Use Of Anion Exchange Membrane Research Articles

Comparison of different types of membrane in alkaline direct ethanol fuel cells

It has been understood that the use of cation-exchange membranes (CEM) and alkali-doped polybenizimidazole membranes (APM) in alkaline direct ethanol fuel cells (DEFC) with an added base in the fuel exhibits performance similar to the use of anion-exchange membranes (AEM). The present work is to assess the suitability of the three types of membrane to alkaline DEFCs by measuring and comparing the membrane properties including the ionic conductivity, the species permeability, as well as the thermal and mechanical properties. The comparison shows that: (i) the AEM is still the most promising membrane for the alkaline DEFC, although the thermal stability needs to be further enhanced; (ii) before solving the problem of the poor thermal stability of AEMs, the CEM is another choice for the alkaline DEFC running at high temperatures (<90 °C); and (iii) the APM can also be applied to the alkaline DEFC operating at high temperatures, but its mechanical property needs to be substantially enhanced and the species permeability needs to be dramatically decreased.

The Use of Ion Exchange Membranes for Isotope Analyses on Soil Water Sulfate: Laboratory Experiments

To investigate the potential use of anion exchange membranes (plant root simulator [PRS] probes) for isotope investigations of the soil sulfur cycle, laboratory experiments were performed to examine the sulfate exchange characteristics and to determine the extent of sulfur and oxygen isotope fractionation during sulfate sorption and desorption on the probes in aqueous solutions and simulated soil solutions. The sulfate-exchange tests in aqueous solutions under varying experimental conditions indicated that the amount of sulfate exchanged onto PRS probes increased with increasing reaction time, initial sulfate concentration, and the number of probes used (= surface area), whereas the percentage of removal of available sulfate was constant irrespective of the initial sulfate concentration. The competition of nitrate and chloride in the solution lowered the amount of exchanged sulfate. The exchange experiments in a simulated soil under water-saturated and water-unsaturated conditions showed that a considerable proportion of the soil sulfate was exchanged by the PRS probes after about 10 d. There was no evidence for significant sulfur and oxygen isotope fractionation between soil sulfate and sulfate recovered from the PRS probes. Therefore, we recommend the use of PRS probes as an efficient and easy way to collect soil water sulfate for determination of its isotope composition.

TEMPORAL CHANGES IN NITRATE STATUS OF ORCHARD SOILS WITH VARYING MANAGEMENT PRACTICES

Two anion exchange membrane systems (Plant Root Simulator probes and Dynambio nitrate selective anion exchange membranes) were evaluated as tools to estimate temporal changes in nitrate nitrogen (NO3-N) in the topsoils of four central Washington, USA apple orchards. Various management practices and different growing conditions were studied in the four orchards. Higher NO3-N was associated with increasing amounts of fertigated N, larger irrigation events, and surface application of alfalfa hay mulch and /or dairy compost. Nitrate nitrogen adsorbed by the membranes was lower when actively growing roots were present in the vicinity of the membranes, suggesting that uptake of NO3-N by apple tree and cover crop roots decreased the concentration of NO3-N in the soil solution. Thus, in the presence of plant roots, the estimate of the amount of phytoavailable NO3-N in the soil provided by the anion exchange membranes may be ambiguous. On the other hand, if roots can be excluded from the immediate vicinity of the membranes, the NO3-N adsorbed by the membranes may estimate the phytoavailability of NO3-N in the soil solution. Because anion exchange membranes provide information about the amount of NO3-N remaining in the soil after plant roots have met their demand, the membranes may be useful for estimating relative potential for NO3-N leaching. In summary, sequential use of anion exchange membranes appears to provide valuable information about temporal changes in the supply of soil NO3-N with various orchard management practices.

Oxidation of carbaryl in aqueous solution by membrane anodic fenton treatment.

Carbaryl, a commonly used insecticide, was used in this study as a probe to investigate a new Fenton treatment technology, ion exchange membrane anodic Fenton treatment (membrane AFT). It was found that the degradation kinetics of carbaryl by membrane AFT obeys a previously published AFT model quite well. The NaCl (electrolyte) concentration in two half-cells was optimized for two kinds of membrane. Effects of the H(2)O(2)/Fe(2+) ratio and the Fenton reagent delivery rate were also investigated. The treatment efficiency for anion membrane AFT is higher than for salt-bridge AFT under the same operating conditions. Decreasing the delivery rate of Fenton reagents and increasing the treatment temperature also increase the treatment efficiency. The activation energy for carbaryl degradation by anion membrane AFT was estimated to be 14.7 kJ x mol(-1). 1-Naphthol, 1,4-naphthoquinone, and (phthalic acid-O-)yl N-methylcarbamate were detected by GC-MS as the degradation products of carbaryl by Fenton treatment. No decrease in carbaryl degradation rate was found during repeated use (100 times) of the anion exchange membrane. High and stable treatment efficiency can be achieved using an anion exchange membrane rather than a salt-bridge in the AFT system. Because of its effectiveness and convenience, the use of an ion exchange membrane as a substitute for the salt-bridge used in the previous AFT system has brought the AFT technology a major step closer to practical application.

Use of an ion-exchange membrane for sample pretreatment of ion chromatography: determination of phosphate ion and sulfate ion in deep subsurface water.

Use of an ion-exchange membrane for sample pretreatment of ion chromatography: determination of phosphate ion and sulfate ion in deep subsurface water.

Use of anion exchange membranes to assess nitrogen needs of perennial grasslands1

Anion exchange membranes (AEMs) have recently become available and have proven effective in measuring phosphorus present in soils as well as nitrate (NO3 ‐) under both cultivated and grassland field conditions. We have attempted to assess the ability of AEM strips to measure NO3 ‐ present under a perennial grassland harvested for hay three times during the growing season. In all cases, we found significant quadratic relationships between nitrogen (N) applied and NO3 ‐ desorbed from the AEM strips. Using both linear‐response‐and‐plateau (LRP) and quadratic‐plateau (QP) models, we found highly significant relationships to relative yield and the ability to predict a critical level (CL) of NO3 ‐‐N necessary to reach maximum yield during two harvest periods. The AEM strips provided a good correlation between NO3 ‐and N rate, and between NC3 ‐ and yield. Critical levels at which subsequent N would need to be applied in order to achieve maximum yield were identified. These need to be further field‐tested for consistency under differing environmental conditions.

Field evaluation of anion exchange membranes as a N soil testing method for grasslands

The in situ use of anion exchange membranes (AEMs) as a soil-testing procedure may provide a more precise evaluation of N availability to forages than standard methods. The main objective of this study was to evaluate the potential of AEMs to predict soil NO3–N availability for forage production in the western part of the province of Quebec, Canada. In 1995 and 1996, AEMs were buried (0–15 cm) in soils at four sites. The fertilizer treatments consisted of five NH4NO3 rates (0, 60, 120, 180, and 240 kg N ha–1). At all sites, NO3−sorbed on the AEMs (NO3AEMs) increased with increasing N fertilizer rates. The NO3AEMs fluxes were significantly related to water soluble NO3–N (NO3w) concentration in soil (R2 varied from 0.35 to 0.98) in the two growing seasons. Forage N uptake was better related with NO3AEMs fluxes (R2 = 0.88 and 0.92 in spring 1996 and 1995, respectively) than with NO3w concentration (R2 = 0.39 and 0.97 in spring 1996 and 1995, respectively). Based on their simplicity, rapidity, and low cost, AEMs have many practical advantages over water NO3–N extraction for assessing grass forage soil N availability in cool continental climates. Key words: Resin, nitrogen, N uptake, grass forage, N mineralization

Refinement of the Anion Exchange Membrane Method for Soluble Phosphorus Measurement

AbstractThe proper use of anion exchange membranes (AEMs) to assess phosphorus availability in situ requires a more thorough understanding of their function under a wide range of soil biophysical conditions. We evaluated the ability of AEMs to sorb selected organic P compounds, determined possible interference of low‐molecular‐weight organic acids and humic substances on AEM‐P sorption, and assessed the efficiency of AEM‐P sorption in the presence of wetland sediments and soil‐sediment microbes. We collected soils, swamp water, and sediments from a cypress swamp‐pine flatwoods ecosystem in north central Florida. Membranes recovered nearly 100% of both ortho and organic P in a study using aqueous solutions of ortho P and organic P compounds. Membrane sorption of ortho P with varying concentrations of oxalate and protocatechuate was close to 100%. There was a reduction of 15 µg P per membrane when AEMs were placed inside low‐molecular‐weight‐cutoff dialysis tubing (&lt;1000 MWCO) in P‐spiked swamp water; however, there was no significant tubing effect in non‐spiked swamp water. In an experiment exploring effects on AEM‐P sorption of P additions to swamp water with or without sediments, AEMs recovered six times more P than measured in non‐spiked swamp water with sediments. When swamp water was treated with chloroform, AEMs sorbed an equal or greater amount of ortho P than ortho P measured in swamp water with no AEMs. Results suggest that AEMs can be used to measure soluble and readily desorbable P in low‐P status soils and sediments with organic acids.

Measurement of soil microbial biomass phosphorus by an anion exchange membrane method

A method to measure soil microbial biomass phosphorus (biomass P) in granitic soils and andosols of high P retention capacity is described. Strips of anion exchange membrane (AEM) were shaken with suspensions of soil in (1) distilled water, (2) a mixture of distilled water and alcohol free chloroform (CHCl 3) liquid, and (3) a standard inorganic P solution (2.5 mg KH 2PO 4P1 −1), to estimate the recovery of CHCl 3-released P. After shaking, the AEM strips were rinsed with distilled water to remove the soils from the AEM strips. Phosphorus adsorbed by the AEM strips was then eluted by 0.5 m HCl, and determined colorimetrically. The amount of CHCl 3-released P was calculated from the difference between the amount of inorganic P adsorbed by AEM in unfumigated and fumigated soils. The high P retention capacity of soils, and the dark color of the extracts solution due to humic substances did not interfere with the measurement of P by this method. Biomass P was calculated from: biomass P = Ep Kp × 100 R , where Ep = (inorganic P released by CHCl 3 and extracted by distilled water) minus (inorganic P released from unfumigated soil), Kp = Biomass P released by CHCl 3 and extracted as inorganic P by distilled water (Kp = 0.40 at 25°C), R = percentage recovery (82.0–91.2%) of added P. Compared to the original CHCl 3-fumigation extraction (FE)-method, the AEM-method is simpler, more accurate, and more flexible, allowing assay of biomass P in soils of high P retention capacity, e.g. andosols. The use of AEM allows quick and efficient adsorption of P in the soil suspensions, and is analytically very convenient.

Determination of 2,4-D Amine in Soils Using Anion Exchange Membranes

A new method for the quantitative determination of 2,4-D in soils by use of anion exchange membranes with GC detection was developed. Preliminary investigation of ion exchange properties of pure 2,4-D acid on the membranes revealed that when a suitable solvent system is used, a quantitative recovery of 2,4-D acid can be achieved. Linear relationships between 2,4-D acid removed by the membrane and 2,4-D concentration in solutions and soils were obtained within the range tested. The developed method was successfully applied for the determination of 2,4-D amine from a commercial formulation applied on soil surfaces. The method was tested in two concentration ranges representing a typical farm-spraying application rate and a spill. The relationship between the amount of 2,4-D amine detected by membranes and the spike level on the soil surface was linear for both concentration ranges. The applicability of the method was examined for a degradation study of 2,4-D amine after a spill. The low detection limit and the simplicity of the procedure make this method very suitable for 2,4-D determination in soils

An electrochemical oxygen separator using an ion-exchange membrane as the electrolyte

An electrochemical oxygen separator based on oxygen reduction at an air cathode and oxygen evolution at an anode has been developed. The device features use of an ion-exchange membrane (Nafion 117) as the sole electrolyte and an air cathode mainly made of carbon. The anode was formed by chemically plating platinum (3.7 mgcm−2) on one side of the Nafion 117 membrane. The air cathode was bonded to the other side of the membrane by spraying a slurry of graphitized furnace black loaded with platinum, followed by hot-pressing. The addition of a Nafion solution and a PTFE dispersion to the slurry was essential. The ultimate loading of platinum for the cathode was 0.2 mg cm−2. An electrochemical oxygen separator with a working area of 100 cm2 was constructed. When the separator was used as an oxygen concentrator it could be operated at 200 mA cm−2 and produced 70.9 cm3 min−1 of oxygen with a purity of 98.4%. When the separator was used as a circulation-type oxygen removal system it reduced the oxygen concentration of a 10-dm3 chamber to less than 0.02% within 70min. When the separator was used as a flow-through-type oxygen remover, air with an oxygen concentration of 0.02% was produced at 100 cm3 min−1.

Use of ion exchange membranes in 81Rb/ 81mKr generators

The use of an ion exchange membrane as the retention medium for rubidium in a 81Rb/ 81 m Kr generator is evaluated. The ion exchange membrane was shown to be less subject to low yields due to drying than ion exchange resins when elution was with air or oxygen to supply 13-s 81 m Kr in the gaseous form. However, elution with dextrose solution in an endeavour to obtain the krypton in solution proved to be unsatisfactory due to leakage of the rubidium off the membrane.