Polyvinylamine-Based Facilitated Transport Membranes for Post-Combustion CO_(2) Capture:Challenges and Perspectives from Materials to Processes

Carbon dioxide(CO_(2))capture by gas-separation membranes has become increasingly attractive due to its high energy efficiency,relatively low cost,and environmental impact.Polyvinylamine(PVAm)-based facilitated transport(FT)membranes were developed in the last decade for CO_(2) capture.This work discusses the challenges of applying PVAm-based FT membranes from materials to processes for postcombustion CO_(2) capture in power plants and cement factories.Experiences learned from a pilot demonstration system can be used to guide the design of other membranes for CO_(2) capture.The importance of module and process design is emphasized in the achievement of a high-performance membrane system.Moreover,the results from process simulation and cost estimation indicate that a three-stage membrane system is feasible for achieving a high CO_(2) purity of 95 vol%.The specific CO_(2) capture cost was found to significantly depend on the required CO_(2) capture ratio,and a moderate CO_(2) capture ratio of 50%presented a cost of 63.7USD per tonne CO_(2) captured.Thus,FT membrane systems were found to be more competitive for partial CO_(2) capture.

PVA/PVP blend polymer matrix for hosting carriers in facilitated transport membranes: Synergistic enhancement of CO2 separation performance

CO2 separation performance in facilitated transport membranes has been reported depended not only on the CO2 carrier properties but also to a great extent on the polymeric matrix regarding the capacity of retaining water and carriers as well as the processability for coating defect-free ultra-thin films. In this study, the blends of hydrophilic polymers polyvinyl pyrrolidone(PVP) and polyvinyl alcohol(PVA) were studied to find an optimal polymer matrix to host carriers in facilitated transport membranes for enhanced CO2 separation. It is found out that the optimized blend is 50/50 PVA/PVP by weight, which shows a significant increase in the water uptake(from 63 to 84%) at equilibrium state compared to the neat PVA. Polyethyleneimine(PEI) was employed to provide sample carriers to evaluate the synergistic effect of PVA and PVP on the CO2 separation performance. A thin film composite(TFC) membrane of the optimized blend(50/50 PVA/PVP with 50 wt% PEI) was fabricated on polysulfone(PSf) porous support. The fabrication of the TFC membranes is simple and low cost, and CO2 permeance of the optimized blend membrane is nearly doubled with the CO2/N2 selectivity remained unchanged, showing great potential for industrial applications of the resulted membranes.

Enhancing CO_(2) transport with plasma-functionalized ionic liquid membranes

The ionic liquid(IL) 1-butyl-3-methylimidazolium tetrafluoroborate treated with radiofrequency plasma is proposed for functionalization and immobilization on polyethersulfone supports to form supported ionic liquid membranes for CO_(2) separation.The effects of treatment time and transmembrane pressure difference on CO_(2) permeance were evaluated.The best gas permeation performance was obtained with a treatment time of 10 min and the transmembrane pressure difference was 0.25 MPa.Characterization of the materials by Fourier transform infrared spectroscopy,x-ray photoelectron spectroscopy and nuclear magnetic resonance spectroscopy demonstrates that the IL is grafted with carboxyl groups and deprotonated through plasma treatment.A preliminary mechanism for the plasma treatment and facilitated transport of CO_(2)has been proposed on this basis.

Facilitated transport separation of CO_(2) and H_(2)S by supported liquid membrane based on task-specific protic ionic liquids

Selective separation of CO_(2) and H_(2)S from CH_(4) is of importance to the natural gas upgrading because of its cor-rosivity. As is well known, amine group can recognize reversibly CO_(2) and H_(2)S with a moderate interaction. Withthis in mind, this work prepared a series of amine-functionalized supported-protic-ionic-liquid membranes(SPILMs) for the selective separation of CO_(2) and H_(2)S from CH_(4) . For comparison, aprotic ionic liquid membranewas also prepared for natural gas sweetening. The effect of temperature and transmembrane pressure differenceon the permeability of single gas and ideal selectivity of CO_(2)/CH_(4) and H_(2)S/CO_(2) were studied. Facilitated transportmechanism was studied by NMR spectra. The permeability of CO_(2) in primary amine functionalized [DMPDAH][Tf_(2)N]-based membrane decreases with the increasing transmembrane pressure, indicating a typical feature offacilitated transport membrane. The permeability of CO_(2) and the ideal selective of CO_(2)/CH_(4) are as high as 2000 barrers and 53.2 at 313.2 K in [DMPDAH][Tf_(2)N] membrane, significantly higher than those in conventional ILsmembrane. It is anticipated that these amine-functionalized SPILMs can provide alternative insight for the se-lective separation of CO_(2) and H_(2)S from CH_(4) .

Elevated NKCC1 transporter expression facilitates early post-traumatic brain injury seizures

As a leading cause for morbidity and mortality in young adults,traumatic brain injury（TBI）,along with the poorly understood TBI-related seizures inducing their predispositions,pose a major health and socioeconomic problem in the world（Huang,2013）.

Effect of Hydrogen Reduction of Silver Ions on the Performance and Structure of New Solid Polymer Electrolyte PEI/Pebax2533/AgBF4 Composite Membranes

In this paper, the effect of hydrogen reduction of silver ions on the performance and structure of new solid polymer electrolyte polyetherimide （PEI）/Pebax2533 （Polynylonl2/tetramethylene oxide block copolymer, PA12-PTMO）/AgBF4 composite membranes is investigated. For PEI/Pebax2533/AgBF4 composite membranesprepared with dillerent AgBF4 concentration, the permeances of propylene and ethylene increase with the increase of AgBF4 concentration due to the carrier-facilitated transport, resulting in a high selectivity. But for propyl- ene/propane mixture, the mixed-gas selectivity is lower than its ideal selectivity. The hydrogen reduction strongly influences the membrane performance, which causes the decrease of propylene permeance and the increase of pro-pane permeance. With the increase of hydrogen reduction time, the membranes show a clearly color change from white to brown, yielding a great selectivity loss. The data of X-ray diffraction and FT-IR prove that silver ions are reduced to Ago after hydrogen reduction, and aggregated on the surface of PEI/Pebax2533/AgBF4 composite mem- branes.

Methyl Cholate and Resorcinarene New Carriers for the Recovery of Cr(Ⅲ) Ions by Supported Liquid Membranes (SLM)s

The technique of supported liquid membranes was used to achieve the facilitated transport of Cr(III) ions, using tow amphiphilic carriers, the methyl cholate and resorcinarene. For prepared SLMs, toluene as organic phase and film of polyvinylidene difluoride, as hydrophobic polymer support with 100 μm in thickness and 0.45 μm as the diameter of the pores. The macroscopic parameters (P and J0) on the transport of these ions were determined for different medium temperatures. For these different environments, the prepared SLMs were highly permeable and a clear evolution of these parameters was observed. The parameter J0 depended on the temperature according to the Arrhenius equation. The activation parameters, Ea, ΔH≠ and ΔS≠, for the transition state on the reaction of complex formation (ST) , were determined. To explain these results for this phenomenon, and achieve a better extraction of the substrate, a model based on the substrate complexation by the carrier and the diffusion of the formed complex (ST) was developed. The experimental results verify this model and determine the microscopic parameters (Kass and D*). These studies show that these parameters Kass and D* are specific to facilitated transport of Cr(III) ions by each of the carriers and they are changing significantly with temperature.

Improved Visa Service New application center in South Africa facilitates travels to China

New application center in South Africa facilitates travels to ChinaAfrica’s first Chinese Visa Application Service Center opened its doors in Johannesburg,South Africa,on March 17 after a whole year’s preparation.The 41st such service center,it is located in the upmarket Sandton City Office Tower building in the affluent northern suburbs,enjoying convenient transportation.Travelers to China,who previously needed to apply for a visa at the Chinese Embassy in Pretona or the Consulate General of China in Johannesburg, can now apply at the center, making the visa application process faster and more convenient. A senior visa officer at the Johannesburg consulate talked to ChinAfrica about the need for the center and how to apply there for a visa.

Continuous water-water hydrogen bonding network across the rim of carbon nanotubes facilitating water transport for desalination

The development of membranes featuring carbon nanotubes(CNTs)have provided possibilities of next-generation solar desalination technologies.For solar desalination,the microstructures and interactions between the filter membrane and seawater play a crucial role in desalination performance.Understanding the mechanisms of water evaporation and ion rejection in confined pores or channels is necessary to optimize the desalting process.Here,using non-equilibrium molecular dynamics simulations,we found that continuous water-water hydrogen bonding network across the rims of CNTs is the key factor in facilitating water transport through CNTs.With the continuous hydrogen bonding network,the water flux is two times of that without the continuous hydrogen bonding network.In CNT arrays,each CNT transports water molecules and rejects salt ions independently.Based on these observations,using CNT arrays consisted with densely packed thin CNTs is the most advisable strategy for evaporation desalination,possessing high transport flux as well as maintaining high salt rejection.

Effects of pressure and temperature on fixed-site carrier membrane for CO_(2) separation from natural gas

In this paper,the effect of testing temperature on the performance of fixed carrier membrane for CO_(2) separation were studied.The blend composite membranes were developed respectively with a blend of PEI-PVA(polyetheleneimine-polyvinyl alcohol)as separation layer and PS(polysulfone)ultrafiltration membranes as the substrates.The permselectivity of the membranes was measured with CO_(2)/CH_(4) mixed gas.The effect of testing temperature on membrane separation performance was investigated.The results showed that both the permeances of CO_(2) and CH_(4) decreased with the increase of temperature,and the permeances decreased more quickly under low pressure than those under high pressure.At the feed pressure of 0.11 MPa,the CO_(2)/CH_(4) selectivity of PEI-PVA/PS blend composite membrane reduced along with temperature increment.Under the feed pressure of 0.21 MPa,as well as 1.11 MPa,the selectivity decreased with the increase of temperature.