| Summary: | Thesis (M. Eng.)--Memorial University of Newfoundland, 1997. Engineering and Applied Science Includes bibliographical references : leaves 95-101 Two natural zeolites, i.e. chabazite (CHB) and clinoptilolite (CLN), and two coal fly ashes, i.e. Lambton fly ash (LBash) and Nova Scotia fly ash (NSash), were studied toward their suitability as construction materials for landfill liners. Lead (Pb2-) and phenol (C6H5OH) were chosen to represent inorganic and organic leachates. The research was focused on (1) the sorption capacity of zeolite and fly ash against Pb2- and phenol; (2) the hydraulic conductivity of these candidate materials when percolated with aqueous solutions of Pb2- (2500 mg/1), phenol (55 mg/1), and Pb27phenoi mixture (Pb2- = 2500 mg/1 and phenol = 55 mg/1), respectively; (3) the interaction among zeolite, fly ash, Pb2-, and phenol; (4) the optimum mix design for zeolite and fly ash in terms of leachate retention and hydraulic performance. -- Material characterization revealed that LBash is distinguished from NSash by its unburnt carbon content and surface functional groups. For zeolites, CHB has a higher chemical activity and larger cation exchange capacity than CLN. Batch tests on the four materials demonstrated that CHB was most powerful in Pb2- sorption (210 mg/g) while LBash was most effective in phenol removal (1.3 mg/g). Experimental preference was then given to CHB, LBash, and their mixes. -- During column leaching tests, Pb2- sorption took place on LBash and CHB solids through physisorption, chemisorption, complexation, precipitation, and ionic sieving of CHB micro-pores. Phenol was attenuated by LBash and CHB via acid-base reaction, dipole attraction, and hydrogen bonding. In CHB and LBash mixes, CHB was the principal sorbent with Pb2-, while LBash was mainly responsible for phenol retention. When Pb2- and phenol coexist in the system, they compete for all sorption sites except for the CHB micro-pores, which cannot accommodate the size of phenol molecules. The hydraulic conductivity values of CHB and LBash with Pb2- or phenol permeant ranged between 1.7 x 10-8 and 7.0 x 10-8 m/s. Mixes of CHB and LBash are less permeable due to a better filling of pore space. Although the three leachates used as permeant had different chemical properties, they were not concentrated enough to alter the hydraulic conductivity of test specimens. -- It was concluded that, under present experimental conditions, a CHB/LBash ratio of 1:1 in weight appeared to be the optimum mix for a liner material which will exhibit a maximum overall retardation of Pb2- and phenol. The 1:1 mixture compacted under standard condition also showed a minimum hydraulic conductivity in the order of 3.0 x10-9 m/s.
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