Investigation of municipal solid waste (MSW) and industrial landfills as a potential source of secondary raw materials

Many of the secondary raw materials (SRM) in landfills constitute valuable and scarce natural resources. It has already been recognised that the recovery of these elements is critical for the sustainability of a number of industries and SRM recov¬ery from anthropogenic waste deposits represents a significant opportunity. In this study, the characterisation of the different waste fractions and the amount of SRM that can potentially be recovered from two landfill sites in Finland is presented. The first site was a municipal solid waste (MSW) landfill site and it was specifically in¬vestigated for its metals, SRM, plastics, wood, paper, and cardboard content as well as its fine fraction (<20 mm). The second site was an industrial landfill site contain¬ing residual wastes from industrial processes including 1) aluminium salt slag from refining process of aluminium scrap and 2) shredding residues from automobiles, household appliances and other metals containing waste. This site was investigated for its metals and SRM recovery potential as well as its fine fraction. Results suggest that the fine fraction offers opportunities for metal (Cr, Cu, Ni, Pb, and Zn) and SRM extraction and recovery from both landfill site types while the chemical composition of the industrial waste landfill offered greater opporutinity as it was comparable to typical aluminium salt slags. Nevertheless, the concentrations of rare earth metals (REE) and other valuable elements were low even in comparison with the concentra¬tions found in the Earth’s crust. Therefore mining landfill sites only for their metals or SRM content is not expected to be financially viable. However, other opportunities, such as waste-derived fuels from excavated materials especially at MSW landfill sites, still exists and fosters the application and feasibility of landfill mining

Assessing the opportunities of landfill mining as a source of critical raw materials in Europe

Many of the metals in landfill constitute valuable and scarce natural resources. It has already been recognised that the recovery of these elements is critical for the sustainability of a number of industries. Arsenic (which is an essential part of the production of transistors and LEDs) is predicted to run out sometime in the next five to 50 years if consumption continues at the present rate. Nickel used for anything involving stainless steel and platinum group metals (PGMs) used in catalytic converters, fertilisers and others are also identified as critical materials (CM) to the EU economy at risk of depletion However, despite the increasing demand, none of this supply is supported by recycling. This is due to the high cost of recovery from low concentrations when compared to conventional mining. As demonstrated by the two pilot case studies of this study, mining landfill sites only for their metals content is not expected to be financially viable. However, other opportunities such as Waste-derived fuels from excavated materials exist which if combined , form the concept of ‘enhanced landfill mining’. have the potential to be highly energetic. The energy potential is comparable to the levels of energy of Refuse-Derived Fuels (RDF) produced from non-landfilled wastes

Computational investigations of 18-electron triatomic sulfur–nitrogen anions

Abstract MRCI-SD/def2-QZVP and PBE0/def2-QZVP calculations have been employed for the analysis of geometries, stabilities, and bonding of isomers of the 18-electron anions N₂S²⁻, NS₂⁻, and NSO⁻. Isomers of the isoelectronic neutral molecules SO₂, S₂O, S₃, and O₃ are included for comparison. The sulfur-centered acyclic NSN2⁻, NSS⁻, and NSO⁻ anions are the most stable isomers of their respective molecular compositions. However, the nitrogen-centered isomers SNS⁻ and SNO⁻ lie close enough in energy to their more stable counterparts to allow their occurrence. The experimental structural information, where available, is in good agreement with the optimized bond parameters. The bonding in all investigated species is qualitatively similar, though electron density analyses reveal important quantitative differences that arise from bond polarization. Most of the investigated systems can be described with a single configuration wave function, the two notable exceptions being isomers SSS and OOO that show some diradical character. The computed MRCI-SD/def2-QZVP absorption maxima for SNS⁻ and NSS⁻ are 342 and 327 nm, respectively. The corresponding PBE0/def2-QZVP values in acetonitrile are 353 and 333 nm. These data support the proposed initial formation of SNS⁻ from electrochemical or chemical reduction of SSNS⁻ based on experimental UV–vis spectra. The interconversion of SNS⁻ and NSS⁻ is calculated to be facile and reversible, leading to an equilibrium mixture that also includes the remarkably stable dianion SNSNSS²⁻. Thus, salts of either SNS⁻ or NSS⁻ with bulky organic cations represent feasible synthetic targets

Possíveis efeitos adversos dos campos eletromagnéticos (50/60 Hz) em humanos e em animais Potential adverse effects of electromagnetic fields (50/60 Hz) on humans and animals

Os avanços tecnológicos têm aumentado o número de equipamentos elétricos e eletrônicos, seja nas residências ou mesmo no ambiente de trabalho, fazendo com que a população conviva com grande número de fontes de irradiação eletromagnética, com os mais diversos níveis de potência e freqüência. Por muitos anos, alguns cientistas e engenheiros acreditaram que o campo eletromagnético (CEM) com freqüência extremamente baixa não pudesse causar efeitos e alterações significantes no material biológico. O objetivo deste trabalho é verificar os possíveis efeitos adversos dos CEMs em humanos e animais, que foram publicados nos últimos anos, através de uma revisão da literatura disponível em Medline, revistas nacionais e internacionais e catálogos de obras de referência na área dos CEM (50/60 Hz). Como resultado foi observado que o CEM (50/60 Hz) é capaz de produzir diversos efeitos adversos em humanos e animais, como por exemplo: distúrbios na reprodução, doenças degenerativas, efeitos psiquiátricos e psicológicos, alterações citogenéticas, alterações no sistema cardiovascular, nervoso e neuroendócrino, bem como nos parâmetros biológicos e bioquímicos. Apesar de todas estas constatações e devido a muitas controvérsias entre vários autores, faz-se necessário um estudo mais específico e aprofundado sobre o assunto.<br>The technologic development has increased the number of electric and electronic devices for household and work environment applications. In this way, we have to cope with a diverse quantity of electromagnetic irradiation sources, with different power and frequency ranges. For many years, some scientists and engineers believed that low-frequencies electromagnetic field (EMF) could not cause any bad effect or substantial alterations on the biologic livings. This work has the objective to perform a literature review of the possible effects of EMF in human beings and animals, that was published in the past years on Medline, international, and national journals about the EMF (50/60Hz). The results showed that extremely low EMF might produce adverse effects, i.e. cancer, reproduction disruption, degenerative illnesses, citogenetic alterations, and cardiovascular, neurologic and neuroendocrine system alterations in humans and animals. The biologic and biochemical parameters suffered interference as well. Despite all these findings, we can find some disagreements among the authors. Hence it is necessary to extend the research about this issue