Design of MFe₂O₄-Based Nanomaterials as Heterogeneous Photocatalysts for Water Treatment

Abstract

The increasing presence of pharmaceutical pollutants in aquatic environments has promoted the development of advanced photocatalytic nanomaterials for efficient wastewater treatment. This dissertation addresses the rational design and synthesis of CuFe2O4-based nanomaterials as heterogeneous photocatalysts for the removal of recalcitrant pharmaceuticals. The CuFe2O4 nanomaterial was selected for its low toxicity, excellent thermal and chemical stability, strong magnetic properties for easy recovery, narrow bandgap, and low-cost synthesis, making it ideal for photocatalytic water treatment applications. A series of heterogeneous CuFe2O4-based photocatalysts, including bio-synthesized CuFe2O4, binary CuFe2O4/g-C3N4 nanocomposites, and ternary CuFe2O4/g-C3N4/MXene, were synthesized. The structural, morphological, optical and surface properties of these nanomaterials were systematically characterized using XRD, FTIR, SEM, TEM, UV-Vis DRS, PL, XPS, BET and XAFS to gain insights into their physicochemical properties. The heterogeneous CuFe2O4-based photocatalysts were developed to improve their photocatalytic activity and stability in photocatalysis and photo-Fenton processes and represent promising solutions for sustainable wastewater treatment. Ciprofloxacin, a commonly prescribed antibiotic, ranitidine and nizatidine, both amine-based pharmaceuticals, were selected as target contaminants in this study. HPLC and LC-MS/MS were used to monitor the degradation profiles, identify transformation products, and elucidate the possible mechanistic pathways for the three contaminants. The prepared photocatalysts followed pseudo-first order kinetics for the degradation of the three pharmaceutical pollutants. TOC analysis was employed to evaluate mineralization efficiency, and EPR was used to identify the reactive oxygen species (ROS) generated during the photocatalytic process.

The first part of this study investigates the eco-friendly synthesis of CuFe2O4 nanoparticles (bio-CuFe2O4) using bio-reducers from plant wastes, including date pulp, date seeds, lemon peels and pollen grains, via a sol-gel auto-combustion method. The synthesized CuFe2O4 catalysts were assessed in the photocatalytic degradation of ciprofloxacin in a peroxymonosulfate-assisted photo-Fenton system under UV-Vis irradiation. This is the first study in which bio-CuFe2O4 was used for ciprofloxacin degradation in the presence of peroxymonosulfate as an oxidant. Among the different bio-CuFe2O4 catalysts, the date pulp-derived catalyst (bio-CuFe2O4/DP) exhibited the highest photocatalytic activity, achieving 97% ciprofloxacin degradation and 69.1% TOC removal. The improved performance was attributed to suppressed charge recombination, faceted nanostructured morphology, and favorable physicochemical properties. In addition, the bio-CuFe2O4/DP catalyst exhibited high stability and recyclability over multiple reaction cycles.

The second part of this study focuses on the preparation of binary CuFe2O4/g-C3N4 nanocomposites for the photocatalytic degradation of nizatidine in a peroxydisulfate-assisted photo-Fenton system under visible LED irradiation. A novel flash heat treatment method was employed for the first time to synthesize 2D g-C3N4 with improved structural and optical properties compared with conventionally prepared g-C3N4 via pyrolysis. Binary nanocomposites were developed by using an ultrasound-assisted approach. The formation of an S-scheme heterojunction between the CuFe2O4 nanoparticles and the flash-heat-treated gC3N4 structure significantly improved the charge carrier separation, leading to the complete removal of nizatidine within 43 min under LED light. In addition, the binary CuFe2O4/g-C3N4 catalyst exhibited excellent reusability and maintained its high photocatalytic efficiency with a minimal drop in performance over several reaction cycles.

In the final study, a novel ternary CuFe2O4/g-C3N4/MXene nanocomposite for visible light photocatalysis is presented, which achieved 96% degradation of ranitidine, with a reaction rate eight times higher than the binary CuFe2O4/g-C3N4. The incorporation of MXene significantly improved the photocatalytic efficiency by facilitating charge transfer through an S-scheme heterojunction, thereby suppressing electron-hole recombination and promoting the generation of ROS. The improved charge separation efficiency resulted in higher redox activity and contributed to the rapid degradation of ranitidine. Moreover, the CuFe2O4/g-C3N4/MXene nanocomposite exhibited excellent reusability and high stability, and mechanistic studies confirmed the dominant role of hydroxyl and superoxide radicals in pollutant degradation.

Overall, this dissertation emphasizes the importance of innovative synthetic strategies, including biogenic strategies, flash heat treatment, and binary and ternary nanocomposites with heterojunctions, to advance the field of photocatalysis. The results highlight the potential of CuFe2O4-based nanomaterials as efficient photocatalysts for environmental decontamination, providing sustainable solutions for water pollution.

Date of Award	16 May 2025
Original language	American English
Supervisor	MOHAMMAD ABU HAIJA (Supervisor)