chameleon behaviour of iodine in recovering noble metals from weee towards sustainability and zero waste

The peculiar properties of iodine and safe lixiviants for sustainable and effective noble-metal recovery from shredded WEEE

Exploiting XPS for the identification of sulfides and polysulfides

The identification of surface sulfide and polysulfide species based on the curve fitting of S2p photoelectron spectra and, for the first time, of X-ray excited S KLL Auger spectra has been performed. The different sulfur chemical states present on the surface (sulfide S2, central S and terminal S in polysulfide chains) could be unambiguously assigned in the chemical state plot. Sulfur atoms in the central or terminal position, respectively, are found on a line with slope ca. 3 irrespective of the cation indicating similar initial state effects. On the other hand, for a given polysulfide, e.g. K2Sn, sulfur atoms both in central or terminal positions are found on the same line with slope 1 indicating similar final state effects. This behavior can be rationalized with the fact that the negative charge in polysulfide chains is located mainly on sulfur atoms in the terminal position; indeed, sulfur present as central S shows a binding energy shift of 0.6 eV with respect to elemental sulfur (S8), and sulfur in terminal S a shift of 2.4 eV. An application of this approach tested on commercial alkali polysulfides is provided for the curve fitting of SKLL signals and sulfur speciation of three different sulfide minerals enargite (Cu3AsS4), chalcopyrite (CuFeS2) and arsenopyrite (FeAsS). Also for the surface of mineral sulfides, terminal S atoms and central S atoms in the polysulfide chains can successfully be identified

Effect of the double doping mechanism on the phase diagram of Y1-xCaxBa2Cu3O6+y

We investigated the effect of hole doping and quenched disorder on the phase diagram of Y1-xCaxBa2Cu3O6+y, by exploiting the double doping mechanism of Y–Ca substitution and O intercalation in the undoped-to-heavily underdoped regime. We show that the insulator to metal transition, governed by the mobile hole concentration, reflects only the charges transferred by chain oxygen (the y fraction in the chemical formula). The transition is preceded by the suppression of antiferromagnetic order, which is replaced by a cluster spin glass ground state. We discuss the effect of doping and disorder on both magnetic states and on the appearance of superconductivit

From trash to resource: a green approach to noble-metals dissolution and recovery

A process based on the lixiviant properties of organic mixtures of dihalogen/S,S-ligands, N,N′-dimethyl-perhydrodiazepine-2,3-dithione (Me2dazdt) and tetraalkylthiuramdisulphide (Et4TDS) in the presence of diiodine, for gold recovery from the non-ferrous metal fraction of real shredded waste electric and electronic equipment (WEEE), is presented here. Selective dissolution of metals is achieved through a sequence of three steps where the oxidation of different kinds of metals is achieved by using: (1) refluxing water solutions of HCl 1:5 under Ar atmosphere (Sn, Zn, etc.); (2) water solutions of NH3/(NH4)2SO4 mixtures in the presence of H2O2 on the resting sample(Cu, Ag); and (3) acetone solutions of Me2dazdt or Et4TDS/I2 mixtures on the final residue (Au). Each step is followed by a further treatment for: (1) metal recovery, in the case of Au, Cu, Ag; and (2) inertization, in the case of heavy metals. As a whole, the process is very promising for effective recovery of gold and other valuable noble-metals and for using non harmful reagents in mild conditions

Effect of the double doping mechanism on the phase diagram of Y1-xCaxBa2Cu3O6+y

We investigated the effect of hole doping and quenched disorder on the phase diagram of Y1-xCaxBa2Cu3O6+y, by exploiting the double doping mechanism of Y–Ca substitution and O intercalation in the undoped-to-heavily underdoped regime. We show that the insulator to metal transition, governed by the mobile hole concentration, reflects only the charges transferred by chain oxygen (the y fraction in the chemical formula). The transition is preceded by the suppression of antiferromagnetic order, which is replaced by a cluster spin glass ground state. We discuss the effect of doping and disorder on both magnetic states and on the appearance of superconductivit

Noble-metals recovery from printed circuit boards: a multidisciplinary approach towards sustainability

A robust database of the noble metals (NM) content of different classes of Printed Circuit Boards (PCB) was build through an accurate characterization of samples of different origin, underwent mechanical comminution and representative sampling, by ICP-AES quantitative chemical analysis, to work as reference for researcher and companies interested in waste valorisation. The results identified RAM and mobile phone’s PCB as the “richest” classes of PCB, while TV PCB as the “poorest” in term of NM content. On these basis, a sustainable three-step NM recovery method, previously set-up on a finely shredded WEEE sample deprived by non-metallic and ferrous materials, was applied on a coarse sample of shredded RAM boards provided by companies, as a case study. Preliminary results highlighted that good NM recovery yields (from 65% to quantitative) and limited by-products formation could be achieved, despite a huge amount of composite materials was present in the mixture. Nevertheless, 10- times increased leaching times found for copper dissolution suggested that improved mechanical pretreatments might increase leaching effectiveness

Noble-metals recovery from printed circuit boards: a multidisciplinary approach towards sustainability

A robust database of the noble metals (NM) content of different classes of Printed Circuit Boards (PCB) was build through an accurate characterization of samples of different origin, underwent mechanical comminution and representative sampling, by ICP-AES quantitative chemical analysis, to work as reference for researcher and companies interested in waste valorisation. The results identified RAM and mobile phone’s PCB as the “richest” classes of PCB, while TV PCB as the “poorest” in term of NM content. On these basis, a sustainable three-step NM recovery method, previously set-up on a finely shredded WEEE sample deprived by non-metallic and ferrous materials, was applied on a coarse sample of shredded RAM boards provided by companies, as a case study. Preliminary results highlighted that good NM recovery yields (from 65% to quantitative) and limited by-products formation could be achieved, despite a huge amount of composite materials was present in the mixture. Nevertheless, 10- times increased leaching times found for copper dissolution suggested that improved mechanical pretreatments might increase leaching effectiveness

Ionic Couple-Driven Palladium Leaching by Organic Triiodide Solutions

Pd dissolution capabilities of a variety of organic triiodides (OrgI3) in organic solvent, where Org+ = 3,5-bis(phenylamino)-1,2-dithiolylium [(PhHN)2DTL+], 3,5-bis(morpholino)-1,2-dithiolylium (Mo2DTL+); tetrabuthylammonium (TBA+); and tetraphenylphosphonium (Ph4P+), toward the crude metal and model-spent three-way catalyst (TWC), are described here. Enhanced Pd-leaching yields from TWC were obtained using OrgI3 solutions (up to 98%) in spite of the fully inorganic KI3 one (38%) in the same mild conditions. The reaction products were isolated and characterized as Org2[Pd2I6]. Crystallographic and DFT studies highlighted the presence of several ion-pair secondary interactions in the products, which can explain the improved effectiveness of the Pd etching by OrgI3. For comparison purposes, the gold leaching by using R2DTLI3 and the obtained Au complexes were investigated. Preliminary results addressed to recover the metal and the reagents from the etching product showed that (PhHN)2DTLI3 is the most promising reagent to improve sustainability in the whole process