Synthesis and characterization of a photocatalyst perovskite composite ABO3/Nano-ferrite MFe2O4: A global decisional approach
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Date
2025-01-29
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National Higher School of Technology and Engineering. Annaba
Abstract
This thesis consists of an eco-design approach of the photocatalyst nanocomposite perovskite BiFeO3/spinel MgFe2O4 Nano-ferrite used in Advanced Oxidation Processes (AOPs). It discusses the conception keys focusing on the synthesis methods, the physicochemical properties of nanomaterials and the effect of precursors and dopants. The Lab-scale Life Cycle Assessment (LCA) is applied to support stakeholders in selecting eco-friendly nanomaterials. The coprecipitation method is used to elaborate three nanomaterial groups: three spinel ferrites (MgFe2O4, MgFe1.95Ce0.05O4 and MgFe1.90Ce0.10O4 calcined at 600°C and Mg0.95Ba0.05Fe2O4 calcined at 800°C/3h), one perovskite (BiFeO3/600°C/2h), and three perovskite-spinel ferrite composites (BiFeO3-MgFe2O4, BiFeO3-MgFe1.95Ce0.05O4, and BiFeO3-MgFe1.90Ce0.10O4 calcined at 600°C). The structural, morphological and physic-chemical properties characterization is carried by using X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), environmental scanning electron microscopy (ESEM-EDX), the Brunauer-Emmett-Teller (BET) method, UV-visible spectrophotometer, and vibrating sample magnetometer (VSM). The photocatalytic and Fenton-like degradations of Methylene blue dye are applied under sunlight irradiation. The Lab-scale LCA is modeled in OpenLCA 2.1.1 software by using Ecoinvent 3.5 databases and CML 2001 method. The LCA shows that the sol-gel method that uses nitrate precursors in MgFe2O4 spinel has the lowest environmental impacts in all categories, comparing to the co-precipitation method that uses chloride precursors because of energy consumption in reaction and calcination steps. The elaboration of spinels has the highest environmental impacts than the use phase of depollution regardless the photocatalytic efficiency. The cerium rare earth dopant reduces the optical band gap from 2.50 to 2.36 eV and dropping the rate of sheet-like nanoparticles present in pure spinel to agglomerated nanoparticles allowing the spinel to be more efficient under the visible light in presence of H2O2 with the 91% of methylene blue degradation in 180 minutes. It also increases the crystallite size from 15.46 to 95.70 nm, but it decreases the magnetic properties and the specific surface area from 57.23 to 47.25 m2/g. The cerium dopants have not significant contribution in all impact categories when they are used. The LCA shows that the elaborated perovskite BiFeO3 has the lowest magnetic properties and environmental impacts than the ferrite spinel MgFe2O4 and the nanocomposites BiFeO3-MgFe2O4, BiFeO3-MgFe1.95Ce0.05O4, and BiFeO3-MgFe1.90Ce0.10O4. The IVnanocomposites doped with cerium performs the lower optical band gap, respectively 1.91 and 1.94 eV. The composite perovskite/spinel allows to achieve a better visible light activity and a long cycle life with the recyclability.