Anion Exchange Resin Membrane Research Articles

Soil properties affecting phosphorus extraction from Portuguese soils by conventional and innovative methods

The conventional Bray 1, Égner‐Riehm, Olsen, and the innovative cation/ anion exchange resin membranes (CAERM) and iron oxide‐impregnated filter paper strips (Pi) procedures were compared as phosphorus (P) extradants from 73 represîntative Portuguese soils. The soils were characterized by wide variability of their pedological, physical, and chemical properties. Eleven FAO‐UNESCO soil units, with prevailing Anthrosol, Calcisol, Cambisol, Fluvisol, Leptosol, Luvisol, and 10 different textural classes, with prevailing loamy sand, sandy loam, loam, silty loam, clay loam, silty clay loam, were recognized. The soils showed the following properties: CaCO3 0.0–50.9 g100 g‐1, organic matter 0.4–8.4 g 100 g‐1, pH‐CaCl2 3.9 to 7.9, cation exchange capacity 1.5–57.6 cmolc kg‐1 Soil‐P (mg kg‐1) ranges were: 0.2–185.9 for Bray 1, 0.6–307.7 for Égner‐Riehm, 1.0–100.5 for Olsen, 1.1–69.4 for Pi, and 0.4–48.8 for CAERM. The P extraction efficiency decreased along with the order Bray 1 > Égner‐Riehm > Olsen > Pi > CAERM, with mean values of 39.7, 34.6, 20.5, 19.0, and 14.8 mg P kg‐1 soil, respectively. All methods, with the relevant exception of Égner‐Riehm, were almost uniformly affected by the considered pedological, chemical and physical features of soils, and well correlated each other. The following conversion equations, by simple linear regressions, were calculated: Olsen‐P=4.118+0.412*Bray 1‐P, R2=0.737; Olsen‐P=‐1.300+1.144*Pi‐P, R2=0.677; Olsen‐P=0.760+1.330* CAERM‐P, R2=0.559; Bray 1‐P=‐3.064+2.249*Pi‐P, R2=0.602; Bray 1‐P=‐0.630+2.722*CAERM‐P, R2=0.538; Pi‐P=3.417+1.053*CAERM‐P, R2=0.677. After performing multiple regressions including the CEC as accessory variable, we obtained significant equations only for the conversions between Égner‐Riehm‐P and Pi‐P or CAERM‐P values, as it follows: Égner‐Riehm‐P=‐24.600+1.630*Pi‐P+1.928*CEC, adj. R2=0.587; Égner‐Riehm‐P=‐23.303+2.183*CAERM‐P+1.747*CEC, adj. R2=0.606. Thus, the innovative Pi‐strips and the cation/anion exchange resin membranes procedures could represent suitable tools for the assessment of soil‐P status and for P fertilizer recommendations. As the future research step, we will verify the reliability of the contrasted soil‐P tests in predicting plant P uptake and yield response.

Impact of tillage and landscape position on nitrogen availability and yield of spring wheat in the Brown soil zone in southwestern Saskatchewan

Nitrogen availability to a spring wheat crop was examined in the cropping season in a side-by-side comparison of no-till (first year) and tillage fallow in an undulating farm field in the Brown soil zone in southwestern Saskatchewan. Thirty different sampling points along a grid in each tillage landscape were randomly selected, representing 10 each of shoulder, footslope and level landscape positions. Nitrogen availability was studied i) by profile inorganic N content ii) by crop N uptake and yield of spring wheat (Triticum aestivum L.) and iii) by 15N tracer technique and in situ burial of anion exchange resin membranes (AEM).Pre-seeding available moisture content of the surface soil samples was significantly higher under no-till compared with tillage fallow. However, no significant differences in pre-seeding profile total inorganic N, crop N uptake and yield were observed between the treatments. At the landform scale, shoulder positions of the respective tillage systems had lower profile inorganic N, crop N uptake and yield compared with other slope positions. Soil N supply power, as determined by 15N tracer and AEM techniques, was not significantly different between the tillage treatments, indicating that N availability is not likely to be greatly affected in initial years by switching to no-till fallow in these soils under normal moisture conditions. Key words: Summerfallow, landscape, nitrogen, wheat

Phosphorus extraction by anion exchange membranes (AEM) in Andisols

Phosphorus (P) extraction by anion exchange resin membranes (AEM, IONICS) was studied in two Andisols from a greenhouse experiment with corn (Zea mays L.). Membranes were sequentially eluted with sodium chloride (NaCl) and sodium bicarbonate (NaHCO3). More P was extracted in the later. Resin eluents were fractionated for P and the different P fractions were correlated with crop yield. In the NaCl eluents, iron (Fe) and silicon (Si) were detected. In addition, aluminum (Al) and organic carbon (OC) were found in the bicarbonate eluents. Strong correlations were observed between P, Al, and OC in the resin eluents corresponding to the different P treatments. Phosphorus increased with OC and Al, suggesting that added inorganic P had reacted with complexes of the type: humus‐Al‐OH (to humus‐Al‐P), and that soil adherence to membranes were not aleatory.

Anion and cation exchange resin membranes to assess the phosphorus status of some Portuguese soils

Ion exchange resin methods were applied to 78 different soils to assess their phosphorus (P) status for predicting their response to P fertilization. The techniques used were anion exchange resin membranes eluted with hydrochloric acid (HCl) (AEM) and cation‐anion exchange resin membranes eluted with HCl (CAEM‐HC1), sodium chloride (NaCl) (CAEM‐NaCl) or water with directly color development (CAEM‐H2O). Greenhouse studies were conducted with the same soils in order to validate laboratory data. Ryegrass was grown with two levels of P: nil and 150 mg P kg‐1 of soil. Results indicate that soil P levels are significantly correlated (p<0.001) if extracted with AEM or CAEM, both eluted with HCl, although the CAEM technique had extracted larger amounts of P. Concerning the type of elution, results did not show significant differences (p<0.05) between CAEM‐HC1 and CAEM‐NaCl, but both were significantly correlated (p<0.001) with the results obtained with CAEM‐H2O. All the techniques used to measure extractable P correlated significantly with relative yield and P uptake by ryegrass, showing their ability to predict soil P availability. Nevertheless, CAEM extraction had higher values of r2. Among the three techniques for elution, the levels of correlation with the biological parameters were equivalent. From these results, it was concluded that: (i) exchange resins, specially CAEM, is an accurate method to assess the P fertility status of soils, and (ii) the traditional step of elution can be avoided, allowing the process to be less time consuming, thus more suitable for routine use.

Developments in some aspects of reactive phosphate rock research and use in New Zealand

Summary. There has been over 50 years of use and research into the agronomic effectiveness of reactive phosphate rocks (RPR) directly applied to New Zealand pastures. In recent years RPR-carrying fertilisers made up about 16% of phosphatic fertiliser sales in the North Island of New Zealand. Most is applied, as maintenance fertiliser, to hill country sheep and beef farms. Use has been recommended on soils with pH &lt;6 and in annual rainfall regimes &gt;800 mm. This is based on the poor performance of Sechura phosphate rock in summer dry areas receiving &lt;750 mm of rainfall annually. Phosphate rocks that have more than 30% of their total phosphate soluble in 2% citric acid have been classed as ‘reactive’ and suitable for direct application. More recent research indicates that extraction with 2% formic acid, or a dissolution test performed in a simulated soil solution at a fixed pH, will provide improved measures of RPR quality. Field trials, undertaken by the New Zealand Ministry of Agriculture and Fisheries [MAF; now AgResearch Crown Research Institute (CRI)] and others, to evaluate the relative agronomic effectiveness of RPR versus soluble P fertilisers in adequate to marginally P-deficient soils have proven to be a painstaking task. Long periods (3–6 years) of fertiliser withdrawal were required for pasture growth on some soils to become significantly responsive to applied P. Only then did differences between P sources become significant. This problem has encouraged efforts to relate measurements of the extent of RPR dissolution in soils to their agronomic effectiveness. Three main modelling approaches have been used to achieve this objective: Kirk and Nye (1986a, 1986b, 1986c); Sinclair et al. (1993a); and Watkinson (1994b). These models are reviewed and their explanation of RPR dissolution in mowing trials tested. Components of each model have then been combined to produce models to predict the agronomic effectiveness of RPR. The development of P tests for soils receiving RPR-containing fertilisers is reviewed. Separate Olsen P test–yield response calibration curves are required for soils fertilised with soluble P fertilisers and soils fertilised with sparingly soluble P sources or soluble P in the presence of heavy lime applications. Whereas alkaline P tests such as Olsen or Colwell underestimate the amount of plant-available P in these soils, acid P tests such as Bray 1 are likely to overestimate the available P. Tests involving cation and anion exchange resin membranes appear to be more appropriate for soils with unknown histories of soluble P and RPR use and may permit the use of single calibration curves. Trends observed in Olsen P soil test values, from farms on the North Island of New Zealand that have a history (3–15 years) of RPR use are presented. A predictive dissolution model is used to explain these trends but it is evident that spatial and temporal variation in soil test results on farmers’ paddocks will be a major constraint to the precision to which this or similar models may be used. The model, however, may provide the basis for sound advice on the strategic use of RPR for direct application to New Zealand pasture soils. It may prove useful in explaining the variation in RPR effectiveness in a wider range of climates and soils.

Assessment of soil phosphorus tests for situations in Australia where reactive phosphate rock and water-soluble phosphorus fertilisers are used

Summary. A selection of commonly used soil phosphorus (P) tests, which included anion and cation exchange resin membranes, were compared in a glasshouse experiment using subterranean clover, and evaluated in the field at 19 sites from the National Reactive Phosphate Rock Project in 1993 and at 6 sites in 1995. The ability of the soil P tests to predict plant response was used to evaluate the tests. In the glasshouse experiment the resin test was less effective than the Bray 1 and Colwell tests in its ability to assess the level of plant-available P from the different fertiliser treatments. Seventy-one percent of the variation in total P content of the subterranean clover shoots was explained by resin-extractable P values, whereas the Colwell procedure accounted for 81% and the Bray 1 procedure accounted for 78%. Water and CaCl2 extracts were poor predictors of P content. In the field experiments all tests evaluated performed poorly in describing the relationship between soil test P and the level of P applied and relative yield and soil test P over a wide range of soil types and environments. The Bray 1 procedure performed best but the relationship was poor.

Crop nitrogen utilization and soil nitrate loss in a lettuce field

Low N use efficiency and high nitrate (NO 3 - ) pollution potentials are problems in intensive vegetable production systems. The purpose of this study was to quantify N utilization by lettuce (Lactuca sativa L. cv Salinas), and identify periods of NO 3 - loss in an on-farm study in the Salinas Valley in coastal California. During autumn and winter, surface moisture remained low, and NO 3 - concentrations increased, reflecting high net mineralizable N, as determined by anaerobic incubation, and nitrification potential, as determined by the chlorate inhibition method. At the onset of a large winter storm, tracer levels of15NO 3 - were injected in the top 5 mm of soil in 30 cm-deep cylinders. After two weeks, most of the15N was present as15NO 3 - at 10–30 cm depth. By difference, losses to denitrification accounted for ~ 25% of the surface-applied15N. Leaching below 30 cm did not occur, since no15N enrichment of NO 3 - -N was measured in anion-exchange resin membranes placed at the base of each cylinder. During the crop period, NO 3 - losses were most pronounced after irrigation events. Uptake of N by two crops of lettuce (above- and belowground material) was approximately equal to fertilizer inputs, yet simulation of N fates by the Erosion/Productivity Impact Calculator (EPIC) model indicated losses of 14.6 g-N m−2 by leaching and 2.5 g-N m−2 by denitrification during the 6-month crop period. The large NO 3 - losses can be attributed to accumulation of soil NO 3 - during winter that was leached or denitrified during the irrigated crop period.

Dual solution-type HCHO fuel cell systems using an anion exchange resin membrane with electroless-plated Cu or Pd anode

Loading characteristics of a prototype HCHO fuel cell systems with an anion exchange membrane which separates the anolyte from the catholyte were investigated. Electrodes of Cu or Pd, deposited by an electroless-plating technique onto the membrane, showed high electrocatalytic activity to the anodic oxidation of HCHO in 1 M NaOH solution. The system with Cu anode and 1 M NaOH for both anolyte and catholyte showed high loading characteristics but poor durability, whereas that with 1 M K2CO3 showed low characteristics because of lowered pH of the anolyte. It was shown that a dual solution-type cell with 1 M K2CO3 anolyte and 1 M NaOH catholyte yielded improved characteristics as compared with the simple K2CO3 system. The output level was, however, at an unsatisfactory level owing to poor membrane conductance. The temperature dependence of the output performance was studied in the range 7–55°C.

Anion Selective Electrode for High Performance Liquid Chromatography Detector Based on Oleophilic Anion-Exchange Resin Membrane

A system is described for the separate determination of anions using HPLC with a potentiometric detector based on an ion selective electrode (ISE). The ISE consists of an oleophilic anion-exchange resin membrane impregnated with an organic solvent. A sodium sulfate solution containing a trace level of a primary ion for the electrode was used as an eluent. Sensitivity and selectivity of the ISE detector varies with a solvent species imbibed in the detector membrane and an ionic form of the membrane. Chromatograms for oxyacid anions (lO3-, BrO3-, ClO3- and NO3-) are shown, and relationships between chromatographic sensitivity and selectivity coefficients of the ISE detector are discussed.

A Reinforced Oleophilic Anion-exchange Resin Membrane as a Sensitive Membrane of Anion-selective Electrodes

Abstract Based on an impregnation technique for the preparation of ion-exchange resin membranes, a simple way was proposed for the preparation of a reinforced oleophilic anion-exchange resin membrane as an anion-selective electrode membrane with a chemically fixed site. The resulting exchange resin membrane is thin (ca. 25 μm) and flexible. It gives anion-selective electrodes with high performances.

Preparation of macroreticular-type oleophilic anion exchange resin membrane and its permselectivity to halides and thiocyanate

Macroreticular-type oleophilic anion exchange resin membranes containing high-molecular-weight ammonium ions such as tri-n-octylbenzylammonium and tri-n-dodecylbenzylammonium as fixed site were freshly prepared. These membranes were wetted well with water-immiscible organic solvents even in aqueous surroundings. The properties of the membrane, i.e. porosity, water and organic solvent content, capacity and conductivity were determined. The permselectivity of the membrane impregnated with nitrobenzene or o-nitrophenyloctylether to halide and thiocyanate ions was evaluated by measurement of bi-ionic membrane potential and electrodialysis. p]The sequence of the permselectivity was Cl − < Br − < I − < SCN −, and was consistent with the Hofmeister anion series. The value of the permselectivity was 10–100 times larger than that of usual hydrophilic anion exchange membranes. It was found that the permselectivity of the present membrane was strongly dependent on the separation factor, which was in turn affected by the hydrophobicity of the membrane. The effect of the ion association between fixed ion-exchange site and counter ion on the specific conductance of the membrane was also discussed.

Anion-selective electrode based on oleophilic anion exchange resin membrane

Anion-selective electrode based on oleophilic anion exchange resin membrane

Measurement of Anion Activity in Electrolytic Solutions with Anion-exchange Resin Membrane Electrodes

Measurement of Anion Activity in Electrolytic Solutions with Anion-exchange Resin Membrane Electrodes