Desenvolvimento de novas rotas hidrometalúrgicas "verdes" para recuperação de metais a partir de lixo eletrônico

Abstract

In this work two methodologies were developed for the recovery of strategic metals from secondary sources, as alkaline batteries and fluorescent lamps, using aqueous two-phase system as extraction technique. The extraction/separation of Zn(II) and Mn(II), from alkaline batteries waste, were studied in terms of extraction percentage (%E) and separation factor (SZn/Mn) in ATPS. The effects of the following parameters: nature and concentration of the extracting agents (PAN, Cyanex 272, Dithizone and D2EHPA); pH (3.00, 6.00 and 11.0), ATPSforming electrolytes (Na2SO4, C6H5Na3O7 or C4H4Na2O6) and copolymers (L35 and L64); tie-line length (TLL) and mass ratio between top and bottom phases (mTP/mBP). The best conditions for selective extraction of the metal ions were achieved using an ATPS composed by L64 + Na2SO4 + H2O at pH = 3.00, TLL = 41.83% w/w and mTP/mBP = 1 using dithizone as the extracting agent and leach liquor with dilution factor equal to 10. This resulted in a value for separation factor of 𝑆Zn/Mn= 1.2 x 106, in one extraction stage. A multivariate study was carried out, using experimental design, for the yttrium extraction in ATPS using alizarin red as the extracting agent. The optimized variables, using fractional desing 26-1, were: pH (3.00 to 9.00), extracting agent concentration (2.3 to 23.0 mmol kg-1), tie line length, ATPS-forming copolymers (L35 and L64) and electrolytes (Na2SO4 and C6H5Na3O7.2H2O) and mass ratio between top and bottom phases (mTP/mTP = 0.5-2.0). It was observed, for the first time, that the metal ions partition in ATPS is directly influenced by the salt-forming anion species distribution as a function of the pH, in high TLL values. The model was optimized in a 23 factorial design with no adjustment lack and was able to predict the yttrium extraction response with accuracy close to 96%. The yttrium extraction in optimized conditions were applied in real samples of phosphorous fluorescent powder leach liquor. After five extraction steps, 90% of yttrium was selectively recovered.