Application of Cr(VI) transport across the polymer inclusion membrane with calixresorcin[4]arene derivative as ion carrier

ABSTRACT

In this study, the experiments were performed to evaluate the Cr(VI) removal efficiency by transport across the polymer inclusion membrane with calixresorcin[4]arene derivative as ion carrier. The several influence factors such as carrier concentration, the amount of plasticizer in the membrane as well the effect of acid type and its concentration in source phase and the membrane stability were investigated. It was found that the immobilized calixresorcin[4]arene derivative in membranes effectively extracted chromium from acidic media. Under optimized conditions, the Cr(VI) removal efficiency was 98.4%.     

Extraction of aconitic acid from mixtures of organic acids and cane molasses solutions using supported liquid membranes

This paper details experimental trials of aconitic acid transport from defined mixtures of organic acids (trans‐aconitic, oxalic, malic and citric) and from cane molasses solutions using a supported liquid membrane (SLM) apparatus. The SLM was impregnated with tributyl phosphate extractant combined with Shellsol 2046 diluent. The transport rates of the organic acids, bulk impurities and glucose were measured. The conditions varied were: extractant to diluent ratio (1:3–3:1), organic acid concentration (2.5–40 mg cm^?3 organic acid), pH of departure phase (1–5.5) and temperature (22–80 °C). Results for the organic acid mixtures showed that aconitic acid and oxalic acid were transported at much greater rates than malic and citric acids. Aconitic acid was transported to a significant degree with recovery of 400 g kg^?1 over a 24 h period. Operation at temperatures higher than 22 °C caused instability of the membrane and bulk leakage across the membrane. With molasses, the purity of the aconitic acid recovered ranged between 400 and 600 g kg^?1 (dry basis) with aconitic acid transport rates of 0.17–0.25 g m^?2 min^?1. The extraction of other acids (oxalic, malic and citric) and impurities was significantly less, hence a process to produce high purity aconitic acid based on this method is technically feasible. © 2002 Society of Chemical Industry     

Synergistic Solvent Extraction and Transport of Zn(II) and Cu(II) across Polymer Inclusion Membranes with a Mixture of TOPO and Aliquat 336

Separation of zinc(II) and copper(II) ions from aqueous solutions by synergistic extraction and transport through polymer inclusion membranes (PIMs) has been investigated. A mixture of trioctylphosphine oxide (TOPO) and trioctymethylammonium chloride (Aliquat 336) was used as a selective extractant as well as an ion carrier in polymer membranes. The effects of hydrochloric acid concentration in the aqueous phase and extractants concentration in the organic phase on the separation process of zinc(II) and copper(II) ions have been studied. Zn(II) ions were successfully separated from Cu(II) ions in solvent extraction process using 0.025 M TOPO and 0.06 M Aliquat 336 in kerosene. Polymer inclusion membranes (PIMs) containing a mixture of TOPO and Aliquat 336 as the ion carrier have been prepared and the facilitated transport of Zn(II) and Cu(II) ions has been studied. The influence of membrane composition on the transport kinetic of Zn(II) and Cu(II) has been evaluated. Zn(II) ions were preferably transported from the aqueous solutions containing Cu(II) and above 87% of Zn(II) ions were effectively recovered from the 0.5 M HCl solution as the source phase through PIM into 0.5 M H₂SO₄ as the stripping phase.     

Separation of Silver(I) and Copper(II) from Aqueous Solutions by Transport through Polymer Inclusion Membranes with Cyanex 471X

In this work the selective transport of silver(I) and copper(II) ions from aqueous nitrate(V) solutions by transport through polymer inclusion membrane (PIM) has been studied. The membrane consisted of cellulose triacatate (CTA) as the polymeric support, o-nitrophenyl pentyl ether (ONPPE) as the plasticizer and Cyanex 471X (triisobutylphosphine sulphide) as the ion carrier. Ag(I) ions were effectively removed from the source phase by transport through PIM into 0.01 M Na₂S₂O₃ as the receiving phase. The influence of membrane composition on the transport of silver(I) ions has been evaluated.     

Performance improvement of direct methanol fuel cells via anodic treatment using various organic acids

Performance improvement of direct methanol fuel cells (DMFCs) was achieved via an anodic treatment technique. Previously, anodic treatment was performed using sulfuric acid as acidic media, but various organic acids including formic, acetic, oxalic, and citric acids were employed in this study to avoid the use of toxic sulfuric acid. By replacing sulfuric acid to organic acids, a potential damage to catalyst layers and other components such as polymer electrolyte membrane and bipolar plates are expected to be minimized. The anodic treatment was performed by applying 0.7 V (vs. reversible hydrogen electrode) at the anode of DMFCs flowing the organic acid solutions for 30min. After the anodic treatment, peak power densities of DMFCs were increased by +7, +32, +23, and ?2.6% when formic, acetic, oxalic, and citric acid solutions were employed, respectively. The enhanced catalytic activity of the DMFCs in the acetic and oxalic acid solutions was confirmed by analyzing electrochemical impedance spectroscopy data.     

PVC/D2EHPA聚合物包容膜对水相中苯酚的分离

以二-(2-乙基己基) 膦酸(D2EHPA,P204)为载体,制备了聚氯乙烯(PVC)为膜基材的系列聚合物包容膜(PD-PIM),用FTIR、XRD及AFM表征了PD-PIM的化学组成、结晶行为和微观形貌.以渗透系数和渗透通量为指标,考察了PD-PIM膜中载体含量、料液相浓度和pH,以及解析相中盐酸浓度对PD-PIM分离苯酚的影响,探讨了实验条件下苯酚通过PD-PIM的传输机制.结果表明:在实验设定的范围内,PD-PIM对苯酚的传质通量随PD-PIM中载体质量分数、料液相中苯酚浓度的增加而增大,并在料液相苯酚浓度为400 mg·L^-1、pH=6,解析相盐酸浓度为0.1 mol·L^-1,载体P204含量为70%(质量)时达到最佳分离效果.PD-PIM对苯酚的传输机制为促进耦合迁移,初期传输符合一级动力学方程.重复使用实验证实PD-PIM具有较高的稳定性.     

Amelioration of ultrafiltration process by lime treatment: Case of landfill leachate

Nowadays membrane ultrafiltration process is generally used in effluents treatment. However, at industrial level, this process has major limitations such as important membrane fouling. In this study, a pre-treatment with lime upstream ultrafiltration was envisaged. The effluent considered is landfill leachate. The final waste storage centres produce leachates resulting from the percolation of waters through the hidden waste mass. These effluents strongly charged in mineral and organic matters, must be treated before their release into natural environment. Concerning the cleaning up, results have shown that the selectivity of membranes has an important influence on elimination of pollution from organic source. As expected, any action of retention on salts and heavy metals has been shown. During the filtration of raw leachate, the fouling of membranes turns to be very important and does not allow reaching satisfactory productivity no matter the cut-off limit. There seems to be no impact from hydrodynamics on velocity circulation higher than 4 m s^− 1; this shows the existence of a dense and adhesive deposit on the membrane. The pre-treatment by lime allows (i) to precipitate carbonates under calcium carbonates form and ii) to eliminate by co-precipitation humic acids that are responsible for irreversible membrane fouling. Industrially, the implementation of the pre-treatment may allow reducing the costs of an ultrafiltration unit at about 50% in terms of investment and from 5 to 30% for operating costs.     

Study of the structure and transport of asymmetric polyamide membranes for reverse osmosis using the electron spin resonance (ESR) method

The electron spin resonance technique (ESR) was used to study the structure and transport of asymmetric aromatic polyamide membranes. TEMPO (2,2,6,6-tetramethyl-1-piperridinyloxy free radical) was used as a spin probe that was brought into the membrane either by (a) immersion ofthe membranes in aqueous TEMPO solutions, (b) reverse osmosis (RO) experiments with feed solutions involving TEMPO or (c) blending TEMPO in casting solutions. The membranes were further tested for the separation of sodium chloride and TEMPO from water by RO. It was concluded that aromatic polyamide membranes contain water channels in the polymer matrix like cellulose acetate membranes. The presence of such water channels allows aromatic polyamide membranes to be used as RO membranes. The diffusion of organic solutes through the water channels seems much slower in aromatic polyamide membranes than in cellular acetate membranes, which probably causes a higher separation of organic solutes by aromatic polyamide membranes than cellulose acetate membranes. A comparison was made with other RO membranes (cellulose acetate, CA) and ultrafiltration membranes (polyethersulphone, PES). It was observed that the ESR technique can be used to study the structure of OF and RO membranes. The presence of water channels in the polymer matrix seems indispensable for the RO membrane.     

Effect of functional group of ferrocene redox substance on the transport properties of newly designed ion exchange membrane prepared from polymer gel

A different newly designed cationic exchange polymer membrane and anionic exchange polymer membrane were introduced, and also the transport properties of these polymeric membranes were investigated in this study. The transport properties of these polymer membranes in contact with ferrocene redox derivatives were estimated by using electrochemical techniques such as cyclicvoltammetry, chronopotentiometry, and chronoamperometry techniques, respectively. The used ferrocene redox substances, which have different functional groups, were (Ferrocenylmethyl) trimethylamonium iodide, FcMA, Ferrocenedimethanol, FcDM, and Ferrocene carboxylic acid, FcCA. It indicated that the performance of a membrane depended on the content of polymer gel, anionic exchange polymer site (20 wt % and 50 wt %) or cationic polymer exchange site (20 wt % and 50 wt %), and the efficiency of the functional groups of cationic and anionic exchange polymer site as well. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

固体聚合物电解质对质子交换膜燃料电池

燃料电池是一种通过电极催化反应过程将化学能直接转化为电能的发电装置．燃料电池反应器是借助于电极催化反应过程实现化学品一电能共生的新型反应器类型．随着燃料电池技术的不断进步,燃料电池反应器已经成为燃料电池应用研究的一个新方向．     

Characterization of gas permeation in the pores of Zn(II)-based metal organic framework (MOF)/polymer composite membranes

ABSTRACT

The separation of greenhouse gases from industrial processes is an ongoing focus for research aimed at mitigating environmental impacts. As a result, it is important to develop experimental techniques for the characterization of the transport of gases through porous crystalline materials with potential applications in gas separations. We report on the fabrication and characterization of gas transport in supported Zn(II)-based MOF membranes. The MOF membranes were used to develop an approach to study membrane quality and determine the transport mechanism through the pores of the crystalline membrane. Membranes were synthesized via a solvothermal method with structural defects sealed by a low-permeability polymer coating, allowing for the measurement of permeation in materials that do not form uniform, defect-free films. Membrane permeation was proportional to the inverse square root of the molecular weight of the permeant gases, indicating that diffusion occurs via Knudsen diffusion. Membrane quality was studied via selectivity measurements as a function of temperature. A study of the gas permeation through a polymer coated sparse MOF membrane, was used to confirm that gas transport occurs through the pores of the MOF, rather than through pinholes or defects in the structure.     

PVC塑料复合材料的热性能和电导率的研究

实验测定了聚氯乙烯-多壁碳纳米管(PVC/MWNT)复合材料在直流、交流条件下的热性能和电导率。采用热压缩法制备了PVC/MWNT复合材料,实验结果显示:材料存在超低渗透阈值(φc)0.045%。电导率对温度的依赖关系表明,在PVC/MWNT复合材料中,离子电导率低于φc,而复合材料中沿MWNT相的电荷输运的电子类型高于(φc)。热力学分析表明,在聚合物基体的体积内形成了一个刚性的填充网络,限制了聚合物向塑性状态的转变。     

Effect of Residual Solvent on Physicochemical Properties of Poly(Phenylene Isophtalamide) Membrane

The influence of a plasticizer in the form of the residual solvent dimethylacetamide on pervaporation and sorption properties of membranes based on poly(phenylene isophtalamide) (PA) was investigated. To analyze the influence of the plasticizer on membrane transport properties, pervaporation of binary water–ethyl acetate mixtures was studied. The method of sorption calorimetry was used to investigate water sorption properties of the studied membranes and PA powder. Moreover, to characterize the PA membranes, contact angle measurements and thermogravimetric analysis (TGA) were applied. It is shown that the presence of a residual organic solvent significantly changes the sorption and transport characteristics of the membranes. The residual organic solvent increases the amount of water absorbed by the polymer membrane. In pervaporation of water/ethyl acetate mixtures, the presence of the residual solvent dimethylacetamide makes the membrane more permeable but less selective for water separation.     

Investigation of the adsorption and transport of natural organic matter (NOM) in ion-exchange membranes

The adsorption and transport characteristics of natural organic matter (NOM) in an ion-exchange (IX) membrane were investigated and the various methods to characterize the properties of NOM and the IX membrane were collectively evaluated in this study. NOM adsorption by an IX membrane is affected by both pH and ion strength. Under alkaline pH and low ionic strength, greater NOM adsorption can be expected. A good relationship was obtained between the amount of adsorbed NOM and the zeta potential. The NOM acids constituents are expected to be transported preferentially through an IX membrane during the electrodialysis (ED) process because of their negative charge density. However, the molecular mass of the NOM acids was too high to allow them to pass through the IX membrane pores, and this caused an accumulation or adsorption of the solutes on the membrane surface. A fractional-rejection method was applied to determine the apparent pore size distribution of IX membranes and the selectivity coefficient was used to calculate apparent charges of NOM. The major apparent pore size distribution (PDS) of the IX membrane used in this study lay in the range 100-200 mass units. The apparent charge of the NOM used was 5.5 (dimensionless).     

Highly Selective Extraction and Transport through a Bulk Liquid Membrane of L-Cysteine Using [K • DC18C6]+ Complexes

It is shown that dicyclohexyl-18-crown-6 (DC18C6) dissolved in chloroform can extract efficiently and selectively the anionic form of L-cysteine from aqueous solutions containing potassium ions. This ability depends on the aqueous phase pH and type of the salt used in this phase. Under optimized conditions L-cysteine can be quantitatively extracted into the organic phase. In such conditions there was no detectable extraction of amino acids tryptophan, tyrosine, leucine, methionine, arginine, asparagine, aspartic acid, glycine, serine, and threonine. The transport of L-cysteine from potassium chloride/potassium hydroxide solution across a bulk liquid membrane containing DC18C6 dissolved in chloroform has been investigated. The parameters influencing the transport efficiency such as the pH of the feed phase, the kind and concentration of the receiving phase, carrier concentration, the kind of organic diluents, and time were examined and optimized. An efficient stripping at the membrane/stripping phase interface was found using hydrochloric acid as strippant. Selectivity of the proposed system was evaluated by performing a series of competitive transport experiments on the binary mixtures containing L-cysteine with the competitor amino acids noted earlier. This investigation exhibits excellent transport selectivity of the process towards L-cysteine with respect to the examined amino acids.     

Pervaporation membranes based on imide‐containing poly(amic acid) and poly(phenylene oxide)

Three imide‐containing poly(amic acids) were synthesized and used for homogeneous and composite membrane preparation. The transport properties of composite membranes consisting of an imide‐containing poly(amic acid) top layer on an asymmetric porous poly(phenylene oxide) support were studied in the pervaporation of aqueous solutions of organic liquids (ethanol, isopropanol, acetone, and ethylacetate) and organic/organic mixtures (ethylacetate/ethanol, methanol/cyclohexane). For most of the aqueous/organic mixtures, the composite membranes exhibited dehydration properties. Dilute aqueous solutions of ethylacetate were an exception. In these solutions, the composite membranes exhibited organophilic properties, high permeability, and selectivity with respect to ethylacetate. In the pervaporation of methanol/cyclohexane mixtures, methanol was removed with very high selectivity. To account for specific features of pervaporation on the composite membranes, the sorption and transport properties of homogeneous membranes prepared from polymers comprising the composite membrane [imide‐containing poly(amic acids) and poly(phenylene oxide)] were studied. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2361–2368, 2003     

Studies on Syntheses and Permeabilities of Special Polymer Membranes. 59. Active Transport of Organic Ions through Crosslinked Chitosan Membrane

Abstract

Active transport of organic ions such as benzenesulfonate and benzoate ions and amino acids was studied through a chitosan–PVA membrane under various conditions. The organic anions of benzenesulfonate and benzoate ions were actively transported through the chitosan–PVA membrane from the acidic side to the alkaline side, but the active transport of amino acid occurred from the alkaline side to the acidic side. These active transports were significantly dependent on a pH difference and electric potential difference between the two sides of the membrane     

Electrical,mechanical, and crystallization properties of ethylene‐tetrafluoroethylene copolymer/multiwalled carbon nanotube composites

Multiwalled carbon nanotubes (MWCNTs) were melt‐mixed in a conical twin‐screw extruder with a random copolymer of ethylene and tetrafluoroethylene. Surprisingly, the electrical percolation threshold of the resultant composites was quite low; ～0.9 wt %. In fact, this value is as low or lower than the value for most MWCNT/semicrystalline polymer composites made with roughly equivalent aspect ratio tubes mixed in a similar manner, for example, melt mixing. This low percolation threshold, suggestive of good dispersion, occurred even though the polymer surface energy is quite low which should make tubes more difficult to disperse. Dynamic mechanical measurements confirmed the rather low percolation threshold. The effect of nanotubes on crystallization kinetics was quite small; suggesting perhaps that a lack of nucleation which in turn reduces/eliminates an insulating crystalline polymer layer around the nanotubes might explain the low percolation threshold. Finally, the modulus increased with the addition of nanotubes and the strain at break decreased. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41052.     

Analysis of Extraction of Cu(II) by Strip Dispersion Hybrid Liquid Membrane (SDHLM) using PMBP as Carrier

A liquid membrane system, denoted a strip dispersion hybrid liquid membrane (SDHLM) containing 1‐phenyl‐3‐methyl‐4‐benzoyl‐pyrazolone –5 as carrier in xylene, was reported for the transport and separation of Cu(II) from Zn (II) ions. The effects of various factors on the transport of copper(II) ions through SDHLM were systematically investigated by orthogonal tests. The optimum transport conditions of copper ions were summarized. In the overall mass transfer process the mass transfer resistance due to the aqueous boundary layer diffusion and diffusion in the microporous membrane is dominant. The accumulation of the Cu(II)‐carrier coordination compound in the membrane shows that the transfer in SDHLM possesses the characteristic of nonequlibrium mass transfer in this study. The rheologic experiments verified that the organic phase in the SDHLM system was the non‐Newtonian fluid and the organic phase after transport of 6 hr was a system of thixotropy in our experimental conditions. The lag ring experiments proved that the thixotropy of the organic phase in the SDHLM system was relevant to the composition of the membrane. In the experimental comparison of two types of liquid membrane, SDHLM has superiority over SLM in respect of transport flux, permeability coefficient, recovery percentage or concentration of solute in the stripping solution, efficiency of uphill transport, loss of membrane solution, and the separation efficiency of the membrane.     

Characterizations of Colloidal Organic Matter Isolated from Surface Water

Abstract

This study investigated the effect of the molecular weight cut-off (MWCO) of a dialysis membrane for the isolation of colloidal organic matter (COM) from surface water. Various dialysis membranes with different MWCO were used for the isolation of COM from Cebron reservoir natural organic matter (CRNOM). The COM included mainly amino sugars (30 ～ 40%) and polysaccharides (30 ～ 40%), with 2 ～ 3 of fatty acids over aromatic acids (F/A ratio), indicating that the COM were derived from microbial substances. As all the COM constituents were found to have similar characteristics, the MWCO of the dialysis membrane was not found to influence the COM characteristics.