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Hazotte, Claire, Meux, Eric, Leclerc, Nathalie and Lapicque, Francois
Chemical Engineering and Processing: Process Intensification, 96:83-93

Mots clefs: Electroassisted leaching Electrodeposition Ni–Cd batteries Solid waste Transport rates

Resume: Abstract Combined leaching of solid wastes to electrodeposition can be an attractive technique for their optimal beneficiation. In most investigations in the area, results are given in terms of energy consumption and selectivity, without thorough analysis of the rates of the various processes involved. The present investigation deals with the significance of transport and transfer phenomena involved in relation to reaction processes, in a cell combining electroassisted leaching to electrodeposition in view to designing treatment processes of manufactured wares after their end of life. The case of the so-called black mass of used Ni–Cd batteries has been considered here, for the separate productions of nickel salts and metal cadmium. First, leaching of the various hydroxides contained in the black mass has been studied either upon addition of acid or by electrochemical generation of H+ at the anode. Moreover, transport of the metal cations produced from the anode compartment to the cathode through the cloth acting as the separator has been investigated through a simple description of transport phenomena. Comparison and discussion of the various transport or reaction rates could show that ion transport through the porous separator could represent the rate-determining step.

Equipe: Département CP2S : Chimie et électrochimie des matériaux

Hazotte, Claire, Leclerc, Nathalie, Diliberto, Sébastien, Meux, Eric and Lapicque, Francois
Environmental Technology, 36(6):796-805

Resume: The aim of this paper is the characterization of spent NiCd batteries and the characterization of an industrial Black Mass obtained after crushing spent NiCd batteries and physical separation in a treatment plant. The characterization was first performed with five cylindrical NiCd batteries which were manually dismantled. Their characterization includes mass balance of the components, active powders elemental analysis and phase identification by X-ray powder diffraction. Chemical speciation of the two metals was also investigated. For cadmium, speciation was previously developed on solid synthetic samples. In a spent battery, the active powders correspond to about 43% of the battery weight. The other components are the separator and polymeric pieces (5%), the support plates (25%) and the carbon steel external case (27%). The sequential procedure shows that the nickel in the positive powders from the dismantled Ni?Cd batteries is distributed between Ni0 (39.7%), Ni(OH)2 (58.5%) and NiOOH (1.8%). Cadmium in the negative powder is about 99.9% as the Cd(OH)2 form with 0.1% of metal cadmium. In the industrial Black Mass, the distribution of cadmium is the same, whereas the distribution of nickel is Ni0 (46.9%), Ni(OH)2 (43.2%) and NiOOH (9.9%). This material contains also 1.8% cobalt and approx. 1% iron.

Equipe: Département CP2S : Chimie et électrochimie des matériaux

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