The Performance of Organophilic Clay on Nonaqueous Phase Liquid Contaminated Sediments Under Anisotropic Consolidation

摘要

Disturbance of a nonaqueous phase liquid (NAPL) contaminated sediment; for example the loading-induced consolidation after placement of a sediment cap, may result in the release of the NAPL. Organophilic clays are reported as effective media in adsorbing NAPLs and organic contaminants. Consolidation tests were performed to evaluate the effectiveness of placement of an organophilic clay layer to capture any such displaced NAPL. NAPL contaminated specimens were tested in a modified triaxial setup under anisotropic loading conditions. Kaolinite was used to represent the sediment solid phase and Soltrol 130 (a type of mineral oil) was used to represent the NAPL. The tests with no organophilic clay showed that higher NAPL saturation resulted in a stiffer soil matrix, which reduced NAPL expulsion. The more organophilic clay was used, the less NAPL release was observed. For the conditions of this study, no NAPL breakthrough was observed, when the initial NAPL saturation of kaolinite was 28 % with a layer of organophilic clay on top. The adsorption capacity of organophilic clay with this oil was approximated as 1.2 ml (0.93 g) per 1 g of organophilic clay solids. Organophilic clay reached its full adsorption capacity independent of the volume and rate of NAPL expulsion during consolidation. These data provide guidance to estimate the quantity of organophilic clay needed for site-specific applications.