Feasibility assessment of using modified clay materials for solid/hazardous waste disposal landfills

Typically, a clay liner at the bottom of the landfill is used to provide protection of the surrounding soil and groundwater from contamination by the leachate which contains high strength of contaminants. Conventional liner materials (e.g. bentonite clays) have a good performance in removing inorganic compounds. Unfortunately, these liners may be attacked by high concentration of organic pollutants in leachate and result in increasing their hydraulic conductivities. In this study, the organically modified clay was employed to remove the high strength organic pollutants. Various factors that affect the ability of clay in removing and retarding the movement of contaminations have been examined. Organoclay BB-40 obtained from Biomin Inc. is used. Organoclay BB-40 is modified by dicetyl dimethyl ammonium chloride that contains the hydrophobic long alkyl chains and allows to form hydrophobic bonding with high hydrophobicity or non-polar organics. The adsorptions of inorganic and organic onto Organoclay BB-40 are found to be significant that might be attributed to the formation of organometallic complexes between metal ions and the hydrophobic long alkyl chains for inorganic adsorption, and as a result of partition reaction for organic removal. The hydraulic conductivities of Organoclay BB-40 under an effective stress of 10 psi are 7xl0-9 cm/set to tap water, 1.6x l0-8cm/set to leachate, and 1.4x 10-7cm/set to synthetic leachate. The amount of uptake of 2,4,6-trichlorophenol in synthetic leachate by Organoclay BB-40 is much higher than that of total organic carbon in real leachate from co-disposal landfill site. All these results suggest that the use of Organoclay as a liner material would provide a barrier with the ability to effectively remove dissolved organic contaminants and to resist the flow of leachate.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 1995