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SM ISO690:2012 DULKSNIS, A., CESIULIS, Henrikas, TSYNTSARU, Natalia. Leaching and electrowinning of Pb and Sn from eco-friendly solutions. In: Materials Science and Condensed Matter Physics, Ed. 9, 25-28 septembrie 2018, Chișinău. Chișinău, Republica Moldova: Institutul de Fizică Aplicată, 2018, Ediția 9, p. 233. |
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Materials Science and Condensed Matter Physics Ediția 9, 2018 |
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Conferința "International Conference on Materials Science and Condensed Matter Physics" 9, Chișinău, Moldova, 25-28 septembrie 2018 | ||||||
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CZU: 539.1+544.6+66 | ||||||
Pag. 233-233 | ||||||
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The European Commission‘s Waste Electrical and Electronic Equipment (WEEE) Directive requires that member states recycle and recover all electrical waste and electronic equipment rather than simply disposing it in landfill sites. E-waste is composed of a large number of components such as Cu, Al, Fe, Sn, Pb, Zn, Ag, Au, Pd, etc. The components are removed through separate treatment and recycling processes. It is convenient to separate Pb and Sn at first stages of WEEE treatment, because their compounds hydrolyzed and form colloidal hydroxides that block filters of e-waste equipment. Thus, the aim was to investigate leaching and recovery of Pb and Sn by electrowinning using environmentally friendly solutions. Experimental procedure: Working electrodes for leaching tests were: Cu rod, Pb (99,998%), Sn (99,998%) wires (Alfa Aesar) with exposed areas of 1 cm2; the reference and counter electrodes were Ag/AgClsat and graphite respectively. The electrochemical experiments were performed at room temperature in a cell connected to the Potentiostat/ Galvanostat AUTOLAB N302. The corrosion current density of Sn, Pb was evaluated using the potentiodynamic polarization technique in 3-electrode cell. Cu plate (as cathode, surface area 8 cm2) and graphite (anode) were used as a working electrode for electrowinning in 2-electrode system. Results: Actually, the leaching of metals and forming of soluble compounds is a process of enforced corrosion. Influence of pH, H2O2, (NH4)2S2O8, C6H8O7, C2H5NO2 on Pb and Sn leaching was investigated. Corrosion of Pb and Sn in glycine solution is extremely slow due to the acid adsorption on the metal surface. Adsorbed layer of glycine inhibits further metal dissolution especially in the case of Sn. Corrosion rate for Pb and Sn is highest in citric acid with the addition of ammonium persulfate at pH 5 ’ 7 and pH 3.8 ’ 5.8, respectively. In the strongly acidic solutions (pH < 5), corrosion rate of lead and tin drops down (Fig. 1). Influence of pH and applied voltage on weight of electrodeposited metals using flat and metal foam electrodes was investigated. The electrowinning was performed using 2-electrodes cell and the compact film containing Pb and Sn could be obtained on the cathode at bath voltage : ΔE = 3.5 V (pH 5.7) or ΔE = 3 V (pH 7.5). |
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