New publication

Separation of rhodium from iridium through synergistic solvent extraction

Andrew I. Carrick, Jane Patrick, Emma R. Schofield, Paul O’Shaughnessy, Barbara Breeze, Jason B. Love, Carole A. Morrison

Sep. Purif. Technol., 2023, 333, 125893. DOI:10.1016/j.seppur.2023.125893

Abstract. There are currently few effective processes for the solvent extraction of rhodium from hydrochloric acid streams, and none that allow rhodium to be selectively extracted over iridium. Realizing this goal could allow rhodium to be recovered earlier in a typical platinum group metal (PGM) refining flowsheet and reduce the environmental impact of PGM refining. In this work, we show that a synergistic combination of a tert-alkyl primary amine L^A and various inner-sphere ligands L can be used to recover rhodium via the complex [RhCl₅L].HL^A₂. Although we show that rhodium is extracted by several extractant combinations, it is only readily stripped from the amine/amide synergistic mixture. As this extraction relies on the inner-sphere coordination of the amide to the metal, this process also demonstrates a route to obtain preferential extraction of rhodium over more inert iridium chloridometalates under industrially relevant conditions.

 

New publication in Angew. Chem.

Efficient Recycling of Gold and Copper from Electronic Waste by Selective Precipitation

Abhijit Nag, Mukesh K. Singh, Carole A. Morrison, Jason B. Love

Angew. Chem. Int. Ed., 2023, DOI:10.1002/anie.202308356

The recycling of metals from electronic waste (e-waste) using efficient, selective, and sustainable processes is integral to circular economy and net-zero aspirations. Herein, we report a new method for the selective precipitation of metals such as gold and copper that offsets the use of organic solvents that are traditionally employed in solvent extraction processes. We show that gold can be selectively precipitated from a mixture of metals in hydrochloric acid solution using triphenylphosphine oxide (TPPO), as the complex [(TPPO)₄(H₅O₂)][AuCl₄]. By tuning the acid concentration, controlled precipitation of gold, zinc and iron can be achieved. We also show that copper can be selectively precipitated using 2,3-pyrazinedicarboxylic acid (2,3-PDCA), as the complex [Cu(2,3-PDCA-H)₂]_n ⋅ 2n(H₂O). The combination of these two precipitation methods resulted in the recovery of 99.5 % of the Au and 98.5 % of the Cu present in the connector pins of an end-of-life computer processing unit. The selectivity of these precipitation processes, combined with their straightforward operation and the ability to recycle and reuse the precipitants, suggests potential industrial uses in the purification of gold and copper from e-waste.

Double success at DYME 2023

An enjoyable trip down to Birmingham for the Dalton Young Members Event for Susanna, Tom, and Joe resulted in two prizes for the Group. Tom was awarded the audience poster prize for his poster: “Probing Uranyl Reduction Chemistry with a Tripodal Pyrrole-Imine Ligand”. Joe was awarded the oral prize for his talk: “Separating the Rare Earths and Beyond: A role for self-assembled supramolecular capsules”.

PhD Studentship available: Towards sustainable and selective metal recovery from end-of-life catalyst supports.

About the Project

More info: http://www.findaphd.com/phds/project/towards-sustainable-and-selective-metal-recovery-from-end-of-life-catalyst-supports/?p156075

Platinum group metal (PGM) nanoparticles on supports such as microporous carbon are widely used as industrial catalysts in a variety of technologies including hydrogen fuel cells. When these materials reach end-of-life, PGM recovery is typically achieved by a pyrolysis treatment which destroys the support and generates CO₂. In this PhD project, alternative routes to both sustainably and selectively recover metals without destroying the catalyst support will be explored. Work will focus on developing metal leaching and separation strategies, as well as characterising and assessing the nature of different supports pre- and post-metal leaching. Comprehensive structural characterisation will include ICP-OES, NMR spectroscopy, MALDI-mass spectrometry and electron microscopy.  

The successful candidates will possess, or expect to obtain, a first class or upper-second class undergraduate degree (or equivalent) in chemistry or a closely related discipline. Essential qualities include a strong background in characterisation techniques (such as NMR spectroscopy and mass spectrometry techniques). Other essential attributes are good presentation and communication skills (written and oral), and an ability to meet deadlines. In the first instance, informal enquiries (including cover letter and CV) should be directed to: Prof. Jason B. Love (J.B.Love@ed.ac.uk) and Prof. Carole A. Morrison (C.Morrison@ed.ac.uk), School of Chemistry, University of Edinburgh, David Brewster Road, Edinburgh EH9 3FJ, UK.

Formal applications to Edinburgh are made through the University’s EUCLID system. http://www.chem.ed.ac.uk/studying/postgraduate-research/applications-and-entry-requirements

The position will remain open until filled and is available to start any time.

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New Publication

Rapid dissolution of noble metals in organic solvents

Abhijit Nag, Carole A. Morrison, Jason B. Love

ChemSusChem, 2022, DOI:10.1002/cssc.202201285.

Abstract: The dissolution of elemental noble metals (NMs) such as gold, platinum, palladium, and copper in organic solutions is necessary for their recycling but carries a high environmental burden due to the use of strong acids and toxic reagents. Herein, a new approach is presented for the rapid dissolution of elemental NMs in organic solvents using mixtures of triphenylphosphine dichloride or oxalyl chloride and hydrogen peroxide, forming metal chloride salts directly. Almost quantitative dissolution of metallic Au, Pd, and Cu was observed within minutes at room temperature. For Pt, dissolution by hydrogen peroxide was inhibited but achieved, albeit more slowly, using the chlorinating oxidant alone. After leaching, transfer of Pt(IV) and Pd(II) chloride salts from the organic phase into a 6 M HCl aqueous phase facilitated the separation of Pt(IV) by precipitation using a simple diamide ligand. In contrast, the retention of Au(III) chloridometalate in the organic phase allowed its selective separation from Ni and Cu from a leachate solution obtained from electronic CPUs. This new approach has potential application in the hydrometallurgical leaching and purification of NMs from ores, spent catalysts, and electronic- and nano-wastes.

New publication

Selective separation of light rare-earth elements by supramolecular encapsulation and precipitation

Nature Communications, 2022, 13, 4497

J. O’Connell-Danes, B. T. Ngwenya, C. A. Morrison, J. B. Love

Abstract: Supramolecular chemical strategies for Rare Earth (RE) element separations are emerging which amplify the small changes in properties across the series to bias selectivity in extraction or precipitation. These advances are important as the REs are crucial to modern technologies yet their extraction, separation, and recycling using conventional techniques remain challenging. We report here a pre-organised triamidoarene platform which, under acidic, biphasic conditions, uniquely and selectively precipitates light RE nitratometalates as supramolecular capsules. The capsules exhibit both intra- and intermolecular hydrogen bonds that dictate selectivity, promote precipitation, and facilitate the straightforward release of the RE and recycling of the receptor. This work provides a self-assembly route to metal separations that exploits size and shape complementarity and has the potential to integrate into conventional processes due to its compatibility with acidic metal feed streams.

New Publication

Exploring the Redox Properties of Bench-Stable Uranyl(VI) Diamido–Dipyrrin Complexes

Karlotta van Rees, Emma K. Hield, Ambre Carpentier, Laurent Maron, Stephen Sproules, Jason B. Love

Inorg. Chem., 2022, DOI:10.1021/acs.inorgchem.1c03744

The uranyl complexes UO₂(OAc)(L) and UO₂Cl(L) of the redox-active, acyclic diamido–dipyrrin anion L^– are reported and their redox properties explored. Because of the inert nature of the complexes toward hydrolysis and oxidation, synthesis of both the ligands and complexes was conducted under ambient conditions. Voltammetric, electron paramagnetic resonance spectroscopy, and density functional theory studies show that one-electron chemical reduction by the reagent CoCp₂ leads to the formation of a dipyrrin radical for both complexes [Cp₂Co][UO₂(OAc)(L^•)] and [Cp₂Co][UO₂Cl(L^•)].

Johnson Matthey ICASE PhD studentship available

A Johnson Matthey iCASE PhD studentship is available in the groups of Jason Love and Carole Morrison (School of Chemistry, The University of Edinburgh; https://jasonlovegroup.wordpress.com/).

The studentship is fully funded for 48 months and covers tuition fees and an annual stipend (starting at £15,609 per annum) for a candidate satisfying EPSRC criteria: https://www.ukri.org/councils/esrc/career-and-skills-development/funding-for-postgraduate-training/eligibility-for-studentship-funding/#contents-list

Project Summary
Why are some PGM complexes respiratory and dermal sensitisers when others are not? Early screening work proposed that it was Pt halides that were allergenic, but a number of non-halide, non-Pt compounds have since also proved sensitising. Knowing whether a new research compound is likely to be sensitising would significantly change practises at Johnson Matthey. However, workplace safety focuses on epidemiology and toxicology studies, and there is a dearth of modern research on the nature of the sensitising complex and the changes it undergoes under physiological conditions. Although chloroplatinates are assumed to be the culprits, occupational exposure limits (OEL) are not measured based on amount of chloroplatinate; only recently has the Advanced Characterisation group at Johnson Matthey Technology Centre devised a method to quantify the Pt and chloride anionic species in air or wipe samples. The aim of this PhD is to synthesise single PGM compounds to specify which are sensitising (in vitro testing), to identify which components of physiological solutions (e.g. alveolar lining fluid) they interact with (computational chemistry and protein interactions), and to understand the processes that convert them into the biological haptan (EXAFS/XANES, thermodynamic/kinetic modelling).

The applicant will require a strong background in chemistry, either through a good chemistry degree or related fields. Because of the multidisciplinary nature of this research, experience in metal coordination chemistry, biochemistry, and computational modelling would be advantageous.

In the first instance, informal enquiries (accompanied by a CV) should be directed to: Prof. Jason Love and Prof. Carole Morrison, School of Chemistry, University of Edinburgh. Email: jason.love@ed.ac.uk; carole.morrison@ed.ac.uk

Competitive PhD studentship available

A PhD studentship as part of the NERC E4-DTP is available: “New approaches to copper production: arsenic capture and solventless extraction.”

For informal enquiries please contact Prof. Jason Love (jason.love@ed.ac.uk), Prof. Carole Morrison (carole.morrison@ed.ac.uk) or Prof. Bryne Ngwenya (bryne.ngwenya@ed.ac.uk).

FindaPhD: https://www.findaphd.com/phds/project/e4-dtp-nerc-new-approaches-to-copper-production-arsenic-capture-and-solventless-extraction/?p137405

The deadline for applications is Thu Jan 06 2022 at 12:00.