Sustainable anode recycling of Ni-MH spent batteries: synthesis of nickel and lanthanide oxides via selective precipitation, sol-gel and coprecipitation methods
Name: ANTONIO AUGUSTO LOPES MARINS
Type: PhD thesis
Publication date: 03/04/2019
Advisor:
Name |
Role |
|---|---|
| MARCOS BENEDITO JOSÉ GERALDO DE FREITAS | Advisor * |
Examining board:
| Name |
Role |
|---|---|
| ADILSON RIBEIRO PRADO | External Examiner * |
| ELOI ALVES DA SILVA FILHO | Internal Examiner * |
| EUSTAQUIO VINICIUS RIBEIRO DE CASTRO | Internal Examiner * |
| JOSÉ MARCOS STELZER ENTRINGER | External Examiner * |
| MARCOS BENEDITO JOSÉ GERALDO DE FREITAS | Advisor * |
Summary: The recycling and recovery of Ni-MH batteries has been investigated by several researchers, however, in recent years there was an intetensification of this kind of study due to the importance of these resources and its environmentally appropriate use to extract the metals contained in these wastes. The present work shows the feasibility of recovering nickel and rare earth metals (RT) from the negative electrode of Ni-MH batteries exhausted by selective precipitation (S1), sol-gel (S2) and coprecipitation (S3), aiming at green chemistry and sustainability. The anode was leached separately with the carboxylic, formic, citric and oxalic acids. From these acids, the respective precursors were synthesized: formates, citrates (sol-gel) and oxalates based on Ni2 + and TR3+, in order to become a mild leaching process, safer, environmentally sustainable and feasible. The precursors (formates, citrates and oxalates) were characterized by infrared spectroscopy (FTIR), Raman spectroscopy, fluorescence and XRD by the powder method. In addition, thermogravimetry (TG) (SEM) and electrochemical characterization of oxides generated by the thermal decomposition of the oxalate precursor. The photoluminescent properties of the TR3+ formates were also investigated. When excited in the 420, 421, 422 and 435 nm regions, the Pr3+ formate exhibited narrow emission bands at 834, 837, 842 and 867 nm, attributed to the characteristic 3H4→3P2 transitions of Pr3+, dominated by the abnormal intensity of the high transition intraconfiguration 1D2→1G4. The Nd3+ formate at the time of excitation in regions 207, 216 and 256 nm presented emission bands at 433, 434 and 527 nm, directed to the transitions 4I9/2→4G11/2, originating from Nd3+ due to the intraconfiguration transition 2D5/2→2P1/2. From the thermal treatments, precursor materials (citrates and oxalates), carried out at temperatures of 1123, 1373 and 1473 K, it was possible to identify the Ni and TR oxides confirmed by XRD, SEM and EDS. The electrochemical properties of the mixed oxides of Ni and TR from oxalate were analyzed by cyclic voltammetry, galvanostatic loading and discharge cycles and impedance spectroscopy. The investigated method showed that the synthesis of ceramic materials containing Ni and TR in its structure made it possible to recycle by leaching the Ni-MH anode with carboxylic acids, presenting a less aggressive and environmentally more sustainable medium.
