. Both lattice ions (Ca(2+) and CO(3)(2-)) adsorb onto the surface and thus alter the surface potential. NaPA adsorbs strongly onto the calcite surface regardless of background electrolyte concentration, and reverses the surface potential to negative values. Chelation of the surface due to NaPA can be partly prevented by adding Ca(2+) to the dispersion.     

部分水解聚甲基丙烯酸甲酯/氢氧化钙复合物对硬质聚氯乙烯热稳定性与透明性及塑化行为的影响

采用溶液沉淀法制备了部分水解的聚甲基丙烯酸甲酯(h-PMMA)/氢氧化钙(Ca(OH)2)复合物.采用X-射线衍射(XRD)、红外光谱(FTIR)、等离子体发射光谱和差示扫描量热表征了h-PMMA/Ca(OH)2复合物的组成与结构;采用刚果红测试、动态热稳定测试和热失重分析(TGA)研究了复合物对聚氯乙烯(PVC)的热稳定效果;通过紫外-可见(UV-Vis)光谱、扫描电镜(SEM)照片和熔融塑化曲线研究了复合物对PVC透明性和塑化行为的影响.结果表明,在Ca(OH)2晶体生长过程中,h-PMMA通过—COO-/Ca2+离子配位作用吸附于Ca(OH)2表面,不仅限制了Ca(OH)2粒子尺寸,且有助于Ca(OH)2在PVC中均匀分散.所得h-PMMA/Ca(OH)2复合物在显著提高PVC热稳定性和塑化能力的同时,还使PVC保持透明性.     

Two-phase synthesis of colloidal annular-shaped Ce(x)La(1-x)CO3OH nanoarchitectures assembled from small particles and their thermal conversion to derived mixed oxides

Undoped and cerium doped LaCO(3)OH annular-shaped nanoarchitectures with high specific surface area have been fabricated via the thermolysis of Ce(x)La(1-x)(oleate)(3) (x = 0-20 mol %) complexes in a toluene-water system containing tert-butylamine/oleylamine. The products exhibit 400 nm-sized monodisperse annular-shaped nanoarchitectures, which are constituted of 3-5 nm-sized primary particles. A possible mechanism of the reaction of Ce(x)La(1-x)(oleate)(3) and tert-butylamine for the formation of annular-shaped Ce(x)La(1-x)CO(3)OH nanoarchitectures is proposed. The thermal conversion of Ce(x)La(1-x)CO(3)OH to Ce(x)La(1-x)(CO(3))O(2) at 600 °C, to Ce(x)La(1-x)(OH)(3) at 800 °C, final to (Ce(x)La(1-x))(2)O(3-δ) at 900 °C were employed, while the original morphology was essentially unchanged. The dopant concentration was varied from 5 to 20 of cerium ions per LaCO(3)OH nanoparticle. The X-ray diffraction (XRD) results reveal that the cerium dopant could enter easily into the LaCO(3)OH structural lattice, whereas copper could unlikely enter into their lattice because of their large ionic radius difference. The cerium oxidation state was controlled by changing doping concentration. The X-ray photoelectron spectroscopy (XPS) results reveal that only one Ce(3+) oxidation state is in the as-synthesized Ce(x)La(1-x)CO(3)OH samples with cerium concentration ranging from 5 to 20 mol %, whereas both 3+ and 4+ ones coexisted in 20 mol % Ce:LaCO(3)OH structure. Remarkable luminescence emission intensity enhancement of 1.5-9.0 times were observed for Ce(x)La(1-x)CO(3)OH samples with cerium concentration ranging from 5 to 20 mol %, after doping with an undoped LaCO(3)OH.     

Low temperature reactivity in agglomerates containing iron oxide

In this study, we have attempted to explain the complex reactions that occur during the dehydration of Ca(OH)₂, in the presence of solid carbon and Fe₂O₃, in order to clarify their role as eventual precursors to the reduction and high temperature strength characteristics in feedstock agglomerates of iron and steelmaking by-products. A series of simultaneous thermo-gravimetric (TG), differential thermal analytic (DTA), and mass spectrometric (MS) tests were performed on agglomerated sample mixes of Ca(OH)₂, C, and Fe₂O₃ to test the influence of heating rate and particle size on the transformations occurring below 1,073 K in inert atmosphere. The overall transformation begins with calcium hydroxide dehydration. Nucleation and growth of CaO grains during dehydration, as well as subsequent gasification of solid carbon, are highly dependent on the governing interstitial particle porosity and mildly dependent on the heating rate in and around agglomerates. The reduction of hematite in current agglomerates is, by association to preceding reactions, partly dependent on porosity and heating rate, but the mechanism of reduction was also found to be highly dependent on the particle size of iron oxides. Furthermore, in areas of intimate contact between CaO and iron oxide, a calcium ferrite phase appears in the form of angular and calcium-rich particles.     

流化床煤气化炉内脱硫的研究Ⅰ．台式流化床煤气化的炉内脱硫试验

采用台式流化床煤气化装置，研究了影响炉内脱硫效率的因素。炉内脱硫对高硫煤特别有效，脱硫效率可达９０％以上。所采用的二种石灰石和一种白云石脱硫效率相近，按Ｃａ／Ｓ比比较则白云石稍好些。虽然脱硫效率随Ｃａ／Ｓ比增加而增加，但当Ｃａ／Ｓ比达到３后几乎不再增加。存在一个最佳脱硫操作温度。在非焙烧区，脱硫率随压力增加而下降，而在焙烧区脱硫率和压力几乎无关。测定了脱硫剂脱硫前后的孔容积分布，发现脱硫之后１～３０ｎｍ的孔容显著减少。     

Electrophoretic Deposition: A Quantitative Model for Particle Deposition and Binder Formation from Alcohol-Based Suspensions

We investigated electrophoretic deposition from a suspension containing positively charged particles, isopropanol, water, and Mg(NO(3))(2), with the aim of describing the deposition rates of the particles and Mg(OH)(2), which is formed due to chemical reactions at the electrode, in terms of quantitative models. LaB(6) particles were used as a model system. The particle layer is consolidated by simultaneous precipitation of Mg(OH)(2) which acts as a binder to hold the particles together. The Mg(OH)(2) content was determined solely by the amount of charge passed through the cell. Quantitative precipitation of all OH(-) formed at the electrode was observed, except at very low current. The occurrence of a minimum current was ascribed to a threshold for Mg(OH)(2) deposition. The same minimum current was observed for particle deposition. In combination with results using NaNO(3), where no adherent layer was formed, this illustrates that Mg(OH)(2) binder is necessary for consolidation. Once the minimum current was exceeded, it was found that all particles that migrate to the electrode under the influence of the electric field contribute to the formation of the layer, i.e., the "sticking coefficient" for the particles equals 1.0. The applicability of the particle and Mg(OH)(2) deposition models was tested by variation of the Mg(NO(3))(2) concentration, pH, and water content. Copyright 2000 Academic Press.     

Homogeneous nucleation of calcium hydroxide

The rate of nucleation of calcium hydroxide in carefully purified supersaturated solution was observed to be about 10(3) particles, cm(-3). sec(-1), in solutions with activity products a(ca)a(OH)(2) around 4 x 10(-5). These data correspond to a homogeneous nucleus containing about 55Ca(OH)(2) units, and a nucleus-solution interfacial tension of 65 erg cm (2).     

团聚铂纳米粒子电极在甲醇氧化中的电催化特性

用H2还原法并以Nafion作为稳定剂合成团聚的Pt纳米粒子，附载于玻碳表面制备电催化剂.透射电子显微镜（TEM）和扫描电子显微镜（SEM）表征结果指出,团聚Pt纳米粒子的平均尺寸约为400 nm.运用电化学循环伏安法(CV)和原位傅立叶变换红外反射光谱（in situ FTIRS）研究甲醇的氧化过程，发现团聚Pt纳米粒子电极具有较高的电催化活性.原位FTIRS研究结果检测到甲醇在所制备的电催化剂上氧化的中间体为线型吸附态CO物种，其红外吸收给出异常红外效应的光谱特征.     

Tetradecanuclear polycarbonatolanthanoid clusters: Diverse coordination modes of carbonate providing access to novel core geometries

The synthesis of two high nuclearity lanthanoid clusters demonstrates the versatility of the carbonate anion as a robust cluster forming agent, potentially allowing for the formation of otherwise inaccessible core topologies. The complexes, [Gd(14)(CO(3))(13)(ccnm)(9)(OH)(H(2)O)(6)(phen)(13)(NO(3))](CO(3))(2.5)·(phen)(0.5) () and [Dy(14)(CO(3))(13)(ccnm)(10)(OH)(H(2)O)(6)(phen)(13)](CO(3))(2.5)·(phen)(0.5) () (ccnm = carbamoylcyanonitrosomethanide, phen = 1,10-phenanthroline), contain a [Ln(14)(CO(3))(13)(OH)] core in which the carbonate anions display four unique coordination modes. The complexes are chiral, and the ccnm ligands also display four unique coordination modes. Extensive intra- and intermolecular π-π stacking between phen ligands leads to the formation of 1D chains in the crystal structure. Both complexes display magnetic properties that are indicative of antiferromagnetic coupling, with complex displaying behaviour consistent with possible single molecule magnet properties.