电化学传感分析平台测定污水中的Cr(VI)

结合微型电化学仪器,研究了一种快速、便携、灵敏的Cr(VI)电化学传感分析平台,用于污水中Cr(VI)的检测。采用三电极体系,差分脉冲阴极溶出伏安法(DPCSV),记录伏安曲线中Cr(VI)的还原峰。Cr(VI)的溶出峰电流与其浓度在2～500 μmol L-1范围内有良好的线性关系,测得Cr(VI)的检测限为0.55 μmol L-1 (28.60 g L-1),达到了国际卫生组织（WHO）规定的饮用水中Cr(VI)的最高含量50 g L-1。测得镀铬厂废水中Cr(VI)含量为2.03 mol L-1,与国标法中光谱学分析法的结果基本一致。该法重现性好、灵敏度高,使其应用在现场实时监测环境中的Cr(VI)具有很大的潜力。     

RECOVERY OF URANIURN FROM CARBONATE SOLUTIONS USING STRONGLY BASIC ANION EXCHANGER 3. THE MECHANISMS OF RECOVERY PROCESSES

INTRODUCTIONForthebinaryionexchangereactionmovingboundarymodelwasreported:(a)undertheassumptionofconstantvolumeofresinbeadsduringionexchange['--21,(b)withchangingsphericalvolumeofion...h..g...[3).Thismodelimpliesthreetypesofrate--determiningsteps:liquid--filmdiffusion,diffusionthroughtheso--calledinertlayerofthesorbent,andchemicalreactiontakingplaceattheboundaryoftheunreactednucleus.SongYlnjie.t.[4]carefullyrededucedsolutionscorrespondingtoabovethreetypesofrate-determiningsteps,andtheexpr…     

Modeling the adsorption of U(VI) onto animal chitin using coupled mass transfer and surface complexation

This paper reports the development of a treatment system, using animal chitin as a passive biosorbent, for removing U(VI) from aqueous waste streams. An integral part of this system is a model that provides for the optimization of the treatment system through simulation of U(VI) removal efficiency based on the characteristics of the influent waste stream. The model accounts for changing solution matrix conditions through the coupling of surface complexation and mass transfer models. Complexation of U(VI) by chitin surface sites was modeled using FITEQL. Application of FITEQL in the “forward” mode provided the sorbed and aqueous phase concentrations needed for the mass transfer model. The mass transfer model was derived for both batch and continuously stirred tank reactor (CSTR) configurations using Fick's Law, reactor mass balances and rate law expressions. The coupled model was successfully validated using CSTR data at pH 6.5 and rate constants determined from batch sorption experiments. The CSTR configuration yields a steady-state, eighty percent U(VI) removal for 1 μM influent U(VI) with a solution-phase pH of 6.5 and 3.9 g l⁻¹ chitin.     

天然水源中微量铀钍含量与摄入量研究

分析了居民饮用水及其天然水源中微量铀，钍的含量，并与尿液中铀，钍含量进行了比较。结果表明，上海地区天然水源在国家规定的允许范围内，接近于尿液中铀，钍的日排出量。     

氢过氧化物-过氧乙酸对皮革中Cr6+形成的影响

使用过氧乙酸模拟油脂氧化的产物-氢过氧化物,使过氧乙酸分别对CrCl3、铬鞣剂、CrCl3-苯甲酸、铬鞣剂-苯甲酸、重铬酸钾溶液进行氧化处理,测定溶液中Cr6+的含量,研究氢过氧化物及羟基自由基清除剂(苯甲酸)对皮革中Cr6+形成的影响作用。利用紫外光谱考察了苯甲酸被Cr6+氧化前后     

铬(Ⅵ)-DBC-HNO_3催化动力学光度法测定痕量铬(Ⅵ)

在硝酸介质中,痕量铬(VI)能灵敏的催化氧化DBC褪色。研究了反应的最佳条件,建立了测定痕量铬(VI)的新方法。检出限可达10-9g/ml,测定范围为0.12-0.7μgCr(VI)/10ml,方法简便、灵敏、快速、准确。用于测定水中的痕量铬(VI),获得了满意的结果。     

Verification of model for adsorption and reduction of chromium(VI) by Escherichia coli 33456 using chitosan bead as a supporting medium

A non-steady-state mathematical model system for the kinetics of adsorption and reduction of Cr(VI) by Escherichia coli (E. coli) biofilm on chitosan bead (EBCB) process was derived. The mechanisms in the model system included Cr(VI) adsorption by chitosan beads, Cr(VI) bioreduction by E. coli cells and Cr(VI) mass transport diffusion. Batch kinetic tests were performed to determine surface diffusivity of Cr(VI), adsorption parameters for Cr(VI) and biokinetic parameters of E. coli 33456. Experiments were conducted using an EBCB reactor system with high recycled rate to approximate a completely-mixed flow reactor for model verification. The experimental results indicated that E. coli biofilm bioregenerated the chitosan beads after E. coli biofilm has grown significantly. Cr(VI) reducing efficiency by E. coli was about 84% when Cr(VI) concentration in the influent was 5 mg/L at a steady-state condition. The concentration of suspended E. coli cells reached up to 10 mg/L while the thickness of attached E. coli cells was estimated to be 150 μm at a steady-state condition by model prediction. The comparisons of experimental data and model simulation show that EBCB model system for Cr(VI) adsorption and reduction can predict the experimental results well.     

Baseline studies of radon/thoron concentration levels in and around the Lambapur and Peddagattu areas in Nalgonda district, Andhra Pradesh, India

Studies conducted by Atomic Minerals Directorate of Exploration and Research (AMD) of Hyderabad, India had established the presence of higher concentrations of uranium in Lambapur and Peddagattu areas of Nalgonda district, AP, India and it was estimated that it could be a viable source for commercial extraction. The envisaged extraction process involves dispersion of radioactive particulate matter into atmosphere. Environmental radioactive studies in and around proposed mining areas at this point of time will be extremely useful for establishing base line data before a large scale uranium extraction process comes into existence. To this end, Solid State Nuclear Track Detectors were installed to evaluate indoor radon and thoron concentration levels in the dwellings of the area. The geometric means of radon and thoron concentration levels were found to be (7.1±0.2)×10¹ and (6.7±0.3)×10¹ Bq/m³, respectively. Simultaneously, natural background radiation measurements were also made and these levels are found to vary from 770 to 3995 μGy/y in the spatial distribution.     

Hydrothermal synthesis and characterization of ZnS hierarchical microspheres

In the present work, wurtzite ZnS hierarchical microsphere nanostructures composed of nanowires were synthesized through hydrothermal method. The morphologies and microstructures of the as obtained wurtzite ZnS sample were investigated by scanning electron microscopy and transmission electron microscopy. The results show that the diameter of the nanowires is about 10 nm, the length is about 500 nm, growing along the [0 0 1] direction. UV–visible spectroscopy shows that the band gap of the as obtained ZnS hierarchical microspheres is 3.4 eV. Room temperature photoluminescence measurements reveals a strong green emission peak at around 516 nm. The N₂ adsorption–desorption isotherms experiment at 77 K exhibits that the surface area of the ZnS sample is 99.87 m² g⁻¹.     

Surface tension and density measurements for indium and uranium using a sessile-drop apparatus with glow discharge cleaning

The sessile-drop method is used to measure the surface tension and density of liquid indium and uranium under high vacuum. Measurements are made over the temperature range 156–500°C for In and at the melting point for U. Surface oxides are efficiently removed with a glow discharge system. Drop profiles are captured by photograph and processed using nonlinear regression to yield the surface tension and density. In this regression procedure, normal distances from calculated profiles to data points are minimized. For indium, the density and surface tension measurements yield _mp = 7.05 × 10³kg/m³, d/dT = −0.776 kg/m³·°C, and γ_mp = 0.568 N/m, dγ/dT = −9.45 × 10⁻⁵ N/m·°C. The results for uranium at the melting point are _mp = 17.47 × 10³ kg/m³ and γ_mp = 1.653 N/m.