Phase Transformation and Thermal Decomposition Kinetics of a Mixed Rare Earth Concentrate.

The Bayan Obo rare earth (BORE) concentrate is the largest light rare earth mineral resource in the world. The decomposition of the BORE concentrate is a principal step to develop new technologies to recover useful elements and is therefore of much importance. In this paper, the phase transformation and thermal decomposition kinetics of the BORE concentrate in air were investigated. The results showed that bastnaesite decomposed upon air roasting. The roasted solid was recovered by sulfuric acid leaching. The activation energy and pre-exponential factor of the roasting reaction of the BORE concentrate were calculated through the isoconversional methods of Flynn-Wall-Ozawa and Kissinger, and the probable mechanism function was estimated through the Coats-Redfern method. The kinetic model that best describes the thermal decomposition reaction for the BORE concentrate is the A2 (Avrami-Erofeev 2) model, and the corresponding probable mechanism function is f(α) = 2(1 - α)[-ln(1 - α)]1/2 and G(α) = [-ln(1 - α)]1/2.

The quality of life and associated factors in patients on maintenance hemodialysis - a multicenter study in Shanxi province.

OBJECTIVES: To assess the quality of life (QOL) and factors affecting QOL in hemodialysis patients so as to improve QOL of dialysis patients and provide the basis for better clinical care. METHODS: A retrospective study was performed to assess the QOL and factors affecting QOL in hemodialysis patients. We recruited 125 patients who had been receiving hemodialysis for at least 2 years in the dialysis units of nine hospitals in Shanxi Province, China, and conducted a multi-center questionnaire survey between 1 May 2015 and 1 July 2016. We investigated the patients' general condition and clinical data and used the Short Form-36 (SF-36) scale to measure QOL in these patients. RESULTS: The overall SF-36 score was 107.55 ± 14.50 in patients who had received hemodialysis for more than 2 years. Age (p < .05, F = 4.972) and gender (p < .01, t = 3.993) significantly affected the overall QOL score in these patients. Education level was also an influencing factor (p < .05, Z= -0.838), especially on the mental health of these patients. In addition, residual urine volume (p < .05, Z= -2.465) and diabetic nephropathy (p < .05, Z= -2.062) were important factors that affected the physical strength and QOL score in these patients. However, sources of medical expenses, marital status and different methods of dialysis, had no effect on the QOL score. CONCLUSION: The overall score of QOL in patients who have received maintenance hemodialysis for more than 2 years is higher in Shanxi Province than that in other provinces of China. Only a few factors influenced the QOL of these patients.

Extraction Behaviors of Heavy Rare Earths with Organophosphoric Extractants: The Contribution of Extractant Dimer Dissociation, Acid Ionization, and Complexation. A Quantum Chemistry Study.

Heavy rare earths (HREs), namely Ho3+, Er3+, Tm3+, Yb3+ and Lu3+, are rarer and more exceptional than light rare earths, due to the stronger extraction capacity for 100 000 extractions. Therefore, their incomplete stripping and high acidity of stripping become problems for HRE separation by organophosphoric extractants. However, the theories of extractant structure-performance relationship and molecular design method of novel HRE extractants are still not perfect. Beyond the coordination chemistry of the HRE-extracted complex, the extractant dimer dissociation, acid ionization, and complexation behaviors can be crucial to HRE extraction and reactivity of ionic species for understanding and further improving the extraction performance. To address the above issues, three primary fundamental processes, including extractant dimer dissociation, acid ionization, and HRE complexation, were identified and investigated systematically. The intrinsic extraction performances of HRE cations with four acidic organophosphoric extractants (P507, P204, P227 and Cyanex 272) were studied by using relativistic energy-consistent 4f core pseudopotentials, combined with density functional theory and a solvation model. Four acidic organophosphoric extractants have been qualified quantitatively from microscopic structures to chemical properties. It has been found that the Gibbs free energy changes of the overall extraction process (sequence: P204 > P227 > P507 > Cyanex 272) and their differences as a function of HREs (sequence: Ho/Er > Er/Tm > Tm/Yb > Yb/Lu) are in good agreement with the experimental maximum extraction capacities and separation factors. These results could provide an important approach to evaluate HRE extractants by the comprehensive consideration of dimer dissociation, acid ionization, and complexation processes. This paper also demonstrates the importance of the P-O bond, the P-C bond, isomer substituent, and solvation effects on the structure-performance relationship that can be used to guide molecular designs of HRE extraction in future.

A solvent extraction route for CaF2 hollow spheres.

A solvent extraction route is proposed to synthesize CaF(2) hollow spheres, which are formed by reversed micelles in a solvent extraction system templating the self-assembly of CaF(2) nanoparticles.

Separation of cobalt and nickel using inner synergistic extraction from bifunctional ionic liquid extractant (Bif-ILE).

The inner synergistic extraction of [tricaprylmethylammonium][sec-octylphenoxy acetate] ([A336][CA-12]) is studied for cobalt and nickel separation. Distribution ratios of [A336][CA-12] for Co(2+) or Ni(2+) are by far higher than those of tricaprylmethylammonium sulfate ([A336](2)SO(4)), sec-octylphenoxy acetic acid (CA-12), mixture of [A336](2)SO(4) and CA-12 at the acidities from 1x10(-5) mol L(-1) to 1x10(-3) mol L(-1). The synergy coefficients of [A336][CA-12] for Co(2+) are higher than the synergy coefficients of [A336][CA-12] for Ni(2+), which can be used for the Co(2+) and Ni(2+) separation. Some thermodynamic properties of the inner synergistic extraction using [A336][CA-12] for Co(2+) and Ni(2+) are also studied, such as influence of temperature, thermodynamic functions, extraction mechanism, separation factors and stripping properties.

The inner synergistic effect of bifunctional ionic liquid extractant for solvent extraction.

The inner synergistic effect of bifunctional ionic liquid extractant (Bif-ILE) for solvent extraction is reported for the first time using [tricaprylmethylammonium][di-2-ethylhexylphosphinate] ([A336][P204]) as n extractant for Eu(III), which can be attributed to better stability and hydrophobicity of the complex formed by [A336][P204] with Eu(III). Some other Bif-ILEs are also found to have the similar inner synergistic effect. Distribution coefficient, stripping property and extraction mechanism of the novel extraction protocol are discussed in this report. The study contributes towards acquiring a new understanding of synergistic extraction and task specific ionic liquid (TSIL), furthermore, providing a positive influence on their potential application in analytical chemistry.

Two Mn(II)(2)Ln(III)(4) (Ln = Gd, Eu) hexanuclear compounds of p-tert-butylsulfinylcalix[4]arene.

Two 3d-4f heterometallic compounds of p-tert-butylsulfinylcalix[4]arene were synthesized by the solvothermal method and characterized by some hinged double-dumbbell-like subunits in which two perpendicular dumbbell entities were constructed by an in-between isosceles triangle Mn(II)Ln(III)(2), and two tail-to-tail calixarene molecules, and hinged by the lanthanide-sulfinyl group bonding. The magnetic properties of the title compounds were examined.

Preparation of TiO2, CeO2, and ZrO2 hierarchical structures in "one-pot" reactions.

In this paper, a novel template of carbon foam is used in building hierarchical structures of TiO(2), CeO(2), and ZrO(2). They had multiscale morphologies, from nanowalls, nanoparticles to layer nanostructures. On a hundred-micron scale, the product was a sponge-like material constructed by nanowalls. On a hundred-nanometer scale, the electron microscope images showed that the nanowalls were porous and assembled by polycrystalline nanoparticles. Meanwhile, on one nanometer scale, many nanoparticles exhibited layer nanostructures with about 1.1 nm of thickness and spacing. In mechanism section, the process analysis and characterizations suggested that the hierarchical structures were the combined result of two templates in a "one-pot" reaction. The mesoporous nanowalls were derived from carbon foams, while the layer nanostructures were the replicas of graphite sheets. The method has potential utilizations in preparation of various adsorbent and catalyst.

A unique Mn2Gd2 tetranuclear compound of p-tert-butylthiacalix[4]arene.

A calixarene complex with tetragonal Mn(II 2Gd(III)2 tetranuclear units was synthesized in solvothermal conditions, where the addition of a small amount of water was crucial for the formation of the target compound. In the structure, two tail-to-tail p-tert-butylthiacalixarenes are located in a C-shaped mode with a dihedral angle of 14.29 degrees but not in the conventional antiparallel arrangement and form a sandwich-like subunit with an in-between Mn2Gd2 unit. Both calixarenes assume similar cone shapes of C2v symmetry but are pinched to different extents. The extended structure is constructed by supramolecular stacking of the sandwich-like units with the interstices filled by the solvent. The magnetic property of the title compound has been examined.

Reversed micelle formation in a model liquid-liquid extraction system.

The formation of reversed micelles and the roles of extractant and extracted complexes were investigated in the Cyanex923/n-heptane/H(2)SO(4) system. Interfacial tension (gamma), electrical conductivity (kappa), and water content measurements showed that Cyanex923 had a tendency to self-assemble, forming reversed micelles. The changes in electrical conductivity with concentration of H(2)SO(4) in the organic phase (C(H2)SO(4), o) exhibited an S-type curve: a correlation was found between the change in electrical conductivity and the water content as a function of C(H2)SO(4), o. The changes of electrical conductivity were mainly induced by the components and microstructure in the organic phase, while the conversion of extracted complex also resulted in the changes of components and microstructure in the organic phase. Fourier transform infrared (FTIR) spectroscopy and dynamic light scattering (DLS) were used to characterize the organic phases and sizes of the reversed micelles, respectively. The extractant and extracted complexes, such as Cyanex923H(2)SO(4), were involved in the formation of reversed micelles.

Synthesis and characterization of ultrafine CeF3 nanoparticles modified by catanionic surfactant via a reverse micelles route.

In this article, we firstly reported on the synthesis and characterization of ultrafine CeF3 nanoparticles (NPs) modified by catanionic surfactant via a reverse micelles-based route. The catanionic surfactant PN was prepared by mixing the di(2-ethylhexyl) phosphoric acid (DEHPA) and primary amine (N1923) with 1:1 molar ratio. It exhibited a high surface activity and formed much small reverse micelles in comparison with its individual component (DEHPA or N1923). The PN reverse micelles were then used as templates to prepare ultrafine CeF3 NPs. The narrow distributed nanoparticles have an average diameter 1.8 nm. FTIR spectra indicated that there existed strong chemical interactions between nanoparticles and the adsorbed surfactants. The modification resulted in the FTIR peak position of PO shifting to lower energy. Due to the effect of modification and small size, the CeF3 NPs showed a remarkable red shift of 54 nm in the fluorescence emission in comparison with that of bulk material and a red shift of 18 nm in contrast with that of the normal CeF3 NPs with an average diameter of 16 nm.

Interfacial behavior of DEHEHP and the kinetics of cerium(IV) extraction in nitrate media.

The effects of diluents, temperature, acidity, and ionic strength of the aqueous phase on the interfacial properties of DEHEHP have been extensively investigated using the Du Nouy ring method. In addition, the effect of cerium(IV) concentration loaded in the organic phase on the interfacial tension has also been studied. With the increase of DEHEHP concentration, the value of interfacial tension (gamma) decreases in the studied system, which shows that DEHEHP has interfacial activity as a kind of surfactant. The surface excess at the saturated interface (Gamma(max)) and the minimum bulk concentration of the extractant necessary to saturate the interface (C(min)) under the different conditions are calculated according to two adsorption equations such as the Gibbs and Szyszkowski functions to be presented in comprehensive tables and figures. The relationship between the interfacial activity of DEHEHP and cerium(IV) extraction kinetics by DEHEHP has been discussed by considering different factors such as the effects of diluents and temperature. However, the interfacial activity parameter of extractant only is a qualitative parameter, but cannot provide strong enough evidence to quantitatively explain the relationship between extraction kinetics and interfacial properties of an extractant.

Interfacial behavior of Cyanex 302 and kinetics of lanthanum extraction.

In this paper, interfacial tension of Cyanex 302 is measured by a Sigma-701 tensiometer and the adsorption parameters are calculated according to the Gibbs and Szyszkowski adsorption isotherms. The interfacial adsorbed behavior of Cyanex 302 is investigated. The results demonstrate that the dimer is the predominant species in the bulk organic phase; however, the monomer is adsorbed at the interface and more interfacially active. The effects of aqueous pH, ion strength, and temperature on the interfacial activity of Cyanex 302 in heptane are discussed and explained in detail. The lower interfacial activity of Cyanex 302 in aromatic hydrocarbon than in aliphatic hydrocarbon has also been determined. The values of interfacial excess at the saturated interface increase in the order n-heptane>cyclohexane>toluene>benzene, which is consistent with the order of extractability of lanthanum by Cyanex 302 in these diluents. The interfacial activity data are used to discuss the kinetic mechanism of lanthanum(III) extraction. It is shown that an interfacial mechanism is very probable, and the extraction limiting step is the reaction between the Cyanex 302 molecules in the organic phase sublayer and the adsorbed intermediate complex.

[Over 55 years-old live-related donor kidney transplants: a report of 12 cases].

OBJECTIVE: To evaluate the risk factors of the over 55-year-old donor and the safety and efficacy of the donor, and the recipient with the immediate and long-term of the kidney. METHODS: The living-related donor kidney transplantation in 15 cases was performed in our unit from October 1999 to April 2002. Of these, 12 donors were over 55 with age ranging from 55 to 73 years-old and mean age of 62, 75 years. 5 donors were male and 7 were female. Father in 5 cases and 6 and 1 were mother and grandmother, respectively. The donors were evaluated depending on general state of health, hypertension, diabate and important organa in condition; and renal function by creatinine (Cre), creatinine clearance (Ccr), Glomerular filtration rate (GFR), B ultrasound and renal arteriograph prior to operation. The all receipients with ages ranging from 14 to 46 years with end-stage renal diseases (ESRD) from and their mean age was 32.9 years. The donor' left nephrectomy was performed in 10 cases and right nephrectomy in 2. Warm-ischemia time was from 70 s to 170 s (mean time, 92 s). Cold-ischemia time was from 60 minutes to 120 minutes and mean 84 minutes. The follow-up is from 12 to 42 months and mean 20, 84 months. RESULTS: All the 12 donors were perfectly recovered during operation and postoperation. During their 11-day stay in the hospital no complications was observed. The donor' creatinine was raised to about 12 to 34 micro mol/L (mean, 22 micro mol/L). One recipient died from lung infection at 28 days postoperative and 1 died due to liver failure with normal graft function after transplanted 6 months and yet one recipient with delayed graft function had recovered by 12 times dialysis. The remain recipient had a better recovered. CONCLUSION: Aged (>or= 55 years-old) donor renal transplantation can be carried out as the poor supply of can be used kidney but must to controled the indication and the prepare to be accomplished seriously.

Kinetics of Cerium(IV) Extraction from H(2)SO(4)-HF Medium with Cyanex 923.

Studies of the extraction kinetics of cerium(IV) from H(2)SO(4)-HF solutions with Cyanex 923 in n-heptane have been carried out using a constant interfacial area cell with laminar flow. The experimental hydrodynamic conditions were chosen so that the contribution of diffusion to the measured rate of reaction was minimized. The data were analyzed in terms of pseudo-first order constants. The results were compared with those of the system without HF. It was concluded that the addition of HF reduces the activation energy for the forward rate from 46.2 to 36.5 kJ mol(-1) while it has an opposite effect on the activation energy for the reverse process(the activation energy increased from 23.3 to 90.8 kJ mol(-1)). Thus, HF can accelerate the rate of cerium(IV) extraction. At the same time, the extraction rate is controlled by a mixed chemical reaction-diffusion rather than by a chemical reaction alone. A rate equation has also been obtained.

Three-phase extraction study of cyanex 923-n-heptane/H(2)SO(4) system.

Phase behavior of the extraction system, Cyanex 923-heptane/H(2)SO(4)-H(2)O has been studied. The third phase appeared at different aqueous H(2)SO(4) concentration with varying initial Cyanex 923 concentration and temperature affects its appearance. Almost all of H(2)SO(4) and H(2)O are extracted into the middle phase. The H(2)SO(4) concentration in the third phase increases with the increasing aqueous acid concentration (C(H(2)SO(4),b)) while the water content first increases and then reaches a constant value at C(H(2)SO(4),b)=11.3 mol l(-1). In the region of C(H(2)SO(4),b) higher than 5.2 mol l(-1), the composition of the middle phase is only related to the equilibrium concentration of H(2)SO(4) in the bottom phase. H(2)SO(4) and H(2)O are transferred into the middle phase mainly by their coordination with Cyanex 923 when C(H(2)SO(4),b) is less than 11.3 mol l(-1). When C(H(2)SO(4),b) is higher than 11.3 mol l(-1), excess H(2)SO(4) is solubilized into the polar layer of the aggregates. In the region considered, the extracted complex changes from C923 . H(2)SO(4) to C923 . H(2)SO(4) . H(2)O and then to C923 . (H(2)SO(4))(2) . H(2)O.