Abstract
Ph.D. (Chemistry)
In this thesis, the use of cactus extracts in water purification as the domain of interest, where the scope includes extraction of vital polysaccharides, nanofiber fabrication and application is presented. The cactus pads (Opuntia ficus indica) used in the study were collected from a neighbouring field to the University of Johannesburg, South Africa.
Water pollution is increasing and lack of cheap and adaptable point-of-use technologies, have recently exacerbated water shortage problem. Globally, the existing water resources may not sustain the demand for domestic and industrial use, if the available amounts cannot be harvested, treated and recycled properly. Based on this concern, the quest for efficient wastewater treatment technologies, is of a particular interest to reserchers.
Critical examination of the isolated polysaccharides revealed that cactus extracts were generally composed of unique lyxose sugars (both in furanose and pyranose forms) along with other hemicellulose sugar residues. Basically, the polysaccharides obtained from cactus were classified as hemicellulose and pectin sugars. Based on these constituents, a hybrid approach was used to study the applicability of cactus extracts in water treatment and filtration. First, direct use of the polysaccharide extracts was assessed. The adsorption of selected metal cations onto the hemicellulose polysaccharide extract was studied as a function of physico-chemical variables including initial metal ion concentration, adsorbent dosage, contact time and pH of the solution.
Results obtained in this study, can be divided into four parts /aspects, as highlighted below.
Part I-Adsorption Isotherms: the models indicated that the adsorption percentage of Pb2+ and Cd2+ increased with contact time, attaining equilibrium at 150 min for Cd2+ and 120 min for Pb2+. At these optimal times, the adsorption capacity of both ions increased with an increase in...