DETERMINATION OF ANTIMONY IN WATER SAMPLES BY FLOW-INJECTION HYDRIDE GENERATION ATOMIC ABSORPTION SPECTROMETRY WITH ON-LINE ION-EXCHANGE COLUMN PRECONCENTRATION

On-line ion-exchange separation and preconcentration were combined with flow-injection hydride generation atomic absorption spectrometry (HGAAS) to determine ultra-trace amounts of antimony in water samples. Antimony(Ⅲ) was preconcentrated on a micro-column packed with CPG-8Q chelating ion-exchanger using time-based sample loading and eluted by 4 mol l^(-1) HCl directly into the hydride generation AAS system. A detection limit (3σ) of 0.0015μg l^(-1) Sb(Ⅲ) was obtained on the basis of a 20 fold enrichment and with a sampling frequency of 60h^(-1). The precision was 1.0% r.s.d.(n=11) at the 0.5μg l^(-1) Sb(Ⅲ) level. Recoveries for the analysis of antimony in tap water, snow water and sea water samples were in the range 97-102%.

Microfluidic Analytical System with On-Line Luminol Chemiluminescence Detection Based on Annular Flow of Phase Separation Multiphase Flow

Microfluidic analytical system was developed based on annular flow of phase separation multiphase flow with a ternary water-hydrophilic/hydrophobic organic solvent solution. The analytical system was combined with on-line luminol chemiluminescence detection for catechin analysis. The water (10 mM phosphate buffer, pH 7.3)-acetonitrile-ethyl acetate mixed solution (3:8:4, volume ratio) containing 60 μM luminol and 2 mM hydrogen peroxide as a carrier was fed into the capillary tube (open-tubular fused-silica, 75 μm inner diameter, 110 cm effective length) at a flow rate of 1.0 μL·min-1. The carrier solution showed stable chemiluminescence as a baseline on the flow chart. Eight catechins were detected as negative peaks for their antioxidant potential with different detection times. The system was applied to analyze the amounts of catechin in commercially available green tea beverages.

Chemical Selectivity of Laser Ion Source for on-Line Mass Separator

Thulium(Tm)atoms are resonantly ionized in a hot tube by stepwise excitations us-ing three dye lasers pumped by a series of copper vapor pulsed at a 10 kHz rate.The chemicalselectivity of the laser ion source is measured as a function of temperature of the tubes made ofTa,Nb-Zr and TaC.The chemical selectivity rises from 50 to 10000 with decreasing tube temp-erature and strongly depends on the tube material.A chemical selectivity of about 10000 withhigh efficiencies is obtained with the Nb-Zr and TaC tubes.Such a laser ion source can be usedin on-line mass separator to obtain isobarically pure ion beams.

Rare Earth Separation in China

During the last decade, China rare earth （RE） industry has made significant progress and become one of the most important producers in the world. In this paper, the recent developments in both fundamental research and industrial application are briefly reviewed： （1） the development and application of Theory of Countercurrent Extraction, （2） the novel solvent extraction process and its application in industry for separating heavy rare earth elements （Tm, Yb, Lu）, yttrium （Y）, and scandium （Sc）, （3） the on-line analysis and automatic control of countercurrent extraction, （4） the eco-friendly process for RE/Th separation of bastnasite in Sichuan Province and electrochemical process for Eu/RE separation, and （5） the optimized flowcharts for typical rare earth minerals in China.

Industrial application of the technique of removing Mo by a combination of moving packed bed and fluidized bed ion exchange

The application of the technique of removing molybdenum by moving packed bedand fluidized bed ion-exchange in a factory was described. The data showed that the Mo removalefficiency is above 99 percent, and the Mo content in APT (Ammonium Paratungstate) is controlledsteadily below 18 X l0^(-6), in the case of treating the feed liquor containing Mo 1.4 g/L. Thetechnique is simple and convenient in operation, good reusability of resin, loss consumption ofdesorption reagent and little pollution on environment. The loss of tungsten is less than 0.5percent. The technique bas been proved to be an economical and efficient process for Mo removal.

Advancing ion-exchange membranes to ion-selective membranes:principles,status,and opportunities

Ion-exchange membranes(IEMs)are utilized in numerous established,emergent,and emerging applications for water,energy,and the environment.This article reviews the five different types of IEM selectivity,namely charge,valence,specific ion,ion/solvent,and ion/uncharged solute selectivities.Technological pathways to advance the selectivities through the sorption and migration mechanisms of transport in IEM are critically analyzed.Because of the underlying principles governing transport,efforts to enhance selectivity by tuning the membrane structural and chemical properties are almost always accompanied by a concomitant decline in permeability of the desired ion.Suppressing the undesired crossover of solvent and neutral species is crucial to realize the practical implementation of several technologies,including bioelectrochemical systems,hypersaline electrodialysis desalination,fuel cells,and redox flow batteries,but the ion/solvent and ion/uncharged solute selectivities are relatively understudied,compared to the ion/ion selectivities.Deepening fundamental understanding of the transport phenomena,specifically the factors underpinning structure-property-performance relationships,will be vital to guide the informed development of more selective IEMs.Innovations in material and membrane design offer opportunities to utilize ion discrimination mechanisms that are radically different from conventional IEMs and potentially depart from the putative permeability-selectivity tradeoff.Advancements in IEM selectivity can contribute to meeting the aqueous separation needs of water,energy,and environmental challenges.

Ultrafine tuning of the pore size in zeolite A for efficient propyne removal from propylene

The removal of trace propyne(C_(3)H_(4))from propyne/propylene(C_(3)H_(4)/C_(3)H_(6))mixtures is a technical and challenging task during the production of polymer-grade propylene in view of their very similar size and physical properties.While some progress has been made,it is still very challenging to use some highly stable and commercially available porous materials via an energy-efficient adsorptive separation process.Herein,we report the ultrafine tuning of the pore apertures in type-A zeolites for the highly efficient removal of trace amounts of C_(3)H_(4)from C_(3)H_(4)/C_(3)H_(6)mixtures.The resulting ion-exchanged zeolite 5 A exhibits a large C_(3)H_(4)adsorption capacity(2.3 mmol g^(-1)under 10^(-4)MPa)and high C_(3)H_(4)/C_(3)H_(6)selectivity at room temperature,which were mainly attributed to the ultrafine-tuned pore size that selectively blocks C_(3)H_(6)molecules,while maintaining the stro ng adsorption of C_(3)H_(4)at low pressure region.High purity of C_(3)H_(6)(>99.9999%)can be directly obtained on this material under ambient conditions,as demonstrated by the experimental breakthrough curves obtained for both 1/99 and 0.1/99.9(V V)C_(3)H_(4)/C_(3)H_(6) mixtures.

Concentration of Hydrochloric Acid by Pervaporation Membrane Separation Process

Hydrogen chlorid (HC1) used in chemical industry and laboratory is usually obtainedfrom concentrated hydrochloric acid (approximately 37% of HC1) through distillation,When the hydrogen chloride content in concentrated hydrochloric acid is extracted

SEPARATION OF DIOXANE/WATER MIXTURES BY PERVAPORATION

Pervaporation as a membrane technique of liquid mixtures separation has been rapidly developed recently. The separation process is as follows: the feed is placed in contact with upstream side of membrane, the downstream side of the membrane is kept under vacuum or under a stream of inert gas. If one of the components of the liquid mixture can

Separation characteristics of boron isotopes in continuous annular chromatography

A well designed continuous annular chromatograph （CAC） column was set to stndy the enrichment of Boron isotopes. The column is 820 mm high and consists of a rotational annulus with an outer diameter of 246 mm and a width of 15 mm. The weak basic resin （Diaion WA21J）, the boric acid and water were used as the absorbent, the feed and the eluent respectively. The effects of CAC rotating speed, concentration of boric acid and flow ratio of eluent to feed on the enrichment of 10B were investigated. The concentration of boron isotope was determined by a Thermal Elemental X7 ICP-MS （Thermo Electron Co., USA）. It is shown from the experimental results that 10B and 11B can be separated effectively by this CAC column. By fitting the experimental elution profiles based on reliable mathematic models and software the mass transfer coefficient k and adsorp- tion equilibrium constant K values of 10B and 11B in CAC column were estimated. It is clear from this study that the CAC has practical continuous operational capabilities in comparison with fixed batch chromatography and is an effective technology for seoarating boron isotones.

A STUDY ON THE KINETICS OF EXCHANGE REACTIONS OF W（Ⅵ） OR Mo（Ⅵ） WITHIN MACROPOROUS ANION EXCHANGE RESIN（D290） PHASE

The exchange behaviors of WO_4￣(2-) MoO_4￣(2-), H_2 W_(12) O_(40)￣(6-) and Mo8 O_(26)￣(4-) anions within macrOPorous exchange resin (D290) phases have been studied.The values of diffusion constant (B), inner diffusion coefficient (D), retarted time (td) half - exchange-period (t1/2), and activation energy (△E) were found from the kinetic analyses. A new method to separate W(Ⅵ) and Mo (Ⅵ) from each other was also suggested.

PURIFICATION OF L-METHIONINE AND N-ACETYL-D-METHIONINE FROM THE MIXTURE OF ENZYMATICALLY DEACYLATED N-ACETYL-DL-METHIONINE

N-acetyl-D-methionine, NaAc and the remains of N-acetyl-L-methionine dramatically affect the purification of L-methionine when purified from the mixture of enzymatically deacylated N-acetyl-DL-methionine, leading to a low yield conventionally. Here, this paper reports a successful separation and purification of both L-methionine and N-acetyl-D-methionine by an H ion-exchange column. The pH, L-Met concentration and the ratio between the content of sodium cation and the ion-exchange capacity were optimized to obtain the maximum yield. Experimental results indicate that, under the optimized conditions, the yields of L-methionine and N-acetyl-D-methionine can reach as high as 85% and 75%, respectively.

Gain deeper insights into traditional Chinese medicines using multidimensional chromatography combined with chemometric approaches

Traditional Chinese medicines(TCMs)possess a rich historical background,unique theoretical framework,remarkable therapeutic efficacy,and abundant resources.However,the modernization and internationalization of TCMs have faced significant obstacles due to their diverse ingredients and unknown mechanisms.To gain deeper insights into the phytochemicals and ensure the quality control of TCMs,there is an urgent need to enhance analytical techniques.Currently,two-dimensional(2D)chromatography,which incorporates two independent separation mechanisms,demonstrates superior separation capabilities compared to the traditional one-dimensional(1D)separation system when analyzing TCMs samples.Over the past decade,new techniques have been continuously developed to gain actionable insights from complex samples.This review presents the recent advancements in the application of multidimensional chromatography for the quality evaluation of TCMs,encompassing 2D-gas chromatography(GC),2D-liquid chromatography(LC),as well as emerging three-dimensional(3D)-GC,3D-LC,and their associated data-processing approaches.These studies highlight the promising potential of multidimensional chromatographic separation for future phytochemical analysis.Nevertheless,the increased separation capability has resulted in higher-order data sets and greater demands for data-processing tools.Considering that multidimensional chromatography is still a relatively nascent research field,further hardware enhancements and the implementation of chemometric methods are necessary to foster its robust development.