This work involves a fundamental investigation of the effect of competitive sorption processes on the equilibrium and kinetics of sorption by two sorbent materials, active carbon granules and nylon 6 powder, using simple aromatic model solutes. In addition the influence on these processes of coating the active charcoal granules with a thin layer of nylon 6 was also studied. The Thesis is divided into three parts, the Introduction, Experimental and Discussion Sections. The Introduction deals with the properties of active carbon and nylon 6. This is then followed by a discussion of the sorption, diffusion and permeability processes in sorbent materials, and the physicochemical factors that influence them. The Introduction is concluded with a section on competitive sorption phenomena. The Experimental section describes the physical characterisation of the sorbent materials. This is followed by details of the determination of the sorption isotherms for the interaction of the model solutes from both single and binary solute solutions with the sorbents. The phenolic compounds were found to have a high affinity for nylon 6 compared to the benzoic derivatives and binary solute mixtures of these phenolic compounds showed competitive sorption phenomena which was accompanied by a co-plasticisation effect at higher concentration. The benzoic acid derivatives showed no competitive effects but a temperature transition effect on sorption was found for these compounds which was absent for the phenolic compounds. Sorption of the model solutes by active carbon from binary solute solution showed evidence that a competitive interaction was occurring, the extent of the competition being related to the concentration of the corapeting species. The application of a thin coat of nylon 6 to the charcoal granules did not result in a significant change in the sorption isotherm type found although the sorption capacity was lowered. The final section of the experimental work deals with the kinetics of sorption of the sorbents, again from both single and binary solute solutions. The presence of the coat and other competing species present in solution were both seen to influence the kinetics of sorption. The final section of the thesis deals with the discussion of the experimental results obtained. The main conclusion drawn is that the interaction of the model solutes with the active carbon and nylon 6 may be accounted for by the concept of the conservation of diffusing mass thus allowing then to be directly compared despite marked differences in their physical nature and sorption characteristics. The mechanisms of competitive sorption are also discussed and compared with models proposed in the literature. The sorption characteristics of the composite sorbent are accounted for in terms of the interaction characteristics of its two components to assess whether selectively permeable film coats could be used to improve the sorption efficiency of active carbon in multi-solute systems.
|Date of Award||1982|