Glory Ollordaa Master’s Thesis Defense, Tuesday, December 2, 2025 @ 10:00 am Central Time

COMMITTEE CHAIR: Dr. Yingchun Li

TITLE: DEGRADATION OF DYE BY GRAPHITIC CARBON NITRIDE (g-C₃N₄) USING H₂O₂

ABSTRACT: The industrialization of sectors such as textiles, leather, and paper has led to severe environmental challenges due to the discharge of synthetic dyes into waterways. These synthetic dyes are toxic, non-biodegradable, and disrupt aquatic ecosystems by affecting photosynthesis and oxygen levels, subsequently entering food chains. Traditional wastewater treatment methods, such as adsorption and biological processes, provide limited solutions and can create secondary pollutants. Advanced oxidation processes (AOPs), particularly those utilizing visible-light photocatalysis, present a promising alternative for generating reactive oxygen species (ROS) via solar energy, thereby facilitating effective dye degradation. This research explores the photocatalytic properties of graphitic carbon nitride (g-C3N4), a metal-free semiconductor, and its caffeine-doped variant. The study assesses their effectiveness in degrading various synthetic dyes under visible light, employing hydrogen peroxide (H2O2) as a co-oxidant to promote ROS generation. Caffeine, with a p-conjugated structure, was introduced to enhance the charge separation, extend light absorption, and improve the electronic properties of g-C3N4, addressing its inherent challenges, such as high electron-hole recombination and a low surface area. The photocatalysts were characterized using the SEM and synthesized through the thermal polymerization of melamine at varying temperatures (600°C, 625°C, 650°C) with the addition of caffeine. The degradation experiments were conducted in batch reactors using white LED light, with dye concentrations measured through UV-Vis spectrophotometry at specific wavelengths for a diverse set of synthetic dyes selected based on their structural properties. Optimal operational parameters, including catalyst dosage, H2O2 concentration, light exposure, and reaction duration, were established. The degradation kinetics followed the Langmuir-Hinshelwood mechanism, indicating that the process adhered to a pseudo-first-order model based on surface adsorption and oxidation by ROS. Results indicated no significant improvement from caffeine doping, as both pristine and doped g-C3N4 achieved nearly complete decolorization within the same timeframe. The study reveals that variations in calcination temperature do not significantly affect the performance of g-C3N4 as a photocatalyst, suggesting that intrinsic properties and interactions with dyes play a more critical role.

Keywords: Photocatalyst, wastewater, dye, degradation, graphitic, carbonnitride

Room Location: E.E. O’Banion Science Building, Room 203