Arvid Ödegaard-Jensen

Dissolution and characterization of HEV NiMH batteries

Metal recovery is an essential part of the recycling of hybrid electric vehicle battery waste and the first step in a hydrometallurgical treatment is dissolution of the solid material. The properties of separated battery electrode materials were investigated. Focus was put on both the solid waste and then the dissolution behaviour. The cathode contains metallic nickel that remains undissolved when utilizing non-oxidizing conditions such as hydrochloric or sulphuric acid in combination with a low oxygen atmosphere. In these conditions the cathode active electrode material is fully dissolved. Not dissolving the nickel metal saves up to 37% of the acid consumption for the cathode electrode material. In the commonly used case of oxidizing conditions the nickel metal dissolves and a cobalt-rich phase remains undissolved from the cathode active material. For the anode material a complete and rapid dissolution can be achieved at mild conditions with hydrochloric, nitric or sulphuric acid. Optimal parameters for all cases of dissolution was pH 1 with a reaction time of approximately ≥ 20,000 s.

Microbial Mobilization of Uranium from Shale Mine Waste

The alum shale in the Billingen area in southern Sweden was mined in Ranstad for 5 years during the 1960s. The crushed tailings (processed and unprocessed) were left behind when the Ranstad mine was closed that has caused leaching of metals to the surroundings. The siderophore producing bacterium Pseudomonas fluorescens (Äspö, SE Sweden) was grown in batch cultures for 5 to 8 days with naturally weathered (unprocessed) uranium ore (0.0029% U by weight), kolm (0.52% U by weight) and acid-leached ore (0.0099% U by weight) in chemically defined media (unbuffered and buffered). Pseudomonas fluorescens grown with ore and unbuffered medium changed the pH from 4.7 to 9.3 and leached out 0.016 to 0.9% (normalized to surface area) of the total amount of U from the different ores. Incubation of the acid-leached ore with bacteria in buffered medium leached out 0.04% of the total U. Uranium was leached out selectively at all conditions, but this could be a pH effect, as pH increased at the same time as the U concentrations did. The observed release of Fe was most likely attributed to the production of microbial siderophores (Fe3+ specific chelators) since Fe3+ has a low solubility at pH > 4. As siderophores contain a number of chelating groups they may still function as complexators even in partly degraded form also for other metals than Fe. Thus, the production of microbial chelators could contribute to the elevated metal concentrations in the drainage water from the closed Ranstad mine, as abiotic processes cannot fully explain these high metal concentrations. In the extension: ligand promoted leaching of toxic elements could also be the key to bioremediation as there is a need for nontoxic cleanup methods for metal contaminated sites.

LJUNGSKILE: a program for assessing uncertainties in speciation calculations.

Speciation calculations are often the base upon which further and more important conclusions are drawn, e.g., solubilities and sorption estimates used for retention of hazardous materials. Since speciation calculations are based on experimentally determined stability constants of the relevant chemical reactions, the measurement and experimental uncertainty in these constants will affect the reliability of the simulation output. The present knowledge of the thermodynamic data relevant for predicting the behaviour of a complex chemical system is quite heterogeneous. In order to predict the impact of these uncertainties on the reliability of a simulation output requires sophisticated modelling codes. In this paper, we will present a computer program, LJUNGSKILE, which utilises the thermodynamic equilibrium code PHREEQC to statistically calculate uncertainties in speciation based on uncertainties in stability constants. A short example is included.

The structure of plutonium(IV) oxide as hydrolysed clusters in aqueous suspensions.

The behavior of plutonium still puzzles scientists 70 years after its discovery. There are several factors making the chemistry of plutonium interesting including its ability to keep several oxidation states. Another unique property is that the oxidation states +III, +IV, +V and +VI may exist simultaneously in solution. Another property plutonium shares with some other tetravalent metal ions is the ability to form stable polynuclear complexes or colloids. The structures of freshly prepared and five-year old plutonium(IV) colloids are compared with crystalline plutonium(IV) oxide using Pu L(3)-edge EXAFS. It was shown that as the plutonium colloids age they do in fact shrink in size, contrary to previous expectations. The aged colloidal particles are indeed very small with only 3-4 plutonium atoms, and with a structure very similar to solid plutonium(IV) oxide, but with somewhat shorter mean Pu-O bond and Pu···Pu distances indicating a partial oxidation. The very small size of the colloidal particles is further supported by the fact that they do not sediment on heavy ultra-centrifugation.

Solid–Aqueous Phase Partitioning of Radionuclides by Complexing Compounds Excreted by Subsurface Bacteria

Radionuclides are present in numerous aerobic and anaerobic subsurface environments due to nuclear weapons testing, leakage from process and storage facilities, and discharge of radioactive waste. The partitioning of radionuclides between liquid and solid phases by complexing compounds excreted by subsurface bacteria was studied. The solid–aqueous phase partitioning of pico- to submicromolar amounts of 59Fe, 147Pm, 234Th, and 241Am was analyzed in the presence of quartz sand and exudates from three species of subsurface bacteria: Pseudomonas fluorescens, Pseudomonas stutzeri, and Shewanella putrefaciens. All were grown under aerobic conditions, and P. stutzeri and S. putrefaciens were grown under anaerobic conditions as well. The supernatants of the aerobic and anaerobic cultures were collected and radionuclide was added. Quartz sand, with a Brunauer, Emmett, and Teller (BET) surface area of 0.1 m2 g–1, was added to the supernatant radionuclide mix, and the pH was adjusted to approximately 8. After centrifuging, the amount of radionuclide in the liquid phase of the samples and controls was analyzed using scintillation. Relative to the control, aerobic supernatants maintained more than 50% of the added 59Fe, 234Th, and 241Am. The highest amount of metal present in the liquid phase of the anaerobic supernatants was found in the case of 241Am, with 40% more 241Am in samples than in controls. Both aerobic and anaerobic supernatants tested positive for complexing compounds when analyzed using the Chrome Azurol S assay. The great amounts of radionuclides in the liquid phases of samples were likely due to complexation with such compounds. Bacterially excreted complexing compounds hence seem able to influence the solid–aqueous phase partitioning of radionuclides. This could influence the mobility of radionuclides in contaminated subsurface environments.

Leaching of Spent Fuel under Anaerobic and Reducing Conditions

Sweden plans to dispose of spent nuclear fuel in a deep geologic repository in granitic rock. The disposal conditions allow water to contact the canisters by diffusion through the surrounding bentonite clay layer. Corrosion of the canister iron insert will consume oxygen and provide actively reducing conditions in the fluid phase. Experiments with spent fuel have been done to determine the dissolution behavior of the fuel matrix and associated fission products and actinides under conditions ranging from inert atmosphere to reducing conditions in solutions. Data for U, Pu, Np, Cs, Sr, Tc, Mo, and Ru have been obtained for dissolution in a dilute NaHCO 3 groundwater for 3 conditions: Ar atmosphere, H 2 atmosphere, and H 2 atmosphere with Fe(II) in solution. Solution concentrations forU, Pu, and Mo are all significantly lower for the conditions that include Fe(II) ions in the solutions together with H 2 atmosphere, while concentrations of the other elements seem to be unaffected by the change of atmospheres or presence of Fe(II). Most of the material that initially dissolved from the fuel has reprecipitated back onto the fuel surface. Very little material was recovered from rinsing and acid stripping of the reaction vessels.

Redox Control in Solvent Extraction Studies Using a PEEK AKUFVE Unit

Abstract When studying actinides or other elements with different possible oxidation states it is important to control which state is present in solution. Earlier redox control has been done by adding some other element to the solution but this approach introduces additional uncertainties. Since the sixties the AKUFVE apparatus has been used for precise solvent extraction studies. Now this equipment has been improved with redox control facilities, additional thermal control, and all parts in contact with the liquids are made of polyetherether ketone (PEEK) to minimize sorption.

Dark oxidation of water in soils

We report the release of oxygen (O2) under dark conditions in aerobic soils. This unexpected process is hidden by respiration which constitutes the dominating reversal O2 flux. By using H2 18O in different soils, we confirmed that 16O18O and 18O2 released under dark soil conditions originated from added H2 18O. Water is the only large-scale source of electrons for reduction of CO2 in soils, but it has not been considered as an electron donor because of the very strong oxidation system needed. A high share of soil inorganic material seems to favor the release of O2.

Testing of Uranium Dioxide Containing Different Levels of Alpha Activity Under Anaerobic and Reducing Conditions

Samples of UO2 containing 5% 235U and 0, 5, or 10% 233U were tested in a dilute simulated groundwater using N 2 or H2 gas as the atmosphere. Some tests included metallic iron in the solution. Each test condition used samples run in triplicate for at least 21 days and each test condition was run for two consecutive test periods. The results show that the dissolution behavior of the samples is the same in both N2 and H2 atmospheres. The amount of U dissolved under these conditions clearly showed the enhancement of dissolution due to oxidation of the sample surface by radiolysis products for conditions without metallic Fe. When a piece of iron was included in the bottom of the test vessel, the amount of dissolution decreased dramatically indicating that the Fe(II) ions released from the corroding iron were able to react with most of the radiolysis products before they could oxidize the UO2 surface.

The effect of Uncertainties in Stability Constants on Speciation Diagrams

Speciation calculations are one of the more common ways to describe a chemical system. Speciation diagrams is a convenient way to display such calculations and may also be the basis on which experiments in neighbouring fields of interest, such as sorption are based. In earlier days only very simple problems could be described, e.g. hydroxide species dominance diagrams versus pH. With the aid of computers, however, more complicated systems such as groundwater chemistry may be used. However, as the complexity increase, so does the effect of uncertainties. In this paper we focus on the effect uncertainties in stability constants may have on speciation calculations. The common belief is that the curves will be replaced by narrow bands, while the truth is far from that. In many cases one or several species cover the entire region between 0 and 100%.