Extraction of rare earth elements from their oxides using organophosphorus reagent complexes with HNO3 and H2O in supercritical CO2

Direct extraction of metals from solids with complexing agents in supercritical CO2(SC-CO2) has recently attracted interests in separation,purification,recovery,and analysis of metals.In the present study,the static/dynamic extraction of rare earth elements(Nd,Ce) from their oxides(Nd2O3,CeO2) with organophosphorus complexes with HNO3 and H2O in SC-CO2 was investigated.The static extraction efficiency of Nd from Nd2O3 with the tri-n-butylphosphate(TBP)-HNO3 complex could reach 95% under optimized experiment...     

Comparison of supercritical fluid extraction and conventional liquid-solid extraction for the determination of benzo[a]pyrene in water-soluble smoke

In patients undergoing bone marrow transplantation cryptococcosis is rarely encountered. We report a fatal case of Cryptococcus meningitis in a 12-year-old girl with acute lymphoblastic leukemia (ALL) in second remission who had a transplant from a human leukocyte antigen (HLA)-identical unrelated bone marrow donor. The conditioning regimen was thiotepa, cyclophosphamide, and total body irradiation (TBI); graft-versus-host disease (GVHD) prophylaxis consisted of cyclosporin A, methotrexate, and antilymphocyte globulin (ALG). The patient experienced stage III GVHD responsive to high-dose corticosteroids. On day +54 a thrombotic microangiopathy occurred. On day +64 neurological status worsened; a brain computed tomographic (CT) scan showed hyperdense lesions suggesting fungal infection. Detection of cryptococcal antigen by latex agglutination was positive but India ink stain and culture were negative. Despite treatment with amphotericin B, 5-flucytosine, and granulocyte-macrophage colony-stimulating factor, the patient died 13 days after the diagnosis.     

A comparison between solid phase extraction and supercritical fluid extraction for the determination of fluconazole from animal feed

The application of supercritical fluid extraction with carbon dioxide and modified carbon dioxide for the determination of fluconazole from an animal feed was studied. A fractional factorial design approach was used to examine the significant experimental variables for quantitative extraction of fluconazole. Gas chromatography with either flame ionisation or mass selective detection was used for quantitation of the extracts. The results indicated that modifier (methanol) had the greatest effect on the recovery of fluconazole from the animal feed.     

Thermal and carbothermic decomposition of Na2CO3 and Li2CO3

In order to elucidate the decomposition mechanism of Na₂CO₃ and Li₂CO₃ in mold-powder systems employed in the continuous casting of steel, decompositions of Na₂CO₃ and Li₂CO₃ were investigated using thermogravimetric (TG) and differential scanning calorimetric (DSC) methods at temperatures up to 1200 °C, under a flow of argon gas. For the case of pure Na₂CO₃, the thermal decomposition started from its melting point and continued as the temperature was increased, but at a very slow rate. For Li₂CO₃, however, the decomposition occurred at much faster rates than that for Na₂CO₃. When carbon black was added to the carbonate particles, the decomposition rates of both Na₂CO₃ and Li₂CO₃ were significantly enhanced. From mass-balanced calulations and X-ray diffraction (XRD) analyses of the reaction products, it is concluded that decompositions of Na₂CO₃ and Li₂CO₃ with carbon black take place according to the respective reactions of Na₂CO₃ (1) + 2C (s) = 2Na (g) + 3CO (g) and Li₂CO₃ (l) + C (s) = Li₂O (s) + 2CO (g). It was found that liquid droplets of Na₂CO₃ were initially isolated due to carbon particles surrounding them, but, as the carbon particles were consumed, the liquid droplets were gradually agglomerated. This effected a reduction of the total surface area of the carbonate, resulting in a dependence of the decomposition rate on the amount of carbon black. For the case of Li₂CO₃, on the other hand, hardly any agglomeration occurred up to the completion of decomposition, and, hence, the rate was almost independent of the amount of carbon black mixed. The apparent activation energies for the decomposition of Na₂CO₃ and Li₂CO₃ with carbon black were found to be similar and were estimated to be 180 to 223 kJ mole⁻¹.     

Sub- and supercritical fluid extraction of trichloropyridinol from soil prior to immunoassay

A comparative study on the extraction of TCP (3,5,6-trichloro-2-pyridinol, a metabolite of chlorpyrifos) from soil with CO2 and H2O is reported. The polarity of the analyte requires the presence of both a cosolvent (methanol) and an ion-pair reagent [(1R)-(-)-10-camphorsulfonic acid ammonium salt] for 95% extraction in 30 min when supercritical CO2 at 40 degrees C and 383 bar is used as extractant. Subcritical water (250 degrees C and 200 bar) enables complete extraction within 15 min without additives. Quantitation of the target analyte is performed by specific immunoassay using a non-commercial monoclonal antibody which provides a linear determination range between 0.005 and 5 micrograms/g, with coefficients of variation of 5.3 and 4.9% for the SC-CO2 and sub-H2O extractions, respectively.     

Effect of La_2O_3on Methanation of CO and CO_2over Ni-Mo/γ-Al_2O_3Catalyst

In the early 1980s, it was reported thatrare earth oxide can improve the properties ofnickel catalysts['J. In this paper, the effect ofLaZO3 on activity of methanation of CO andCOb over Ni-Mo/Y-A12O3 was studied. The relationship between catalytic activity, surfacebehaviour and the role of LaZO3 in Mi-Mo-La/Y-Allot catalyst were investigated by means oftransmission electron microscope (TEM ), Xray photoelectron spectroscopy (XPS ), andchemisorption of CO.1 Experimental1. I Prepara…     

The nu1 + 5nu3 Dyad of 12CO2 and 13CO2

It has been recently shown that intraventricular injections of nerve growth factor (NGF) prevent the effects of monocular deprivation in the rat. We have tested the localization and the molecular nature of the NGF receptor(s) responsible for this effect by activating cortical trkA receptors in monocularly deprived rats by cortical infusion of a specific agonist of NGF on trkA, the bivalent antirat trkA IgG (RTA-IgG). TrkA protein was detected by immunoblot in the rat visual cortex during the critical period. Rats were monocularly deprived for 1 week (P21-28) and RTA-IgG or control rabbit IgG were delivered by osmotic minipumps. The effects of monocular deprivation on the ocular dominance of visual cortical neurons were assessed by extracellular single cell recordings. We found that the shift towards the ipsilateral, non-deprived eye was largely prevented by RTA-IgG. Infusion of RTA-IgG combined with antibody that blocks p75NTR (REX), slightly reduced RTA-IgG effectiveness in preventing monocular deprivation effects. These results suggest that NGF action in visual cortical plasticity is mediated by cortical TrkA receptors with p75NTR exerting a facilitatory role.     

CO/CO2 potentiometric titrations of carbon monoxide dehydrogenase from Clostridium thermoaceticum and the effect of CO2

Acetogenic carbon monoxide dehydrogenases catalyze the reversible oxidation of CO to CO2 and the synthesis of acetyl-coenzyme A, utilizing two novel Ni-Fe-S active sites (the C- and A-clusters, respectively) and an [Fe4S4]2+/1+ cluster (the B-cluster) that serves to transfer electrons. Enzyme samples were titrated under equilibrium conditions using various partial pressures of CO in Ar and CO2 atmospheres. EPR signal intensities from each cluster were analyzed as a function of potential using the Nernst equation. The presence of CO2 raised the reduction potentials of the A-, B-, and C-clusters, and it appeared to increase the strength of CO (substrate for acetyl-CoA synthesis) binding to the reduced A-cluster. Carbon dioxide also appeared to stabilize an intermediate EPR-silent state of the C-cluster and alter the saturation/relaxation properties of the reduced B-cluster. Simulations assuming n values (number of e- involved in reduction) larger than appropriate for the individual reactions generally fit better to the titration data than those which assumed the appropriate n, indicating positive redox cooperativity. Carbon dioxide did not inhibit 1,10-phenanthroline from removing the labile Ni from the A-cluster, but it did inhibit the CO/acetyl-coenzyme A exchange activity, probably by causing CO to bind more tightly to the A-cluster. Taken together, these results indicate a significant CO2-dependent conformational change affecting the properties of all three clusters and both subunits. Since the enzyme operates in vivo in a CO2 environment, the CO2-induced conformation may be mechanistically important.     

CeO2-Co3O4 Catalysts for CO Oxidation

CeO2-Co3O4 catalysts for low-temperature CO oxidation were prepared by a co-precipitation method. In combination with the characterization methods of N2 adsorption/desorption, XRD, temperature-programmed reduction （TPR）, and FT-IR, the influence of the cerium content on the catalytic performance of CeO2-Co3O4 was investigated. The results indicate that the prepared CeO2-Co3O4 catalysts exhibit a better activity than that of pure CeO2 or pure Co3O4. The catalyst with the Ce/Co atomic ratio 1 ： 16 exhibits the best activity, which converts 77% of CO at room temperature and completely oxidizes CO at 45 ℃.     

Comparison of different purification procedure for extraction of staphylococcal enterotoxin A from foods

Different procedures commonly used for extraction, purification, and concentration of staphylococcal enterotoxins from foods were investigated with 131I- and 125I-labeled staphylococcal enterotoxin A. Loss of labeled enterotoxin A was compared with loss of total nitrogen. The results showed that in most of the common procedures, such as gel filtration, ion exchange, and heat treatment, the percentage of loss of labeled enterotoxin A was greater than the loss of total nitrogen. Chloroform extraction and acid precipitation with hydrochloric acid had nearly the same effect on the purification of both labeled enterotoxin A and total nitrogen. Ammonium sulfate precipitation proved to be practical and was successfully used for purification of enterotoxin A from sausage extract. Simultaneous use of trypsin and Pseudomonas peptidase for treatment of food extracts considerably reduced food proteins capable of interfering with serological detection of enterotoxins but did not essentailly influence the loss of enterotoxin A.     

利用Na2CO3处理铝电解槽炭渣的研究

铝电解槽炭渣是铝工业冶炼生产过程中产生的一种危险废物。炭渣的大量堆存,在浪费电解质资源的同时,也会造成大气、土壤以及水体的污染。本试验以炭渣为原料,Na₂CO₃为添加料,对炭渣的焙烧?水浸工艺回收炭粉和冰晶石的可行性与过程进行了研究。试验结果表明,将质量比为2.5∶1的Na₂CO₃与炭渣混合后置于坩埚电阻炉中,在950 ℃下焙烧2 h,炭渣中氧化铝、冰晶石和亚冰晶石被Na₂CO₃消耗,焙烧后混合料由C、Na₂CO₃、NaF、NaAlO₂组成。焙烧后混合料在pH为13、浸出温度为25 ℃的条件下浸出1 h,固液分离后的浸出渣经过水洗、烘干后得到炭粉,其纯度可达89%。利用碳酸化法回收浸出液中F?,可获得主成分合格的粉状冰晶石。适当地提高焙烧温度和延长保温时间可提高炭和电解质的分离效率。研究经济而有效的炭渣处理方法,不仅可以解决炭渣带来的环境污染问题,还对社会的可持续发展产生深远影响。      

Coupled process of reaction and solvent extraction: I. The reaction between CO2 and SrCl2 coupled with solvent extraction of HCl

In order to ensure the continual reaction between CO₂ and SrCl₂ to produce SrCO₃, it is necessary to neutralize produced HCl or to remove it to another phase. Coupling the reaction with solvent extraction is a way to lower the acidity of the aqueous solution and to allow the reaction to proceed continually. Based on this coupled process, a new flow sheet for producing strontium carbonate from celestite is proposed. The factors influencing equilibrium of the coupled process of strontium carbonate production with solvent extraction have been studied.     

Histological integration of allogeneic cancellous bone tissue treated by supercritical CO2 implanted in sheep bones

Different chemical or physical methods of bone processing have been developed to decrease the antigenicity of allogeneic bone which may delay or prevent graft integration. We have developed a method based on delipidation and deproteination of the bone with a supercritical fluid and hydrogen peroxide. Cylinders of cancellous allogeneic bone treated in this way were implanted for four weeks, four months or eight months in holes drilled in sheep condyles or tibial plateau. Histological sections were then processed and analysed qualitatively and quantitatively using an image analysis software coupled to a light microscope. Measurements were made of the trabecular bone surface (BS/TS), the relative osteoid surface (OS/BS), the active osteoid surface (OS/BS), active resorption surface (Oc.S/BS) and the relative surface of newly formed bone. After four weeks, the control cylinders (non-treated allogeneic bone) had been invaded by cellular tissue composed of lymphocytes and plasmocytes surrounding remnants of the donor bone marrow tissue. The processed cylinders showed osteoid apposition at the surface of their external trabeculae. The trabecular bone and osteoid surfaces were significantly higher in the processed bone sections than in the control bone sections. After four months, most of the control material had been osteolysed and replaced by connective tissue containing lymphocyte islets, while the processed materials showed a large amount of bone synthesized at the surface of implant trabeculae which appeared fragmented and disseminated within the newly formed bone. All the histomorphometric parameters measured were significantly different from those of the control. By eight months, most of the control material had been totally osteolysed with very little bone ingrown in the implantation site. Only one control implant had been integrated. The processed cylinders were difficult to discern from the bone in which they were implanted. The parameters measured on the processed cylinders were significantly higher than those measured on the control sections. IN CONCLUSION: the treatment applied to the bone enhanced allogeneic bone integration and could provide a new kind of tissue treatment for bone banking.     

Comparison and significance of respiration and glycolysis of prostatic tissue from various species

The respiration and glycolysis of prostatic tissue from baboons, rhesus monkeys, dogs and rats were compared to the respiration and glycolysis in human prostatic tissue. All the primate prostates had a high glycolytic ability and a low respiration in contrast to the rat and dog prostate. Treatment of baboons with drugs clinically effective against prostatic cancer did not change the prostatic metabolism despite a marked prostatic atrophy. In vitro the drugs reduced respiration markedly. The metabolic similarity between the human and the baboon and rhesus monkey prostate indicates that nonhuman primates should be investigated in the evaluation of chemotherapeutic agents for treatment of prostatic cancer.     

Fat content for nutritional labeling by supercritical fluid extraction and an on-line lipase catalyzed reaction

A method using sequential supercritical fluid extraction (SFE) and enzymatic transesterification has been developed for the rapid determination of total nutritional fat content in meat samples. SFE conditions of 12.16 MPa and 50 degrees C were utilized to extract lipid species from the sample matrix. The enzymatic transesterification of the lipids by methanol was catalyzed by an immobilized lipase isolated from Candida antarctica. Conversion of the triglycerides to fatty acid methyl esters was monitored by supercritical fluid chromatography, while the fatty acid content of the extract was determined by capillary gas chromatography (GC). Total fat, saturated fat and monounsaturated fat contents were calculated from the GC data and compared to values from traditional extraction and lipid determination methods. Both off-line SFE and automated SFE followed by on-line GC analysis using two different instruments were utilized in this study. The enzymatic-based SFE method gave comparable results to the organic solvent extraction-based method followed by conventional BF3-catalyzed esterification.     

废SCR催化剂碳酸钠焙烧浸出回收二氧化钛

以火力发电厂SCR废催化剂为研究对象,分析焙烧过程物相变化,探究钠化焙烧工艺对二氧化钛回收率的影响。采用正交试验得出各因素对二氧化钛焙烧浸出率影响的主次关系依次为:焙烧温度碳酸钠添加量焙烧时间物料粒度。钠化焙烧工艺参数为:焙烧温度700℃、焙烧时间3.0h、物料粒度-106μm、Na_2CO_3与原料质量比3.0,钛的浸出率可以达到94%。     

Comparison of orthorhombic and alpha-two titanium aluminides as matrices for continuous SiC-reinforced composites

The attributes of an orthorhombic Ti aluminide alloy, Ti-21Al-22Nb (at. pct), and an alpha-two Ti aluminide alloy, Ti-24Al-11Nb (at. pct), for use as a matrix with continuous SiC (SCS-6) fiber reinforcement have been compared. Foil-fiber-foil processing was used to produce both unreinforced (“neat”) and unidirectional “SCS-6” reinforced panels. Microstructure of the Ti-24A1-11Nb matrix consisted of ordered Ti₃Al (α ₂) + disordered beta(β), while the Ti-21 Al-22Nb matrix contained three phases: α₂, ordered beta (β ₀), and ordered orthorhombic(O). Fiber/ matrix interface reaction zone growth kinetics at 982 °C were examined for each composite system. Although both systems exhibited similar interface reaction products(i.e., mixed Ti carbides, silicides, and Ti-Al carbides), growth kinetics in theα ₂ +β matrix composite were much more rapid than in theO +β ₀ +α ₂ matrix composite. Additionally, interfacial reaction in theα ₂ +β} composite resulted in a relatively large brittle matrix zone, depleted of beta phase, which was not present in theO +β ₀+α ₂ matrix composite. Mechanical property measurements included room and elevated temperature tensile, thermal stability, thermal fatigue, thermo-mechanical fatigue (TMF), and creep. The three-phase orthorhombic-based alloy outperformed the α₂+β alloy in all of these mechanical behavioral areas, on both an absolute and a specific(i.e., density corrected) basis.     

Effect of Na2O on the Reduction of Fe2O3 Compacts with CO/CO2

Compacts of Fe₂O₃ and Fe₂O₃ doped with varying amounts of Na₂O were isothermally reduced at several temperatures, using CO/CO₂ mixed gas in a vertical resistance furnace. To determine the effect of Na₂O on the reduction of Fe₂O₃ compacts, the mass loss due to oxygen removal was continuously recorded, from which the reduction rate and rate constant were obtained. Na₂O was found to retard the reduction of Fe₂O₃ compacts. The apparent activation energy (E _a) of reaction and the mathematical relationship for pore gas diffusion suggested that the reduction behavior at the initial stages was controlled by a combination of pore gas diffusion and interfacial chemical reaction. At the intermediate and late stages of reduction, pore gas diffusion was the sole contributing factor. Morphological examination of the reduced compacts showed the formation of a liquid phase during the reduction process, which appeared to lower the rate of reaction.