Extraction, isolation and physicochemical studies of natural pheophytin complexes

Thesis (D.Phil) North-West University, Mafikeng Campus, 2005A simple, rapid and efficient method for the extraction and purification of chlorophyll-a from plant sources has been developed. And with it, a new method for the ·extraction of chlorophyll in winter, which has been previously problematic, has been developed. The methods are summarized in flow diagrams showing the elimination of carotene and xanthophylls. The chlorophyll-a isolated has been demetallated to obtain pheophytin-a that in tum has been complexed with cobalt(II), copper(II), zinc, nickel(II) and chromium(Ill) ions. The resulting metal pheophytin complexes, chlorophyll-a and pheophytin-a have been fully characterized by ultraviolet-visible and Fourier transform infrared spectroscopies, electrospray ion mass spectrometry and elemental analysis. For the first time, the kinetics of the oxidation of cobalt(II) pheophytin-a by chromium(III) has been followed spectrophotometrically at temperatures ranging from 313 to 333 K. The reaction has been found to be first order in the concentration of the hexaaquachromium(III) cation. The oxidation-reduction mechanism proposed for the reaction is an outer-sphere electron tunnelling mechanism. The ease of demetallation and complexation of chlorophyll-a has highlighted the problem caused by acidity and the presence of these metal ions in soils, on the chlorophyll content of leaves.Doctora

Morphological Characterization of Soot from the Atmospheric Combustion of Kerosene

Kerosene has been used as a precursor for the production of carbon nanomaterial without a catalyst precursor. Nanomaterials formed in the process have been analysed by Raman, Scanning electron microscope (SEM), x-Ray diffraction (XRD) and by Energy dispersive spectroscopy (EDS). Carbon nanomaterial produced show the morphology of carbon nanospheres with diameters of about 0.3 µm

A Comparative Study of Carbon Nanotubes Synthesized from Co/Zn/Al and Fe/Ni/Al Catalyst

The catalyst systems Fe/Ni/Al and Co/Zn/Al were synthesized and used in the synthesis of carbon nanotubes. The carbon nanotubes produced were characterized by Field Emission Scanning Electron Microscope (FE-SEM), Energy Dispersive x-ray Spectroscopy (EDS), Raman spectroscopy, Thermogravimetric Analysis (TGA) and Transmission Electron Microscope (TEM). A comparison of the morphological profile of the carbon nanotubes produced from these catalysts indicates the catalyst system Fe/Ni/Al to have produced higher quality carbon nanotubes than the catalyst system Co/Zn/Al

Kinetic Studies of Reduction of Tris-(1,1,1,5,5,5-hexafluoroacetylacetonato) ruthenium(III) in Methanol, Ethanol and Propanol

The complex tris-(1,1,1,5,5,5-hexafluoroacetylacetonato-) ruthenium(III), hereafter referred to as Ru(hfacac)3, has been synthesized. Ultraviolet and visible spectroscopic measurements of the complex in ethanol revealed three prominent absorption bands at 287, 374 and 525 nm with molar absorptivity coefficients of 4.113, 3.885 and 3.59 respectively. Magnetic susceptibility measurements between 78 and 296 K revealed the complex to assume a low spin configuration of e0 t2g5 and an oxidation state of +3 as inferred from a value of 1.92 Bohr magneton. Kinetic investigation of the reduction of the complex in methanol, ethanol and propanol indicate the reduction to proceed in the order methanol > ethanol > propanol. The energies of activation of the reduction in methanol and ethanol were found to be 85.4 and 108 kJ/mol respectively

Polyvinyl chloride Waste as an Adsorbent for the Sorption of Pb 2+ from Aqueous Solution

The sorption of Pb 2+ from solution by polyvinyl chloride waste was investigated. The morphological features of the polymer sample were studied using the energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), X-ray diffraction spectroscopy (XRD), and the Fourier transform infrared spectroscopy (FTIR). Equilibrium, kinetic, and thermodynamic batch adsorption experiments were carried out by the concentration, time, and temperature effects, respectively. The morphological image of the polymer showed irregular small size particles which indicated a high surface area and porosity that facilitated sorption. The adsorption studies recorded relatively rapid uptake of Pb 2+ by the polymer which was mainly diffusion controlled and followed a second order kinetic process. The thermodynamic studies suggested relatively low temperature (low energy) favoured sorption which was exothermic with a physisorption mechanism

Equilibrium, kinetic and thermodynamic studies of the uptake of copper by layered double hydroxide

This study explored the adsorption capacity of Mg/Al layered double hydroxide (LDH) for the removal of Cu2+ from aqueous solutions after synthesis and characterization. The effect of various operational parameters such as concentration, temperature and sorption time on the adsorption of Cu2+ was investigated using batch adsorption process experiments. It was found that layered double hydroxide (LDH) can be used as adsorbent for the removal of copper ions in aqueous solution containing low concentration of the metal salt. The average values of activation energy, isosteric heat of adsorption, entropy and enthalpy were 1.447, 12.9, 0.0137 and –4.8390 kJ/mol, respectively. This shows that the adsorption of the metal ion on the adsorbent follows a physical adsorption mechanism. The kinetic results conform to pseudo-second order model (R2 = 0.9959) and second order kinetic model (R2 = 0.9952) while the adsorption characteristics of the adsorbent followed both Langmuir and Freundlich adsorption isotherm models