Sorption Characteristics of Organic Compounds in Landfill Leachate by Modified Clays

Abstract

Natural clays were modified by substituting inorganic ions with the organic cations hexadecyltrimethylammonium (HDTMA), dodecyltrimethylammonium (DDTMA) and Tetramethylammonium (TMA). This resulted in the clays having significantly higher organic matter contents in proportion to the amount of carbon in each organic cation. The sorption behavior of different molecular-weight organic compounds from leachate by different sorbents was also investigated. The batch experiments indicated that the sorption of modified clays is more sensitive to pH than granular activated carbon (GAC). In general, the sorption capacities of the modified clays increased with increasing sorbate molecular weights. In contrast, the activated carbon was found to be an effective sorbent rather than modified clays for organic compounds with small molecular weights. Moreover, the surface characteristics of sorbents with their sorption behaviors indicated that the sorption mechanism of modified clays is different from that in activated carbon. The uptake of organic compounds in landfill leachates by modified clays depends on the organic contents of the modified clays, and the sorption mechanism of activated carbon is surface adsorption. Experimental results indicated that GAC combined with a modified clay effectively reduces leachate Chemical Oxygen Demand (COD), and might be further used to enhance the containment capabilities of clay landfill liners.