18 research outputs found
Electrodialysis for concentrating cobalt, chromium, manganese, and magnesium from a synthetic solution based on a nickel laterite processing route
[EN] Due to environmental and human health concerns, the need for cleaner techniques able to extract and recover metals from mining process solutions has been increasing. In this work, the use of electrodialysis for recovering cobalt, magnesium, manganese, and chromium ions from an acid multicomponent solution generated in the nickel laterite processing was evaluated. Values of percent extraction above 98% were obtained for Co2+, Mn2+, and Mg(2+ )ions. For Cr3+, the greatest percent extraction obtained was 83%. The results of percent concentration of the species showed the same trend: for Cr3+ ions, it was significantly lower than the others. Such difference in the transport of the metals through the membranes may have occurred due to the lower molar concentration, lower diffusion coefficient, and greater Stokes radius of chromium ions. Thus, the transfer of Cr3+ was hindered by the presence of other cationic species. This was also evidenced by the results of current efficiency and energy consumption associated with each species in solution. Lastly, the results of solution pH throughout the experiments and the final condition of the membranes, which were analyzed by SEM/EDS, indicated that the water dissociation phenomenon occurred at their surfaces.The authors gratefully acknowledge the financial support given by funding agencies CNPq (Process 141346/2016-7; 171241/2017-7; 160320/2019-4) and FAPESP (Process 2012/51871-9) . This study was financed in part by the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior-Brasil (CAPES) -Finance Code 001 (Processes 88881.190502/2018-01 and 88887.362657/2019-00) .Feijoo, GC.; Santana-Barros, K.; Scarazzato, T.; Espinosa, D. (2021). Electrodialysis for concentrating cobalt, chromium, manganese, and magnesium from a synthetic solution based on a nickel laterite processing route. Separation and Purification Technology. 275. https://doi.org/10.1016/j.seppur.2021.11919227
Evaluation of the transport properties of copper ions through a heterogeneous ion-exchange membrane in etidronic acid solutions by chronopotentiometry
[EN] The transport properties of copper chelates across an anion-exchange membrane were investigated by means of chronopotentiometry. Several solutions containing etidronic acid, copper sulfate and potassium chloride were evaluated. Tests were accomplished in a three-compartment reactor using a heterogeneous membrane containing quaternary ammonium functional groups. Results showed a strong relation between the amount of chelated anions and the limiting current density, the electrical resistance and the concentration polarization. An increase in the anionic equivalent charge of the solutions modified the three regions of the current-voltage curves. The acid medium was found to be less favorable because of the possibility of the formation of non-charged species in overlimiting regions. The presence of chloride anions increased the limiting current density, especially when the chloride concentration exceeded the etidronic acid concentration.Authors would like to thank the Institute for Technological Research (IPT), the Institute for Technological Research Foundation (FIPT), to the São Paulo Research Foundation (Fapesp - processes 2012/51871-9, 2014/21943-3 and 2014/13351-9) and the National Council for Scientific and Technological Development.Scarazzato, T.; Panossian, Z.; García Gabaldón, M.; Ortega Navarro, EM.; Tenório, J.; Pérez-Herranz, V.; Espinosa, D. (2017). Evaluation of the transport properties of copper ions through a heterogeneous ion-exchange membrane in etidronic acid solutions by chronopotentiometry. Journal of Membrane Science. 535:268-278. https://doi.org/10.1016/j.memsci.2017.04.048S26827853
Novità sul Mesolitico dell’Italia settentrionale: gli ultimi cacciatori-raccoglitori di pianura e il caso-studio dell’area delle Sorgenti del Sile
Novità sul Mesolitico dell’Italia settentrionale: gli ultimi cacciatori-raccoglitori di pianura e il caso-studio dell’area delle Sorgenti del Sile / Something new on the Mesolithic of Northern Italy: the last hunter-gatherers of the plain and the case-study of the river Sile spring area
Condicionantes solares como princípio orientador da forma urbana: estudo de caso contextualizado no Distrito Federal
Electrodialysis in Hydrometallurgical Processes
Electrodialysis (ED) is an ionic exchange membrane process for separation of different components and species. In desalination, a large part of the energy is used to sustain a concentration difference between the solutions, but in the processes of exchanging in selective manners, the energy need is lower and more directed towards ohmic losses in the membranes. The latter has relevance to several hydrometallurgical industries, as they very often accumulate undesired species in their process streams and currently apply intensive (energy and chemical) routes to remove these species. Here, we describe the principle of ED and discuss opportunities for component and salt separation using ion-exchange membranes by providing a brief review of ED in the hydrometallurgical sector
General circulation of the Eastern Mediterranean
A novel description of the phenomenology of the Eastern Mediterranean is presented based upon a comprehensive pooled hydrographic data base collected during 1985-1987 and analyzed by cooperating scientists from several institutions and nations (the POEM project). Related dynamical process and modeling studies are also overviewed. The circulation and its variabilities consist of three predominant and interacting scales: basin scale, subbasin scale, and mesoscale. Highly resolved and unbiased maps of the basin wide circulation in the thermocline layer are presented which provide a new depiction of the main thermocline general circulation, composed of subbasin scale gyres interconnected by intense jets and meandering currents. Semipermanent features exist but important subbasin scale variabilities also occur on many time scales. Mesoscale variabilities modulate the subbasin scale and small mesoscale eddies populate the open sea, especially the south-eastern Levantine basin. Clear evidence indicates Levantine Intermediate Water (LIW) to be present over most of the Levantine Basin, implying that formation of LIW is not localized but rather is ubiquitous. The Ionian and Levantine basins are confirmed to form one deep thermohaline cell with deep water of Adriatic origin and to have a turnover time of one and a quarter centuries. Prognostic, inverse, box and data assimilative modeling results are presented based on both climatological and POEM data. The subbasin scale elements of the general circulation are stable and robust to the dynamical adjustment process. These findings bear importantly on a broad range of problems in ocean science and marine technology that depend upon knowledge of the general circulation and water mass structure, including biogeochemical fluxes, regional climate, coastal interactions, pollution and environmental management. Of global ocean scientific significance are the fundamental processes of water mass formations, transformations and dispersion which occur in the basin. © 1992
General circulation of the Eastern Mediterranean
A novel description of the phenomenology of the Eastern Mediterranean is presented based upon a comprehensive pooled hydrographic data base collected during 1985-1987 and analyzed by cooperating scientists from several institutions and nations (the POEM project). Related dynamical process and modeling studies are also overviewed. The circulation and its variabilities consist of three predominant and interacting scales: basin scale, subbasin scale, and mesoscale. Highly resolved and unbiased maps of the basin wide circulation in the thermocline layer are presented which provide a new depiction of the main thermocline general circulation, composed of subbasin scale gyres interconnected by intense jets and meandering currents. Semipermanent features exist but important subbasin scale variabilities also occur on many time scales. Mesoscale variabilities modulate the subbasin scale and small mesoscale eddies populate the open sea, especially the south-eastern Levantine basin. Clear evidence indicates Levantine Intermediate Water (LIW) to be present over most of the Levantine Basin, implying that formation of LIW is not localized but rather is ubiquitous. The Ionian and Levantine basins are confirmed to form one deep thermohaline cell with deep water of Adriatic origin and to have a turnover time of one and a quarter centuries. Prognostic, inverse, box and data assimilative modeling results are presented based on both climatological and POEM data. The subbasin scale elements of the general circulation are stable and robust to the dynamical adjustment process. These findings bear importantly on a broad range of problems in ocean science and marine technology that depend upon knowledge of the general circulation and water mass structure, including biogeochemical fluxes, regional climate, coastal interactions, pollution and environmental management. Of global ocean scientific significance are the fundamental processes of water mass formations, transformations and dispersion which occur in the basin. © 1992