Abstract
Ph.D. (Chemistry)
This study explored preparation, characterisation and applications of different types of carbon and metal oxide semiconductors-based anodes for the electrochemical/photoelectrocatalytic oxidation of some selected organic contaminants.
Exfoliated graphite (EG), a form of carbon, was prepared by acids intercalation of natural graphite flakes and thermal treatment. Expanded graphite – diamond (EG-diamond) composite prepared by solution mixing of EG and diamond powder was fabricated into electrodes and characterised. Raman spectrometry and x-ray diffraction (XRD) patterns revealed peaks that are characteristic of EG and diamond. Scanning electron microscopy (SEM) images showed that the diamond particles were well dispersed within sheets of EG. Cyclic voltammetry (CV) showed that the EG electrode exhibited faster electron transfer while the composite electrode gave enhanced current peak. The electrolysis of acid blue 40 (AB 40) in 0.1 M Na2SO4 electrolyte resulted in ca. 80% dye removal at the EG-Diamond electrode and 66% removal at the pristine EG electrode at a current density of 20 mAcm-2 after 4 h. However, in a chlorine mediated electrolysis (NaCl as supporting electrolyte), the decolourisation of the dye was very rapid with over 98% decolourisation in 25 min. The extent of mineralisation was measured by total organic carbon (TOC). EG-Diamond and EG electrodes yielded TOC removal of 44% and 26% respectively in the electrochemical cell with Na2SO4 supporting electrolyte. While NaCl cell presented faster decoulorisation, the TOC decay was much slower compared to the Na2SO4 cell. The degradation of AB 40 follows pseudo first-order kinetic model with apparent rate constants of 2.34 x 10-3 min-1 and 4.41 x 10-3 min-1 obtained at EG and EG-diamond electrodes respectively. The EG-diamond electrode was further applied in the degradation of orange II dye (OG II) and a mixture of OG II and AB 40 with a TOC removal of 49 % for the dye mixture...