Cobalt and nickel uptake by silica-based extractants

Pepper, Sarah E.,Whittle, Karl R.,Harwood, Laurence M.,Cowell, Joseph,Lee, Taek Seung,Ogden, Mark D. M. Dekker 2018 Separation science and technology Vol.53 No.10

<P>The pK(a)s of ethyl/butyl phosphonate silica (EBP-Si) have been determined, and the removal of cobalt and nickel from solution was investigated as a function of various parameters and compared with those of Purolite S950. pH uptake experiments suggested a combination of ion exchange and acid dissociation of the surface occurring. Isotherm data, fitted using the Langmuir and Dubinin-Radushkevich (D-R) models, indicated that stronger complexes formed with S950 than with EBP-Si. Kinetic data, fitted using a pseudo-second-order model, suggested that the rate-determining process is the reaction of metal ions with the chelating functionality of the resin. Uptake by EBP-Si is two to three times faster than that on S950.</P>

The Soil Health-human Health Nexus

Ian L. Pepper 한국토양비료학회 2014 한국토양비료학회 학술발표회 초록집 Vol.2014 No.6

Multi-fidelity uncertainty quantification of high Reynolds number turbulent flow around a rectangular 5:1 Cylinder

Mayu Sakuma,Nick Pepper,Suneth Warnakulasuriya,Francesco Montomoli,Roland Wüchner,Kai-Uwe Bletzinger 한국풍공학회 2022 Wind and Structures, An International Journal (WAS Vol.34 No.1

In this work a multi-fidelity non-intrusive polynomial chaos (MF-NIPC) has been applied to a structural wind engineering problem in architectural design for the first time. In architectural design it is important to design structures that are safe in a range of wind directions and speeds. For this reason, the computational models used to design buildings and bridges must account for the uncertainties associated with the interaction between the structure and wind. In order to use the numerical simulations for the design, the numerical models must be validated by experi-mental data, and uncertainties contained in the experiments should also be taken into account. Uncertainty Quantifi-cation has been increasingly used for CFD simulations to consider such uncertainties. Typically, CFD simulations are computationally expensive, motivating the increased interest in multi-fidelity methods due to their ability to lev-erage limited data sets of high-fidelity data with evaluations of more computationally inexpensive models. Previous-ly, the multi-fidelity framework has been applied to CFD simulations for the purposes of optimization, rather than for the statistical assessment of candidate design. In this paper MF-NIPC method is applied to flow around a rectan-gular 5:1 cylinder, which has been thoroughly investigated for architectural design. The purpose of UQ is validation of numerical simulation results with experimental data, therefore the radius of curvature of the rectangular cylinder corners and the angle of attack are considered to be random variables, which are known to contain uncertainties when wind tunnel tests are carried out. Computational Fluid Dynamics (CFD) simulations are solved by a solver that employs the Finite Element Method (FEM) for two turbulence modeling approaches of the incompressible Navier-Stokes equations: Unsteady Reynolds Averaged Navier Stokes (URANS) and the Large Eddy simulation (LES). The results of the uncertainty analysis with CFD are compared to experimental data in terms of time-averaged pressure coefficients and bulk parameters. In addition, the accuracy and efficiency of the multi-fidelity framework is demonstrated through a comparison with the results of the highfidelity model.

Double-row transport in quantum wires of shallow confinement

Hew, W.K.,Thomas, K.J.,Pepper, M.,Farrer, I.,Anderson, D.,Jones, G.A.C.,Ritchie, D.A. North-Holland 2010 Physica E, Low-dimensional systems & nanostructure Vol.42 No.4

The bifurcation of the electron system in a quantum wire has been observed in the form of the suppression and disappearance of the quantised conductance plateau at 2e<SUP>2</SUP>/h. We now present low-temperature transport measurements of a top-gated split-gate quantum wire that serve to further characterise this double-row regime of transport. A small distortion of the confinement caused by asymmetrical biasing of the split gates gives rise to a radical change in the conductance characteristics of the wire, beginning with the introduction of a plateau at G=e<SUP>2</SUP>/h which rises to around 0.7x2e<SUP>2</SUP>/h with greater differential bias between the split gates. DC source-drain bias measurements in this regime show a split zero-bias peak at low conductances merging into a single peak around G=0.7xe<SUP>2</SUP>/h, which then persists up to the plateau at 4e<SUP>2</SUP>/h.

Mid-IR spectroscopy of Fe:ZnSe quantum dots

Myoung, NoSoung,Park, Jung Su,Martinez, Alan,Peppers, Jeremy,Yim, Sang-Youp,Han, Won Seok,Fedorov, Vladimir V.,Mirov, Sergey B. The Optical Society 2016 Optics express Vol.24 No.5

Impact of copper(II) on activation product removal from reactor decommissioning effluents in South Korea

J.T.M. Amphlett,S.E. Pepper,A.L. Riley,L.M. Harwood,J. Cowell,K.R. Whittle,T.S. Lee,M.D. Ogden 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.82 No.-

Decommissioning is one of the most important phases in the life of a nuclear reactor, having a majorinfluence on public perception of such technology. Therefore, development of technologies that makedecommissioning more safe, effective and efficient is integral to the success of the nuclear industry. Inthis paper, phosphonic acid functionalised silica has been studied to determine its suitability for treatingnuclear decommissioning effluents produced in the HYBRID process, developed in South Korea. Cu2+recovery from HCl media in both static and dynamic modes was investigated, as well as the effect of Cu2+on Co2+ and Ni2+ recovery in a column loading system. Isothermal loading studies predicted a maximumloading capacity for Cu2+ of 22.82 mg g 1, however complex loading behaviour was observed. Cu2+sorption followed pseudo-second order kinetics with rapid uptake. Thermodynamic parameters havebeen extracted from collected kinetic data. Cu2+ outcompetes both Co2+ and Ni2+ for binding to the silicain column studies, which has implications for the use of phosphonic acid functionalised silica in treatingdecommissioning effluents. This work presents initial lab scale experiments, but shows the potential of Sibased extractants for use in metals recovery in the nuclear industry.

Formation and speciation of haloacetic acids in seawater desalination using chlorine dioxide as disinfectant

유혜원,오상근,In S. Kim,Ian Pepper,Shane Snyder,장암 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.26 No.-

To evaluate the formation potential of disinfection byproducts (DBPs) in a SWRO system when chlorine dioxide (ClO2) is used as a chemical disinfectant, the impact of principle precursors such as natural organic matter (NOM) and bromide ion on haloacetic acids (HAAs) formation and its speciation was investigated. In the presence of high bromide levels found in seawater, the active oxidizing agents formed by the action of ClO2 can react with NOM, resulting in halogenation reactions, and the production of brominated DBPs as the predominant byproducts. Elevating the initial levels of organic substances and bromide ions not only enhanced the total content of HAA5 formed, but also shifted the speciation of HAAs from the chlorinated to fully brominated forms at higher disinfectant doses and longer contact times of ClO2 disinfection. In addition, HAA5 formation potential increased in the order of transphi- lic > hydrophobic > hydrophilic NOM, suggesting HAA5 yield formed during ClO2 disinfection significantly depends on the characteristics of NOM that can lead to different speciation distribution of DBPs. However, at high doses of ClO2, it was observed that the disinfectant dose plays a more important role in speciation distribution of HAA5 than the characteristics of organic precursors.

Coupled double-row formation in a quasi-1D wire

Smith, L.W.,Hew, W.K.,Thomas, K.J.,Pepper, M.,Farrer, I.,Anderson, D.,Jones, G.A.C.,Ritchie, D.A. North-Holland 2010 Physica E, Low-dimensional systems & nanostructure Vol.42 No.4

We investigate one-dimensional (1D) quantum wires in the weak confinement regime, where, at certain densities, the 1D system of electrons bifurcates into two rows. We show that the two rows are coupled, forming bonding and antibonding states, and that the coupling persists in magnetic fields from 0 to 16 T. In order for a double row to form, the Coulomb interactions in the channel must overcome the confining potential, which can be achieved by tuning the density and confinement. Using a split-gate device with a top gate and back gate, we observe a transition from single-row to double-row behaviour in the weak confinement regime. We further probe the characteristics of the coupled double row regime with dc source-drain bias measurements.

Formation and speciation of haloacetic acids in seawater desalination using chlorine dioxide as disinfectant

Yu, H.W.,Oh, S.G.,Kim, I.S.,Pepper, I.,Snyder, S.,Jang, A. Korean Society of Industrial and Engineering Chemi 2015 Journal of industrial and engineering chemistry Vol.26 No.-

To evaluate the formation potential of disinfection byproducts (DBPs) in a SWRO system when chlorine dioxide (ClO<SUB>2</SUB>) is used as a chemical disinfectant, the impact of principle precursors such as natural organic matter (NOM) and bromide ion on haloacetic acids (HAAs) formation and its speciation was investigated. In the presence of high bromide levels found in seawater, the active oxidizing agents formed by the action of ClO<SUB>2</SUB> can react with NOM, resulting in halogenation reactions, and the production of brominated DBPs as the predominant byproducts. Elevating the initial levels of organic substances and bromide ions not only enhanced the total content of HAA<SUB>5</SUB> formed, but also shifted the speciation of HAAs from the chlorinated to fully brominated forms at higher disinfectant doses and longer contact times of ClO<SUB>2</SUB> disinfection. In addition, HAA<SUB>5</SUB> formation potential increased in the order of transphilic>hydrophobic>hydrophilic NOM, suggesting HAA<SUB>5</SUB> yield formed during ClO<SUB>2</SUB> disinfection significantly depends on the characteristics of NOM that can lead to different speciation distribution of DBPs. However, at high doses of ClO<SUB>2</SUB>, it was observed that the disinfectant dose plays a more important role in speciation distribution of HAA<SUB>5</SUB> than the characteristics of organic precursors.

Synthesis of Prussian blue-embedded porous polymer for detection and removal of Cs ions

Namgung, Ho,Gwon, Young Jin,Kim, Jongho,Jang, Geunseok,Pepper, Sarah E.,Ogden, Mark D.,Whittle, Karl R.,Harwood, Laurence M.,Lee, Taek Seung Elsevier 2018 Polymer Vol.158 No.-

<P><B>Abstract</B></P> <P>A Prussian blue (PB)-embedded coordination polymer (COP) was prepared by simple incorporation of PB into a COP composed of 1,1,2,2-tetrakis(4-carboxyphenyl)ethane and the Zn ion during the synthesis of COP. The PB-COP was prepared as micro-sized particles with green emission (490 nm) from the strongly fluorescent tetraphenylethene group in the solid state through aggregation-induced emission. The PB-COP showed particle shape with sizes ranging from 1 to 6 μm. As the PB in PB-COP efficiently adsorbed Cs ions, the microstructure of PB-COP was degraded to smaller particles, along with a concomitant decrease in the green fluorescence of the PB-COP. Such a decrease in the green emission of PB-COP was used as a signal for the presence of Cs ions, in which the limit of detection for Cs ions was found to be 73.8 ppb. The hybridized material of the PB-COP can be used as both an efficient adsorbent and a sensor for Cs ions, achieving simultaneous removal and detection.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A hybrid material was prepared with coordination polymer (COP) and Prussian blue (PB). </LI> <LI> COP was prepared by ionic interaction between COOH of organic molecules and Zn ions. </LI> <LI> The hybrid materials could remove efficiently Cs ions via adsorption on PB. </LI> <LI> The fluorescence of COP in hybrid materials also decreased upon exposure to Cs ions. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>