Recovery of rare earth metals through biosorption： An overview

Rare earth metals (REMs) are a series of 17 elements that have widespread and unique applications in high technology, power generation, communications, and defense industries. These resources are also ...     

Aerosol laser time-of-flight mass spectrometer for the on-line measurement of secondary organic aerosol in smog chamber

An aerosol laser time of flight mass spectrometer (ALTOFMS) that can be used for real-time measurement of the size and composition of individual aerosol particles has been designed and utilized to provide on-line measurement of secondary organic aerosol (SOA) particles resulted from Cl-initiated oxidation of toluene in smog chamber. Both the size and chemical compositions of individual aerosol particles were obtained in real-time. According to a large number of single aerosol diameters and mass spectra, the size distribution and chemical composition of aerosol were determined statistically. Experimental results indicate that aerosol particles produced from Cl-initiated oxidation of toluene were predominantly in the form of PM 2.5 particles, and nine positive laser desorption/ionization mass spectra peaks: m/z 18, 29, 30, 44, 46, 52, 65, 77, and 94 may come from the fragment ions of the products of the SOA: aromatic aldehydes, aromatic acids, phenolic compounds, and nitrogenated organic compounds. These results were in good agreement with those ones from previous Cl-initiated oxidation of toluene. These were demonstrated that ALTOFMS is a useful tool to reveal the formation and transformation processes of SOA particles in smog chamber.     

顺酐溶剂吸收装置的关键控制工艺分析

吐哈石化厂通过引进意大利CONSER公司的溶剂吸收工艺,对原有水吸收工艺进行改造。通过对CONSER溶剂吸收工艺的研究,分别对溶剂吸收装置中的溶剂吸收系统、溶剂解析系统和溶剂洗涤系统操作过程中的关键控制工艺进行分析,提出了可行的生产控制指导建议。     

稀盐酸储槽抽裂事故的分析

分析了盐酸脱吸工序中稀盐酸储槽抽裂事故产生的原因；通过稀盐酸储槽的压力式液位计DCS历史曲线记录来间接分析稀盐酸储槽内压力变化情况，剖析负压的形成过程。结果表明：脱吸塔产生较大的负压是因为系统急停、温度下降后在略低于盐酸溶液恒沸点时发生冷凝相变而引起的。     

Experimental and numerical study of the isotherms and determination of physicochemical parameters of the hydrogen absorption/desorption process by the metal hydrides

In this work, absorption/desorption isotherms of the LaNi_3·6Mn_0·3Al_0·4Co_0.7 alloy, have been determined from the experimental data at three temperatures (T_Fluid = 298 K, T_Fluid = 303 K, and T_Fluid = 313 K). However, the experimental isotherms are compared with a proposed theoretical model. The physicochemical parameters of the proposed model are determined from the experimental data. Using these parameters, the absorption and desorption processes of hydrogen by the LaNi_3·6Mn_0·3Al_0·4Co_0.7 alloy can be compared. During the absorption/desorption process, the behaviors of each parameter are studied under the effect of temperature and pressure. In addition, internal energy, entropy, and enthalpy are calculated by using the proposed model. On the other hand, the temperature and pressure effects on the variation of these functions have been studied. The calculated physicochemical parameters suggested that the hydrogen absorption/desorption process in the LaNi_3·6Mn_0·3Al_0·4Co_0.7 alloy was feasible, spontaneous and exothermic in nature.     

LiAlH4–ZrCl4 mixtures for hydrogen release at near room temperature

The dehydrogenation temperature of LiAlH₄ was significantly reduced by the production of mixtures with ZrCl₄. Stoichiometric 4:1, and 5 mol % mixtures of LiAlH₄ and ZrCl₄ were produced by ball milling at room temperature and ?196 °C, and tested for dehydrogenation at low temperature. Cryogenic ball-milling resulted in an effective way to produce reactive mixtures for hydrogen release; because of achieving small aggregates size (5–20 μm) in 10 min of cryomilling while preventing substantial decomposition during preparation. Dehydrogenation reaction in the mixtures LiAlH₄/ZrCl₄ started around 31–47 °C under different heating rates. Partial dehydrogenation was proved at 70 °C: 4.4 wt % for the 5 mol% ZrCl₄–LiAlH₄ mixture, and 3.4 wt % for the best 4:1 stoichiometric mixture. Complete dehydrogenation up to 250 °C released 6.4 wt% and 4.1 wt%, respectively. Dehydrogenation reactions are exothermic, and the LiAlH₄/ZrCl₄ mixtures are unstable and difficult to handle. The activation energy of the exothermic reactions was estimated as 113.5 ± 9.8 kJ/mol and 40.6 ± 6.6 kJ/mol for 4LiAlH₄+ZrCl₄ and 5%mol ZrCl₄+LiAlH₄ samples milled in cryogenic conditions, respectively. The dehydrogenation pathway was changed in the LiAlH₄/ZrCl₄ mixtures as compared to pure LiAlH₄. Dehydrogenation reaction is proposed to form Al, LiCl, Zr, and H₂ as main products. Modification of the dehydrogenation reaction of LiAlH₄ was achieved at the cost of reducing the total hydrogen release capacity.     

Design modelling and measured performance of the vacuum system of the Diamond Light Source storage ring

A one-dimensional diffusion model of the Diamond Light Source storage ring vacuum system is described and its predictions are compared with actual measured static (without beam) and dynamic (with beam) pressures over more than 2000 A h of beam conditioning at 3 GeV. An average specific thermal outgassing yield of 1·10⁻¹¹ mbar l/(s cm²) during initial beam circulation is obtained, which reduces to 2·10⁻¹² mbar l/(s cm²) after an accumulated beam dose of 1000 A h and an elapsed time of 769 days. In the presence of stored electron beam, the pressure rises as expected due to photon stimulated desorption (PSD). The PSD yield reduces with beam dose according to a (−2/3) power law as was applied in the model. Predicted and measured dynamic pressures generally agree within a factor of 2 over the whole range of beam conditioning dose studied.     

Catalytic effect of melt-spun Ni3FeMn alloy on hydrogen desorption properties of nanocrystalline MgH2 synthesized by mechanical alloying

To improve hydrogen desorption properties of magnesium hydride, a composite material with composition of MgH₂-5 at% Ni₃FeMn has been prepared by co-milling MgH₂ powder with Ni₃FeMn alloy either in the form of as-cast (sample A) or melt-spun ribbon (sample B). The study has shown that the addition of Ni₃FeMn alloy to magnesium hydride can yield a finer particle size after mechanical alloying (MA). As a consequence, the desorption temperature of mechanically activated MgH₂ for 30 h has decreased from 319 °C to 307 °C for sample A and to 290 °C for sample B. Furthermore, some favorable effects of Ni₃FeMn alloy on hydrogen desorption kinetics have been observed. Further improvement in the hydrogen desorption of melt-spun containing composite can be related to higher hardness value of the melt-spun powder compared to the as-cast alloy, and probably a more homogeneous distribution of the alloyed elements.     

钨中氘氦行为的高分辨热脱附谱实验方法研究

氢同位素在材料中的扩散、捕获和滞留等行为可通过热脱附谱实验方法进行研究。为实现对同时含有氘氦的钨材料进行热脱附测量并研究钨中氘氦滞留行为，搭建了1套基于高分辨四极质谱仪的热脱附实验系统HiTDS。HiTDS实现了1.2×10^-6 Pa的高本底真空度，速率为1 K/s的精确线性升温，最高加热温度达1423 K，能准确测量样品中气体元素的脱附速率和脱附量。通过配备高分辨四极质谱仪，HiTDS可快速分辨氘氦元素并测量其脱附速率。HiTDS经过调谐校准、标定系数标定后，对氘氦等离子体辐照钨样品进行了热脱附测量。测得的氘氦热脱附谱显示，纯氘脱附量与剂量正相关，而氦的引入显著抑制氘滞留并使其趋于饱和。热脱附实验结果与类似辐照条件的其他研究成果基本一致，检验了该实验方法的有效性。     

Anodic behaviour of carbon materials in NaCl saturated NaAlCl4 fused electrolyte at low temperatures: A cyclic voltammetric study

The anodic behaviour of compacted graphite, graphite powder, glassy carbon and reticulated vitreous carbon electrodes in basic sodium chloroaluminate melt in the temperature range 428–573 K was studied using cyclic voltammetry. Chlorine evolution (> + 2.1 V vs Al) alone was the predominant reaction on the compact glassy carbon and fresh RVC electrodes. On compacted graphite, chlorine-assisted chloroaluminate intercalation was found to be a competitive process to the chlorine evolution. At high sweep rates, intercalation/deintercalation near the graphite lattice edges occur faster than chlorine evolution. Subsequent intercalation, however, is a slow process. Chlorine evolution predominates at higher temperatures and at higher anodic potentials. On graphite powders, a more reversible free radical chlorine adsorption/desorption process also occurs in the potential region below chlorine evolution. The process occurs at the grain boundaries, edges and defects of the graphite powder material. Intercalation/deintercalation processes are mainly responsible for the disintegration of graphitic materials in low-temperature chloroaluminate melts. Repeated intercalation/deintercalation cycles result in the irreversible transformation of the electrode surface and electrode characteristics. The surface area of the electrode is increased substantially on cycling. Electrode materials and operating conditions suitable for chlorine generation, intercalation/deintercalation and chlorine adsorption/desorption and power sources based on these processes are identified in this work.