在线双毛细管火焰原子吸收法测定矿石中高量铅

本文采用双毛细管在线稀释法测定矿石中高含量铅。样品经消解后定容,利用提升量比为18的双毛细管进样,用原子吸收法测定。该方法操作简便,精密度(RSD,n=10)小于1.615,适于矿石中0.x%～x×10%含量的铅组分测定。     

Electrodialytic remediation of soil fines (<63 μm) in suspension—Influence of current strength and L/S

Current treatment of the remaining soil fines from soil wash is onerous and expensive, and therefore, in this work, we investigated the feasibility of electrodialytic remediation (EDR) as an alternative treatment. The study focuses on EDR efficiency as a function of current strength, liquid-to-solid-ratio (L/S), pH and time. We found out that during the experiments, Pb was easily dissolved by the acidification resulting from water splitting at the anion-exchange membrane. When higher currents and/or higher L/S ratios were applied, it was found that water splitting occurring at the cation-exchange membrane increased the pH, and this resulted in decreased remediation efficiency. It was shown that complete remediation of the soil-fines is possible, with the majority of the Pb being transported into the catholyte and precipitated at the cathode. Based on the results it is recommended that EDR is implemented using a number of reactors in series, where the initial reactor works at the highest possible removal rate, and the final reactor works at the target Pb-concentration.     

狗经氡子体暴露后血、毛中~(210)Pb 和~(210)Po 含量的动态变化

本文叙述了实验狗经氡子体暴露后血、毛中~(210)Po、~(210)Pb 含量、~(210)po/~(210)Pb 比率及血中~(210)Po,~(210)Pb 排出的动态变化。     

Thermophysical properties of some key solids: An update

In 1985, the CODATA Bulletin published a Report of its Task Group on Thermophysical Properties of Solids which analyzed available data on, and gave recommended values for, the heat capacity of Cu, Fe, W, and Al₂O₃, the thermal expansion of Cu, Si, W, and Al₂O₃, the electrical resistivity of Cu, Fe, Pt, and W, the thermal conductivity of Al, Cu, Fe, and W, and the absolute thermopower of Pb, Cu, Pt, and W. The analysts for the different properties were R. B. Castanet, S. J. Collocott, P. D. Desai, C. Y. Ho, J. G. Hust, R. B. Roberts, C. A. Swenson, and G. K. White. The present paper is an updated version of the earlier report and includes more recent data which change some of the recommended values. notably the heat capacity of Cu and W and the thermal expansion of Si and W.     

Preparation and characterization of glassy and superconducting (Bi,Pb, Sb)-Sr-Ca-Cu-O systems

Superconducting compounds with nominal compositions Bi_1.7Pb_0.3Sr_1.6Ca₂ Cu_3.4O _x and Bi_1.9Sb_0.1Sr₂Ca₂Cu₃O _y have been synthesized by ceramic and glass routes and characterized by X-ray diffraction, electrical resistivity and dielectric constant measurements. The zero-electrical resistance temperatures are about 70K. The dielectric constant of the glasses at room temperature is around 30.     

The antiproton depth-dose curve measured with alanine detectors

In this paper we report on the measurement of the antiproton depth-dose curve, with alanine detectors. The results are compared with simulations using the particle energy spectrum calculated by FLUKA, and using the track structure model of Hansen and Olsen for conversion of calculated dose into response. A good agreement is observed between the measured and calculated relative effectiveness although an underestimation of the measured values beyond the Bragg-peak remains unexplained. The model prediction of response of alanine towards heavy charged particles encourages future use of the alanine detectors for dosimetry of mixed radiation fields.     

Comparative study of depth-dose distributions for beams of light and heavy nuclei in tissue-like media

We study the energy deposition by beams of light and heavy nuclei in tissue-like media for their possible application in charged-particle cancer therapy. The depth-dose distributions for protons, ³He, ¹²C, ²⁰Ne and ⁵⁸Ni nuclei are calculated within a Monte Carlo model based on the GEANT4 toolkit. These distributions are compared with each other and with available experimental data. It is demonstrated that nuclear fragmentation reactions essentially reduce the peak-to-plateau ratio of the dose profiles for deeply penetrating energetic ions heavier than ³He. On the other hand, the shapes of depth-dose profiles for all projectiles up to ⁵⁸Ni were found similar at low penetration depths.     

Adsorption and desorption behaviour of Pb(II) on a natural kaolin: equilibrium,kinetic and thermodynamic studies

BACKGROUND: Pb(II) is common in both waste‐waters and gas emissions. In developing countries, public health problems have been reported concerning Pb(II) pollution, so that stringent measures are required to deal with it. MAJOR RESULTS: The adsorption and desorption behaviour of Pb(II) has been investigated on a natural Chinese kaolin. Several factors, including initial concentration, pH, equilibration time, dosage and temperature correlated positively with Pb(II) adsorption. The Pb(II) adsorption capacity of natural kaolin was 165.117 mg g^?1. A kinetic study shows that Pb(II) adsorption on purified kaolin equilibrates within 35 min. The enthalpy changes of Pb(II) adsorption on purified kaolin were 63.683, 20.488 and 21.371 kJ mol^?1 with entropy changes 262.250, 112.210 and 105.120 J mol^?1 K^?1 for solutions containing 50, 100 and 200 mg L^?1 Pb(II) respectively, indicating an endothermic and spontaneous adsorption process. The desorption of Pb(II) from kaolin was difficult with more than 85% Pb(II) removal. Based on X‐ray diffraction (XRD) analysis, the Pb(II) adsorption on natural and purified kaolin was attributed mainly to the magnesite component and complexation with the mineral surface. CONCLUSIONS: Natural kaolin exhibits a satisfactory performance for adsorption of Pb(II) from aqueous solution. The optimum conditions for adsorption were: ionic strength = 0.01 mol L^?1; pH ≥ 7.2; dosage = 10 g L^?1; temperature = 25 °C; duration ≥ 16 h (C_i = 80 mg L^?1); and the optimum conditions for desorption were ionic strength = 0.1 mol L^?1 and pH ≤ 5.0. Copyright © 2009 Society of Chemical Industry