Developing a novel alkaline anion exchange membrane derived from poly(ether‐imide) for improved ionic conductivity

We have developed a novel alkaline anion exchange membrane derived from poly(ether‐imide) for improved ionic conductivity. The effects of several important parameters on the chloromethylation of the membrane were investigated. These parameters included reaction temperature, reaction time, concentration of chloromethylation agent, concentration of polymer, and the amount of catalyst. The quaternization of the synthesized chloromethylated polymer was studied as well. The results show that all the studied parameters exhibited significant impacts on chloromethylation. Among them, the concentration of the chloromethylation agent played a key role in increasing the chloromethyl functional group attachment onto the polymer. It was found that the gelation could be avoided if these reaction parameters were controlled. It was also found that using an appropriate quaternization approach could significantly improve the ionic conductivity and optimize the conductivity of the membrane even though the functional chloromethyl groups attached to the polymer are limited. Copyright © 2009 John Wiley & Sons, Ltd.     

A new biosynthetic tracer for the inline measurement of virus retention in membrane processes: part II. Biochemical and physicochemical characterizations of the new tracer

In a previous work, a reproducible procedure to produce a new biosynthetic tracer was developed. This new tracer is an MS2 bacteriophage with enzymatic probes grafted on its surface, which can induce enzymatic activity of the tracer. In this paper, the biochemical and physicochemical characteristics of this new tracer are determined. A protocol was developed to determine the specific enzymatic activity kcat_TRACER of the tracer, which was found to be 2.93 ± 0.78 × 10⁴ min⁻¹ on average. Physicochemical characterizations of this new tracer showed that it is representative of viruses and may thus be used as a virus surrogate to assess the virus retention of membrane systems inline. Notably, the mean diameter and molecular weight of the tracer were found to be respectively 64.1 ± 0.3 nm and 12140 ± 3654 kDa, which are within the size and molecular weight ranges of pathogenic viruses carried by water. The tracer surface was also studied and revealed the considerable porosity of the grafted probe layer, with a mean porosity of 88%, which could explain why the zeta potential of the tracers (−14.34 ± 1.66 mV) was nearly the same as that of the native MS2 phages. Finally, a comparison between filtration of the reference microorganism used for membrane performance assessment (the MS2 phage) and the tracer suspensions showed the same filtration behaviour.     

A new biosynthetic tracer for the inline measurement of virus retention in membrane processes: part I--Synthesis protocol

In this study, a new biosynthetic tracer was developed to characterize the virus retention dynamics of membrane systems. This new tracer is a modified bacteriophage obtained by the grafting of enzymatic probes to an MS2 bacteriophage, one of the smallest non-pathogenic bacteria viruses, with an average diameter of about 30 nm. A protocol for the synthesis and purification of this new tracer was developed in this work. The production of this biosynthetic tracer was first qualitatively shown by a chromatographic characterization and an enzymatic test. The average number of probes grafted per phage was then quantified for three batches of tracers made from the same native phage suspension and the same batch of enzymatic probes. This quantification demonstrated the reproducibility of the synthesis protocol developed.     

Numerical Accuracy of Ladder Schemes for Parallel Transport on Manifolds

Parallel transport is a fundamental tool to perform statistics on Riemannian manifolds. Since closed formulae do not exist in general, practitioners often have to resort to numerical schemes. Ladder methods are a popular class of algorithms that rely on iterative constructions of geodesic parallelograms. And yet, the literature lacks a clear analysis of their convergence performance. In this work, we give Taylor approximations of the elementary constructions of Schild’s ladder and the pole ladder with respect to the Riemann curvature of the underlying space. We then prove that these methods can be iterated to converge with quadratic speed, even when geodesics are approximated by numerical schemes. We also contribute a new link between Schild’s ladder and the Fanning scheme which explains why the latter naturally converges only linearly. The extra computational cost of ladder methods is thus easily compensated by a drastic reduction of the number of steps needed to achieve the requested accuracy. Illustrations on the 2-sphere, the space of symmetric positive definite matrices and the special Euclidean group show that the theoretical errors we have established are measured with a high accuracy in practice. The special Euclidean group with an anisotropic left-invariant metric is of particular interest as it is a tractable example of a non-symmetric space in general, which reduces to a Riemannian symmetric space in a particular case. As a secondary contribution, we compute the covariant derivative of the curvature in this space.

     

Preparation of alkaline anion exchange membranes based on functional poly(ether-imide) polymers for potential fuel cell applications

A novel poly(ether-imide)-based alkaline anion exchange membrane with no free base has been prepared and characterized for its ionic conductivity in water, which is a critical metric of its applicability in a liquid-fed direct methanol fuel cell. The poly(ether-imide)-based membranes were prepared by chloromethylation, quaternization and alkalization of commercial poly(ether-imide) and the derivatives were characterized by NMR. The chemical and thermal stabilities were investigated by measuring changes of ionic conductivities when the membranes were placed in various alkaline concentrations and temperatures for 24 h. The membranes were stable at all concentrations of KOH at room temperature, but not at elevated temperatures. The membranes were stable in 1.0 M KOH solution up to 80 °C without losing membrane integrity. The measured conductivity of the formed membrane ranged from 2.28 to 3.51 × 10⁻³ S/cm at room temperature. This preliminary study indicates that functionalized poly(ether-imide) has suitable conductivity suggesting that it can be used as an alkaline anion exchange membrane in fuel cell applications.     

Hydrated Eutectic Electrolytes Stabilizing Quasi-Underpotential Mg Plating/Stripping for High-Voltage Mg Batteries

Aqueous rechargeable Mg batteries (ARMBs) usually fail from severe anode passivation, alternatively, executing quasi-underpotential Mg plating/stripping chemistry (UPMC) on a proper heterogeneous metal substrate is a crucial remedy. Herein, a stable UPMC on Zn substrate is initially achieved in new hydrated eutectic electrolytes (HEEs), delivering an ultralow UPMC overpotential and high energy/voltage plateau of ARMBs. The unique eutectic property remarkably expands the lower limit of electrochemical stability window (ESW) of HEEs and undermines the competition between hydrogen evolution/corrosion reactions and UPMC, enabling a reversible UPMC. The UPMC is carefully revealed by multiple characterizations, which shows a low overpotential of 50 mV at 0.1 mA cm⁻² over 550 h. With sulfonic acid-doped polyaniline (SPANI) cathodes, UPMC-based full cells show high energy/power densities of 168.6 Wh kg⁻¹/2.1 kWh kg⁻¹ and voltage plateau of 1.3 V, far overwhelming conventional aqueous systems.