292 research outputs found
Green chemistry for precious metals recovery from WEEE
No full textHydrometallurgical methods for precious metal (PM) recovery from complex matrices, such as waste, have been mostly inherited from the well-known processes conventionally applied to ores and jewelry ashes: despite the risks related to their use, cyanidation and aqua-regia leaching remain the most widely used chemical processes for PM dissolution and recovery on an industrial scale in the case of waste electrical and electronic equipment. This is mainly due to the effectiveness of these reagents in PM dissolution and the common awareness that these metals, showing high reduction potential and lower reactivity with respect to most elements, seem to require aggressive reactants in order to obtain effective metal dissolution. In this chapter, the peculiar contribution of coordination and green chemistry in designing new safer reagents and processes for effective and selective metal dissolution and recovery, will be discussed, highlighting the state-of-the-art on promising effective sustainable lixiviants and the future perspectives of these early-stage multidisciplinary studies
Hi-Tech waste as “Urban Mines” of precious metals: new sustainable recovery methods
No full textPrecious metals (PMs) are valuable components of Hi-Tech goods such as electrical and electronic equipment, catalysts, advanced materials. These relatively recent applications and the growth of their market due to the fast technological development, heavily contribute to the high rate of element consumption and Hi-Tech waste accumulation of the modern consumer society. Looking at these wastes with new eyes, encouraged by the recent world-wide regulations aimed to the sustainable waste management and raw materials preservation, we can appreciate the value contained in and turn them in secondary resources of raw materials. In this context, a sustainable approach in PMs recovery from Hi-Tech waste, built on green chemistry principles and addressed to find a ready technological transfer, is described here
A lab experiment on metals separation and recovery from waste ink-jet cartridges as a non-formal appealing learning activity for students of secondary schools
No full textSince 2004, the Italian Ministry of Education, University and Research (MIUR), the Conference of Science and Technology Headmasters, and Confindustria, have been promoting the National Plan for Scientific Degrees (PLS) aimed at supporting students in acquiring scientific skills better responding to contemporary society challenges and increasing vocations in basic sciences. This paper describes a successful experience of the University of Cagliari together with selected local secondary schools, in which the hot topic of technological waste valorization was selected to create an orientation laboratory for students towards chemistry disciplines. Specifically, students and teachers were guided into the challenging world of e-waste production and treatment through the practical activity of noble metals recovery from real waste ink-jet cartridges. A specific emphasis was placed on fundamental chemical aspects – separation and recovery of metals driven by redox processes favored by a complexing agent – as well as on the chance to play on coordination chemistry to promote a green chemistry approach. The close collaboration between school and university teachers in planning and implementing laboratory activities is the element that characterizes PLS actions and promotes the development and strengthening of relations between secondary school and university courses in science, technology, engineering, and mathematics (STEM)
Sketching web services backends with SERPE
No full textIn the face of current strong commercial interest in services that, from an implementation point of view, consist of databases provided with a web API and/or a front end, there is a scarcity of tools that allow quickly sketching the service backend in order to deliver an interactive prototype. SERPE consists of an online Python programming environment that hides the complexities of the MVC model, databases, objects and object relational mapping and builds on Google's services, letting the service designer think in terms of a simple tagindexed persistent store. A Twitter clone and a service that allows control of a large lamp are presented as typical SERPE projects.IO-StudiolabIndustrial Design Engineerin
NIR-emissive Erbium Quinolinolate Complexes
No full textStudies addressed to a deep understanding of the structure/property relationship on the near infrared (NIR)-emissive erbium-quinolinolate complexes, which are of interest for low-cost photonic systems, are reviewed. The role of the 8-quinolinolate ligand (Q), which studies also as sensitizer to overcome the weak absorptivity of lanthanide ion, is discussed. Synthetic and structural aspects are reported to revise the old assumption that these complexes are analogous in structure to AlQ3 and to point out the specificity of the lanthanide coordination chemistry. In fact depending on reaction conditions, species with high coordination numbers and differing for nuclearity and stoichiometry have been isolated and fully characterized. In some instances it has been shown that coordinated water molecules directly bounded to the emitting erbium ion definitely represent the most effective quenchers for the luminescence at 1.5μm. Additionally, the combined optical and structural investigation of water-free Er-quinolinolate complexes, allows one to conclude that the C-H groups sitting in the Er3+ inner coordination sphere represent a very severe limit to the near-infrared emission yield. Implementation of structural/spectroscopic data into a theoretical model based on Förster's energy transfer resonant theory provides a comprehensive analysis of the near infrared emission quenching in erbium complexes useful to predict the quenching effects in luminescent lanthanide-complexes from the measurements of the vibrational absorption spectrum of the compound, the lanthanide radiative lifetime, and the minimum distance between the emitting ion and the quenchers. On that basis, in order to significantly improve the near-infrared emission yield, ligands which do not bear NH, CH or OH groups at a distance shorter than 7-8Å from the emitting ion are required. At the same time high sensitization efficiency of near-infrared emission and population saturation of trivalent erbium is achieved in these complexes, photoexcited into the absorption band of the quinolinolate sensitizer. It is concluded that a fully halogenated quinolinolate ligand can be an optimal candidate to improve the luminescent properties of erbium complexes. © 2011 Elsevier B.V
“CT complexes of dithioxamides with dihalogens as powerful reagents for noble metals dissolution”
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