基于Donnan渗析的阴离子交换膜分离饮用水中Cr(Ⅵ)研究

基于Donnan渗析原理,研究阴离子交换膜分离饮用水中的Cr（Ⅵ）,探讨受体液种类、受体液NaCl浓度、给体液初始pH值以及给体液进水流速对Cr（Ⅵ）分离的影响。结果表明,不同驱动离子条件下给体池中Cr（Ⅵ）的分离去除率从大到小依次为Cl-、HCO3-、SO24-,而离子通量从大到小依次为Cl-、SO24-、HCO3-。驱动离子宜为水合半径较小的单价Cl-,受体液应为相对廉价常见的NaCl溶液。当受体液NaCl浓度由0增加至0.100mol/L时,给体池中Cr（Ⅵ）的分离去除率变化不大,而离子通量由0显著提高至7.34×10-5mg/（cm^2.min）;进一步增加受体液NaCl浓度至0.5 mol/L,给体池中Cr（Ⅵ）的分离去除率和离子通量的增加较小。当给体液初始pH值为1.0时,给体池中Cr（Ⅵ）的分离去除率和离子通量较小,并随给体液初始pH值的增大而增大。该Cr（Ⅵ）分离过程在饮用水常规pH值范围（6.5~8.5）内均能得到较好的效果。当给体液进水流速由1.0 mL/min增加至5.0mL/min时,给体池中Cr（Ⅵ）的分离去除率由89.3%降低至73.5%,离子通量由6.25×10-5mg/（cm^2.min）增加至8.91×10-5mg/（cm^2.min）。饮用水中背景组分对Cr（Ⅵ）分离的影响不大。

荷电镶嵌膜Donnan平衡理论模型的研究

推导了荷电镶嵌膜单盐溶液和混合盐溶液的Donnan平衡模型 ,指出荷电镶嵌膜对无机电解质具有较低的截留率 ,可实现电解质与低分子有机物的有效分离 .对于理想的荷电镶嵌膜 ,电解质能自由地通过 ;在混合盐体系中 ,离子的分配系数有可能大于 1 ,导致离子的负截留率 .Donnan平衡模型可定性地预测电解质的截留率关系 ,并由截留率关系判断膜的正、负荷电性 .

Poisson-Boltzmann与Donnan模型计算压实膨润土孔隙水与外部溶液间离子平衡的差异性比较

压实膨润土孔隙水与外部溶液之间的离子平衡是影响离子在压实膨润土中扩散的影响因素之一,表征这一平衡的离子平衡系数可用压实膨润土的宏观属性参数通过Donnan模型计算得到.通过对膨润土主体矿物蒙脱石的TOT层结构单元进行简化,构建了一个压实膨润土的单类孔隙结构模型,辅以一个尺度变量H,用Poisson-Boltzmann(PB)理论模型计算上述离子平衡系数.对比计算结果,发现PB模型计算的离子平衡系数总是大于Donnan模型的结果,而参数H是联系这两种模型之间的桥梁.通过对参数H取极限H→0,实现了从PB模型到Donnan模型的数学变换,并从机理上讨论了两种模型之间的差异及其在实际扩散问题中的应用.分析表明PB模型更符合离子在压实膨润土中扩散的实际情况,更适于处理实际扩散问题.

矿质营养教学中“Donnan平衡”的计算

植物生理学中常用Donnan平衡来解释不消耗代谢能也可以逆浓度梯度积累离子的现象。一些教科书在推导因Donnan平衡所引起的离子浓度变化时设想的条件是:一膜将溶液分为两部分,膜内为非扩散性带负电荷的蛋白质Pr^-和可扩散的阳离子K^+,浓度均为C_i,膜外为可扩散性离子K^+和Cl^-,浓度均为C_0。因膜内无Cl^-,Cl^-将沿浓度梯度向膜内扩散,同时与Cl^-等量的K^+也透入膜内,使电荷保持平衡。假定平衡时有一定量x的K^+与Cl^-进入膜内,这时膜内的K^+浓度为C_i+x,Cl^-浓度为x,膜外的K^+和Cl^-的浓度均为C_0-x(图1)。

Donnan渗析分离含盐废水中的氨氮

通过Donnan渗析去除含盐废水中的氨氮,研究了盐水初始浓度、NaCl与氨氮比例、搅拌强度以及温度等对氨氮分离的影响。结果表明,降低盐水浓度、NaCl与氨氮比可提高氨氮的去除率,搅拌速度由200 r/min提高到500 r/min时,氨氮的去除率从49.6%提高到54.3%,处理时间缩短。适当提高温度,可有效提高氨氮的分离效果。

Phosphate removal from aqueous solution by Donnan dialysis with anion-exchange membrane

The removal of phosphate from aqueous solution by Donnan dialysis with anion-exchange membrane was investigated.The results show that phosphate could be removed from aqueous solution without supplying external high pressure or electrical potential.Under the conditions of influent phosphate of 2.0 mg/L,counterion(Cl-)concentration of 0.1 mol/L,stirring speed of 500 r/min and phase temperature of 298 K,the removal of phosphate achieves 70.0%.Decreasing counterion concentration has little influence on the removal of phosphate,but phosphate amount in anion-exchange membrane increases significantly.With the increase of stirring speed and phase temperature,the removal efficiency of phosphate greatly is improved.Existing forms of phosphate in aqueous solution affected transport of phosphate and only strong acidic pH of feed solution(pH=3.0)decreases the removal of phosphate.Transport of phosphate is also accompanied by change of pH value of feed solution.In consequence,it might be a promise potential process for phosphate advanced wastewater treatment,especially in the area where high salted nature water can be utilized.

A NEW PRODUCTION METHOD OF AMMONIUM METATUNGSTATE—DONNAN DIALYSIS METHOD

A new method for production of ammonium metatungstate (AMT) directly from ammonium tungstate solution—Donnan dialysis method is advanced. Laboratory experiments are conducted by a Donnan dialysis cell with the membrane area of 140 mm×200 mm. The result shows that the transformation rate of AMT reaches 370 g WO 3/(m 2·h), the recovery ratio of AMT by the Donnan dialysis method is nearly 100%, and the loss of tungsten is less than 0.2%. It has been proved that the Donnan dialysis method is effective for production of AMT.

高分子溶液的渗透压及Donnan平衡

本文从不同角度导出了在不同条件下高分子溶液的渗透压公式的表示形式，揭示了Ｄｏｎｎａｎ平衡原理。

Donnan Electric Potential Dependence of Intraparticle Diffusion of Malachite Green in Single Cation Exchange Resin Particles: A Laser Trapping-Microspectroscopy Study

A laser trapping-microspectroscopy technique combined with excitation energy transfer from a fluorescent cationic dye (Rhodamine B, RB+) to a non-fluorescent cationic dye (Malachite Green, MG+) was employed to study pH effects on the diffusion coefficients of MG+ (D(MG+)) in single cation-exchange resin microparticles with the diameters of 16 μm. When RB+-pre-adsorbed resin particles were soaked in an aqueous MG+ solution, the RB+ fluorescence was quenched gradually with the soaking time. The time course of the quenching efficiency of RB+ by MG+ was then used to evaluate the D(MG+) value in the particle. The D(MG+) value increased from 1.1 × 10-11 to 4.3 × 10-11 cm2.s–1 on going the solu- tion pH value from 9 to 4. The results were explained reasonably by a Donnan electric potential model.

Donnan Dialysis Removal of Nitrate from Water: Effects of Process Parameters

Excess or lack of levels of nitrate in drinking water is harmful to the human health, the concentration of NO-3 ions must be maintained at 50 mg/l. Donnan dialysis (DD) used as a driving force of the concentration gradient is an effective and simple technique for nitrate removal. In this paper, the transport of nitrate through an AMX anion-exchange membrane has been studied as a function of driving ion nature, receiver phase concentration, flow rate, temperature and agitation rate under Donnan dialysis condition. It was observed that the hydrodynamic conditions and temperature were the main variables affecting the transmembrane flow. As the driving ion, the chloride ion is more efficient than the hydrogeneocarbonate ion. The systematic study of the different parameters involved showed that the nitrate removal efficiency obtained with a feed synthetic nitrate solution (62 ppm) was off 96%. This efficiency slightly decreases for a tap water containing the same nitrate concentration;it was about 84%. This can be attributed to the complex ionic composition of the natural water.

Application of Donnan Dialysis Coupled to Adsorption onto Activated Alumina for Chromium (VI) Removal

The aim of this paper is the assessment of Donnan dialysis coupled to adsorption process for the removal of chromium from aqueous solutions. This study was conducted in order to benefit from each process, and it was an original and new combination. The coupling was a solution to improve the contact time and the amount of chromium (VI) removed. The coupling was successfully performed with 90% of chromium (VI) removed after 6 hours.

Optimization of Chromium (Vi) Removal by Donnan Dialysis

The removal of chromium (VI) from aqueous solutions by Donnan dialysis has been investigated in this paper. In this process, two anion-exchange membranes (AEMs) were used: Selemion? AMV and Neosepta? AFN. The amount of chromium (VI) removed was determined in terms of the following parameters: initial concentration of chromium (VI), type of anion-exchange membrane, concentration of counter-ion and magnetic stirring rate. A 24 full factorial design analysis was performed to screen the parameters affecting the Cr (VI) removal efficiency. Using the experimental results, a linear mathematical model representing the influence of the different parameters as well as their interactions was obtained. Analysis of the variance (ANOVA), the F-test and the student’s test shows that the type of anion-exchange membrane is the most significant parameter affecting the chromium (VI) removal. The statistical analysis of the experimental data assumes it to be a normal distribution.

Recovery of Heavy Metal Using Solvent Impregnated Resin (SIR) Coupled with Donnan Dialysis

A membrane process for metal recovery from aqueous solutions was studied. Metal ions diffused from the feed compartment to the stripping compartment through an hybrid Donnan dialysis which consists to combine two ion exchange membranes with solvent impregnated resin (SIR). The aim of this work is to study the recovery of Pb(II), Ag(I) and Cu(II) from nitrate solutions by using SIR combined with classical Donnan dialysis. The resin has been prepared by impregnating the Amberlite XAD-4 using three different extractants namely: di-2-ethyl hexyl phosphine acide (D2EHPA), tris-octyl phosphine oxide (TOPO) and Diphenylthiourea (DPT). Experiments were performed as a function of nature of the extractant impregnated on the XAD-4 resin as well as the concentration in the resin phase, the stripping pH, the concentration ratio of metal ions in the feed compartment and the nature of the counter ions in strip compartment. The results show that the D2EHPA is the better extractant for the metal ions used in this work, and it’s shown a good selectivity for the separation between ions.

Gibbs-Donnan Potential as a Tool for Membrane Vesicles Polarization

It has been theoretically predicted that under conditions leading to Gibbs-Donnan equilibrium in case when size of one compartment is very different from another (as in system “membrane vesicle/liposomes—incubation medium”) stable transmembrane potential can be formed, which value is sufficient to fit requirement of real transmembrane potential. Four partial cases were considered with different location and charge of impermeable ion and it was concluded that locations of impermeable ions in medium provide stable transmembrane potential with sufficient value of 60 - 70 mV. Potential-sensitive probe, such as DiOC6(3) and oxonol VI, were used to confirm the calculated potential. According to the change in fluorescence level and emission/excitation shift, a stable and relatively high transmembrane potential can be formed if salt of impermeable ion is located in incubation medium. Impermeable cations and anions may be used to create positive and negative transmembrane potential respectively.

Measurement of free heavy metal ion concentrations in soils using Donnan membrane technique

In natural systems heavy metals are present in very low concentrations (less than micro-molar), so precise measurement of the free metal ions is difficult. Recently, a new method has been developed called the Donnan membrane technique (DMT). Several heavy metals could be measured simultaneously using this method. Furthermore, all the metals did not interfere with each other, and the balance between the measured system and the surrounding condition could not be disturbed. Improvements were made according to the internal condition. The free heavy metal ion concentrations were measured in different systems using the improved method, and satisfied results have been obtained.

Hybrid Donnan dialysiseelectrodialysis for efficient ammonia recovery from anaerobic digester effluent

Ammonia recovery from wastewater is crucial,yet technology of low carbon emission and high ammonia perm-selectivity against complex stream compositions is urgently needed.Herein,a membrane-based hybrid process of the Donnan dialysiseelectrodialysis process(DDeED)was proposed for sustainable and efficient ammonia recovery.In principle,DD removes the majority of ammonia in wastewater by exploring the concentration gradient of NH4 t and driven cation(Nat)across the cation exchange membrane,given industrial sodium salt as a driving chemical.An additional ED stage driven by solar energy realizes a further removal of ammonia,recovery of driven cation,and replenishment of OHtoward ammonia stripping.Our results demonstrated that the hybrid DDeED process achieved ammonia removal efficiency>95%,driving cation(Nat)recovery efficiency>87.1%for synthetic streams,and reduced the OH-loss by up to 78%compared to a standalone DD case.Ammonia fluxes of 98.2 gN m^(-2)d^(-1)with the real anaerobic digestion effluent were observed using only solar energy input at 3.8 kWh kgN^(-1).With verified mass transfer modeling,reasonably controlled operation,and beneficial recovery performance,the hybrid process can be a promising candidate for future nutrient recovery from wastewater in a rural,remote area.

响应面分析法耦合调节Donnan效应优化苦参提取液的纳滤浓缩工艺

目的利用响应面分析和增强Donnan效应耦合技术对苦参碱的纳滤浓缩工艺进行优化。方法以苦参碱及总生物碱截留率为指标，在明确操作压力、温度、平衡体积等因素影响的基础上，采用Box-Behnken中心组合设计建立数学模型，考察截留相对分子质量、指标成分质量浓度、pH值，得出各因素对截留率的影响程度，设定溶液pH值6～7，以乙醇体积分数调节苦参碱与纳滤膜间的Donnan效应，优选纳滤浓缩参数。结果乙醇体积分数与生物碱截留率呈正相关，优选出纳滤浓缩参数为纳滤膜截留相对分子质量150，pH值6．19，苦参碱质量浓度204．3μg／mL，总生物碱质量浓度603．1μg／mL，乙醇体积分数10％，苦参碱截留率为94．41％，总生物碱截留率97．63％。结论以乙醇溶液调节Donnan效应与响应面法相结合，可用于优选中药纳滤浓缩的参数，为热敏性中药成分的纳滤浓缩提供基础。

基于Donnan膜效应的树脂基水合氧化铁的制备及对砷的吸附性能研究

以大孔强碱性离子交换树脂D201为载体,利用FeCl3-HCl-NaCl溶液特有的性质制备出一种基于Donnan膜效应的新型树脂基水合氧化铁D201-HFO.研究结果表明,D201-HFO对砷的吸附容量较美国同类专利产品ArsenX有较大提高,同时该材料表现出对砷良好的吸附选择性和吸附动力学性能.固定床吸附结果表明,通过D201-HFO的吸附处理,受污染水体中砷的含量可降至10μg/L(我国生活饮用水新标准GB5749-2006)以下,吸附后的D201-HFO可被NaOH-NaCl溶液彻底再生.稳定性实验表明,HFO在D201树脂孔道内较为稳定,D201-HFO是一种性能优良、具有广泛应用前景的除砷吸附剂.

基于Donnan渗析离子交换膜分离水中的Cd(Ⅱ)

基于Donnan渗析原理构建了离子交换膜反应器,探讨了受体池溶液种类和浓度、给体和受体池搅拌功率以及给体池溶液的初始pH、进水流量和Cd(Ⅱ)进水浓度等因素对Cd(Ⅱ)分离效果的影响。结果表明,随着搅拌功率由0.035W增大为0.162 W,Cd(Ⅱ)分离去除率与离子通量显著增加。当受体液NaCl浓度为0～0.5 mol·L-1时,Cd(Ⅱ)分离去除率随着受体液浓度的增加而显著增加。当给体池进水Cd(Ⅱ)溶液初始pH≤8时,Cd(Ⅱ)分离去除率随受体液pH的增加而增加。此外,给体池中Cd(Ⅱ)分离去除率与Cd(Ⅱ)初始浓度以及给体池进水流量成反比。在本实验条件下,Cd(Ⅱ)的分离去除率最高可达85.51%。

电辅助磺化聚砜膜分离医药废水传递机理的分子动力学模拟研究

医药生产废水的膜法分离技术对实现绿色医药化工意义重大。其中,通过电场辅助强化膜分离效率,阻止荷电医药分子迁移、离子跨膜传递,有较好的应用前景。但目前尚无分子尺度模型揭示相关膜界面和膜传递通道内的分离机制,也制约了相关新型膜材料设计和膜技术研发。利用分子动力学模拟(MD)技术,从分子层面上探究电场辅助下的磺化聚砜膜(SPSf)分离头孢呋辛钠医药废水的机理,并模拟膜内含水量对离子传递行为的影响。模拟过程中能量、温度波动低于10%,证明模型设定与计算方法可靠;所构建模型玻璃化转变温度与实验值接近,证明所选力场合适,所得数据可用于后处理及结果分析。结果表明,外加电场增强膜表面带电基团对同性离子的排斥能力。随着电场在一定程度上的增强(0~0.15 V·Å^(-1)),解离后的荷电膜对带负电粒子排斥能力增强(SPSf解离后,膜表面头孢呋辛离子强度下降15.7%),对Na+吸附更强(Na+强度增加19.4%),证明电增强Donnan效应与电增强吸附/脱附是电辅助荷电纳滤膜分离医药废水的主要作用机理。此外,分析了电场强度与膜内含水量对离子在SPSf膜体系中扩散的影响。在模拟实验范围内,随着含水量与电场强度增大,荷电膜内离子扩散能力增强;在膜内含水量λ=2.0、0.10 V·Å^(-1)时,Na+扩散系数与头孢呋辛离子扩散系数相差1.54×10^(-6)cm^(2)·s^(-1),在这种条件下离子选择性最高。通过分子动力学模拟技术(MD)从微观层面解释电辅助荷电膜分离医药工业废水的调控机理,为理性设计和选择荷电膜材料与膜表面的基团改性提供了有益的理论参考。