Synthesis and Characterization of MFe2O4 Nanoparticles for Photocatalytic Remediation of Water

Abstract

Photocatalytic ozonation (PCO) technology offers effective strategies for improving photocatalytic efficiency in pharmaceutical degradation by promoting the generation of reactive oxygen species (ROS). In addition, ferrite-based materials are becoming increasingly attractive as heterogeneous photocatalysts and have found applications in a variety of fields including water remediation. This dissertation explores the application of novel ferrite materials for the degradation of Lomefloxacin in photocatalytic ozonation system.

In this thesis, novel phosphorus-modified ferrite-based photocatalysts were prepared and tested for the photocatalytic ozone degradation of lomefloxacin (LOM). Although the photocatalytic degradation of LOM was investigated using a variety of different catalysts, its degradation using photocatalytic ozonation system has never been studied. For the reactivity test, copper ferrite (CuFe2O4), magnesium ferrite (MgFe2O4), phosphorus-modified copper ferrites (PxCu1-xFe2O4 (x=0.035,0.07,0.1)) and phosphorus modified magnesium ferrites (PxMg1-xFe2O4 (x=0.035,0.07,0.1)) were prepared by the sol-gel auto combustion method.

Our experiments show that the photocatalytic ozonation system demonstrated significantly higher TOC removal compared to photolysis alone, with an approximately tenfold increase in efficiency. This was ascribed to the addition of the prepared photocatalysts. Furthermore, phosphorus modification led to substantial improvements, with TOC removal increasing by two orders of magnitude for P-MgFe2O4 and four orders of magnitude for P-CuFe2O4 compared to their unmodified counterparts. The ferrites with the lowest phosphorus content (P0.035Mg0.965Fe2O4 and P0.035Cu0.965Fe2O4)showed the highest k constant values and highest TOC removal percentages in each group. High-performance liquid chromatography (HPLC) analysis revealed that the degradation of LOM reached 99.98% and 99.94% reduction for P0.035Mg0.965Fe2O4 and P0.035Cu0.965Fe2O4 after 90 minutes in the photocatalytic ozonation system. The degradation kinetics of lomefloxacin followed a pseudo-first-order reaction.

In this thesis, it was proposed that the degradation of LOM occurs by the attack of the generated radicals on both the piperazinyl and quinolone moieties, resulting in the ring opening and the oxidation of 3-(methyl)piperazine moiety or through the defluorination, the cleavage of the piperazine ring, the deethylation, and demethylation. The results of this dissertation show that the introduction of the phosphorus modification into the ferrite photocatalyst led to an increase in both the specific surface area and the total pore volume. Compared to Pure ferrites, all samples with phosphorus exhibited the formation of new micropores with a radius in the range of 1 to 2 nm. In addition, the incorporation of phosphorus promoted the efficient separation of electron-hole pairs by trapping electrons in the conduction band, thus increasing the degradation efficiency.

In this dissertation, a multiphysics computational fluid dynamics (CFD) model was employed to simulate and validate the photocatalytic degradation of LOM in a continuous flow recirculating photocatalytic ozonation micro-slit reactor using P0.035Mg0.965Fe2O4. Kinetic constants for LOM photocatalytic oxidation were determined experimentally by varying flow rates and initial concentrations. The CFD model offers valuable insights into the reactor's inner workings and addresses the challenge of mass transfer limitations often encountered in kinetic studies involving immobilized photocatalysts in microreactors. The optimal conditions for the process were a flow rate of 10 ml/min and an initial concentration of 10 mg/L. Under these conditions, the reaction rate constant (k) was 1.877 hr-1 , resulting in a 7.7% reduction in TOC.

This dissertation is expected to pave the way for the development of more effective photocatalytic systems for wastewater treatment This PhD thesis aims to direct future experimental endeavors in the synthesis of high-performance P-modified ferrite photocatalysts for water treatment and pharmaceutical degradation, encourage the use of microreactors and CFD models to study how changes in water conditions and quality affect photocatalytic performance and promote the integration of photocatalytic processes into large-scale systems.

Date of Award	18 Dec 2024
Original language	American English
Supervisor	Giovanni Palmisano (Supervisor)