Synthesis of NiFe2O4 from nickel recycled from spent Ni-MH batteries and its multifunctional applications as a catalyst in a photo-Fenton process and as an electrochemical pseudocapacitor
Name: LUMA BARBOSA MAGNAGO
Type: MSc dissertation
Publication date: 16/03/2018
Advisor:
Name |
Role |
|---|---|
| MARCOS BENEDITO JOSÉ GERALDO DE FREITAS | Advisor * |
Examining board:
| Name |
Role |
|---|---|
| GEISAMANDA PEDRINI BRANDÃO ATHAYDE | Internal Examiner * |
| LUIZ CARLOS PIMENTEL ALMEIDA | External Examiner * |
| MARCOS BENEDITO JOSÉ GERALDO DE FREITAS | Advisor * |
| MARIA DE FÁTIMA FONTES LELIS | Co advisor * |
Summary: In this study, a co-precipitation method was used for the synthesis of undoped ferrites (Fe2O3/Fe3O4-R) and nickel-doped ferrites from nickel reagents (NiFe2O4-R) and from nickel recycled from spent nickelmetal hydride (Ni-MH) batteries (NiFe2O4-B). Ferrite structure and composition were confirmed by X-ray diffraction (XRD), energy dispersive X-ray (EDX) and inductively coupled plasma optical emission spectrometry (ICP-OES). Scanning electron microscopy (SEM) showed agglomerated particles of different sizes and shapes and the transmission electron microscopy (TEM) revealed spherical particles of 50 nm. Ferrites are a multifunctional material that can be used as a catalyst and pseudocapacitor. The catalytic properties of ferrites were analyzed by measuring the decolorization of methylene blue (MB) in a photo-Fenton process under solar radiation. The experimental design ranked ferrites in the following order of MB decolorization efficiency: NiFe2O4-B = NiFe2O4-R > Fe2O3/Fe3O4-R. Using NiFe2O4-B, MB solutions were decolorized with more than 90% efficiency in 90 min. ICP-OES analyzes of the solution contained in detected concentrations of (0.00057 ± 0.00067) mg L-1 of nickel ions and undetected concentration of iron ions. The concentrations of nickel and iron ions are lower than the standard effluent release concentrations indicated CONAMA resolution 430/2011. NiFe2O4-B ferrite does not transfer metals ions present in its composition to the solution. Analysis of the MB solution by ion chromatography after the NiFe2O4-B-catalyzed decolorization showed the presence of formic, acetic, and propionic acids. Pseudocapacitive properties, analyzed by cyclic voltammetry, showed that NiFe2O4-B have higher charge efficiency (84.3%) when compared with NiFe2O4-R (65.5%) and Fe2O3/Fe3O4-R (57%) after 1000 cycles. Ferrite NiFe2O4-B is an efficient catalyst for MB degradation and as pseudocapacitor.
