膜分离现状及发展趋向

本文简要综述了近年来国内外反渗透、超过滤、微孔过滤、扩散渗析、电渗析、气体分离、液膜、渗透蒸发、蒸发渗透等一些主要膜分离过程,特别是有关新膜研制方面的开发现状及其发展趋向。     

纳滤膜对电解质溶液分离特性的理论研究(II): 混合电解质溶液

假定纳滤膜具有狭缝状孔, 使用纯水透过系数、膜孔径及膜表面电势来表征纳滤膜的分离特征, 用流体力学半径和无限稀释扩散系数表征了离子特性. 采用扩展Nernst-Planck方程、Donnan平衡模型和Poisson-Boltzmann理论描述了混合电解质溶液中离子在膜孔内的传递现象, 计算了三种商用纳滤膜(ESNA1-LF, ESNA1和LES90)对同阴离子、同阳离子和含四种离子的混合电解质体系中离子的截留率, 并与实验数据进行了比较. 计算结果表明, 电解质溶液中离子在纳滤膜孔内传递的主要机理是离子的扩散和电迁移, 纳滤膜对混合电解质溶液中离子的分离效果主要由空间位阻和静电效应决定. 该模型在低浓度时对含一价离子的混合电解质溶液通过纳滤膜的截留率计算结果比较准确, 但对高浓度或含高价离子的混合电解质溶液则偏差较大.     

Three-dimensionally ordered macro-porous Pt/TiO2 catalyst used for water-gas shift reaction

Three-dimensionally ordered macro-porous (3DOM) Pt/TiO2 catalysts were prepared by template and impregna-tion methods, and the resultant samples were characterized by using TG-DTA, XRD, SEM, TEM, and TPR techniques. The catalytic performance for water-gas shift (WGS) reaction was tested, and the influences of some conditions, such as reduction temperature of catalysts, the amount of Pt loadings and space velocity on catalytic performance were investigated. It was shown that Pt particles were homogeneously dispersed on 3DOM TiO2. The reduction of TiO2 surface was important for the catalyticperformance. The activity test results showed that the 3DOM Pt/TiO2 catalysts exhibited very good catalytic performance for WGS reaction even at high space velocity, which was owing to the better mass transfer of 3DOM porous structure besides the high intrinsic activity of Pt/TiO2.     

NEWS

膜分离技术在污水处理、中水回用、水质净化、海水淡化、血液透析和生物制药等领域得到了广泛应用。然而,膜在运行过程中出现的膜污染问题严重限制了该技术的发展。膜污染不仅会引起膜通量和分离性能下降,影响膜的长期稳定运行,而且污染后膜的清洗和更换也大大提高了运行成本。为了深入     

Micromegas prototypes with thermo-bond film separators

In this paper we report the results of Micromegas prototypes constructed by attaching micromesh to an anode using thermo-bond films. The excellent metal attaching ability and good dielectical property of this kind of film make it a promising material to be used as avalanche gap spacers. Several prototypes are successfully made. The electron transmission properties are first studied and then the gas gain is measured in argon-isobutane mixtures. The maximum gain of more than 10⁴ is easily obtained. The energy resolutions for ⁵⁵Fe 5.9 keV K_α ray can be better than 20% over one magnitude in gain for different operational gas mixtures and the best energy resolution of 13.7% (FWHM) can be achieved with the gas mixture of 94% argon concentration. The preliminary test results of the prototypes with sensitive area of 45 mm×45 mm without internal support show good uniformity across the sensitive area.     

冠醚石墨烷对氦气分离性能的理论研究

氦气(He)在众多科学和工业领域中都具有非常广泛的应用, He资源的短缺和需求的不断增长使得He分离具有极其重要的意义.石墨烷合成简单、晶体结构稳定,是一种用于构建气体分离膜的潜在理想二维材料.本文通过第一性原理计算,对四种具有不同尺寸冠醚孔的石墨烷膜(crown ether graphane-n, CG-n,n=3, 4, 5, 6)的He分离性能进行了研究.计算结果表明,四种冠醚石墨烷结构都具有较高的热力学、化学稳定性,并且CG-5和CG-6具有合适的孔径,可用于He的有效筛分.在11种气体分子(He, Ne, Ar, H₂, CO,NO, NO₂, N2, CO₂, SO₂和CH₄)中, He最容易通过CG-n膜,其能垒分别为4.55, 1.05, 0.53和0.01 eV.据我们所知, He通过CG-6的能垒是迄今为止报道的最低值,将可显著地提升He的分离效率.基于阿伦尼乌斯方程的选择性计算结果表明, CG-5在较宽的温度范围内(0—600 K)都表现出优异的He选择性...     

以P507为载体的支撑液膜体系中Ni^2＋离子的迁移

本工作研究了以Ｐ５０７为载体的支撑液膜体系中，搅拌速率、温度、原料相中Ｎｉ＾２＋离子起始浓度、载体浓度以及反萃相酸度等因素对Ｎｉ＾２＋离子迁移的影响。实验表明，搅拌速率达到５００ｒｐｍ以上对Ｎｉ＾２＋离子迁移通量影响不大；迁移通量随着原料相中Ｎｉ＾２＋离子起始浓度增加到４．５ｍｍｏｌ／ｌ以上时基本上不再增加，这说明此时膜内络合物浓度已接近炮和；从Ａｒｒｈｅｎｉｕｓ关系得到的迁移活化能为３６．６ｋＪ     

在多孔γ-Al2O3氧化铝载体上微波合成NaA分子筛膜及气体渗透分离性能

The paper presented novel synthesis of NaA zeolite membrane with good performance using microwave heating. The method involved two steps, prior seeding 120 nm of LTA crystals on substrate and then employing a secondary hydrothermal synthesis. Effects of seeding times, synthesis time and synthesis times were investigated in this work. The quality evaluation of membranes respectively used single component gases (HE and N2) and H2/N2 (equivalent volume) mixture. The ideal H2,/N2 selectivity increased from 1.90 of the substrate to 6.37 of the three-stage synthesized membrane, which was distinctly higher than the corresponding Knudsen diffusion selectivity of 3.74. However, the real H2/N2 selectivity of the three-stage synthesis was much lower than the corresponding ideal selectivity and close to the corresponding Knudsen diffusion selectivity of 3.74.