Selective recovery of copper from a synthetic metalliferous waste stream using the thiourea-functionalized ion exchange resin Puromet MTS9140

The extraction of Cu from mixed-metal acidic solutions by the thiourea-functionalized resin Puromet MTS9140 was studied. Despite being originally manufactured for precious metal recovery, a high selectivity towards Cu was observed over other first-row transition metals (>90% removal), highlighting a potential for this resin in base metal recovery circuits. Resin behaviour was characterised in batch-mode under a range of pH and sulphate concentrations and as a function of flow rate in a fixed-bed setup. In each instance, a high selectivity and capacity (max. 32.04 mg/g) towards Cu was observed and was unaffected by changes in solution chemistry. The mechanism of extraction was determined by XPS to be through reduction of Cu(II) to Cu(I) rather than chelation. Elution of Cu was achieved by the use of 0.5 M–1 M NaClO3. Despite effective Cu elution (82%), degradation of resin functionality was observed, and further detailed through the application of IC analysis to identify degradation by-products. This work is the first detailed study of a thiourea-functionalized resin being used to selectively target Cu from a complex multi-metal solution

Effect of gamma radiation on sealing capacity characteristics of three commercially available nitrile rubber samples compared against an industrial seal used in AGR power plants

The maintenance of the Fuelling Machine operating in an AGR reactor consumes a large number of working hours and operational budget. As part of an optimisation programme research work is currently being carried out to investigate the degradation mechanism on the dynamic seal on one of these machines. The aim of this work is to understand seal behaviour under reactor working conditions in a bid to develop a mechanistic understanding of its long-term degradation and optimise the component’s maintenance schedule. The deleterious operational conditions have been identified as; activation of the sealing face through compression, exposure to a low radiation dose and cycle exposure to pressurised carbon dioxide. This part of the work investigates the effect of radiation damage on the CO2 uptake and swelling behaviour, mechanical properties and physical and chemical structure of three commercially available nitrile rubber samples which are then compared against the characteristics for the chosen seal. Exposure to radiation resulted in increased mechanical strength and resilience of the rubber as well as decreased CO2 loading capacity and swelling, further supporting the theory of cross-link formation. The seal was more resistant to the effects of radiation than the three nitrile rubber samples, however scanning electron microscopy identified the initiation and propagation of cracks without any external stress applied on the irradiated samples, the result of in-built stresses created during the manufacturing process. The next stage of this work will investigate the effect of the local environment on the radiation-induced changes in the sample’s ultimate sealing capacity

Polymeric seal degradation in nuclear power plants: Determination of physical and mechanical properties

To assess the suitability of different materials as polymeric seals in the Nuclear Industry three commercial samples of nitrile rubber at grades BA40, BA50, and BA60 have been tested. Differential scanning calorimetry was used to find the glass transition temperature (Tg) and a Lloyds Texture Analyser 500 (TA500) was used to find the ratio of energy returned during relaxation against energy applied during compression. The mechanical properties determined from these experiments were then compared against the materials infrared spectra to infer structural characteristics. These were in turn cross-analyzed against the materials ability to swell in a liquid solvent and absorption behavior in a gaseous solvent. From this information, a statement could be made about each material's capacity to perform as a seal. It was thus found that the high energy retention and low absorption characteristics of BA40 made this material the best choice out of those studied for use as a polymeric seal in the nuclear industry. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 135, 45814

A paradigm shift on beta-thalassaemia treatment : how will we manage this old disease with new therapies?

Beta-thalassaemia causes defective haemoglobin synthesis leading to ineffective erythropoiesis, chronic haemolytic anaemia, and subsequent clinical complications. Blood transfusion and iron chelation allow long-term disease control, and haematopoietic stem cell transplantation offers a potential cure for some patients. Nonetheless, there are still many challenges in the management of beta-thalassaemia. The main treatment option for most patients is supportive care; furthermore, the long-term efficacy and safety of current therapeutic strategies are limited and adherence is suboptimal. An increasing understanding of the underlying molecular and cellular disease mechanisms plus an awareness of limitations of current management strategies are driving research into novel therapeutic options. Here we provide an overview of the current pathophysiology, clinical manifestations, and global burden of beta-thalassaemia. We reflect on what has been achieved to date, describe the challenges associated with currently available therapy, and discuss how these issues might be addressed by novel therapeutic approaches in development

Effect of logic family on radiated emissions from digital circuits

Radiated emissions were measured for simple digital circuits designed to operate with various logic families. Emissions in the near and far field were found to depend both on the circuit layout and the choice of logic family. However, the difference in peak emissions between any two logic families was found to be independent of circuit layout. The greatest difference in peak emissions was between high-speed 74ACT logic and low-speed 4000 CMOS logic devices, with a mean value of approximately 20 dB. Emissions from a more complex circuit were compared with the measurements on simple loop circuits. Test circuits were used to measure the propagation delay, the rise and fall times, the maximum operating frequency and the transient switching currents between two successive logic gates for each logic family. Empirical formulas have been derived that relate relative peak emissions to these switching parameters. It is hoped that these will assist designers to assess the effect of choice of logic family on electromagnetic compatibility

Diffusion in supersonic, turbulent, compressible flows

We investigate diffusion in supersonic, turbulent, compressible flows. Supersonic turbulence can be characterized as network of interacting shocks. We consider flows with different rms Mach numbers and where energy necessary to maintain dynamical equilibrium is inserted at different spatial scales. We find that turbulent transport exhibits super-diffusive behavior due to induced bulk motions. In a comoving reference frame, however, diffusion behaves normal and can be described by mixing length theory extended into the supersonic regime.Comment: 11 pages, incl. 5 figures, accepted for publication in Physical Review E (a high-resolution version is available at http://www.aip.de./~ralf/Publications/p21.abstract.html

An alternative to cyanide leaching of waste activated carbon ash for gold and silver recovery via synergistic dual-lixiviant treatment

This study reports the development of a hydrometallurgical treatment for activated carbon ash (ACA); a waste product of the carbon-in-pulp (CIP) process used in the gold mining industry, rich in adsorbed precious metals. After an initial screening of known leaching chemistries, the research focusses on dual-lixiviant (thiourea and thiocyanate) and thiourea systems, both of which have lower environmental impact than traditional cyanide leaches. Comparing ferric sulfate and hydrogen peroxide as oxidants showed that a thiourea leach is more suited to ferric sulfate whereas the dual-lixiviant leach achieved greater extraction with hydrogen peroxide. This was believed to be due to a more favourable effective [thiourea]:[thiocyanate] molar ratio in solution. The latter demonstrated faster kinetics and improved efficiency for dissolution of gold and silver. However, both leaches had issues with silver extraction due to formation of passivating layers on the surface of the silver nanoparticles. Kinetic modelling showed both systems tended towards a mixed-controlled process. Gold extraction of 89%, with leaching reaching equilibrium within 100 min, using the dual-lixiviant process demonstrated that there is an alternative to cyanide leaches employed in gold recovery

The Influence of the effect of solute on the thermodynamic driving force on grain refinement of Al alloys

Grain refinement is known to be strongly affected by the solute in cast alloys. Addition of some solute can reduce grain size considerably while others have a limited effect. This is usually attributed to the constitutional supercooling which is quantified by the growth restriction factor, Q. However, one factor that has not been considered is whether different solutes have differing effects on the thermodynamic driving force for solidification. This paper reveals that addition of solute reduces the driving force for solidification for a given undercooling, and that for a particular Q value, it is reduced more substantially when adding eutectic-forming solutes than peritectic-forming elements. Therefore, compared with the eutectic-forming solutes, addition of peritectic-forming solutes into Al alloys not only possesses a higher initial nucleation rate resulted from the larger thermodynamic driving force for solidification, but also promotes nucleation within the constitutionally supercooled zone during growth. As subsequent nucleation can occur at smaller constitutional supercoolings for peritectic-forming elements, a smaller grain size is thus produced. The very small constitutional supercooling required to trigger subsequent nucleation in alloys containing Ti is considered as a major contributor to its extraordinary grain refining efficiency in cast Al alloys even without the deliberate addition of inoculants.The Australian Research Council (ARC DP10955737)

Moderating influences on the firm's strategic orientation-performance relationship

This paper is focused on the factors that moderate the relationship between firm's strategic orientation and performance in small and medium-sized firms. Much prior research has focused simply on identifying environmental conditions conducive to the effectiveness of the strategic orientation approach. However, recent research has called for studies focused on investigating internal moderators of the strategic orientation-performance relationship. As a result, we propose a contingency framework, considering how corporate and competitive strategies, top management characteristics, and environmental conditions may moderate this relationship. Based on a survey of 295 small and medium sized enterprises pertaining to seven manufacturing sectors, our study shows that the positive influence of firm's strategic orientation may be moderated by the environment conditions, the previous experience of top management team, and the corporate and competitive strategies developed by the firm