1,721,189 research outputs found
Gold precipitation by diamides - ICP-OES and NMR data
No full textThe efficient separation of gold and other metals from their ores and composite secondary sources such as electronic waste is necessary to realising circularity in metal supply chains. Processes based on precipitation are becoming increasingly popular and their development is reliant on designing and understanding chemical recognition to achieve selectivity. Here we show that the simple tertiary diamide PhC(O)NMe(CH2CH2)NMeC(O)Ph (L) precipitates gold selectively and directly from aqueous acidic solutions as the ion pair [HL][AuCl4], including from aqua regia solutions of electronic waste. The X-ray crystal structure of the precipitate displays an infinite chain of diamide cations, formed through an intermolecular proton chelate, interleaved with tetrachloridoaurate. Gold is released quantitatively from the isolated precipitate as HAuCl4 on contact with water, enabling ligand recycling. The diamide is highly selective, with its addition to a mixture of 29 metals in 2 M HCl resulting in 70% gold uptake and minimal removal of all other metals. Increasing the HCl concentration to 6 M allows complete collection of gold, iron, tin, and platinum, demonstrating that L is an adaptable selective metal precipitant controlled by just one variable. Thus, this discovery could be exploited in metal refining and recycling processes due to its tuneable selectivity under different metal leaching conditions, the avoidance of organic solvents inherent to biphasic extraction, and the straightforward recycling of the precipitant
Rare-earth precipitation by capsule formation
No full textQuantitative ICP-MS data for rare-earth precipitations, nuclear magnetic resonance (NMR) spectroscopic data, infrared and Raman spectroscopic data, electrospray-ionisation mass spectrometry (ESI-MS) data
Targeted ligand design using a combined computational and experimental approach to unlock new metal separations
No full textAs societal demand for metals grows, sustainable routes to their efficient recovery from primary ores and secondary waste streams have become increasingly important. In this regard, understanding the chemical detail of metal separations is implicit to designing more efficient and environmentally benign processes. Herein, we report a combined computational and experimental approach to targeted ligand design by modification of a simple diamide (L), previously reported as a selective precipitant for Au. This afforded three new reagents through the addition of electron-donating (LOMe) and withdrawing (LCl) groups, and the inversion of the amide linkage (Linv). Computational studies confirmed the expected trends in protonation of the amide and subsequent metal uptake experiments showed all ligands act as selective precipitants for Au at low acid concentrations in the presence of an excess of ligand. Significantly however, the use of stoichiometric amounts of LOMe and LCl resulted in a switch in selectivity from square-planar (AuCl4-) to tetrahedral metalates (GaCl4- and FeCl4-), with precipitation suppressed for Linv. Computational modelling rationalised this reversal in metalate selectivity with LOMe and LCl on thermodynamic grounds, while Hirshfeld surfaces, NCI plots and QTAIM analyses highlighted halogen bonding as the most important structure directing interaction. Importantly, preliminary studies with LOMe suggested a viable pathway to the separation of Ga and Fe from industrially generated waste streams, which could be exploited in the recycling of zinc residues and end-of-life GaN light-emitting diodes
Copper precipitation and carbon analysis
No full textQuantitative ICP-OES and ICP-MS data for all precipitation and solvent extraction experiments, infrared spectroscopic data, powder X-ray diffraction data, X-ray fluorescence data, life cycle inventory, nuclear magnetic resonance (NMR) spectroscopic data and matrix assisted laser desorption/ionisation mass spectrometry (MALDI-MS) data.Excel workbook: Raw_Data_Vance_Chatzisymeon_Morrison_Love comprising ICP, FTIR, PXRD and XRF raw data
Excel workbook: Life_Cycle_Inventory_Vance_Chatzisymeon_Morrison_Love comprising inventory data used for life-cycle analysi
Triggering redox activity in a thiophene compound: radical stabilization and coordination chemistry
Full text linkThe synthesis, metalation, and redox properties of an acyclic bis(iminothienyl)methene L− are presented. This π-conjugated anion displays pronounced redox activity, undergoing facile one-electron oxidation to the acyclic, metal-free, neutral radical L* on reaction with FeBr2. In contrast, reaction of L− with CuI forms the unique, neutral Cu2I2(L*) complex of a ligand-centered radical, whereas reaction with the stronger oxidant AgBF4 forms the metal-free radical dication L*2+
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Controlled photocatalytic hydrocarbon oxidation by uranyl complexes
Full text linkControlled, photocatalytic C−H bond activations are key reactions in the toolkits of the modern synthetic chemist. While it is known that the uranyl(VI) ion, [UVIO2]2+, the environmentally dominant form of uranium, is photoactive, most literature examines its luminescent properties, neglecting its potential synthetic utility for photocatalytic C−H bond cleavage. Here, we synthesise and fully characterise an air‐stable and hydrocarbon‐soluble uranyl phenanthroline complex, [UVIO2(NO3)2(Ph2phen)], UPh2phen, and demonstrate that it can catalytically abstract hydrogen atoms from a variety of organic substrates under visible light irradiation. We show that the commercially available parent complex, uranyl nitrate ([UVIO2(NO3)2(OH2)2]⋅4H2O; UNO3), is also competent, but from electronic spectroscopy we attribute the higher rates and selectivity of UPh2phen to ligand‐mediated electronic effects. Ketones are selectively formed over other oxygenated products (alcohols, etc.), and the catalytic oxidation of substrates containing a benzylic C−H position is particularly improved for UPh2phen. We also show uranyl‐mediated photocatalytic C−C bond cleavage in a model lignin compound for the first time
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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