Browsing by Author "Evans, JV"

Now showing 1 - 7 of 7
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    Cation-exchange removal of copper from ammoniacal aqueous solution
    (Australian Atomic Energy Commission, 1973-03) Bull, PS; Evans, JV
    This report examines the nature of the adsorbed copper-ammine species in the resin phase, evaluates their stability constants and compares them with published data obtained in aqueous solution. It extends the study of the adsorption of copper by a strong acid-cation exchanger to solutions containing low concentrations of ammonia (0-0.032 M), and copper (10-lfM) and differentiates between the role of the ammonium ion and the free ammonia in the ion-exchange process.
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    Corrosion of aluminium in pure water and dilute solutions
    (Australian Atomic Energy Commission, 1973-07) Berzins, A; Evans, JV; Lowson, RT
    An investigation into the corrosion of aluminium in flowing near-neutral water at 50 C is reported. The corrosion rate passed through a minimum as the pH was changed from pH 5.0 to 8.0. The pH at the point of minimum corrosion was sensitive to atmosphere, being highest in oxygen-saturated water. The corrosion rate was reduced and spallation of the oxide film prevented by saturating the water with oxygen.
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    Dynamic membranes
    (Institution of Chemical Engineers, 1975-08-20) Evans, JV
    Dynamic membranes are formed when water containing membrane-forming additives is circulated under pressure over a porous surface to deposit a thin membrane layer at the interface. In-situ procedures of this type have the potential advantage that membranes may be removed when performance becomes unsatisfactory and replaced without disassembly of equipment. Dynamic membranes are capable of a very high flux and, compared to conventional film membranes, hold promise of providing more economic processing, particularly for the high-fouling feeds often found in waste water treatment. Kraus, Johnson and co-workers at the Oak Ridge National Laboratory have investigated a range of ion exchange membranes dynamically prepared from organic polyelectrolytes including poly-acrylic acid, polyvinyl sulphonic acid, polyvinyl pyridine, and humic acid, and from inorganic polyelectrolytes formed from solutions of hydrolysable metal ions. It is also sometimes possible to form such membranes from polyelectrolytes already present in waste waters such as sewage. Because their rejection properties are based upon relatively long-range coulombic forces, ion-exchange membranes have the potential to function with a more open structure than that required of neutral membranes and hence to allow a greater flux. Conventional ion-exchange membranes, when manufactured with sufficient strength for reverse osmosis applications, are too impermeable. The dynamic technique provides a method for forming very thin ion-exchange membranes which are capable of use at high pressure and which have a very high flux. The performance of these membranes, as with other ion-exchange membranes, deteriorates with increasing feed concentration and the presence of polyvalent counter-ions. Their usefulness for single-stage seawater desalination thus appears doubtful, but they have promise for waste water treatment, where very high salt rejection is not always required. Dynamic membranes have also been formed from a range of neutral additives including hydroxyethyl cellulose, polyvinyl pyrrolidone and polyethylene oxides.4 Although often successful in removing large molecules by ultrafiltration, the salt rejection of these membranes is poor, usually less than 30 per cent. Neutral membranes are difficult to prepare by this technique because polymer additives which are soluble enough to form dynamic membranes are too hydrophilic to form membranes of low enough water content for good salt rejection. Whilst exhibiting poor salt rejection in their neutral form, dynamic ion-exchange membranes can still act as ultrafiltration membranes.
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    Mass transfer of corrosion products in high temperature, high pressure water circuits, part 2 - preliminary experiments
    (Australian Atomic Energy Commission, 1976-07) Evans, JV; Nicholson, FD
    The behaviour of iron oxide crud was studied at 25ºC and over the range 240 to 270ºC in a high pressure water loop. Crud deposition and removal was measured in two parallel, heated Zircaloy-2 tubes using iron-59 as a radioactive tracer. This proved to be a powerful technique capable of detecting crud deposits less than 3 run thick. Rapid deposition of crud was observed following injection into the loop of an iron oxide suspension or a ferric nitrate solution. Crud deposited preferentially on heated surfaces when they were present but not to the exclusion of deposition elsewhere; hot spots on heated surfaces attracted additional deposits. Subcooled boiling appeared to be a more important factor than bulk boiling in the enhancement of crud deposition. The initial rapid deposition of the bulk of the crud throughout the loop was usually followed by a slower transfer of crud from other surfaces to any heated surface present. Unsteady operating conditions, e.g. a change in power, temperature or pH, frequently caused crud bursts, but once steady conditions were re-established the entrained crud was quickly redeposited. The bulk of deposited crud was not readily re-entrained, particularly from heated surfaces, so that crud bursts involved only a fraction of the total crud deposited. Ferric nitrate solutions injected into the loop formed haematite which deposited more slowly and formed more mobile deposits than magnetite which was injected directly into the loop as a slurry. Examination of deposits from both sources showed them to be even and tightly adherent, being removed only with difficulty.
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    The performance of powdered ion-exchange resins
    (Australian Atomic Energy Commission, 1973-03) Bull, PS; Evans, JV; Nicholson, FD
    The coating properties and ion exchange performance of powdered ion-exchange resins were examined in a small test facility. Satisfactory resin coatings were obtained with cation:anion resin ratios in the range 1:1 to 3:1 but use of a 9:1 resin ratio resulted in a high pressure drop across the coating. The 'settled resin volume proved to be a reliable guide to the coating performance of resin slurries. The ion-exchange capacity of the cation resin increased to a small extent with a decrease in sodium concentration in the influent water down to 500 μg ℓ-1. Within the ranges examined, resin ratio, resin loading and flow rate had no significant effect on cation capacity. The effect of exhaustion on the pressure drop characteristics and flocculating properties of various resin ratio's was investigated. The thermal stability of the powdered anion resin was markedly less than that quoted elsewhere for anion bead resin.
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    The rum Jungle tailings dam - chemical profile of the subsoil
    (Australian Nuclear Science and Technology Organisation, 1987-09) Lowson, RT; Evans, JV; Sarbutt, JV; Sinclair, G; Folk, E
    In a survey of soils below the Rum Jungle uranium mine tailings dam parameters measured were pH moisture content particle distribution total Cu water-extractable Cu, Ca and SO4 and acid-extractable Ra. The cation profile had a marked discontinuity at the soil/tailings interface. This was attributed to a complex hydrogeology and to the presence of a reduction zone in the soil immediately below the tailings. The tailings acted as an aquaclude to a water table which fluctuated with the monsoonal season. The reduction zone acted as a cation trap preventing cation transport. The radium concentration dropped to levels acceptable to public health within a few centimetres of the soil/tailings interface.
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    Zirconium molybdate gel as a generator for technetium-99m
    (Australian Atomic Energy Commission, 1984-12) Evans, JV; Shying, ME
    A new (99m)Tc generator based on zirconium molybdate gel is described. Essentially the gel is a cation ion exchanger which permits the elution of the pertechnetate ion. The high molybdenum content of this gel its stability under self-irradiation and the absence of organic materials during preparation provide a generator concept that eliminates high processing costs active waste storage costs and stability problems in other types of generator.