Metal recovery in Chile

Mary Healy, Carole Morrison, and Jason love have just returned from Chile where they were hosted by Alvaro Videla and Rene Rojas of the Pontifical University of Chile in Santiago. Lots of great interactions with academics and industrialists, plus visits to mines, recovery plants, and the Atacama desert!

Shown here is a copper solvent extraction plant (Amalia Catemu) where we saw the whole recovery process for copper, and the Andes in the Atacama desert, the location of Chuquicamata, one of the largest copper mines in the world.

mixer-settlerandes_2017

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Urban mining

An episode of BBC Scotland’s ‘Brainwaves’ science programme discussing urban mining with contributions from the Edinburgh Metal Recovery Group is available for download

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Government 20

An overview of some of the work carried out by the Metal Recovery Group at Edinburgh is provided in the Pan European Network “Government 20” publication (Page 154).

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Competitive PhD studentship available

Recycling of waste electronics using environmentally sustainable processes

A competitive PhD studentship position on the NERC E3 Doctoral Training Programme is available, supervised by Jason Love, Carole Morrison (Chemistry), and Bryne Ngwenya (Geosciences). Applications should be made through the E3 DTP website – Deadline 16 Jan 2017, 5 pm.

See: http://e3dtp.geos.ed.ac.uk/projects.html; http://www.ed.ac.uk/geosciences/postgraduate/phd/programmes-supervisors/physical-sciences/phd-projects

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New publication

new-toc

James R. Pankhurst, Nicola L. Bell, Markus Zegke, Lucy N. Platts, Carlos A. Lamfsus, Laurent Maron, Louise S. Natrajan, Stephen Sproules, Polly L. Arnold*, Jason B. Love*

“Inner-sphere vs. outer-sphere reduction of uranyl supported by a redox-active, donor-expanded dipyrrin.” Chem. Sci., 2016DOI:10.1039/c6sc02912d.

Abstract: The uranyl(VI) complex UO2Cl(L) of the redox-active, acyclic diimino-dipyrrin anion, L is reported and its reduction by inner-sphere and outer-sphere reductants studied. Voltammetric and EPR-spectroscopic and X-ray crystallographic studies, show that chemical reduction by the outer-sphere reagent CoCp2 initially reduces the ligand to a dipyrrin radical, and imply that a second equivalent of CoCp2 reduces the U(VI) centre to form U(V). Cyclic voltammetry indicates that further outer-sphere reduction to form the putative U(IV) trianion only occurs at strongly cathodic potentials. The initial reduction of the dipyrrin ligand is supported by emission spectra and DFT calculations, and the latter also shows that these outer-sphere reactions are exergonic and proceed through sequential, one-electron steps. Reduction by the inner-sphere reductant [TiCp2Cl]2 is also likely to result in ligand reduction in the first instance but, in contrast to the outer-sphere case, reduction of the uranium centre becomes much more favoured, allowing the formation of a crystallographically characterised, doubly-titanated U(IV) complex. In the case of inner-sphere reduction only, ligand-to-metal electron-transfer is thermodynamically driven by coordination of Lewis-acidic Ti(IV) to the uranyl oxo, and is energetically preferable over the disproportionation of U(V). Overall, the involvement of the redox-active dipyrrin ligand in the reduction chemistry of UO2Cl(L) is inherent to both inner- and outer-sphere reduction mechanisms, providing a new route to accessing a variety of U(VI), U(V), and U(IV) complexes.

 

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New publication

solextractionexch2016 

The influence of the Hofmeister bias and the stability and speciation of chloridolanthanates on their extraction from chloride media.

Euan D Doidge, Innis Carson, Jason B Love*, Carole A Morrison* and Peter A Tasker*

Solvent Extraction and Ion Exchange, 2016

The possibility of recovering rare earth elements from solutions containing their chloridometalate anions [LnClx](x-3)− via the process: LnClx(x-3)− + (x-3)Lorg + (x-3)H+ ⇌ [(LH)x-3LnClx]org has been tested using 2-(1,3-bis(hexylamino)-1,3-dioxopropan-2-yl)-4,6-di-tert-butylpyridine (PMA), tri-n-butylphosphate (TBP) and tri-n-octylamine (TOA) which are known to be strong extractants for transition metal chloridometalates. While DFT calculations indicate that the formation of the neutral assembly [(PMAH)3LaCl6] in the gas phase is favourable, no uptake of La(III) from 6 M HCl by toluene solutions of PMA (or of TBP or TOA) was observed in solvent extraction experiments. Successful uptake of the [PtCl6]2- dianion by PMA and the failure to extract the [IrCl6]3- trianion under the same conditions indicates that the higher hydration energy of the latter makes transfer to the toluene solution less favourable and that this militates against extraction of La(III) chlorido complexes carrying charges of -3 or larger in which all the inner sphere water molecules have been replaced. Computational results confirm literature observations that, in contrast to transition metal trications, formation of REE metalate anions such as [LnClx](x-3)− is not very favourable, particularly so for chloride, compared with nitrato or sulfato systems. Also, they indicate that the formation of outer sphere assemblies such as {[La(H2O)9].xCl} in which water ligands are retained in the inner sphere, H-bonded to anions, are more stable than inner sphere complexes containing an equivalent number of anions. The high level of hydration of such species militates against their transfer into non-polar water-immiscible solvents. It is unlikely that recovery of [LnClx](x-3)− from acidic solutions can be achieved efficiently using currently available anion exchange extractants operating in a ‘pH-swing’ process. Receptors giving very high binding energies to chloridolanthanates will be needed to offset the high dehydration energies required.

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Welcome Liam

liam-donnelly

 

Liam Donnelly has joined the group as part of the CRITICAT CDT and is jointly supervised by Dr Stephen Thomas. He’ll be working on the use of high oxidation state complexes as catalysts for reduction reactions

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