| dc.description.abstract | Nickel metal hydride batteries contain nickel, cobalt and other valuable metals to a lesser extent. Therefore, recycling Ni/HM batteries is important not only for environmental reasons but for economic ones also. Hydrometallurgical processes are widely used for the recovery of Ni, Co, Cd and other metals from nickel metal hydride batteries, so usually performed acid leaching to extract the electrode material values. To obtain the final product are carried out various stages and processes, most notably precipitation, as it is a method widely used by many researchers because of its high rates of efficiency and be simple and inexpensive process to recover metals . Ferrites are widely used materials in the electronics industry mainly due to their magnetic properties, chemical stability and easy to machine, in general formula wherein M represents MFe2O4 one or more divalent metals and crystallizes in a cubic system.
Based on the foregoing, the aim of this thesis is the synthesis and characterization of Ni based ferrites from nickel metal hydride batteries using the electrode material leaching, precipitation of precursors and finally calcination to obtain the final product as a possible alternative for the treatment and recycling of Ni/HM.
H2SO4 was used to leach the battery electrode material, analyzing the effect of acid concentration (1 and 2M) and the leaching temperature (50 and 80 °C) on the percentage recovery of metals content. The ratio Fe:Me was set to 2:1 for the precipitation of precursors of ferrite, according to infrared spectroscopy (IR) were sulfates, hydroxides and carbonates, which were obtained using NH4HCO3 and NH4OH as precipitating agents subsequently analyzed the effect of calcination temperature (700 and 900 °C) on the formation of spinel phase. X-ray diffraction (XRD) reveals that from 700 °C is present as a single phase ferrite present. For characterization of the calcined product was used a Scanning Electron Microscope (SEM), a vibrating sample magnetometer (VSM) atomic absorption spectrometer (AA) and a thermobalance to determine the Curie temperature (TC). The results indicate that the calcination temperature affects mainly the magnetic properties of the ferrite, since the samples heat treated at 900 °C have an average particle size of 265nm, a TC = 508 °C and a saturation magnetization of 29.22 emu/g. | |
