Abstract
M.Sc. (Chemistry)
In the recent years, organic pollutants such as dyes, endocrine disrupting chemicals, pharmaceuticals etc. have escalated in water bodies thus aggravating the struggle for access to fresh clean water. Such pollutants have become a serious environmental issue as they present carcinogenic, endocrine disrupting, mutagenic and other toxic effects to humankind. Several physico-chemical technologies have therefore been explored in the decontamination of organic pollutants from water.
In this study, polyaniline nanofibers (PANI NFs) were investigated as potential adsorbents for the removal of methyl orange dye and Bisphenol A as model organic pollutants from aqueous solutions. This nanostructured adsorbent was characterized using Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR), Field Emission-Scanning Electron Microscope (FE-SEM), High Resolution-Transmission Electron Microscope (HR-TEM), Thermogravimetric analysis (TGA), Brunauer-Emmet-Teller surface area analysis (BET), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS) and the Malvern Zeta-sizer. The efficiency of the adsorbents was evaluated through batch and fixed bed adsorption systems.
From the fixed bed adsorption studies, methyl orange dye was used as an adsorbate to assess the effects of parameters such as flow rate, bed mass and influent solution concentration at pH 4. The breakthrough curves were best fitted by Thomas and Yoon-Nelson models. 6 g mass of PANI NFs successfully treated 29.16 L of 25 mg/L MO solution. The performance of the adsorption system was strongly influenced by flow rate, bed mass and initial influent concentration. Consequently, the best column performance was given by 25 mg/L, 6 g and 3 mL/min influent concentration, bed mass and flow rate, respectively.
For the batch adsorption studies, Bisphenol A was employed as an adsorbate in evaluating the critical parameters; pH, initial adsorbate concentration, adsorbent dose, contact time and temperature. The BPA adsorption process proved to be independent of solution pH but was highly influenced by the adsorbent dose. The adsorption was modelled by both Langmuir and Freundlich isotherm models but the Langmuir model fitted better. The adsorption kinetics were modelled by pseudo-first-order model, pseudo-second-order and intraparticle diffusion models. The results showed that the pseudo-second-order model best described the BPA adsorption process and the intra-particle diffusion model revealed that the adsorption...