Abstract
Ph.D. (Chemistry)
The release of poorly treated dye effluents into the environment is currently under scientific scrutiny due to the adverse effects they cause to the ecosystem. These effluents are typically composed of pigments, dyes, dyestuffs, metals, organic matter, surfactants and suspended solids. The complex nature, recalcitrance and poor biodegradability properties of these pollutants limit their efficient removal by conventional wastewater treatment processes (WWTPs). Therefore, the WWTPs are usually complimented by advanced oxidation processes (AOPs) for quantitative removal of organic pollutants from the coloured wastewater. The AOPs involve the use of hypochlorite; ozone and hydrogen peroxide in the absence or presence of UV radiation; Fenton´s reactions; photocatalysts; among others. The basic principle of AOPs relies on the generation of highly reactive hydroxyl radicals capable of oxidizing unsaturated carbon bonds in organic pollutants including dye molecules.
The use of TiO2 nanoparticles for the degradation of organic materials in water samples is extensively reported in the open literature. However, regardless of the photocatalytic activity observed, the use of powdery photocatalysts is often accompanied by difficulties involving the recovery of the spent catalyst after use either for recycling or disposal. These challenges usually result in secondary pollution as the nanocatalysts are not quantitatively recovered from the treated effluents. Hence, the aim of this study was to carry out the immobilization of nanocatalysts on the surface of nanofibers functionalized with chelating agents. In this manner, the leaching of metal oxides into the treated wastewater would be minimized while maintaining the photocatalytic properties.
The methodology involved preparation of the electrospun polyacrylonitrile nanofibers (PAN NFs) and it was carried out through electrospinning followed by surface impregnation of ethylenediaminetetraacetic acid (EDTA) using the ethylenediamine (EDA) cross-linker. Textural and chemical characterizations of the nanofibers were carried out by analysis of the specific surface area (Brauner Emmet and Teller (BET)) and thermogravimetric analyses (TGA), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy.
The results showed that impregnation of EDA and EDTA chelating agents on the surface of PAN changed the distribution of nanofibers as proximity is increased (accompanied by reduced softness), but the nanofibrous structure of the pristine PAN NFs was not substantially altered. Adsorption equilibrium studies were performed with Freundlich, Langmuir and Temkin isotherm models with the former providing better...